State-of-the-Art Management of Colorectal Cancer: Treatment Advances and Innovation

Colorectal cancer (CRC) remains a significant global health challenge, ranking among the leading causes of cancer-related morbidity and mortality worldwide. Recent advancements in molecular characterization have revolutionized our understanding of the heterogeneity within colorectal tumors, particularly in the context of tumor sidedness. Tumor sidedness, referring to the location of the primary tumor in either the right or left colon, has emerged as a critical factor influencing prognosis and treatment responses in metastatic CRC. Molecular underpinnings of CRC, the impact of tumor sidedness, and how this knowledge guides therapeutic decisions in the era of precision medicine have led to improved outcomes and better quality of life in patients. The emergence of circulating tumor DNA as a prognostic and predictive tool in CRC heralds promising advancements in the diagnosis and monitoring of the disease. This innovation facilitates better patient selection for exploration of additional treatment options. As the field progresses, with investigational agents demonstrating potential as future treatments for refractory metastatic CRC, new avenues for enhancing outcomes in this challenging disease are emerging.

Neoadjuvant Stereotactic MR-Guided Ablative Radiation Therapy (SMART) and Surgical Outcomes in Patients with Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

The benefit of neoadjuvant radiation therapy for patients undergoing surgery for pancreatic ductal adenocarcinoma (PDAC) remains unclear. Stereotactic MR-guided adaptive radiation therapy (SMART) treatment to ablative doses is a newer technique that is well tolerated and has increased local control in unresectable pancreatic cancer. For resectable pancreatic cancer, neoadjuvant SMART has the potential to decrease local recurrence risk and positive margin rates. However, there is concern for perioperative risks associated with ablative dose treatments. We report the efficacy and safety of surgical resection in patients who have received neoadjuvant SMART at our institution.

MATERIALS/METHODS

We conducted a retrospective analysis of all consecutive patients diagnosed with PDAC who had noted vascular involvement of the celiac axis, superior mesenteric, and/or portal vessels between January 2016 and December 2022 at a single, high-volume, academic institution. Perioperative events were defined according to the Clavien-Dindo classification. The Kaplan Meier method was applied to estimate disease free survival (DFS) and overall survival (OS).

RESULTS

Seventeen patients with PDAC and vessel involvement at time of diagnosis who received SMART were included. Median follow-up time was 14.3 months; all patients underwent surgery, at a median time after radiation of 28 days (range: 15 - 90). Median length of postoperative stay was 7 days (range: 3 - 15). Five patients (29%) underwent vascular resection. Fifteen patients (88%) achieved R0 resection, with two R1 resections noted at the SMA and pancreatic neck respectively. Seven patients (41%) had adverse events attributable to surgery, with the majority being defined as abscess or infection (n = 5; 29%). One (6%) Clavien-Dindo grade III or higher toxicity was observed - a cortical cerebrovascular event following surgery. No major bleeding events requiring surgical intervention were noted. At time of event censorship, there were no observable locoregional failures. The median DFS and OS were not reached; however, 1-year DFS and OS were 62% and 87%, respectively.

CONCLUSION

Neoadjuvant SMART appears to be safe, with low rates of surgical complications and promising outcomes. Further identification of patients for this approach requires additional investigation.

Abstract 4861: Copanlisib enhances the effectiveness of anti-PD1 therapies for colorectal cancer

Introduction: Immunotherapies are increasingly being used for patients diagnosed with cancer, however, for metastatic colorectal cancer (CRC), more than 95% of patients have shown little to no clinical benefit to immunotherapy. Previous work from our lab has shown that copanlisib, a PI3K inhibitor, was found to enhance MHC class I expression in Kras mutant CT26 murine colon cancer cells. Here we examine the potential for anti-cancer activity with the combination of copanlisib and anti-PD1 treatments using this model.

Methods: The impact of copanlisib on CT26 cells was performed using the WST assay and the expression of MHC class I was assessed using flow cytometry. CT26 flank allografts were generated in Balb/C mice and subsequently treated for 15 days with copanlisib (10 mg/kg), anti-PD1 (0.2 mg, BioXCell) or the combination. An IgG2a antibody (BioXCell) was used as a control. Tumors were measured twice a week using a caliper. Tumors were excised, and prepared for immunohistochemistry for CD8, CD4, perforin, granzyme B, and F480 was performed. Staining was quantified as the number of positive staining cells per 20X field of view (FOV).

Results: CT26 viability in response to 200 nM copanlisib was relatively unchanged as compared with untreated controls. Via flow cytometry, a 75% increase in mean fluorescent intensity (MFI) for MHC class I was observed comparing control to copanlisib (p=0.003). In vivo, after 15 days there was no difference in the growth rate of those cancers treated with control versus copanlisib or anti-PD1. A significant reduction in growth rate was observed with the combination of anti-PD1 with copanlisib compared to the other arms (median fold change=3.62; control: 7.49, p=0.002, copanlisib: 8.88, p=0.003; anti-PD1: 8.93, p=0.002). There were no differences in CD8 T cell and perforin expression between the treatment groups. Granzyme B expression was higher in the combination compared (median/FOV= 44) to the control (27, p= 0.01). Additionally, a significant reduction in F480 expression was seen in the combination compared to the other treatment groups (median/FOV=43; control: 139, p<0.001, copanlisib: 110, p<0.001; anti-PD1:149, p<0.001).

Conclusions: In conclusion, copanlisib in combination with anti-PD1 demonstrated enhanced anti-tumor activity in Balb/c mice that were injected with CT26 CRC cells. This response was correlated with increased granzyme B expression and a reduction in macrophages with the combination treatment. Further studies will expand on the mechanism of this combination therapy.

Citation Format: Alexa E. Schmitz, Kennedy J. Maduscha, Sarbjeet Makkar, Cheri A. Pasch, Rebecca A. DeStefanis, Philip B. Emmerich, Dustin A. Deming. Copanlisib enhances the effectiveness of anti-PD1 therapies for colorectal cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4861.

Abstract 5177: Nilotinib suppresses the myofibroblastic cancer-associated fibroblast phenotype

Background: Cancer-associated fibroblasts (CAFs) modulate the tumor immune microenvironment and are an exciting target for improving response to immunotherapy. Major roles of CAFs in the immune microenvironment include deposition of extracellular matrix (ECM) to prevent immune cell infiltration, a function associated with myofibroblastic CAFs (myCAFs), and production of cytokines to alter the immune milieu, associated with inflammatory CAFs (iCAFs). Recently we have demonstrated the potential for tyrosine kinase inhibitors (TKIs) to alter CAF phenotypes. Here we investigate the ability of dasatinib and nilotinib to alter the immune regulatory functions of CAFs.

Methods: Bulk RNA sequencing comparing the effects of nilotinib and dasatinib on primary-derived patient CAFs was performed. CAFs from two rectal cancer patient tumors were isolated, cultured, and treated for 96 hours with 2.5μM nilotinib, 100nM dasatinib, or control feeding media. RNA isolation, library preparation, sequencing, data processing, and differential expression analysis was done through the University of Wisconsin - Madison Gene Expression Center, Biotechnology Center, and Bioinformatics Resource. Gene set enrichment analyses were done using GSEA 4.2.3 (Broad Institute) and all other analyses done in R.

Results: The primary variance in samples is between CAF lines (RC1 and RC2), followed by treatments. RNA expression markers for myCAFs significantly associate with the Gene Ontology molecular function ECM structural constituent (q < 0.001). Nilotinib decreased expression of this gene set in RC1 (q < 0.001), while dasatinib treatment increased these genes in RC2, though not significantly (q = 0.2). Both dasatinib and nilotinib downregulated immune-related hallmark gene sets including IL6/JAK/STAT3 signaling (RC2 dasatinib q < 0.05, q < 0.001 for others) and TNFα signaling through NFκB (RC1 dasatinib q < 0.001, RC2 niltoinib q < 0.05, others q = 0.001,). Additionally, dasatinib induced increased expression of genes involved in myogenesis in both CAF lines (RC1 q = 0.001, RC2 q < 0.001), while nilotinib significantly decreased these genes in RC1 (q = 0.001). MYOCD is a transcription factor involved in myogenesis that regulates important myCAF genes such as ACTA2 and TAGLN. Nilotinib treatment decreased expression of MYOCD (RC1 log2FC -1.3 q < 0.001, RC2 -0.75 q < 0.05) and its target genes in both lines, whereas dasatinib did not significantly alter expression.

Conclusions: CAFs derived from different cancers harbor different transcriptional profiles and have different responses to TKIs. Dasatinib treatment led to an increase in expression of ECM genes associated with the myCAF phenotype, while nilotinib decreased this phenotype, potentially by inhibiting MYOCD expression. Further investigation into the mechanisms by which nilotinib treatment decreases expression of ECM genes and whether these trends continue in vivo are warranted.

Citation Format: Katherine Anne Johnson, Yousef Gadalla, Cheri A. Pasch, Dustin A. Deming. Nilotinib suppresses the myofibroblastic cancer-associated fibroblast phenotype. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5177.

Case report: Radiographic complete response of radiation-induced glioblastoma to front-line radiotherapy: A report and molecular characterization of two unique cases

Radiation-induced gliomas (RIGs) are an uncommon disease type and a known long-term complication of prior central nervous system radiation exposure, often during childhood. Given the rarity of this malignancy subtype, no clinical trials have explored optimal therapy for these patients, and the literature is primarily limited to reports of patient cases and series. Indeed, the genomic profiles of RIGs have only recently been explored in limited numbers, categorizing these gliomas into a unique subset. Here, we describe two cases of RIG diagnosed as glioblastoma (GB), IDH-wildtype, in adults who had previously received central nervous system radiation for childhood cancers. Both patients demonstrated a surprising complete radiographic response of the postoperative residual disease to front-line therapy, a phenomenon rarely observed in the management of any GB and never previously reported for the radiation-induced subgroup. Both tumors were characterized by next-generation sequencing and chromosomal microarray to identify potential etiologies for this response as well as to further add to the limited literature about the unique molecular profile of RIGs, showing signatures more consistent with diffuse pediatric-type high-grade glioma, H3-wildtype, and IDH-wildtype, WHO grade 4. Ultimately, we demonstrate that treatment utilizing a radiation-based regimen for GB in a previously radiated tissue can be highly successful despite historical limitations in the management of this disease.

Phase 2, multicenter, open-label basket trial of nab-sirolimus for patients with malignant solid tumors harboring pathogenic inactivating alterations in TSC1 or TSC2 genes (PRECISION I)

TPS597

Background: Albumin-bound ( nab)-sirolimus, a novel mTOR inhibitor (mTORi) that utilizes nanoparticle technology to preferentially target tumors, is approved in the US for the treatment of adults with malignant PEComa. In an exploratory analysis of the AMPECT registrational trial of nab-sirolimus in advanced malignant PEComa (NCT02494570), 8/9 (89%) and 1/5 (20%) patients with TSC1 and TSC2 inactivating alterations, respectively, had confirmed response (Wagner, J Clin Oncol. 2021). Importantly, both TSC1 and TSC2 alterations have been observed in patients with various gastrointestinal cancers (Table). Overall, most treatment-related adverse events (TRAEs) in AMPECT were grade 1/2 and manageable for long-term treatment; no grade ≥4 TRAEs occurred. Methods: PRECISION I (NCT05103358) is a phase 2, open-label, multi-institutional basket trial evaluating efficacy and safety of nab-sirolimus in patients with alterations in TSC1 (Arm A) and TSC2 (Arm B). Patients ≥12 years old with malignant solid tumors harboring pathogenic inactivating alterations in TSC1 or TSC2 (confirmed by central review of next-generation sequencing reports) who have progressed on standard therapies and are mTORi-naïve are eligible. nab-Sirolimus 100 mg/m2 will be administered weekly as an intravenous infusion over 30 minutes on Days 1 and 8 of each 21-day cycle. The primary endpoint is overall response rate determined by independent review using RECIST v1.1; other endpoints include duration of response, disease control rate, time to response progression-free survival by independent radiographic review, overall survival, patient-reported quality of life, and safety. Enrollment is ongoing. The most frequent tumor types expected in this tissue-agnostic trial are bladder, hepatobiliary, endometrial, soft tissue sarcoma, ovarian, and esophagogastric based on the prevalence of TSC1 or TSC2 alterations (Table). Clinical trial information: NCT05103358 . [Table: see text]

Phase II/III study of circulating tumor DNA as a predictive biomarker in adjuvant chemotherapy in patients with stage II colon cancer: NRG-GI005 (COBRA)

TPS259

Background: Detection of circulating tumor DNA (ctDNA) shed into the bloodstream represents a highly specific and sensitive approach for identifying microscopic or residual tumor cells after surgical resection. For patients (pts) with colon cancer (CC), the detection of ctDNA is associated with persistent disease after resection and outperforms traditional clinical and pathological features in prognosticating risk for recurrence. However, for pts with stage II CC, there are currently no validated biomarkers predicting benefit in identifying pts whose residual disease cancer be cleared by adjuvant chemotherapy. We hypothesize that for pts whose stage II colon cancer has been resected and who have no traditional high-risk features, a positive ctDNA status may identify those who will benefit from adjuvant chemotherapy. Methods: In this prospective phase II/III clinical trial, pts (N=1,408) with resected stage II CC without traditional high-risk features and whom the evaluating oncologist deems suitable for active surveillance (i.e., not needing adjuvant chemotherapy) will be randomized 1:1 into 2 arms: standard-of-care/observation (Arm A), or prospective testing for ctDNA (Arm B). Postoperative blood will be analyzed for ctDNA with the Guardant Reveal assay, covering CC-relevant mutations and CC-specific methylation profiling. Pts in Arm B with ctDNA detected will be treated with 6 months of adjuvant (FOLFOX) chemotherapy. For all pts in Arm A, ctDNA status will be analyzed retrospectively at the time of endpoint analysis. The primary endpoints are clearance of ctDNA with adjuvant chemotherapy (phase II) and recurrence-free survival (RFS) for “ctDNA-detected” pts treated with or without adjuvant chemotherapy (phase III). Secondary endpoints will include time-to-event outcomes (OS, RFS, TTR) by ctDNA marker status and treatment, prevalence of detectable ctDNA in stage II CC, and rates of compliance with assigned intervention. Archived normal and matched tumor and blood samples will be collected for exploratory correlative research. Enrollment continues across North America to the 540-patient phase II endpoint. Support: U10CA180868, -180822; UG1CA189867; GuardantHealth. Clinical trial information: NCT04068103 .

