SEAMARK: phase II study of first-line encorafenib and cetuximab plus pembrolizumab for MSI-H/dMMR BRAFV600E-mutant mCRC

Patients with both BRAF V600E mutations and microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC) have poor prognosis. Currently, there are no specifically targeted first-line treatment options indicated for patients with mCRC whose tumors harbor both molecular aberrations. Pembrolizumab is a checkpoint inhibitor approved for the treatment of MSI-H/dMMR mCRC, and the BRAF inhibitor encorafenib, in combination with cetuximab, is approved for previously treated BRAF V600E-mutant mCRC. Combination of pembrolizumab with encorafenib and cetuximab may synergistically enhance antitumor activity in patients with BRAF V600E-mutant, MSI-H/dMMR mCRC. SEAMARK is a randomized phase II study comparing the efficacy of the combination of pembrolizumab with encorafenib and cetuximab versus pembrolizumab alone in patients with previously untreated BRAF V600E-mutant, MSI-H/dMMR mCRC.

Institution-Wide Retreats Foster Organizational Learning and Action at a Comprehensive Cancer Center

Providing safe and informed healthcare for sexual and gender minority (SGM) individuals with cancer is stymied by the lack of sexual orientation and gender identity (SOGI) data reliably available in health records and by insufficient training for staff. Approaches that support institutional learning, especially around sensitive topics, are essential for hospitals seeking to improve practices impacting patient safety and research. We engineered annual institutional retreats to identify and unify stakeholders, promote awareness of gaps and needs, identify initiatives, minimize redundant projects, and coordinate efforts that promote improvements in SGM cancer care, education, and research. The 2022 and 2023 retreats employed a 4-h hybrid format allowing virtual and in-person engagement. Retreat organizers facilitated small-group discussions for brainstorming among participants. We performed descriptive statistics from retreat evaluations. The retreats engaged 104 attendees from distinct departments and roles. Participants expressed robust satisfaction, commending the retreat organization and content quality. Notably, the first retreat yielded leadership endorsement and funding for a Quality Improvement pilot to standardize SOGI data collection and clinical staff training. The second retreat provided a platform for updates on focused efforts across the institution and for receiving direction regarding national best practices for SGM care and research. We report the processes and outcomes of institution-wide retreats, which served as a platform for identifying gaps in organizational healthcare practices and research for SGM individuals with cancer. The strategies described herein may be readily scaled at other cancer hospitals seeking to learn and enact system-wide practice changes that support the needs of SGM patients and families.

Daily Vaginal Dilator Use During Radiation for Women With Squamous Cell Carcinoma of the Anus: Vaginal Wall Dosimetry and Patient-Reported Sexual Function

PURPOSE

At our institution, we treat patients with a daily vaginal dilator (VD) during chemoradiation (CRT) for squamous cell carcinoma of the anus (SCCA). We evaluated compliance with daily VD use, radiation dose to the vaginal wall (VW), and anterior vaginal wall (AVW), and patient-reported long-term sexual function.

METHODS AND MATERIALS

We included women with SCCA who received definitive, intensity-modulated radiation therapy-based CRT. Women who were alive without evidence of disease received a patient-reported outcome survey, which included the Female Sexual Function Index (FSFI). We identified factors associated with FSFI, such as radiation dose to the VW and AVW using linear regression models and used Youden index analysis to estimate a dose cutoff to predict sexual dysfunction.

RESULTS

Three hundred thirty-nine consecutively treated women were included in the analysis; 285 (84.1%) were treated with a daily VD. Of 184 women alive without disease, 90 patients (49%) completed the FSFI, and 51 (56.7%) were sexually active with valid FSFI scores. All received therapy with a daily VD. Forty-one women (80%) had sexual dysfunction. Univariate analysis showed higher dose to 50% (D50%) of the AVW correlated with worse FSFI (β -.262; P = .043), worse desire FSFI subscore (β -.056; P = .003), and worse pain FSFI subscore (β -.084; P = .009). Younger age correlated with worse pain FSFI subscale (β .067; P = .026). Age (β .070; P = .013) and AVW D50% (β -.087; P = .009) were significant on multivariable analysis. AVW D50% >48 Gy predicted increased risk of sexual dysfunction.