Phase 2, multicenter, open-label basket trial of nab-sirolimus for patients with malignant solid tumors harboring pathogenic inactivating alterations in TSC1 or TSC2 genes (PRECISION I)

TPS818

Background: Albumin-bound ( nab)-sirolimus, a novel mTOR inhibitor (mTORi) that utilizes nanoparticle technology to preferentially target tumors, is approved in the US for the treatment of adults with malignant PEComa. In an exploratory analysis of the AMPECT registrational trial of nab-sirolimus in advanced malignant PEComa (NCT02494570), 8/9 (89%) and 1/5 (20%) patients with TSC1 and TSC2 inactivating alterations, respectively, had confirmed response (Wagner, J Clin Oncol. 2021). Importantly, both TSC1 and TSC2 alterations have been observed in patients with various gastrointestinal cancers (Table). Overall, most treatment-related adverse events (TRAEs) in AMPECT were grade 1/2 and manageable for long-term treatment; no grade ≥4 TRAEs occurred. Methods: PRECISION I (NCT05103358) is a phase 2, open-label, multi-institutional basket trial evaluating efficacy and safety of nab-sirolimus in patients with alterations in TSC1 (Arm A) and TSC2 (Arm B). Patients ≥12 years old with malignant solid tumors harboring pathogenic inactivating alterations in TSC1 or TSC2 (confirmed by central review of next generation sequencing reports) who have progressed on standard therapies and are mTORi-naïve are eligible. nab-Sirolimus 100 mg/m2 will be administered weekly as an intravenous infusion over 30 minutes on Days 1 and 8 of each 21-day cycle. The primary endpoint is overall response rate determined by independent review using RECIST v1.1; other endpoints include duration of response, disease control rate, time to response, progression-free survival by independent radiographic review, overall survival, patient-reported quality of life, and safety. Enrollment is ongoing. The most frequent tumor types expected in this tissue-agnostic trial are bladder, hepatobiliary, endometrial, soft tissue sarcoma, ovarian, and esophagogastric based on the prevalence of TSC1 or TSC2 alterations (Table). Clinical trial information: NCT05103358 . [Table: see text]

Phase Ib of pembrolizumab (pem) in combination with stereotactic body radiotherapy (SBRT) for resectable liver oligometastatic MMR-proficient (pMMR) colorectal cancer (CRC): Final results

161

Background: SBRT is a standard treatment option for oligometastatic CRC and is associated with an increase in immunogenic antigen release and influx of immune cells. We hypothesized that radiation would enhance the immunogenicity of pMMR CRC and potentiate the effectiveness of PD-1 blockade. This phase Ib study examined the safety and efficacy of the sequential combination of SBRT and Pem in patients (pts) undergoing resection of their disease. Additionally, the accumulation and proteolysis of versican (VCAN), an immunoregulatory tumor matrix proteoglycan was examined as a novel immunotherapy biomarker. Proteolysis of VCAN results in the release of an immunostimulatory fragment, versikine. Cancers with low VCAN and high versikine (VCAN proteolysis predominant (VPP)) are hypothesized to respond better to immunotherapies. Methods: Eligibility criteria included resectable liver-confined metastatic pMMR CRC. Prior surgery and systemic chemotherapy were allowed. Subjects received sequential SBRT and cycle 1 of Pem prior to operative management and adjuvant Pem. The primary objectives were to determine the safety/tolerability of this regimen and the recurrence free survival (RFS) at 1 year following operative management. Correlative studies examined tumor infiltrating CD8+ T lymphocytes (TILs), VCAN, and versikine using immunohistochemistry. Results: 15 pts (median age 61.5 [range 39-69], 26% female) were enrolled. All pts had prior FOLFOX. The number of liver lesions ranged from 1-6. SBRT median dose was 50 Gy (40-60 Gy) to 1-2 liver lesions. Grade 3/4 AEs included one case of biliary tract injury and biloma, and one case of G3 hypophosphatemia. No grade 3/4 immune-related AEs occurred. All pts completed a minimum follow-up of 1 year post resection (median follow-up 41 months [range 15-64]). In the intention to treat analysis, the 1 year RFS was 67% (historic control 50%), 40% of patients remained cancer free, and 67% of pts are still alive. 2 of 3 pts with BRAF V600E mutations have had early recurrences. 2 pts had VCAN high tumors and both recurred prior to 1 year. 6 pts had VPP cancers and 83% were recurrence free at 1 year and 66% are currently without evidence of cancer. Conclusions: The combination of SBRT with Pem was well tolerated with no signal of increased immunotherapy-related toxicity. This study met its primary endpoint and this regimen deserves further investigation in confirmatory studies. Additionally, VCAN accumulation and proteolysis are promising biomarkers in this setting. Clinical trial information: NCT02837263 .

NRG GI008: Colon adjuvant chemotherapy based on evaluation of residual disease (CIRCULATE-US)

TPS260

Background: Currently, there are no biomarkers validated prospectively in randomized studies for resected colon cancer (CC) to determine need for adjuvant chemotherapy (AC). However, circulating tumor DNA (ctDNA) represents a highly specific and sensitive approach (especially with serial monitoring) for identifying minimal/molecular residual disease (MRD) post-surgery in CC patients (pts), and may outperform traditional clinical and pathological features in prognosticating risk for recurrence. CC pts who do not have detectable ctDNA (ctDNA-) are at a much lower risk of recurrence and may be spared the toxicities associated with AC. Furthermore, for CC pts with detectable ctDNA (ctDNA+) who are at a very high risk of recurrence, the optimal AC regimen has not been established. We hypothesize that for pts whose CC has been resected, ctDNA status may be used to risk-stratify for making decisions about AC. Methods: In this prospective phase II/III trial, up to 1,912 pts with resected stage III A, B (all pts) and stage II, IIIC (ctDNA+ only) CC will be enrolled. Based on the post-operative ctDNA status using personalized and tumor-informed assay (Signatera™, bespoke assay), those who are ctDNA- (Cohort A) will be randomized to immediate AC with fluoropyrimidine (FP) + oxaliplatin (Ox) for 3-6 mos per established guidelines vs . serial ctDNA monitoring. Patients who are ctDNA+ post-operatively or with serial monitoring (Cohort B) will be randomized to FP+Ox vs . more intensive AC with addition of irinotecan (I) for 6 mos. The primary endpoints for Cohort A are time to ctDNA+ status (phase II) and disease-free survival (DFS) (phase III) in the immediate vs . delayed AC arms. The primary endpoint for Cohort B is DFS in the FP+Ox vs FP+Ox+I arms for both phase II and phase III portions of the trial. Secondary endpoints include prevalence of detectable ctDNA post-operatively, time-to-event outcomes (overall survival and time to recurrence) by ctDNA status, and the assessment of compliance to adjuvant therapy. Biospecimens including archival tumor tissue, as well as post-operative plus serial matched/normal blood samples, will be collected for exploratory correlative research. Active enrollment across the NCTN started in June, 2022. Support: U10-CA-180868, -180822; UG1CA-189867; Natera, Inc. Clinical trial information: NCT05174169 .

Treatment of Metastatic Colorectal Cancer: ASCO Guideline

PURPOSE

To develop recommendations for treatment of patients with metastatic colorectal cancer (mCRC).

METHODS

ASCO convened an Expert Panel to conduct a systematic review of relevant studies and develop recommendations for clinical practice.

RESULTS

Five systematic reviews and 10 randomized controlled trials met the systematic review inclusion criteria.

RECOMMENDATIONS

Doublet chemotherapy should be offered, or triplet therapy may be offered to patients with previously untreated, initially unresectable mCRC, on the basis of included studies of chemotherapy in combination with anti-vascular endothelial growth factor antibodies. In the first-line setting, pembrolizumab is recommended for patients with mCRC and microsatellite instability-high or deficient mismatch repair tumors; chemotherapy and anti-epidermal growth factor receptor therapy is recommended for microsatellite stable or proficient mismatch repair left-sided treatment-naive RAS wild-type mCRC; chemotherapy and anti-vascular endothelial growth factor therapy is recommended for microsatellite stable or proficient mismatch repair RAS wild-type right-sided mCRC. Encorafenib plus cetuximab is recommended for patients with previously treated BRAF V600E-mutant mCRC that has progressed after at least one previous line of therapy. Cytoreductive surgery plus systemic chemotherapy may be recommended for selected patients with colorectal peritoneal metastases; however, the addition of hyperthermic intraperitoneal chemotherapy is not recommended. Stereotactic body radiation therapy may be recommended following systemic therapy for patients with oligometastases of the liver who are not considered candidates for resection. Selective internal radiation therapy is not routinely recommended for patients with unilobar or bilobar metastases of the liver. Perioperative chemotherapy or surgery alone should be offered to patients with mCRC who are candidates for potentially curative resection of liver metastases. Multidisciplinary team management and shared decision making are recommended. Qualifying statements with further details related to implementation of guideline recommendations are also included.Additional information is available at www.asco.org/gastrointestinal-cancer-guidelines.

Stromal remodeling regulates dendritic cell abundance and activity in the tumor microenvironment

Stimulatory type 1 conventional dendritic cells (cDC1s) engage in productive interactions with CD8⁺ effectors along tumor-stroma boundaries. The paradoxical accumulation of “poised” cDC1s within stromal sheets is unlikely to simply reflect passive exclusion from tumor cores. Drawing parallels with embryonic morphogenesis, we hypothesized that invasive margin stromal remodeling generates developmentally conserved cell fate cues that regulate cDC1 behavior. We find that, in human T cell-inflamed tumors, CD8⁺ T cells penetrate tumor nests, whereas cDC1s are confined within adjacent stroma that recurrently displays site-specific proteolysis of the matrix proteoglycan versican (VCAN), an essential organ-sculpting modification in development. VCAN is necessary, and its proteolytic fragment (matrikine) versikine is sufficient for cDC1 accumulation. Versikine does not influence tumor-seeding pre-DC differentiation; rather, it orchestrates a distinctive cDC1 activation program conferring exquisite sensitivity to DNA sensing, supported by atypical innate lymphoid cells. Thus, peritumoral stroma mimicking embryonic provisional matrix remodeling regulates cDC1 abundance and activity to elicit T cell-inflamed tumor microenvironments.

T cell-inflamed tumor microenvironments are a prerequisite for immunotherapy efficacy; however, why some tumors are inflamed and others not remains poorly understood. Papadas et al. link stromal reaction dynamics with T cell-induced inflammation. Peritumoral stroma emulating embryonic provisional matrix remodeling regulates cDC1-NK-CD8⁺ crosstalk to promote T cell repriming and penetration into tumor nests.

A randomized phase 2 trial of nivolumab, gemcitabine, and cisplatin or nivolumab and ipilimumab in previously untreated advanced biliary cancer: BilT-01

Background

Gemcitabine and cisplatin has limited benefit as treatment for advanced biliary tract cancer (BTC). The addition of an anti‐programmed death receptor (PD‐1)/PD‐ligand (L1) antibody to either systemic chemotherapy or anti‐cytotoxic T‐lymphocyte‐associated protein 4 (CTLA4) antibody has shown benefit in multiple solid tumors.

Methods

In this phase 2 trial, patients 18 years or older with advanced BTC without prior systemic therapy and Eastern Cooperative Oncology Group Performance Status 0–1 were randomized across six academic centers. Patients in Arm A received nivolumab (360 mg) on day 1 along with gemcitabine and cisplatin on days 1 and 8 every 3 weeks for 6 months followed by nivolumab (240 mg) every 2 weeks. Patients in Arm B received nivolumab (240 mg) every 2 weeks and ipilimumab (1 mg/kg) every 6 weeks.

Results

Of 75 randomized patients, 68 received therapy (Arm A = 35, Arm B = 33); 51.5% women with a median age of 62.5 years. The observed primary outcome of 6‐month progression‐free survival (PFS) rates in the evaluable population was 59.4% in Arm A and 21.2% in Arm B. The median PFS and overall survival (OS) in Arm A were 6.6 and 10.6 months, and in Arm B 3.9 and 8.2 months, respectively, in patients who received any treatment. The most common treatment‐related grade 3 or higher hematologic adverse event was neutropenia in 34.3% (Arm A) and nonhematologic adverse events were fatigue (8.6% Arm A) and elevated transaminases (9.1% Arm B).

Conclusions

The addition of nivolumab to chemotherapy or ipilimumab did not improve 6‐month PFS. Although median OS was less than 12 months in both arms, the high OS rate at 2 years in Arm A suggests benefit in a small cohort of patients.

Immune checkpoint inhibition alone or in combination with chemotherapy as first‐line therapy does not appear to improve efficacy when compared to chemotherapy alone for patients with advanced biliary cancer in the United States. However, at least one third of the patients were alive at 2 years in the chemoimmunotherapy arm, and additional studies are ongoing to investigate this result, and importantly, evaluate biomarkers predictive for benefit from this treatment regimen.

Abstract 1128: MTORC1/2 and HDAC1/2 inhibition promote tumor response through inhibition of MYC

Background: The identification of treatment strategies targeting PIK3CA mutant colorectal cancer (CRC) are of great clinical interest. Previous work from our lab has identified MTORC1/2 and HDAC1/2 inhibition with copanlisib (cop; PI3K/MTOR) and romidepsin (romi; HDAC1/2) as a potential therapeutic strategy. We hypothesized that changes in c-MYC protein levels and c-MYC target gene (CTG) alterations might be a potential mechanism of action for this combination.

Methods: Known CTGs were identified and their expression levels were examined in PIK3CA mutant vs WT CRCs using the cBioPortal Colorectal Adenocarcinoma (TCGA, PanCancer Atlas) dataset. Murine derived cancer organoids (MDCO) were generated from adenocarcinomas of Apc and Pik3ca mutant transgenic mice (F1 (FVB x B6) Apcfl/+ Pik3caH1047R/+). MDCO results were corroborated using the human 2D isogenic cell lines SW48 and SW48PIK3CA-H1047R (SW48PK) and RAS/RAF WT patient derived cancer organoids (PDCO) generated from CRC patient samples under approved IRB protocols. Immunoblots (IB) were used to assess c-MYC levels after treatment with cop, romi, and the combination across all models. RNA sequencing was conducted on PDCOs and SW48PK cells and changes in 16 CTGs were examined. An aggregate score was created for each treatment group where a statistically significantly altered CTG with log fold change ≥1.5 added one point and ≤-1.5 subtracted one point. All others were scored 0.

Results: c-MYC target genes were assessed for differential expression in PIK3CA mutant CRC vs PIK3CA WT CRC with only 1/16 genes decreased in PIK3CA mutant CRC (GADD45A: log ratio -0.21, q=0.01). Next, MDCOs treated with the combination showed a decrease in total c-MYC levels in the combination therapy. These results were corroborated in two human 2D CRC cell lines, SW48 and SW48PK and a panel of PDCOs. Interestingly, c-MYC levels decreased in both romi alone and the combination in both the SW48 and SW48PK cell lines after 24 hours of treatment. However, the extent to which c-MYC levels were decreased was not as substantial in the panel of PDCOs. Across all in vitro models a decrease in PI3K signaling, as illustrated by decreased pRPS6 and p4EBP1 in response to cop treatment and an increase in H3K27 acetylation in response to romi, was observed in the single agent and combination therapies. RNA sequencing demonstrated that cop, romi, and combo had a CTG score of 0, -4, and -7 respectively in the PIK3CA mutant PDCO. Similar results were seen in an additional RAS/RAF WT PDCO (0, 1, and -4, respectively) and SW48PK cells (0, -3, and -7, respectively).

Conclusion: A potential mechanism by which cop and romi treatment promote tumor response is through a decrease in c-MYC protein levels and expression of downstream c-MYC target genes. This regimen deserves further mechanistic investigations in vivo.

Citation Format: Rebecca A. DeStefanis, Autumn M. Olson, Alyssa K. DeZeeuw, Susan N. Payne, Cheri A. Pasch, Linda Clipson, Dustin A. Deming. MTORC1/2 and HDAC1/2 inhibition promote tumor response through inhibition of MYC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1128.

Abstract 2673: Combined inhibition of PI3K and HDAC1/2 as a novel treatment strategy for RAS/RAF wildtype colorectal cancer in a patient derived organoid model

Background: Treating colorectal cancer (CRC) using targeted therapies based on each patient’s individual mutational profile continues to gain interest. Oncogenic mutations of the PIK3CA gene leads to tumor initiation and progression. Copanlisib inhibits the PI3K pathway and has proven to be an effective treatment strategy for various cancers characterized by overactivation of the PI3K signaling cascade. However, resistance mechanisms to targeted therapies such as copanlisib are frequently encountered, and can be overcome through combination with another molecule such as romidepsin, a histone deacetylase (HDAC) inhibitor. Here we aim to identify a novel therapeutic regimen for improved treatment of the molecular subtypes of CRC that can be targeted with PI3K inhibition.

Methods: Organoids were derived from colorectal cancer tumor tissue from two different biopsy sites from one patient with PIK3CA mutant rectal cancer (RC46A and RC46B), as well as from a patient with APC and TP53 mutant CRC (MTB74) under approved IRB protocols. All organoids were plated and allowed to mature for 24 to 48 hours before treatment and baseline images were obtained. The organoids were imaged again 48 hours later, and response was determined by measuring the change in organoid diameter using ImageJ. Additionally, organoids were collected for immunoblotting to examine alterations in the PI3K pathway as well as histone acetylation, and proteins involved in apoptosis.

Results: Control organoids demonstrated increased median relative changes in diameter of +53.38%, +43.04% and +46.2% for RC46A, RC46B and MTB74, respectively. In comparison, the combination treatment group exhibited median relative changes for RC46A, RC46B and MTB74 as -29.19%, -46.46% and -100% (p<0.001). These results were supported with immunoblot analysis that revealed a synergistic increase in histone acetylation with the combination treatment. Single agent copanlisib treatment elicited alterations in PI3K signaling including downregulation of pS6, pAKT, p4EBP1 as expected. Lastly, an increase in cleaved PARP was observed in combination treated organoids which is indicative of increased apoptosis.

Conclusions: As molecular diagnostic technology continues to advance, treating each individual cancer with a targeted therapy based on molecular profiling is becoming more feasible. Dual inhibition of the PI3K pathway and HDAC is effective in reducing cell growth and proliferation of CRC organoids characterized by PIK3CA mutations, as well as other molecular subtypes such as cancers with APC and TP53 mutations. This combination strategy shows promise for improving treatment response and reducing resistance in patients across these molecular subtypes.

Citation Format: Alyssa K. DeZeeuw, Rebecca A. DeStefanis, Susan N. Payne, Autumn M. Olson, Cheri A. Pasch, Linda Clipson, Dustin A. Deming. Combined inhibition of PI3K and HDAC1/2 as a novel treatment strategy for RAS/RAF wildtype colorectal cancer in a patient derived organoid model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2673.

Abstract 3533: Effects of tyrosine kinase inhibitors imatinib, dasatinib, and nilotinib on cancer-associated fibroblast phenotypes in colorectal cancer

Background: Cancer-associated fibroblasts (CAFs) are major regulators of the immune microenvironment and therapeutic response in colorectal cancer (CRC). Neutralizing their role in modulating the immune landscape could be the key to enhancing immunotherapy success. Imatinib, dasatinib, and nilotinib are tyrosine kinase inhibitors with several kinase targets.

Methods: Tissue microarrays spanning 153 patients were stained for αSMA, TAGLN, PDPN, ICAM1, and CD8. CD8 stains were quantified as number of tumor infiltrating lymphocytes per high powered field (TILs/HPF) in the epithelial compartment. All other stains were quantified by intensity on a 0-3+ scale. Scores for αSMA and TAGLN were combined into a myCAF score, and PDPN and ICAM1 into an iCAF score. myCAF gene expression signatures derived from a re-analysis of scRNA-seq data previously done by our lab were entered into the LINCS database to discover potential drugs to reverse the phenotype. Primary cancer associated fibroblasts were derived from patient tumor samples, then treated with clinically relevant concentrations of imatinib, dasatinib, or nilotinib for 96 hours. RNA was isolated and RT-qPCR was performed to quantify the myCAF genes ACTA2, COL11A1, and TAGLN, and the iCAF genes ICAM1, PDPN, IL1R1, CXCL1 and CXCL2. TGFB1 expression was also measured. Expression was normalized to untreated cells and GAPDH expression levels.

Results: Cancers with high expression of myCAF markers but low expression of iCAF markers had the most CD8+ TILs (average 10.2; median 1.5; range 0-73), while cancers with low myCAF scores and high iCAF scores had the least (average 1.5; median 0; range 0-19; p < 0.01). Reversing the myCAF signature relative to iCAFs in the LINCs database revealed nilotinib as a top hit. Treatment with imatinib did not significantly alter the expression of myCAF genes (control vs. max dose: p = 0.06 for ACTA2, COL11A1 p =0.2, TAGLN p = 1), while treatment with dasatinib significantly increased these genes (ACTA2 1.4x higher, p < 0.001; COL11A1 2.6x higher, p < 0.01; TAGLN 1.5x higher, p < 0.001). Only treatment with nilotinib significantly decreased myCAF genes (ACTA2 2.2x lower, p <0.001; COL11A1 1.3x lower, p =0.05; TAGLN 1.9x lower, p < 0.01). All three drugs decreased iCAF gene CXCL1, and all but dasatinib decreased CXCL2. All three drugs significantly decreased TGFB1, a potential functional marker for altering myCAF phenotype (dasatinib 1.1x lower, p = 0.1; imatinib 1.6x lower, p < 0.001; nilotinib 1.5x lower, p < 0.05).

Conclusions: myCAFs may be major actors in immune exclusion in the microenvironment, and the reversal of the myCAF phenotype may be a target for treatment with immunotherapy. Nilotinib, but not imatinib or dasatinib, is effective at decreasing expression of myCAF genes. Further research is warranted into the mechanisms of this drug on altering expression and whether these trends continue in vivo.

Citation Format: Katherine Anne Johnson, Anna L. Lippert, Sean G. Kraus, Grace E. McGrath, Philip B. Emmerich, Cheri A. Pasch, Linda Clipson, Kristina A. Matkowskyj, Wei Zhang, Dustin A. Deming. Effects of tyrosine kinase inhibitors imatinib, dasatinib, and nilotinib on cancer-associated fibroblast phenotypes in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3533.

Abstract 3198: Validation and analysis of cancer associated fibroblast subtype markers in metastatic colorectal cancer

Background: Cancer Associated Fibroblasts (CAFs) are a significant component of tumor stroma, and have an important impact on immune infiltration in the tumor microenvironment (TME). Two major subtypes of CAFs have been previously identified by literature: myofibroblastic (myCAF) and inflammatory (iCAF). Our lab has identified subtype markers for each CAF phenotype and previously analyzed a sampling of 153 colorectal cancer (CRC) patients. Here, we validate these subtype markers and investigate CAF phenotypes in metastatic colorectal cancer patients.

Methods: Dual immunofluorescence on formalin fixed paraffin embedded tissue sections was performed to analyze co-staining between combinations of myCAF markers, αSMA and TAGLN, and iCAF markers, PDPN and ICAM1. Slides were imaged using a fluorescent microscope. Also, tissue microarrays sampling 212 CRC patients spanning all stages of disease, 90 with matched metastatic cores, were stained via immunohistochemistry (IHC) for the CAF subtype markers then quantified on an intensity scale from 0-3+. iCAF and myCAF marker scores were averaged to get a composite score for each, then split into low (average score <2) and high (average score ≥2) groups. CD8 IHC stains were quantified as the number of tumor infiltrating lymphocytes (TILs) per high power field (HPF) in the epithelial compartment.

Results: Significant co-staining was observed between iCAF markers PDPN and ICAM1, as well as myCAF markers αSMA and TAGLN. Co-staining did not occur, or was minimal, between combinations of myCAF and iCAF markers. There is not significant different in abundance of iCAFs or myCAFs in primary site cores of patients with metastatic versus non-metastatic disease (p = 0.67 for iCAF, p = 0.57 for myCAF). Of matched primary and metastatic samples able to be scored, 43.3% of samples had a decrease in iCAF score from primary to metastatic site while only 18.8% increased. Overall, 34.4% of samples had a decrease in score of more than 1 and only 2.2% of samples had an increase of more than 1. However, the percentage of samples that had a decrease in myCAF score was 32.2% while 22.2% increased. In all primary cores of patients with metastatic disease, there was higher average CD8+ TILs in those with high iCAF scores compared to those with low iCAF scores (12.0 vs 5.5, p=0.03). There was not a significant difference in average CD8+ TILs in those with high myCAF scores compared to those with low myCAF scores (9.3 vs 7.1, p=0.7).

Conclusions: Here, we validate the myCAF markers TAGLN and αSMA, as well as, iCAF markers ICAM1 and PDPN by demonstrating co-staining between CAFs of the same subtype and exclusion between different subtypes. These data indicate that that CAF phenotype correlates with CD8 T cell infiltration into the TME. iCAFs correlate with immune infiltration and myCAFs with immune exclusion.