CONCLUSIONS

Daily VD use is safe and well tolerated during CRT for SCCA. Using a VD during treatment to displace the AVW may reduce the risk for sexual dysfunction. Limiting the AVW D50% <48 Gy may further reduce the risk but additional data are needed to validate this constraint.

Salvage Treatment of Recurrent or Persistent Anal Squamous Cell Carcinoma: The Role of Multi-modality Therapy

BACKGROUND

The standard treatment for recurrent or persistent anal squamous cell carcinoma is surgical salvage, but disease control and survival are suboptimal.

PATIENTS/METHODS

Patients treated for recurrent or persistent anal squamous cell carcinoma at our institution from 2002 to 2022 were included. Patients were classified by type of salvage treatment received: surgery alone vs. reirradiation followed by surgery and by whether they received intraoperative radiation at the time of surgery. Clinical and pathologic variables were collected and assessed for association with risk of second local recurrence and death from any cause.

RESULTS

Sixty four patients were included; 55(85.9%) were treated with surgery alone and 9 (14.1%) were treated with reirradiation followed by surgery. Median (IQR) follow up from the time of salvage treatment was 40.0 (20.3-68.0) months. The 3-year cumulative incidence of second local recurrence (95% CI) after salvage surgery was 36% (24%-48%); 39% (26%-52%) for patients treated with surgery alone and 15% (0.46%-51%) for patients treated with reirradiation followed by surgery. Factors associated with increased second local recurrence after salvage surgery included a locoregional recurrence, lymphovascular space invasion and positive surgical margins. The 3-year overall survival (95% CI) after salvage surgery was 70% (59%-83%); 68% (7%-56%) after surgery alone and 89% (10.5%-70.6%) after reirradiation followed by surgery. Factors associated with worse overall survival included male sex, a larger recurrent tumor and positive surgical margins.

CONCLUSIONS

Approximately 60% of patients achieved pelvic control after salvage therapy for recurrent or persistent anal squamous cell carcinoma. Although receipt of reirradiation and intraoperative radiation were not associated with improved second local recurrence or overall survival in our cohort, patients with positive surgical margins and lymphovascular space invasion on surgical pathology had higher rates of pelvic recurrence after salvage surgery and may benefit from escalated salvage therapy.

Lung surveillance following colorectal cancer pulmonary metastasectomy: Utilization of clinicopathologic risk factors to guide strategy

BACKGROUND

Appropriately selected patients clearly benefit from resection of colorectal cancer (CRC) pulmonary metastases (PMs). However, there remains equipoise surrounding optimal chest surveillance strategies following pulmonary metastasectomy. We aimed to identify risk factors that may inform chest surveillance in this population.

METHODS

Patients who underwent CRC pulmonary metastasectomy were identified from a single institution's prospectively maintained surgical database. Clinicopathologic and genomic characteristics were collected. Patients were stratified by diagnosis of subsequent PM within 6 months of the index lung resection. Multivariate modeling was used to evaluate risk factors.

RESULTS

A total of 197 patients met the study's inclusion criteria, of whom 52.3% (n = 103) developed subsequent PM, at a median of 9.51 months following the index metastasectomy. Patients with KRAS alterations (odds ratio [OR], 3.073; 95% confidence interval [CI], 1.363-6.926; P = .007), TP53 alterations (OR, 3.109; 95% CI, 1.318-7.341; P = .010) were found to be at risk of PM diagnosis within 6 months of the index metastasectomy, while those with an APC alteration (OR, .218; 95% CI, 0.080-0.598; P = .003) were protected. Moreover, patients who received systemic therapy within 3 months of the initial PM diagnosis also were more likely to develop early lung recurrence (OR, 2.105; 95% CI, 0.971-4.563; P = .059).