Citation Format: Anna L. Lippert, Katherine A. Johnson, Cheri A. Pasch, Sean G. Kraus, Philip B. Emmerich, Linda Clipson, Kristina A. Matkowskyj, Wei Zhang, Dustin A. Deming. Validation and analysis of cancer associated fibroblast subtype markers in metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3198.

Abstract 3842: Versican proteolysis is a predictive biomarker of tumor infiltrating lymphocytes within primary and metastatic colorectal cancer tumors

Background: A major roadblock to immune-therapy response in many solid malignancies is the lack of tumor-infiltrating lymphocytes (TILs) found within their immune micro-environments. These immunologically cold tumors have lower response rates to immune-based therapies and among all colorectal cancers (CRC), only about six percent of patients have an objective response to immune checkpoint blockade (ICB). Versican (VCAN) accumulation has been found to be negatively correlated with TILs and its proteolysis into versikine (Vkine) correlates with higher TILs. In this study we analyze the association between VCAN accumulation/proteolysis and TILs in CRC from patients with both resectable primary CRCs and matched liver metastases.

Methods: VCAN, Vkine, and TIL abundance were assessed via immunohistochemistry, with VCAN and Vkine being measured using an intensity binning system ranging from 0-3+ and TILs counted at 40X magnification for each tumor. Tumors were then designated as high (2 or 3+) or low (0 or 1) for both VCAN and Vkine. Tumors that were designated VCAN low and Vkine high are considered VCAN proteolytic predominant (VPP) and all other combinations are considered VCAN proteolytic weak (VPW).

Results: 53% of both primary and metastatic tumors were designated VCAN low and 47% VCAN high. 59% of metastases from patients with VCAN-high primary tumors were also designated VCAN high, whereas 43% of metastases from patients with VCAN low primary tumors were designated VCAN high. When assessing proteolysis, it was found that 37% of primary tumors were designated VPP but only 26% of metastases were found to be VPP. When comparing proteolysis in a pairwise fashion, it was found that only 37% of VPP primaries had a VPP metastasis. An inverse correlation was again found between VCAN accumulation and TILs within primary CRCs. Tumors containing high levels of VCAN had an average of three TILs/high powered field (HPF), whereas tumors with low levels of VCAN had an average of 16 TILs/HPF (p=0.007). VPW tumors had an average of three TILs/HPF and VPP cores had an average of 21 TILs/HPF (p=0.009). VPW metastatic tumors had an average of eight TILs/HPF, whereas those that were VPP had an average of 15 TILs/HPF (p=0.01).

Conclusion: Overall, these data confirm the inverse correlations between VCAN accumulation and TILs in primary CRCs. Additionally, VCAN proteolysis correlates with TILs in primary tumors and metastases. The potential for different VCAN accumulation/proteolysis in the primary tumor and metastatic disease will be an important consideration when studying VCAN further as a potential biomarker of immunotherapy response.

Citation Format: Sean G. Kraus, Kristina A. Matkowskyj, Philip B. Emmerich, Wei Zhang, Linda Clipson, Cheri A. Pasch, Dustin A. Deming. Versican proteolysis is a predictive biomarker of tumor infiltrating lymphocytes within primary and metastatic colorectal cancer tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3842.

Abstract 3721: MTORC1/2 and HDAC1/2 inhibition as therapy for colorectal cancer with PIK3CA mutation

Introduction: Colorectal cancer (CRC) is a leading cause of cancer-related deaths. PIK3CA mutations are found in 18% of CRCs which lead to the constitutive activation of the PI3K/MTOR pathway and can promote tumorigenesis. Here, we examine the efficacy of the FDA approved inhibitors copanlisib, a PI3K/MTOR inhibitor, and romidepsin, a HDAC1/2 inhibitor, in CRC with a PIK3CA mutation.

Methods: CRC mouse derived cancer organoids (MDCOs) were derived from Apc and Pik3ca mutant mice (Fc1Apcfl/+Pik3caH1047R/+). Brightfield images of the MDCOs were taken prior to treatment with copanlisib, romidepsin, or the combination and 48 hours post-treatment. The change in diameter of each organoid over the 48-hour treatment was determined. Additionally, immunoblotting was performed to confirm known targets of copanlisib and romidepsin were altered in response to drug treatment. MTORC1/2 and HDAC1/2 inhibition were also investigated in vivo. SW48 and SW48PIK3CA-H1047R (SW48PK) xenograft mice were treated with a vehicle control, copanlisib, romidepsin, or the combination therapy.

Results: In the diameter analysis study, the combination therapy had the largest effect size compared to control (Glass’s Δ 2.82). Single agents copanlisib and romidepsin had smaller effect sizes (Glass’s Δ 1.75 and 2.04, respectively). Immunoblotting results indicated a decrease in phosphoAKT (Ser473) and pRPS6 (Ser235/236) in the copanlisib treated samples and an increase in H3K27 acetylation was seen in the romidepsin treated samples. There was also increased cleaved PARP, an indicator of apoptosis, in the romidepsin and combination therapy treatment groups. In vivo, SW48 xenografts showed a greater response in the combination therapy compared to either single agent therapy (median relative change in tumor volume: control=339%; combination therapy=107%(p-value<0.05), copanlisib=225%(p-value=0.17), romidepsin=200%). A similar trend was seen in the SW48PK xenograft mice (median relative change in tumor volume: control=241%; combination therapy=70% (p-value<0.05), copanlisib=132%(p-value<0.05), romidepsin=177%).

Conclusion: MDCOs with Apc and Pik3ca mutations had an increased response to treatment with the combination therapy as compared to the single agents alone. Additionally, in vivo studies with human CRC xenografts showed enhanced inhibition of tumor growth with both MTORC1/2 and HDAC1/2 inhibition. These data demonstrate potential for this combination treatment strategy for the treatment of PIK3CA mutant CRC and this combination warrants further investigation in other models and clinically.

Citation Format: Autumn M. Olson, Rebecca A. DeStefanis, Alyssa K. DeZeeuw, Susan N. Payne, Cheri A. Pasch, Linda Clipson, Dustin A. Deming. MTORC1/2 and HDAC1/2 inhibition as therapy for colorectal cancer with PIK3CA mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3721.

Technologies to Assess Drug Response and Heterogeneity in Patient-Derived Cancer Organoids

Patient-derived cancer organoids (PDCOs) are organotypic 3D cultures grown from patient tumor samples. PDCOs provide an exciting opportunity to study drug response and heterogeneity within and between patients. This research can guide new drug development and inform clinical treatment planning. We review technologies to assess PDCO drug response and heterogeneity, discuss best practices for clinically relevant drug screens, and assert the importance of quantifying single-cell and organoid heterogeneity to characterize response. Autofluorescence imaging of PDCO growth and metabolic activity is highlighted as a compelling method to monitor single-cell and single-organoid response robustly and reproducibly. We also speculate on the future of PDCOs in clinical practice and drug discovery.Future development will require standardization of assessment methods for both morphology and function in PDCOs, increased throughput for new drug development, prospective validation with patient outcomes, and robust classification algorithms.

Colon adjuvant chemotherapy based on evaluation of residual disease (CIRCULATE-US): NRG-GI008

TPS3643

Background: Currently, there are no biomarkers validated prospectively in randomized studies for resected colon cancer (CC) to determine need for adjuvant chemotherapy (AC). However, circulating tumor DNA (ctDNA) represents a highly specific and sensitive approach (especially with serial monitoring) for identifying minimal/molecular residual disease (MRD) post-surgery in CC patients (pts), and may outperform traditional clinical and pathological features in prognosticating risk for recurrence. CC pts who do not have detectable ctDNA (ctDNA-) are at a much lower risk of recurrence and may be spared the toxicities associated with AC. Furthermore, for CC pts with detectable ctDNA (ctDNA+) who are at a very high risk of recurrence, the optimal AC regimen has not been established. We hypothesize that for pts whose CC has been resected, ctDNA status may be used to risk stratify for making decisions about AC. Methods: In this prospective phase II/III trial, up to 1,912 pts with resected stage III A, B (all pts) and stage II, IIIC (ctDNA+ only) CC will be enrolled. Based on the post-operative ctDNA status using personalized and tumor informed assay (SignateraTM, bespoke assay), those who are ctDNA- (Cohort A) will be randomized to immediate AC with fluoropyrimidine (FP) + oxaliplatin (Ox) for 3-6 mos per established guidelines vs . serial ctDNA monitoring. Patients who are ctDNA+ post-operatively or with serial monitoring (Cohort B) will be randomized to FP+Ox vs . more intensive AC with addition of irinotecan (I) for 6 mos. The primary endpoints for Cohort A are time to ctDNA+ status (phase II) and disease-free survival (DFS) in phase III in the immediate vs . delayed AC arms. The primary endpoint for Cohort B is DFS in the FP+Ox vs FP+Ox+I arms for both phase II and phase III portions of the trial. Secondary endpoints include prevalence of detectable ctDNA post-operatively, time-to-event outcomes (overall survival and time to recurrence) by ctDNA status, and the assessment of compliance to adjuvant therapy. Biospecimens including archival tumor tissue, post-operative and serial matched/normal blood samples will be collected for exploratory correlative research. Active enrollment across the NCTN started in early 2022. Support: U10-CA-180868, -180822; UG1CA-189867; Clinical trial information: NCT05174169.

Phase I/II trial of perioperative avelumab in combination with chemoradiation (CRT) in the treatment of stage II/III resectable esophageal and gastroesophageal junction (E/GEJ) cancer

4034

Background: Neoadjuvant CRT followed by surgery is the standard of care for patients (pts) with stage II/III E/GEJ cancer, yet recurrence rates remain high. Immunotherapy has demonstrated activity in advanced E/GEJ cancer and was recently approved for adjuvant treatment of early stage disease. This trial evaluated the safety and efficacy of avelumab with perioperative CRT in resectable E/GEJ cancer. Methods: This is a two part phase I/II trial. Phase I was a safety run-in of 6 pts. Phase II planned to enroll an additional 18 pts in an expansion cohort. Pts with E/GEJ adenocarcinoma or squamous cell cancer received CRT (41.4 Gy in 23 fractions) with weekly carboplatin and paclitaxel. Three doses of avelumab (10 mg/kg IV, q14 days) were administered starting on day 29 of treatment, to coincide with the last chemotherapy dose. Surgery was performed 8-10 weeks after CRT completion. Pts received 6 doses of avelumab after resection (10 mg/kg IV, q14 days). The primary endpoint of the Phase 1 was safety and tolerability. The primary endpoint of the Phase II was pathologic complete response (pathCR) rate, assessing patients from the safety run in and expansion cohorts. Results: Between 6/2018 and 10/2021, 22 pts (20 males, median age 64) enrolled in the study. Enrollment was stopped after 16 patients in the expansion cohort due to accrual delays and changes in standard treatment. 19/22 patients (86%) had adenocarcinoma; 15/22 (68%) had lymph node positive disease at diagnosis. 19 pts underwent successful resection while on study. 3 pts went off study before resection due to grade 3 avelumab-related infusion reaction (1), patient preference (1), and non-adherence (1). There were no unexpected surgical complications. 4 pts (21%) had R1 resection with 3/4 having positive radial margin and 1/4 positive proximal margin. At resection, 5 pts (26%) had pathCR (3/16 adenocarcinomas, 2/3 squamous cell), 4 ypT1N0 disease, and 14/19 were ypN0. 42% had tumor regression score of 0 or 1. The combination of CRT and avelumab had an acceptable toxicity profile. No grade ≥3 immune-related AEs were observed. Immune-related hypothyroiditis was seen in 2 patients (grade 2). Three patients had grade 2 infusion-related reaction, but were able to continue with treatment. 21/22 pts had reversible grade ≥3 lymphopenia; 13/22 grade ≥ 3 wbc decrease; 6/22 grade 3 neutropenia. As of data cutoff on 2/1/2022, 1 patient remains on study treatment, 15 in follow up, 5 expired, 1 off study. Additional efficacy data is being collected. Correlative studies are ongoing. Conclusions: Perioperative CRT with avelumab is well tolerated with no unexpected toxicities. Neoadjuvant chemoradiation with immunotherapy is a promising approach for patients with E/GEJ tumors. Additional safety, efficacy and correlative analysis from this study will be presented at the meeting. Clinical trial information: NCT03490292.

Predictive value of MAOB gene expression for targeted therapy in patients (pts) with metastatic colorectal cancer (mCRC) enrolled in CALGB (Alliance)/SWOG 80405

3580

Background: Monoamine oxidases (MAOs), including MAOA and MAOB, are mitochondrial enzymes responsible for catalyzing monoamine oxidation. Increased expression of MAOs were found in several cancer types and high MAOB was associated with worse disease stage and poorer survival in CRC. Positive and negative correlations of MAOB expression with mesenchymal type and epithelial type gene expressions, respectively, have been reported. Hence, we investigated whether MAOB expression is predictive for targeted therapies in mCRC. Methods: 430 mCRC pts treated with either bevacizumab (BEV, n = 224) or cetuximab (CET, n = 206) in combination with first-line chemotherapy within the CALGB/SWOG 80405 trial were included in the analysis. MAOB RNA was isolated from FFPE tumor samples and sequenced on the HiSeq 2500 (Illumina). Overall survival (OS) and progression-free survival (PFS) were compared between groups of pts categorized by tertiles of MAOB expression into high (H), medium (M) and low (L). Hazard ratios (HR) and 95% confidence intervals (CI) were computed from multivariable Cox proportional hazards model, adjusting for age, sex, location, number of metastases, KRAS, MSI status, and treatment with FOLFOX or FOLFIRI. Sensitivity analyses were conducted after stratifying by sex. Logrank P-values describe differences without adjustment for patient characteristics. Results: In CET-treated pts, MAOB-L showed significantly longer OS (median 39.2 vs 30.9 vs 15.9 months, logrank P = 4.7E-05, L vs H (as reference) adjusted HR 0.42, 95% CI [0.27, 0.65]) and PFS (median 13.2 vs 11.8 vs 7.6 months, logrank P = 0.006, L vs H adjusted HR 0.59 [0.40, 0.88]) compared to MAOB-M and MAOB-H, respectively. Similar results were observed when evaluating MAOB expression as a continuous variable. In BEV-treated pts, no significant differences were observed when comparing MAOB expression tertiles; however, pts with lower MAOB expression had significantly better OS, but not PFS, when evaluating MAOB as a continuous variable (Cox LRT P = 0.015, covariate adjusted). In CET-treated pts, the effect of MAOB expression was observed in male but not female pts (OS: median 40.3 vs 30.9 vs 16.1 months by MAOB-L, M, H, respectively, logrank P = 6.8E-05, L vs H adjusted HR 0.33 [0.19, 0.59]; PFS: median 13.8 vs 12.6 vs 7.9 months, logrank P = 0.001, L vs H adjusted HR 0.46 [0.28, 0.79]). A significant interaction was observed between MAOB expression and treatment for OS ( P = 0.010) in males and females combined, but only in males ( P = 0.018) when stratified by sex. Conclusions: Our results suggest that pts with MAOB-L tumors may have greater benefit from CET-based treatment and that targeting MAOB may be a promising strategy to improve patient outcomes. Further validation studies are warranted to develop a novel personalized approach based on MAOB expression in mCRC pts. Clinical trial information: NCT00265850.

Phase II Study of Copanlisib in Patients With Tumors With PIK3CA Mutations: Results From the NCI-MATCH ECOG-ACRIN Trial (EAY131) Subprotocol Z1F

PURPOSE

Activating mutations in PIK3CA are observed across multiple tumor types. The NCI-MATCH (EAY131) is a tumor-agnostic platform trial that enrolls patients to targeted therapies on the basis of matching genomic alterations. Arm Z1F evaluated copanlisib, an α and δ isoform-specific phosphoinositide 3-kinase (PI3K) inhibitor, in patients with PIK3CA mutations (with or without PTEN loss).

PATIENTS AND METHODS

Patients received copanlisib (60 mg intravenous) once weekly on days 1, 8, and 15 in 28-day cycles until progression or toxicity. Patients with KRAS mutations, human epidermal growth factor receptor 2-positive breast cancers, and lymphomas were excluded. The primary end point was centrally assessed objective response rate (ORR); secondary end points included progression-free survival, 6-month progression-free survival, and overall survival.

RESULTS

Thirty-five patients were enrolled, and 25 patients were included in the primary efficacy analysis as prespecified in the Protocol. Multiple histologies were enrolled, with gynecologic (n = 6) and gastrointestinal (n = 6) being the most common. Sixty-eight percent of patients had ≥ 3 lines of prior therapy. The ORR was 16% (4 of 25, 90% CI, 6 to 33) with P = .0341 against a null rate of 5%. The most common reason for protocol discontinuation was disease progression (n = 17, 68%). Grade 3/4 toxicities observed were consistent with reported toxicities for PI3K pathway inhibition. Sixteen patients (53%) had grade 3 toxicities, and one patient (3%) had grade 4 toxicity (CTCAE v5.0). Most common toxicities include hyperglycemia (n = 19), fatigue (n = 12), diarrhea (n = 11), hypertension (n = 10), and nausea (n = 10).

CONCLUSION

The study met its primary end point with an ORR of 16% (P = .0341) with copanlisib showing clinical activity in select tumors with PIK3CA mutation in the refractory setting.

Inhibition of B-cell lymphoma 2 family proteins alters optical redox ratio, mitochondrial polarization, and cell energetics independent of cell state

SIGNIFICANCE

The optical redox ratio (ORR) [autofluorescence intensity of the reduced form of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H)/flavin adenine dinucleotide (FAD)] provides a label-free method to quantify cellular metabolism. However, it is unclear whether changes in the ORR with B-cell lymphoma 2 (Bcl-2) family protein inhibition are due to metabolic stress alone or compromised cell viability.

AIM

Determine whether ABT-263 (navitoclax, Bcl-2 family inhibitor) changes the ORR due to changes in mitochondrial function that are independent of changes in cell viability.

APPROACH

SW48 colon cancer cells were used to investigate changes in ORR, mitochondrial membrane potential, oxygen consumption rates, and cell state (cell growth, viability, proliferation, apoptosis, autophagy, and senescence) with ABT-263, TAK-228 [sapanisertib, mammalian target of rapamycin complex 1/2 (mTORC 1/2) inhibitor], and their combination at 24 h.

RESULTS

Changes in the ORR with Bcl-2 inhibition are driven by increases in both NAD(P)H and FAD autofluorescence, corresponding with increased basal metabolic rate and increased mitochondrial polarization. ABT-263 treatment does not change cell viability or induce autophagy but does induce a senescent phenotype. The metabolic changes seen with ABT-263 treatment are mitigated by combination with mTORC1/2 inhibition.

CONCLUSIONS

The ORR is sensitive to increases in mitochondrial polarization, energetic state, and cell senescence, which can change independently from cell viability.

Clinical utility of a regional precision medicine molecular tumor board and challenges to implementation

Purpose

Molecular tumor boards provide precision treatment recommendations based on cancer genomic profile. However, practical barriers limit their benefits. We studied the clinical utility of the precision medicine molecular tumor board (PMMTB) and described challenges with PMMTB implementation.

Methods

An observational cohort study included patients reviewed by the PMMTB between September 2015 to December 2017. Patients who had consented to the registry study were included. The primary endpoint of this study was time on treatment (ToT) ratio. Clinical utility was established if the primary endpoint had least 15% of patients achieving a ToT ratio of ≥1.3.

Results

Overall, 278 patients were presented to the PMMTB and 113 cases were included in the final analysis. The PMMTB identified at least one nonstandard of care (SOC) clinically actionable mutation for 69.0% (78/113) of cases. In patients who received non-SOC treatment, 43.8% (7/16) achieved a ToT ratio of 1.3 or more (p < 0.001). Fifty-nine patients did not receive non-SOC recommendations. Reasons for not pursuing treatment included 35.6% having response to current treatment, 20.3% died prior to starting or considering PMMTB recommendations, 13.6% pursued other treatment options based on clinician discretion, another 10.2% pursued other treatment options because clinical trials recommended were not geographically accessible, 8.5% had rapid decline of performance status, 6.8% lacked of financial support for treatment, and 5.1% were excluded from clinical trials due to abnormal laboratory values.

Conclusion

The regional PMMTB non-SOC recommendations benefitted a majority of patients and additional processes were implemented to assist with non-SOC treatment accessibility.

Impact of baseline culture conditions of cancer organoids when determining therapeutic response and tumor heterogeneity

Representative models are needed to screen new therapies for patients with cancer. Cancer organoids are a leap forward as a culture model that faithfully represents the disease. Mouse-derived cancer organoids (MDCOs) are becoming increasingly popular, however there has yet to be a standardized method to assess therapeutic response and identify subpopulation heterogeneity. There are multiple factors unique to organoid culture that could affect how therapeutic response and MDCO heterogeneity are assessed. Here we describe an analysis of nearly 3500 individual MDCOs where individual organoid morphologic tracking was performed. Change in MDCO diameter was assessed in the presence of control media or targeted therapies. Individual organoid tracking was identified to be more sensitive to treatment response than well-level assessment. The impact of different generations of mice of the same genotype, different regions of the colon, and organoid specific characteristics including baseline size, passage number, plating density, and location within the matrix were examined. Only the starting size of the MDCO altered the subsequent growth. These results were corroborated using ~ 1700 patient-derived cancer organoids (PDCOs) isolated from 19 patients. Here we establish organoid culture parameters for individual organoid morphologic tracking to determine therapeutic response and growth/response heterogeneity for translational studies.

Phase II/III study of circulating tumor DNA as a predictive biomarker in adjuvant chemotherapy in patients with stage II colon cancer: NRG-GI005 (COBRA)

TPS233

Background: There are currently no validated predictive biomarkers for stage II resected colon cancer (CC) after adjuvant chemotherapy. However, circulating tumor DNA (ctDNA) shed into the bloodstream represents a highly specific and sensitive approach for identifying microscopic or residual tumor cells. For patients (pts) with CC, the detection of ctDNA is associated with persistent disease after resection and may outperform traditional clinical and pathological features in prognosticating risk for recurrence. We hypothesize that for pts whose stage II colon cancer has been resected and who have no traditional high-risk features, a positive ctDNA status may identify those who will benefit from adjuvant chemotherapy. Methods: In this prospective phase II/III clinical trial, pts (N = 1,408) with resected stage II CC without traditional high-risk features and whom the evaluating oncologist deems suitable for active surveillance (i.e., not needing adjuvant chemotherapy) will be randomized 1:1 into 2 arms: standard-of-care/observation (Arm A), or prospective testing for ctDNA (Arm B). Postoperative blood will be analyzed for ctDNA with the Guardant Reveal assay, covering CC-relevant mutations and CC-specific methylation profiling. Pts in Arm B with ctDNA detected will be treated with 6 months of adjuvant (FOLFOX) chemotherapy. For all pts in Arm A, ctDNA status will be analyzed retrospectively at the time of endpoint analysis. The primary endpoints are clearance of ctDNA with adjuvant chemotherapy (phase II) and recurrence-free survival (RFS) for “ctDNA-detected” pts treated with or without adjuvant chemotherapy (phase III). Secondary endpoints will include time-to-event outcomes (OS, RFS, TTR) by ctDNA marker status and treatment, prevalence of detectable ctDNA in stage II CC, and rates of compliance with assigned intervention. Archived normal and matched tumor and blood samples will be collected for exploratory correlative research. Enrollment continues across North America to the 540-patient phase II endpoint. Support: U10-CA-180868, -180822; UG1CA-189867; GuardantHealth. Clinical trial information: NCT04068103.

NRG-GI008: Colon adjuvant chemotherapy based on evaluation of residual disease (CIRCULATE-US)

TPS212

Background: Currently, there are no biomarkers validated prospectively in randomized studies for resected colon cancer (CC) to determine need for adjuvant chemotherapy (AC). However, circulating tumor DNA (ctDNA) shed into the bloodstream represents a highly specific and sensitive approach (especially with serial monitoring) for identifying microscopic or residual tumor cells in CC patients (pts) and may outperform traditional clinical and pathological features in prognosticating risk for recurrence. CC pts who do not have detectable ctDNA (ctDNA-) are at a much lower risk of recurrence and may not need AC. Furthermore, for CC pts with detectable ctDNA (ctDNA+) who are at a very high risk of recurrence, the optimal AC regimen has not been established. We hypothesize that for pts whose colon cancer has been resected, ctDNA status may be used to risk stratify for making decisions about AC. Methods: In this prospective phase II/III trial, up to 1,912 pts with resected stage III A, B (all pts) and stage II, IIIC (ctDNA+ only) CC will be enrolled. Based on the post-operative ctDNA status using Natera’s Signatera assay, those who are ctDNA- (Cohort A) will be randomized to immediate AC with fluoropyrimidine (FP) + oxaliplatin (Ox) for 3-6 mos per established guidelines vs serial ctDNA monitoring. Patients who are ctDNA+ post-operatively or with serial monitoring (Cohort B) will be randomized to FP + Ox vs more intensive AC with addition of irinotecan (I) for 6 mos. The primary objectives for Cohort A are time to ctDNA+ status (phase II) and disease-free survival (DFS) in phase III in the immediate vs delayed AC arms. The primary objective for Cohort B is DFS in the FP + Ox vs FP + Ox + I arms for both phase II and phase III portions of the trial. Secondary objectives include prevalence of detectable ctDNA post-operatively, time-to event outcomes (overall survival & time to recurrence) by ctDNA status, and the assessment of compliance to adjuvant therapy. Biospecimens including archival tumor tissue, post-operative and serial matched/ normal blood samples will be collected for exploratory correlative research. Study will activate in early 2022 across the NCTN. NCT#: Pending. Support: U10-CA-180868, -180822; UG1CA-189867; Natera.