CONCLUSIONS

Patients with KRAS alterations, TP53 alterations, and no APC alterations developed early recurrence in the lung following pulmonary metastasectomy, as did those who received chemotherapy after their initial PM diagnosis. As such, these groups benefit from early lung imaging after metastasectomy, as chest surveillance protocols should be based on patient-centered clinicopathologic and genomic risk factors.

Do resected colorectal cancer patients need early chest imaging? Impact of clinicopathologic characteristics on time to development of pulmonary metastases

BACKGROUND AND OBJECTIVES

For patients with colorectal cancer (CRC), the lung is the most common extra-abdominal site of distant metastasis. However, practices for chest imaging after colorectal resection vary widely. We aimed to identify characteristics that may indicate a need for early follow-up imaging.

METHODS

We retrospectively reviewed charts of patients who underwent CRC resection, collecting clinicopathologic details and oncologic outcomes. Patients were grouped by timing of pulmonary metastases (PM) development. Analyses were performed to investigate odds ratio (OR) of PM diagnosis within 3 months of CRC resection.

RESULTS

Of 1600 patients with resected CRC, 233 (14.6%) developed PM, at a median of 15.4 months following CRC resection. Univariable analyses revealed age, receipt of systemic therapy, lymph node ratio (LNR), lymphovascular and perineural invasion, and KRAS mutation as risk factors for PM. Furthermore, multivariable regression showed neoadjuvant therapy (OR: 2.99, p < 0.001), adjuvant therapy (OR: 6.28, p < 0.001), LNR (OR: 28.91, p < 0.001), and KRAS alteration (OR: 5.19, p < 0.001) to predict PM within 3 months post-resection.

CONCLUSIONS

We identified clinicopathologic characteristics that predict development of PM within 3 months after primary CRC resection. Early surveillance in such patients should be emphasized to ensure timely identification and treatment of PM.

Association of Emotional Exhaustion With Career Burnout Among Early-Career Medical Oncologists: A Single-Institution Study

PURPOSE

Burnout is a psychological occupational syndrome defined by the Maslach Burnout Inventory (MBI) as emotional exhaustion, depersonalization, and a low sense of personal accomplishment. We sought to characterize the prevalence of burnout among early-career medical oncologists at The University of Texas MD Anderson Cancer Center (MDACC).

METHODS

For this institutional review board-approved study, an electronic survey was developed for Assistant Professors in the MDACC Division of Cancer Medicine. All participants were involved directly in patient care. Our survey included questions assessing self-reported burnout, nine questions validated in the abbreviated MBI, and 31 questions to assess potential contributors to burnout. Each question was scaled 1-5, with higher scores associated with higher burnout. Descriptive statistics were used to estimate the prevalence of burnout, and logistic regression analyses were performed to identify contributing factors.

RESULTS

Among 86 Assistant Professors, 56 (65%) responded to the survey. The mean duration on faculty was 3.1 years. The mean clinical effort was 67% (range, 19-95). Fifty-four percent of respondents self-reported symptoms of burnout including 21% indicating severe burnout. Using the MBI, sentiments of being emotionally drained (54%), fatigued facing another day on the job (45%), and becoming more callous (30%) were especially notable. Twenty-five percent of respondents exhibited severe emotional exhaustion, which was more prevalent (P < .0001) than depersonalization (6%) or lack of personal accomplishment (17%).

CONCLUSION

Burnout exists with high prevalence among early-career medical oncologists, with emotional exhaustion being the most common manifestation of burnout. Interventions focusing on reducing emotional exhaustion are needed to reduce burnout among early-career medical oncologists.

Endoscopic and imaging outcomes of PD-1 therapy in localised dMMR colorectal cancer

BACKGROUND

Neoadjuvant immune checkpoint blockade (IO) is emerging as a therapeutic option for patients with deficient mismatch repair (dMMR) colorectal cancer (CRC) given high pathological response rates. The aim of the study was to characterise imaging and endoscopic response to IO.

METHODS

A retrospective analysis of patients with localised dMMR CRC that received at least one cycle of neoadjuvant anti-PD-1 therapy was conducted. Endoscopy, imaging, and pathological outcomes were reviewed to determine response to treatment according to standardised criteria.

RESULTS

Thirty-eight patients had received IO for the treatment of localised CRC (median eight cycles). Among evaluable cases (n = 31 for endoscopy and n = 34 for imaging), the best endoscopic response was complete response (CR) in 45% of cases, and the best radiographic response was CR in 23% of cases. Imaging CR rate after ≤4 cycles of IO (n = 1) was 6% compared to 44% after >4 IO cycles (n = 7). Among 28 patients with imaging and endoscopy available, a discrepancy in best response was noted in 15 (54%) cases. At a median follow-up of 28.2 months from IO start, 18 patients underwent surgical resection of which 11 (61%) had pathological CR (pCR). Despite pCR or no evidence of progression ≥6 months after completion of IO among non-operatively managed patients, 72% and 42% of patients had non-CR on imaging and endoscopy, respectively.

CONCLUSIONS

Discrepancies between imaging and endoscopy are prevalent, and irregularities identified on these modalities can be identified despite pathological remission. Improved clinical response criteria are warranted.

Salvage Abdominoperineal Resection for Locally Recurrent or Persistent Anal Squamous Cell Carcinoma after Definitive Chemoradiation

PURPOSE/OBJECTIVE(S)

Initial treatment for patients with squamous cell carcinoma of the anal canal includes definitive chemoradiation. Salvage abdominoperineal resection (APR) is the treatment of choice for recurrent or persistent disease. Older studies suggest approximately 50% successful salvage of recurrent or persistent disease with APR. Risk factors for failure after salvage APR are incompletely characterized.

MATERIALS/METHODS

Using a single institutional database, patients were identified who underwent salvage APR after definitive intensity-modulated radiotherapy-based chemoradiation between 2003 and 2022. Clinical and pathologic variables analyzed included age at APR, sex, race, HIV status, initial cT stage, initial cN stage, radiation dose, recurrent vs persistent disease, recurrent pT stage, recurrent pN stage, the presence of LVSI, PNI or <2mm surgical margins, and the use of either intraoperative radiation or another treatment modality in addition to APR. The log rank test was used to determine differences in time from APR to events (local recurrence, distant metastasis and death) based on clinical and pathologic variables. The Cox Proportional Hazard Model was used to perform multivariable analysis for all factors with a univariate P-value <0.1.

RESULTS

Of 628 patients with anal squamous cell carcinoma, 50 (8.0%) were treated with abdominoperineal resection for locally recurrent (n = 29, 58%) or locally persistent (n = 21, 42%) disease. Median [interquartile range] follow up was 40.0 months [15.2-68.0 months] from APR. Median local recurrence-free survival was not reached; 1- and 2-year local recurrence-free survival was 81% (95% CI 72-92%) and 76% (64-89%). On multivariable analysis, pathologic T-stage of the recurrence (3.85 (1.07-13.9); P = .040), the presence of lymphovascular space invasion (9.1 (1.12-73.62); P = .038) and surgical margins <2mm (8.81 (2.11-36.73); P = .003) were all significantly associated with higher rates of local recurrence. Median distant metastasis-free survival was not reached; 1- and 2-year distant metastasis-free survival was 88% (81-98%) and 79% (67-92%). On multivariable analysis, only persistent (versus recurrent) local disease was significantly associated with higher rates of distant metastasis (1.23 (1.05-5.55) P = .043). Median overall survival was not reached; 1- and 2-year overall survival was 90% (81-98%) and 78% (65-90%). On multivariable analysis, only recurrent pT stage (T3/4 vs T1/2) was associated with higher rates of death (5.87 (1.02-33.65); P = .047).