Nivolumab (NIVO) + 5-fluorouracil/leucovorin/oxaliplatin (mFOLFOX6)/bevacizumab (BEV) versus mFOLFOX6/BEV for first-line (1L) treatment of metastatic colorectal cancer (mCRC): Phase 2 results from CheckMate 9X8

8

Background: Standard 1L therapies for mCRC include a fluoropyrimidine with oxaliplatin and/or irinotecan, and a biologic agent. NIVO may enhance antitumor activity in combination with 1L standard therapies within a subset of patients (pts) with mCRC. CheckMate 9X8 evaluated NIVO + mFOLFOX6/BEV vs mFOLFOX6/BEV in 1L mCRC (NCT03414983). Methods: Adults with previously untreated, unresectable, mCRC were randomized 2:1 to NIVO 240 mg + mFOLFOX6/BEV Q2W (NIVO + standard-of-care [SOC]) or mFOLFOX6/BEV Q2W (SOC). Primary endpoint was progression-free survival (PFS) assessed by blinded independent central review (BICR) per RECIST v1.1. Key secondary endpoints included objective response rate (ORR), disease control rate (DCR), time to response (TTR), duration of response (DOR), overall survival (OS), and safety. Results: 195 pts were randomized to NIVO + SOC (n = 127) or SOC (n = 68). Median (range) follow-up was 23.7 (0–33.2) months (mo; NIVO + SOC) vs 23.2 (0–32.3) mo (SOC). Median (range) duration of therapy was 9.9 (0.1–31.8+) mo (NIVO + SOC) and 7.7 (0.1–26.7+) mo (SOC). The HR (95% CI) for PFS was 0.81 (0.53–1.23; P = 0.30), which did not meet the prespecified threshold for statistical significance (median PFS, 11.9 mo in both arms; Table). PFS rates after 12 mo were higher with NIVO + SOC vs SOC (Table). ORR was 60% (NIVO + SOC) and 46% (SOC; odds ratio 1.72 [95% CI 0.96–3.10]) and median (95% CI) DOR was 12.9 (9.0–13.1) mo (NIVO + SOC) and 9.3 (7.5–11.3) mo (SOC; Table). Rates of grade 3−4 treatment-related adverse events (TRAEs) were higher with NIVO + SOC; however, no new safety signals were identified (Table). Biomarker analyses, including tumor mutational burden and baseline CD8 levels, will be presented. Conclusions: The primary endpoint of PFS was not met; however, NIVO + SOC showed higher PFS rates after 12 mo, a higher response rate, and more durable responses compared with SOC, along with acceptable safety, in 1L mCRC. Clinical trial information: NCT03414983. [Table: see text]

Metastatic bulk to predict subclonal heterogeneity by ctDNA in RAS/RAF-wildtype colorectal cancer

186

Background: Distinct molecular subgroups of colorectal cancer (CRC) have been afforded with use of next-generation sequencing (NGS) as standard in clinical practice for advanced disease. We have previously demonstrated that disease bulk predicts clinical resistance to EGFR inhibition in RAS/RAF-wildtype (WT) CRC. We hypothesized bulky disease would predict advanced subclonal heterogeneity by circulating tumor DNA (ctDNA) in RAS/RAFWT CRC. Methods: Following IRB-approval, a retrospective review of molecular profiles in advanced CRC (n = 965) were compiled from the Veteran Administration’s (VA) National Precision Oncology Program (NPOP) and University of Wisconsin Precision Medicine Molecular Tumor Board (MTB). Disease bulk was defined as the longest diameter of metastatic disease or short axis for advanced lymphadenopathy. Molecular profiling was performed using commercially available platforms including Strata Oncology (MTB) and FoundationOne (NPOP). Bulky was compared as categorical (> 35 cm) and continuous variable against the count of pathologic variants. Results: The population was largely representative of advanced CRC with alterations in TP53 (80.5%), KRAS (44.8%), PIK3CA (22.0%) and BRAF (12.8%). Veterans had increased frequency of alterations in PIK3CA (22.7% v. 13.0%, p < 0.02) and BRAF (13.3% v. 6.9%, p < 0.05). There was no difference in metastatic bulk at the time of NGS for tissue biopsy between MTB and NPOP populations (t = 0.80). Disease bulk did not predict the number of pathologic variants from tissue sampling in RAS/RAFWT CRC (n = 96, t = 0.24). RAS/RAFMT cancers had increased frequency of subclonal alterations by ctDNA (9.1±4.0) v. RAS/RAFWT (4.5±3.4, p < 0.0001). Using ctDNA, bulky disease in RAS/RAFMT CRC was not predictive of increased pathologic variants (8.8±3.5 v. 9.5±4.8, t = 0.62). Bulky disease (> 35mm) in RAS/RAFWT CRC predicted increased subclonal variants (6.2±3.6 v. 3.5±2.9, p < 0.02). As a continuous variable, disease bulk predicted the number of pathologic variants in RAS/RAFWT CRC (R = 0.51). Conclusions: These data indicate that metastatic bulk is a predictor of subclonal heterogeneity by ctDNA in RAS/RAFWT CRC. Molecular profiling of tissue alone did not predict differences in subclonal heterogeneity when stratified by disease bulk in RAS/RAFWT CRC. Limited subclonal heterogeneity in non-bulky cancers support ongoing prospective investigations to select non-bulky cancers for early incorporation of anti-EGFR inhibition (NCT04587128).

Validation of genetic classifiers derived from mouse and human tumors to identify molecular subtypes of colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer death in the United States. Standard treatment for advanced-stage CRC for decades has included 5-fluorouracil-based chemotherapy. More recently, targeted therapies for metastatic CRC are being used based on the individual cancer's molecular profile. In the past few years, several different molecular subtype schemes for human CRC have been developed. The molecular subtypes can be distinguished by gene expression signatures and have the potential to be used to guide treatment decisions. However, many subtyping classification methods were developed using mRNA expression levels of hundreds to thousands of genes, making them impractical for clinical use. In this study, we assessed whether an immunohistochemical approach could be used for molecular subtyping of CRCs. We validated two previously published, independent sets of immunohistochemistry classifiers and modified the published methods to improve the accuracy of the scoring methods. In addition, we evaluated whether protein and genetic signatures identified originally in the mouse were linked to clinical outcomes of patients with CRC. We found that low DDAH1 or low GAL3ST2 protein levels in human CRCs correlate with poor patient outcomes. The results of this study have the potential to impact methods for determining the prognosis and therapy selection for patients with CRC.

Live cell molecular analysis of primary prostate cancer organoids identifies persistent androgen receptor signaling

Prostate Cancer (PC) is a disease with remarkable tumor heterogeneity that often manifests in significant intra-patient variability with regards to clinical outcomes and treatment response. Commonly available PC cell lines do not accurately reflect the complexity of this disease and there is critical need for development of new models to recapitulate the intricate hierarchy of tumor pathogenesis. In current study, we established ex vivo primary patient-derived cancer organoid (PDCO) cultures from prostatectomy specimens of patients with locally advanced PC. We then performed a comprehensive multi-parameter characterization of the cellular composition utilizing a novel approach for live-cell staining and direct imaging in the integrated microfluidic Stacks device. Using orthogonal flow cytometry analysis, we demonstrate that primary PDCOs maintain distinct subsets of epithelial cells throughout culture and that these cells conserve expression of androgen receptor (AR)-related elements. Furthermore, to confirm the tumor-origin of the PDCOs we have analyzed the expression of PC-associated epigenetic biomarkers including promoter methylation of the GSTP1, RASSF1 and APC and RARb genes by employing a novel microfluidic rare-event screening protocol. These results demonstrate that this ex vivo PDCO model recapitulates the complexity of the epithelial tumor microenvironment of multifocal PC using orthogonal analyses. Furthermore, we propose to leverage the Stacks microfluidic device as a high-throughput, translational platform to interrogate phenotypic and molecular endpoints with the capacity to incorporate a complex tumor microenvironment.

Multi-ancestral origin of intestinal tumors: Impact on growth, progression, and drug efficacy

Background

Data are steadily accruing that demonstrate that intestinal tumors are frequently derived from multiple founding cells, resulting in tumors comprised of distinct ancestral clones that might cooperate or alternatively compete, thereby potentially impacting different phases of the disease process.

Aim

We sought to determine whether tumors with a multi‐ancestral architecture involving at least two distinct clones show increased tumor number, growth, progression, or resistance to drug intervention.

Methods

Mice carrying the Min allele of Apc were generated that were mosaic with only a subset of cells in the intestinal epithelium expressing an activated form of PI3K, a key regulatory kinase affecting several important cellular processes. These cells were identifiable as they fluoresced green, whereas all other cells fluoresced red.

Results

Cell lineage tracing revealed that many intestinal tumors from our mouse model were derived from at least two founding cells, those expressing the activated PI3K (green) and those which did not (red). Heterotypic tumors with a multi‐ancestral architecture as evidenced by a mixture of green and red cells exhibited increased tumor growth and invasiveness. Clonal architecture also had an impact on tumor response to low‐dose aspirin. Aspirin treatment resulted in a greater reduction of heterotypic tumors derived from multiple founding cells as compared to tumors derived from a single founding cell.

Conclusion

These data indicate that genetically distinct tumor‐founding cells can contribute to early intratumoral heterogeneity. The coevolution of the founding cells and their progeny enhances colon tumor progression and impacts the response to aspirin. These findings are important to a more complete understanding of tumorigenesis with consequences for several distinct models of tumor evolution. They also have practical implications to the clinic. Mouse models with heterogenous tumors are likely better for predicting drug efficacy as compared to models in which the tumors are highly homogeneous. Moreover, understanding how interactions among different populations in a single heterotypic tumor with a multi‐ancestral architecture impact response to a single agent and combination therapies are necessary to fully develop personalized medicine.

Abstract 2734: Impact of the mutation profile and versican status on lymphocyte infiltration in early age onset colorectal cancer

Background: The incidence of colorectal cancer (CRC) in those of pre-screening age continues to rise. A deeper understanding of the differences in tumor biology in early age onset (EAO) cancers is needed. Differences in the tumor microenvironment have been understudied in this setting. We previously have identified versican (VCAN), a large matrix proteoglycan, as an important factor in lymphocyte exclusion in CRC. Here we explore the impact of the mutation profile and VCAN status on the infiltration of CD8+ and CD4+ lymphocytes in EAO CRC.

Methods: Cancer tissues from 153 patients with CRC were stained via immunohistochemistry for CD4, CD8, and VCAN. CD4 and CD8 stains were quantified by number of positive-staining tumor-infiltrating lymphocytes per high powered field (TILs/HPF). VCAN stains were quantified on an intensity scale from 0-3+. 121 of these patients had tissue that was sequenced using the Qiagen Comprehensive Cancer targeted sequencing panel, and variations were called using Strelka. Patients were split by age into early-onset (EAO; age at diagnosis &lt;50) and later-onset (LAO; age at diagnosis 50 or later).

Results: Mutations in BRAF and APC were significantly more common in LAO cancers (p&lt;0.05 for both). TP53 mutations were correlated with significantly lower CD4+ and CD8+ TILs/HPF in the LAO cohort (12.6 CD4+ TILs/HPF for TP53-wild type [WT] vs 3.5 for TP53-mutant, p&lt;0.001; 10.0 CD8+ TILs/HPF for WT vs 3.2 for mutant, p&lt;0.01), but trended opposite, though not statistically significant, in the EAO group (2.4 vs 5.9 CD4+ TILs/HPF; 3.0 vs 5.9 CD8+ TILs/HPF). PIK3CA mutations were correlated with an increase in CD8+ TILs in the LAO cohort (5.3 vs 11.9 CD8+ TILs/HPF; p&lt;0.05) but a decrease in CD4+ TILs in the EAO cohort (4.9 vs 0.8 CD4+ TILs/HPF; p&lt;0.05). TP53-WT tumors are disproportionately low in VCAN in the LAO cohort (p&lt;0.01). Differences in VCAN accumulation could account for the changes in CD8+ and CD4+ T lymphocyte infiltration across the age cohorts and TP53 mutation status.

Conclusions: The impacts of TP53 and PIK3CA mutations on immune infiltration in CRC differ in EAO compared to later onset cancers, indicating that the processes controlling immune infiltration vary between age cohorts. Such differences in immune infiltration may be linked to changes in microenvironmental factors such as VCAN. These data warrant further investigation into the relationship between tumor microenvironment and mutation profiles in EAO CRC.

Citation Format: Katherine A. Johnson, Philip B. Emmerich, Anna L. Lippert, Cheri A. Pasch, Linda Clipson, Wei Zhang, Kristina A. Matkowskyj, Dustin A. Deming. Impact of the mutation profile and versican status on lymphocyte infiltration in early age onset colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2734.

Abstract 1944: Navitoclax enhances the efficacy of copanlisib predominantly through inhibition of BCLxL in PIK3CA mutant colorectal cancer

Background: Mutations in PIK3CA occur in 18% of colorectal cancers (CRC) and result in constitutive activation of the PI3K pathway. Previous work from our lab has determined that MTORC1/2 inhibition, with copanlisib (cop), a PI3K/MTOR inhibitor, is sufficient to induce a treatment response. We hypothesized that the BCL2 family inhibitor navitoclax (nav), a BCL2/BCLxL inhibitor, would enhance the therapeutic response of cop and increase the induction of apoptosis.

Methods: Murine derived cancer organoids (MDCOs) were generated from adenocarcinomas arising in Apc and Pik3ca mutant transgenic mice ((FVB x B6) F1 Apcfl/+ Pik3caH1047R/+). MDCOs were plated and matured for 24 hours. MDCOs were treated for 48 hours. Change in diameter was used to assess response. Additionally, human 2D isogenic cell lines SW48 and SW48PIK3CA-H1047R (SW48PK) were plated and treated for 48 hours. WST-1 proliferation assay was used to determine response. In vivo response was assessed as median relative change (MRC) in tumor volume of SW48 and SW48PK xenografts in immunocompromised Rag2-Il2rg-/- (R2G2) mice. Induction of apoptosis was determined with immunoblotting (IB) for PARP cleavage.