CONCLUSION

APR is a successful salvage modality for anal squamous cell carcinoma with recurrent or persistent disease after chemoradiation results. Patients with pT3/4 disease, lymphovascular space invasion, surgical margins <2 mm may be associated with higher re-recurrence rates and may benefit from more frequent monitoring or treatment escalation.

Sexual Orientation and Gender Identity (SOGI) Data Collection: Opportunities to Advance Best Clinical Practices for LGBTQ+ Patients in Radiation Oncology

PURPOSE/OBJECTIVE(S)

A long-standing barrier to progress against health disparities is the lack of data regarding cancer risks, prevalence, treatment, and outcomes for sexual and gender minority (SGM) patients. Sexual orientation and gender identity (SOGI) data are not routinely collected by individual oncologists, cancer centers, or most non-federal hospital systems. Alarmingly high proportions of SGM patients report discrimination in healthcare or avoid routine care due to perceived lack of acceptance in the healthcare system. For these and other reasons, healthcare institutions must adopt practices that promote an inclusive environment for all patients including those self-identified from SGM groups. One strategy to achieve this aim is through SOGI data collection. The purpose of this study was to pilot new procedures and training for SOGI data collection, the aims of this project were to standardize the collection of SOGI data for all new patients referred to the Division of Radiation Oncology; promote clinical staff awareness of SGM health disparities and strategies for fostering an inclusive hospital environment; and to provide SGM patients and caregivers educational resources and support systems tailored to their needs.

MATERIALS/METHODS

We designed a Quality Improvement program for collecting SOGI data, which was approved by our institution's QIAB. Patient access specialists (PAS) were trained to collect SOGI data from newly registered patients and enter the data into the electronic health record. Radiation Oncology staff completed surveys before and after SOGI training to estimate its impact on the provision of patient care. A Fisher's exact test was utilized to evaluate associations between training and provider-reported outcomes.

RESULTS

Within a 3-week period starting in January 2023, two 1-hour interactive training sessions were offered to twenty-five PAS. Three 1-hour training sessions were offered to twenty-seven Radiation Oncology clinical staff. (1) Confidence for incorporating SOGI classifiers around patients improved from before training (52%, 13/25) to after training (100%, 17/17) among medical providers surveyed (odds ratio (OR) 32, 95% confidence interval (CI) 0.70-1493, p = 0.005). Use of SOGI data in clinical decision making increased from before training (9/25, 36%) to after training (100%, 17/17) among medical providers (OR 60.79, 95% CI 3.271-1130, p<0.0001). (2) A clinical pathway for SGM patients was developed to facilitate referral to our institution's SGM patient support group and distribution of patient education materials focused on sexual health.

CONCLUSION

Establishing standardized SOGI data collection can facilitate the provision of tailored resources and care that meets the needs of patients and staff in a large comprehensive cancer center. Specialized training for staff developed through this initiative helps foster an inclusive and welcoming environment that promotes the integration, visibility, and advancement of SGM cancer care at our institution.

Outcomes and after Hyperfractionated, Accelerated Reirradiation for Recurrent Anal Squamous Cell Carcinoma

PURPOSE/OBJECTIVE(S)

Abdominoperineal resection (APR) is the standard salvage treatment for recurrent or persistent squamous cell carcinoma of the anus (SCCA). However, reirradiation (reRT) can be used preoperatively or for those who are not candidates for surgery.

MATERIALS/METHODS

Using a single institutional database, patients were identified who underwent reRT for SCCA from 2003 to 2022. Response to reRT and outcomes after reRT were recorded. Variables analyzed included age at reRT, sex, reason for reRT (recurrent SCCA vs new SCCA after pelvic radiation for a different malignancy), interval between initial radiation and reRT, reRT dose, concurrent chemotherapy, receipt of APR and the presence of distant metastases at the time of reRT. Cox Proportional Hazard Model was used; multivariable analysis for all factors with a univariate P-value <0.1 on univariable analysis.

RESULTS

A total of 42 patients received reRT, which consisted of 1.5 Gray (Gy) twice daily fractions with ≥6-hour interval to a total dose ranging 30Gy to 54Gy (median [IQR] 39Gy [39-42Gy]. Thirty-eight patients (90.5%) received concurrent chemotherapy; most often with weekly cisplatin and 5-fluorouracil (N = 23, 54.8%). Median [IQR] follow-up after reRT was 11.4 months [4.9-40.8 months]. Median [IQR] initial radiation dose was 54Gy [54-58Gy], and median [IQR] interval between initial radiation and reRT was 3.6 years [2.1-6.0 years]. For 8 patients (19.1%), the initial radiation was given for a different pelvic malignancy prior to being diagnosed with SCCA. Four of these patients received brachytherapy alone or in conjunction with external beam. For the remaining 34 patients, the initial radiation was for SCCA and the reRT was for recurrent SCCA either in the anal canal (N = 23, 67.6%) or regional nodes (N = 11, 32.3%). Four patients (9.5%) had distant disease at the time of reRT. Eleven patients (26.2%) had planned APR after preoperative reRT; 1 patient had a pathologic complete response (pCR), 2 patients had a near pCR (<5% viable cancer). Twenty-nine patients (69.0%) were treated with reRT alone; 15 (51.7%) attained a clinical CR. Two patients (4.8%) were treated with palliative intent and response was not assessed. Median local recurrence free survival (LRFS) was 9.9 months; 2- and 3-year LRFS were both 41%. Median distant metastasis free survival (DMFS) was 11.8 months; 2- and 3-year DMFS were 38% and 34%, respectively. Median overall survival (OS) was 40.5 months; 2- and 3-year OS were 54% and 51%, respectively. On multivariable analysis, only the presence of distant disease at the time of reRT was significantly associated with worse LRFS (HR (95% CI) 4.14 (1.34-12.81); P = .014), worse DMFS (4.06 (1.37-12.06); P = .012) and worse OS (5.73 (1.57-20.9); P = .008).

CONCLUSION

ReRT is an option for patients presenting with either recurrent SCCA or new SCCA after prior pelvic radiation for a different malignancy. ReRT can be given prior to planned salvage APR or alone for patients who are not surgical candidates with an approximate 50% cCR rate.

Factors associated with receipt of pulmonary metastasectomy in patients with lung-limited metastatic colorectal cancer: Disparities in care and impact on overall survival

OBJECTIVES

Pulmonary metastasectomy (PM) for colorectal cancer may provide respite from systemic therapy and prolonged disease-free intervals. We sought to identify factors associated with PM and to characterize the differential impact on overall survival for those offered lung resection.

METHODS

The National Cancer Database was queried for stage IV colorectal cancer patients with lung-limited metastatic disease between 2010 and 2016. Among patients who underwent primary tumor resection, those who underwent PM were compared with those who did not. Penalized regression with the least absolute selection and shrinkage operator was used to determine factors associated with receiving metastasectomy as well as overall survival.

RESULTS

In total, 867 (15.1%) patients underwent resection of both primary tumor and pulmonary metastases whereas 4864 (84.8%) had primary tumor resection alone. In unadjusted analyses, metastasectomy patents were younger, more often privately insured, more educated, and traveled farther to receive care (all P < .001). In multivariable analyses, younger age, traveling >25 miles, and care at high-volume hospitals were associated with PM (P < .01). In addition, primary site surgery without PM was associated with worse overall survival (hazard ratio, 1.35; confidence interval, 1.23-1.49), even after adjusting for patient, tumor, and hospital-related factors.