Results: MDCOs were treated with cop (200nM) or nav (250nM) alone and in combination. Single agent cop resulted in -16% MRC (p&lt;0.001). Nav alone did not have an effect (+95% p&lt;0.07). Enhanced therapeutic response was seen in the combination therapy compared to cop alone (cop -16% vs combo -100%; p&lt;0.001). In SW48 and SW48PK with cop (1nM or 10nM) or nav (250nM) alone and in combination, a greater response was seen in the combination therapy in both cell lines compared to either single agent alone (p&lt;0.005). SW48 and SW48PK xenograft studies demonstrated significant activity of this combination in vivo. SW48 tumor growth was limited with either cop (10mg/kg), nav (80mg/kg), or the combination compared to control (control +5.0 MRC, cop +3.4, nav +2.6, combo +2.6; control vs combo p&lt;0.01; cop vs combo p=0.29). Enhanced activity of this combination was observed in SW48PK tumors compared to SW48. Growth was significantly more limited with the combination (control +5.0 MRC, cop +3.4, nav +4.5, combo +0.7; control vs combo p&lt;0.01; cop vs combo p=0.06). IB of cleaved PARP showed induction of apoptosis was the highest in the combination therapy in all in vitro models and seen as early as 6 hours post treatment. To identify which BCL2 family member nav was primarily targeting, cop was combined with WEHI539 (BCLxL inhibitor; 250nM) or ABT199 (BCL2 inhibitor; 250nM). BCL2 inhibition did not enhance the efficacy of cop in the MDCOs or isogenic lines. However, BCLxL inhibition did enhance the efficacy of cop in both in vitro models.

Conclusion: These data indicate that navitoclax, through BCLxL inhibition, enhances the efficacy of copanlisib with a greater induction of apoptosis in several models of PIK3CA mutant CRC.

Citation Format: Rebecca Anna DeStefanis, Alyssa DeZeeuw, Gioia Sha, Autumn Olson, Samantha J. Anderson, Christopher P. Babiarz, Cheri A. Pasch, Linda Clipson, Dustin A. Deming. Navitoclax enhances the efficacy of copanlisib predominantly through inhibition of BCLxL in PIK3CA mutant colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1944.

Abstract 3166: Impact of cancer associated fibroblast phenotypes on the infiltration of t-lymphocytes in early age onset colorectal cancer

Background: Incidences of early age onset colorectal cancer (CRC) (those diagnosed before age 50) have been increasing by 2% every year since the 1990s, with the rate expecting to double by 2030. Although there has been some research done on differences in mutational profiles between patients diagnosed before and after age 50, little research has been done to understand the immune and stromal environments of early age onset (EAO) CRC. As identified by previous literature, there are two distinct phenotypes of cancer associated fibroblasts (CAFs): myofibroblastic (myCAFs) and non-myofibroblastic (non-myCAFs). Here, we evaluate both CAF environments as well as immune infiltrating cells in context of EAO CRC.

Methods: A total of 153 CRC patient samples were obtained with matching adjacent normal tissue. Of these, 60 patients had EAO CRC. Tissue slides were stained via immunohistochemistry (IHC) for the CAF subtype markers αSMA, FAP, PDPN, and MMP2, by Masson's Trichrome for collagen, and then quantified on an intensity scale from 0-3. MyCAF and non-myCAF scores were calculated by averaging the scores of αSMA and collagen, or FAP, PDPN, and MMP2, respectively. Once these scores were determined, they were split into low (average score &lt;2) and high (average score ≥2) groups. CD4 and CD8 IHC stains were quantified as the number of tumor infiltrating lymphocytes (TILs) per high power field (HPF) in the epithelial compartment.

Results: Cancers with a low myCAF and non-myCAF score display the highest average number of CD4+ (10.6) and CD8+ (10.3) TILs across both age groups. Furthermore, cancers with both myCAF and non-myCAF high scores had reduced average CD4+ and CD8+ TILs when compared to both CAF scores being low (p value: 0.018 for CD8+ TILs, &lt;0.001 for CD4+ TILs). Also, cancers that show myCAF high and non-myCAF low scores show the overall lowest average CD8+ TILs. Comparing the age groups directly, there are significantly higher CD4+ TILs in the 50+ age group in all CAF phenotypes except non-myCAF high (p-values 0.01 myCAF low, 0.05 myCAF high, 0.007 non-myCAF low, 0.36 non-myCAF high). However, for CD8+ TILs, the EAO CRC group trends towards higher CD8+ TILs in the myCAF high (3.7 vs 2.1) and non-myCAF high cancers (5.7 vs 3.3), but lower CD8+ TILs in myCAF low (6.8 vs 10.5) and non-myCAF low cancers (4.0 vs 8.4) when compared to the 50+ age group.

Conclusions: Here we demonstrate that there are differences in the stromal and immune microenvironments between both age groups of CRC. We indicate that increased myCAF and non-myCAF scores are associated with T cell exclusion. However, the extent of T cell exclusion is different in EAO CRC compared to patients diagnosed after age 50. The reasoning for the difference in T-cell exclusion remains unknown and this implicates the importance for further research into the stromal and immune microenvironments of EAO CRC.

Citation Format: Anna Lippert, Katherine A. Johnson, Philip B. Emmerich, Cheri A. Pasch, Linda Clipson, Kristina A. Matkowskyi, Wei Zhang, Dustin A. Deming. Impact of cancer associated fibroblast phenotypes on the infiltration of t-lymphocytes in early age onset colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3166.

Volumetric growth tracking of patient-derived cancer organoids using optical coherence tomography

Patient-derived cancer organoids (PCOs) are in vitro organotypic models that reflect in vivo drug response, thus PCOs are an accessible model for cancer drug screening in a clinically relevant timeframe. However, current methods to assess the response of PCOs are limited. Here, a custom swept-source optical coherence tomography (OCT) system was used to rapidly evaluate volumetric growth and drug response in PCOs. This system was optimized for an inverted imaging geometry to enable high-throughput imaging of PCOs. An automated image analysis framework was developed to perform 3D single-organoid tracking of PCOs across multiple time points over 48 hours. Metabolic inhibitors and cancer therapies decreased PCOs volumetric growth rate compared to control PCOs. Single-organoid tracking improved sensitivity to drug treatment compared to a pooled analysis of changes in organoid volume. OCT provided a more accurate assessment of organoid volume compared to a volume estimation method based on 2D projections. Single-organoid tracking with OCT also identified heterogeneity in drug response between solid and hollow PCOs. This work demonstrates that OCT and 3D single-organoid tracking are attractive tools to monitor volumetric growth and drug response in PCOs, providing rapid, non-destructive methods to quantify heterogeneity in PCOs.

Abstract 2969: Impact of baseline culture condition on the growth and treatment response of mouse derived cancer organoids

Impact of baseline culture condition on the growth and treatment response of mouse derived cancer organoidsAuthors: Autumn Olson, Rebecca A. DeStefanis, Alyssa DeZeeuw, Samantha Anderson, Gioia Sha, Jeremy Kratz, Cheri Pasch, Linda Clipson, Dustin A. DemingIntroduction: Colorectal cancer (CRC) is a leading cause of cancer related deaths and there has been an increased focus on developing therapies targeted to the mutational profile of individual patients. Mouse derived cancer organoids (MDCOs) are used as a model for therapeutic drug testing. How the culture conditions can impact the determination of treatment response from MDCOs has been understudied and is the focus of these investigations. Here, we examine how baseline size, passage number, plating density, location within the Matrigel droplet, and lineage impact MDCO growth and treatment response.Methods: CRC MDCOs were derived from multiple tumors across several Apc and Pik3ca mutant mice (Fc1 Apcfl/+ Pik3caH1047R/+) totaling 3,152 individual MDCOs. Untreated MDCO growth was analyzed across 902 MDCOs. Additionally, the PI3K pathway inhibitors, AZD2014, Everolimus, BEZ235, MLN0128, Palbociclib, and Copanlisib were analyzed across 2,250 MDCOs. In each study, baseline brightfield images of the MDCOs were taken and following 48 hours. Individual MDCOs were evaluated for the impact of baseline size, passage number (passage 1-15), plating density, location within the Matrigel droplet, and the generation of MDCOs across different mice on MDCO growth and treatment response. A change point analysis was used to assess the impact of baseline size. The percent relative change in diameter over 48 hours was compared to each other culture condition by calculating an R2 value.Results: A change in the organoid baseline growth rate was observed if the MDCOs were greater than 0.373 mm in baseline was identified. There were no significant differences in growth due to changes in the other culture conditions for the untreated MDCOs. The R2 values comparing the percent relative change in diameter over 48 hours to the culture conditions of passage number, plating density, location within the Matrigel droplet, and from which mouse the MDCOs were derived from were 0.0103, 0.0243, 0.0001, and 0.0295, respectively. There were no significant differences in the response to PI3K pathway inhibition of the MDCOs related to passage number, plating density, location within the Matrigel droplet, and from which mouse the MDCOs were derived from (R2 values: 0.1174, 0.0979, 0.0221, and 0.1267, respectively).Conclusions: Mouse derived cancer organoids are a useful tool in modeling drug response of cancers with specific mutational profiles. While the baseline size of MDCOs can change the growth rate, the growth rate and treatment response of MDCOs is not impacted by the passage number, plating density, location within the Matrigel, and from which mouse the MDCOs were derived.

Citation Format: Autumn Olson, Rebecca A. DeStefanis, Alyssa DeZeeuw, Samantha Anderson, Gioia Sha, Jeremy Kratz, Cheri Pasch, Linda Clipson, Dustin A. Deming. Impact of baseline culture condition on the growth and treatment response of mouse derived cancer organoids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2969.

Phase II/III study of Circulating tumOr DNA as a predictive BiomaRker in Adjuvant chemotherapy in patients with stage II colon cancer: NRG-GI005 (COBRA)

TPS3622

Background: There are currently no validated predictive biomarkers for stage II resected colon cancer (CC) after adjuvant chemotherapy. However, circulating tumor DNA (ctDNA) that is shed into the bloodstream represents a highly specific and sensitive approach for identifying microscopic or residual tumor cells. For patients (pts) with CC, the detection of ctDNA is associated with persistent disease after resection and may outperform traditional clinical and pathological features as a prognostic factor to assess risk for recurrence. We hypothesize that for pts whose stage II colon cancer has been resected and who have no traditional high-risk features, a positive ctDNA status may identify those who will benefit from adjuvant chemotherapy. Methods: In this prospective phase II/III clinical trial, pts (N = 1,408) with resected stage II CC without traditional high-risk features and whom the evaluating oncologist deems suitable for no adjuvant chemotherapy will be randomized 1:1 into 2 arms: standard-of-care/observation (Arm A), or prospective testing for ctDNA (Arm B). Postoperative blood will be analyzed for ctDNA with the GuardantHealth LUNAR panel, covering CC-relevant mutations and CC-specific methylation profiling. Pts in Arm B with ctDNA detected will be treated with 6 months of adjuvant (FOLFOX) chemotherapy. For all pts in Arm A, ctDNA status will be analyzed retrospectively at the time of endpoint analysis. The primary endpoints are clearance of ctDNA with adjuvant chemotherapy (phase II) and recurrence-free survival (RFS) for “ctDNA-detected” pts treated with or without adjuvant chemotherapy (phase III). Secondary endpoints will include time-to-event outcomes (OS, RFS, TTR) by ctDNA marker status and treatment, prevalence of detectable ctDNA in stage II CC, and rates of compliance with assigned intervention. Archived normal and matched tumor and blood samples will be collected for exploratory correlative research. The trial is actively accruing towards the phase II endpoint in North America. NCT#: 04068103. Support: U10-CA-180868, -180822; UG1CA-189867; GuardantHealth. Clinical trial information: NCT04068103.

Autofluorescence Imaging of Treatment Response in Neuroendocrine Tumor Organoids

Gastroenteropancreatic neuroendocrine tumors (GEP-NET) account for roughly 60% of all neuroendocrine tumors. Low/intermediate grade human GEP-NETs have relatively low proliferation rates that animal models and cell lines fail to recapitulate. Short-term patient-derived cancer organoids (PDCOs) are a 3D model system that holds great promise for recapitulating well-differentiated human GEP-NETs. However, traditional measurements of drug response (i.e., growth, proliferation) are not effective in GEP-NET PDCOs due to the small volume of tissue and low proliferation rates that are characteristic of the disease. Here, we test a label-free, non-destructive optical metabolic imaging (OMI) method to measure drug response in live GEP-NET PDCOs. OMI captures the fluorescence lifetime and intensity of endogenous metabolic cofactors NAD(P)H and FAD. OMI has previously provided accurate predictions of drug response on a single cell level in other cancer types, but this is the first study to apply OMI to GEP-NETs. OMI tested the response to novel drug combination on GEP-NET PDCOs, specifically ABT263 (navitoclax), a Bcl-2 family inhibitor, and everolimus, a standard GEP-NET treatment that inhibits mTOR. Treatment response to ABT263, everolimus, and the combination were tested in GEP-NET PDCO lines derived from seven patients, using two-photon OMI. OMI measured a response to the combination treatment in 5 PDCO lines, at 72 h post-treatment. In one of the non-responsive PDCO lines, heterogeneous response was identified with two distinct subpopulations of cell metabolism. Overall, this work shows that OMI provides single-cell metabolic measurements of drug response in PDCOs to guide drug development for GEP-NET patients.

Breast cancer immunotherapy: current biomarkers and the potential of in vitro assays

Breakthroughs in metastatic breast cancer care require new model systems that can identify the unique features and vulnerabilities of each cancer. Primary tumor cultures are proposed to efficiently screen multiple treatment options in a patient-specific strategy to maximize therapeutic benefit, minimize toxicity, and enable mechanistic insights that inspire future biomarkers for patient selection. To realize the potential of patient-specific cultures, new tools are needed to capture cell-by-cell variability in behavior and dynamic response to treatments in living 3D specimens. Potential bioengineering tools that can achieve this include optical microscopy to image single-cell dynamics and microphysiological in vitro systems to evaluate cell-cell interactions and immunotherapies.

Phase II/III study of circulating tumor DNA as a predictive biomarker in adjuvant chemotherapy in patients with stage II colon cancer:NRG-GI005 (COBRA)

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Background: There are currently no validated predictive biomarkers for stage II resected colon cancer (CC) after adjuvant chemotherapy. However, circulating tumor DNA (ctDNA) that is shed into the bloodstream represents a highly specific and sensitive approach for identifying microscopic or residual tumor cells. For patients (pts) with CC, the detection of ctDNA is associated with persistent disease after resection and may outperform traditional clinical and pathological features as a prognostic factor to assess risk for recurrence. We hypothesize that for pts whose stage II colon cancer has been resected and who have no traditional high-risk features, a positive ctDNA status may identify those who will benefit from adjuvant chemotherapy. Methods: In this prospective phase II/III clinical trial, pts (N=1,408) with resected stage II CC without traditional high-risk features and whom the evaluating oncologist deems suitable for no adjuvant chemotherapy will be randomized 1:1 into 2 arms:standard-of-care/observation (Arm A), or prospective testing for ctDNA (Arm B). Postoperative blood will be analyzed for ctDNA with the GuardantHealth LUNAR panel, covering CC-relevant mutations and CC-specific methylation profiling. Pts in Arm B with ctDNA detected will be treated with 6 months of adjuvant (FOLFOX) chemotherapy. For all pts in Arm A, ctDNA status will be analyzed retrospectively at the time of endpoint analysis. The primary endpoints are clearance of ctDNA with adjuvant chemotherapy (phase II) and recurrence-free survival (RFS) for “ctDNA-detected” pts treated with or without adjuvant chemotherapy (phase III). Secondary endpoints will include time-to-event outcomes (OS, RFS, TTR) by ctDNA marker status and treatment, prevalence of detectable ctDNA in stage II CC, and rates of compliance with assigned intervention. Archived normal and matched tumor and blood samples will be collected for exploratory correlative research. The trial is actively accruing towards the phase II endpoint across all US and Canadian cooperative groups. Support:U10-CA-180868, -180822; UG1CA-189867; GuardantHealth. Clinical trial information: NCT04068103.

Sensitivity of HER2-amplified colorectal organotypic cancer spheroids at ex vivo resistance to panitumumab and trastuzumab

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Background: HER2 amplification is an emerging biomarker in colorectal cancer (CRC) with increased copy number associated with improved clinical outcomes to HER2 targeting. RAS/RAF wildtype CRC also benefit from use of epidermal growth factor receptor inhibition (EGFRi). The sequencing of EGFRi versus HER2 inhibition in low copy number HER2 amplified CRC remains uncertain. Patient-derived cancer organoids (PDCOs) allow an ex vivo method to assess treatment sensitivity. We examined treatment sensitivity of a HER2 amplified PDCO at baseline and following resistance to panitumumab and trastuzumab. Methods: Following IRB-approval, fresh CRC tissue was cultured to maturation. After expansion, subcultures were treated with stepwise (20%) increase to physiologic Cmax of panitumumab (230ug/mL) and trastuzumab (180ug/mL). Threshold for escalation was median relative growth of +20% at 96h. Sensitivity was assessed on primary culture (RC1), panitumumab resistance (RC1-P) and trastuzumab resistance (RC1-T) using 96h of physiologic Cmax panitumumab, trastuzumab, and combination trastuzumab/pertuzumab. Individual sphere response was assessed for change in mean NADH autofluorescence intensity and ratio of NADH/FAD signal. Response was assessed at 96h in comparison to control using effect size of Glass’s Delta (GΔ). Results: Molecular profiling revealed HER2 copy number of 14 with no concurrent alterations in RAS, RAF, or PIK3CA. Time to resistance was similar between panitumumab (55 days) and trastuzumab (51 days). RC1 had baseline growth (+116%) which was reduced with single agent panitumumab (+17%, GΔ=1.40) with intermediate sensitivity to trastuzumab (+48%, GΔ=0.95) and trastuzumab/pertuzumab (46%, GΔ=0.99). Normalized NADH/FAD ratio revealed significant metabolic response to panitumumab (-20%, GΔ=0.66) and trastuzumab/pertuzumab (-35%, GΔ=1.16) with insignificant effect of single agent trastuzumab (-14%, GΔ=0.46). Following resistance to panitumumab, RC1-P had persistent growth with trastuzumab (+68%) which improved in combination trastuzumab/pertuzumab (+34%, GΔ=1.16). Following resistance to trastuzumab, RC1-T was insensitive to EGFRi with panitumumab including persistent growth (+58%, GΔ=0.70) and unchanged metabolism (+2%, GΔ=-0.10). Conclusions: Therapeutic dose escalation in a single PDCO of HER2 amplified CRC suggests improved sensitivity to EGFRi and dual HER2 targeting with trastuzumab/pertuzumab. Resistance to EGFRi resulted in persistent sensitivity to dual HER2 inhibition using trastuzumab/pertuzumab, however resistance to single agent trastuzumab. Resistance to trastuzumab resulted in future insensitivity to EGFRi. Molecular profiling at resistance revealed no pathologic alterations in EGFR or ERBB2 signaling, with ongoing analysis of transcriptional changes by RNAseq.

Tumor bulk as a prognostic biomarker and predictor of benefit from anti-EGFR therapy in patients with metastatic colorectal cancer: Analysis of 476 patients from the ARCAD Clinical Trials Program

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Background: Primary tumor sidedness has emerged as a prognostic and predictive biomarker for patients (pts) with metastatic colorectal cancer (mCRC). Tumor bulk has also been postulated to predict response to anti-EGFR therapy. We sought to evaluate the role of tumor bulk as a predictive biomarker to anti-EGFR therapy in pts with left- (LS) and right-sided (RS) mCRC. Methods: Data from 476 pts with mCRC enrolled across 2 first-line trials of anti-EGFR plus chemotherapy versus chemotherapy were pooled. Pts were included if there was available information on tumor sidedness and tumor bulk. All were KRAS wild-type and BRAF wild-type or unknown BRAF status. The right colon was defined as the cecum through the transverse colon, and the left colon as the splenic flexure through the rectum. Tumor bulk was the mean tumor size of target lesions at baseline, bulky defined as > 3.5 cm. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier and Cox models adjusting for performance status (PS), platelet count, primary tumor (PT) resection, number of metastatic sites, and stratified by study. Results: Pts with bulky tumors (211, 44%) had higher PS, white blood cell and platelet counts, higher CEA, fewer sites of metastatic disease, more liver than lung metastases, and fewer had PT resection. OS and PFS medians in months (mos) are presented in the table with 95% confidence intervals (95%CIs). Bulky tumors had inferior median OS compared with non-bulky (mOS, 17.9 vs. 21.3 mos, HRadj 1.33, 95% CI 1.05-1.69, P = 0.016) although median PFS was similar (mPFS, 8.6 vs. 8.7 mos, HRadj 1.15, 95% CI 0.92-1.42, P = 0.21). Conclusions: Tumor bulk is an independent prognostic factor for OS in KRAS wild-type and BRAF wild-type or unknown BRAF status pts. Pts with non-bulky RS tumors have survival outcomes similar to pts with bulky LS tumors. Although the mPFS for pts with RS tumors treated with anti-EGFR therapy was the lowest across subgroups, this finding was not statistically significant. Further research is warranted into whether pts with bulky RS tumors benefit from anti-EGFR therapy. Clinical trial information: NCT00182715, NCT00640081. [Table: see text]

ctDNA applications and integration in colorectal cancer: an NCI Colon and Rectal-Anal Task Forces whitepaper

An increasing number of studies are describing potential uses of circulating tumour DNA (ctDNA) in the care of patients with colorectal cancer. Owing to this rapidly developing area of research, the Colon and Rectal-Anal Task Forces of the United States National Cancer Institute convened a panel of multidisciplinary experts to summarize current data on the utility of ctDNA in the management of colorectal cancer and to provide guidance in promoting the efficient development and integration of this technology into clinical care. The panel focused on four key areas in which ctDNA has the potential to change clinical practice, including the detection of minimal residual disease, the management of patients with rectal cancer, monitoring responses to therapy, and tracking clonal dynamics in response to targeted therapies and other systemic treatments. The panel also provides general guidelines with relevance for ctDNA-related research efforts, irrespective of indication.

Abstract B27: MTORC1/2 inhibition as a treatment strategy for PIK3CA mutant colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer-related death. PIK3CA mutations are common, leading to a constitutively active phosphoinositide-3 kinase (PI3K). An effective means to target this pathway has yet to be identified. We investigated the use of a panel of inhibitors targeting the PI3K pathway including copanlisib (dual PI3K/mTOR), BYL-719 (alpha isomer specific PI3K), GDC-0941 (pan PI3K), and TAK-228 (MTORC1/2). To test the efficacy of these inhibitors in CRC, murine organotypic cancer spheroids (MDOCS) were generated from the invasive adenocarcinomas of Apc and Pik3ca transgenic mice. These inhibitors were investigated at clinically relevant doses (100-400nM). Copanlisib and TAK-228 were the only inhibitors to result in a significant reduction in the size of the MDOCS (200nM; 27% p-value&lt;0.001, 18% p-value&lt;0.001, respectively). This result correlated with a decrease in the phosphorylation of AKT (ser473), RPS6, and 4EBP1. Minimal induction of apoptosis was observed using these inhibitors alone as measured by cleaved PARP and cleaved caspase 3. These results were confirmed in vivo using transgenic mice with TAK-228 (1mg/kg/day) and copanlisib (10mg/kg q2d x5) resulting in a reduction in lumen occlusion of the colon tumors. Persistent BCL-2 and BCL-xL signaling was hypothesized to be preventing the induction of apoptosis. To determine if inhibition of these BCL-2 family members would further sensitize these MDOCS to copanlisib and TAK-228, these inhibitors were tested in combination with navitoclax (ABT-263; BCL-2 family inhibitor). A dramatic enhanced sensitivity was observed in MDOCS (30% p-value&lt;0.001, 23% p-value&lt;0.001, respectively). This correlated with an induction of apoptosis as measured by cleaved caspase 3. Next a panel of eight CRC patient-derived organotypic cancer spheroids (PDOCS) were treated with the combination of TAK-228 and navitoclax. Differential sensitivity was observed across the panel (25% resistant, 37.5% intermediate, and 37.5% highly sensitive) owing to the importance of mutational profile with targeted therapies. These studies indicate the benefit of MTORC1/2 for the treatment of PIK3CA mutant CRC and with enhanced activity of the combination of MTORC1/2 inhibition in combination with BCL-2 family inhibition. These therapies deserve further investigation for the treatment of patients with PIK3CA mutant CRC.

Citation Format: Rebecca A. DeStefanis, Susan N. Payne, Devon Miller, Cheri A. Pasch, Christopher Babiarz, Alyssa DeZeeuw, Stephanie L. Fricke, Carley Sprackling, Alexander E. Yueh, Demetra P. Korkos, Dana R. Van De Hey, Gioia Sha, Aurora Greane, Jeremy D. Kratz, Linda Clipson, Kristina A. Matkowskyj, Michael A. Newton, Dustin A. Deming. MTORC1/2 inhibition as a treatment strategy for PIK3CA mutant colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr B27.

Small Bowel Adenocarcinoma, Version 1.2020, NCCN Clinical Practice Guidelines in Oncology

Small bowel adenocarcinoma (SBA) is a rare malignancy of the gastrointestinal tract that has increased in incidence across recent years. Often diagnosed at an advanced stage, outcomes for SBA are worse on average than for other related malignancies, including colorectal cancer. Due to the rarity of this disease, few studies have been done to direct optimal treatment, although recent data have shown that SBA responds to treatment differently than colorectal cancer, necessitating a separate approach to treatment. The NCCN Guidelines for Small Bowel Adenocarcinoma were created to establish an evidence-based standard of care for patients with SBA. These guidelines provide recommendations on the workup of suspected SBA, primary treatment options, adjuvant treatment, surveillance, and systemic therapy for metastatic disease. Additionally, principles of imaging and endoscopy, pathologic review, surgery, radiation therapy, and survivorship are described.