CONCLUSIONS

Patients who were older, who received care closer to home, and who were treated at low-volume hospitals were less likely to receive metastasectomy for lung-limited colorectal cancer after definitive resection of their primary tumor. Failure to receive PM resulted in worse overall survival, emphasizing the strong need for efforts to provide uniform, equitable care to all patients.

Novel Clinical Tool to Estimate Risk of False-Negative KRAS Mutations in Circulating Tumor DNA Testing

PURPOSE

In metastatic colorectal cancer, the detection of RAS mutations by circulating tumor DNA (ctDNA) has emerged as a valid and noninvasive alternative approach to determining RAS status. However, some RAS mutations may be missed, that is, false negatives can occur, possibly compromising important treatment decisions. We propose a statistical model to assess the probability of false negatives when performing ctDNA testing for RAS.

METHODS

Cohorts of 172 subjects with tissue and multipanel ctDNA testing from MD Anderson Cancer Center and 146 subjects from Massachusetts General Hospital were collected. We developed a Bayesian model that uses observed frequencies of reference mutations (the maximum of APC and TP53) to provide information about the probability of KRAS false negatives. The model was alternatively trained on one cohort and tested on the other. All data were collected on Guardant assays.

RESULTS

The model suggests that negative KRAS findings are believable when the maximum of APC and TP53 frequencies is at least 8% (corresponding posterior probability of false negative <5%). Validation studies demonstrated the ability of our tool to discriminate between false-negative and true-negative subjects. Simulations further confirmed the utility of the proposed approach.

CONCLUSION

We suggest clinicians use the tool to more precisely quantify KRAS false-negative ctDNA results when at least one of the reference mutations (APC, TP53) is observed; usage may be especially important for subjects with a maximum reference frequency of <8%. Extension of the methodology to predict false negatives of other genes is possible. Additional reference genes can also be considered. Use of personal training data sets is supported. An open-source R Shiny application is available for public use.

A phase I trial of the pan-ERBB inhibitor neratinib combined with the MEK inhibitor trametinib in patients with advanced cancer with EGFR mutation/amplification, HER2 mutation/amplification, HER3/4 mutation or KRAS mutation

PURPOSE

Aberrant alterations of ERBB receptor tyrosine kinases lead to tumorigenesis. Single agent therapy targeting EGFR or HER2 has shown clinical successes, but drug resistance often develops due to aberrant or compensatory mechanisms. Herein, we sought to determine the feasibility and safety of neratinib and trametinib in patients with EGFR mutation/amplification, HER2 mutation/amplification, HER3/4 mutation and KRAS mutation.

METHODS

Patients with actionable somatic mutations or amplifications in ERBB genes or actionable KRAS mutations were enrolled to receive neratinib and trametinib in this phase I dose escalation trial. The primary endpoint was determination of the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT). Secondary endpoints included pharmacokinetic analysis and preliminary anti-tumor efficacy.

RESULTS

Twenty patients were enrolled with a median age of 50.5 years and a median of 3 lines of prior therapy. Grade 3 treatment-related toxicities included: diarrhea (25%), vomiting (10%), nausea (5%), fatigue (5%) and malaise (5%). The MTD was dose level (DL) minus 1 (neratinib 160 mg daily with trametinib 1 mg, 5 days on and 2 days off) given 2 DLTs of grade 3 diarrhea in DL1 (neratinib 160 mg daily with trametinib 1 mg daily). The treatment-related toxicities of DL1 included: diarrhea (100%), nausea (55.6%) and rash (55.6%). Pharmacokinetic data showed trametinib clearance was significantly reduced leading to high drug exposures of trametinib. Two patients achieved stable disease (SD) ≥ 4 months.

CONCLUSION

Neratinib and trametinib combination was toxic and had limited clinical efficacy. This may be due to suboptimal drug dosing given drug-drug interactions.

TRIAL REGISTRATION ID

NCT03065387.

Hepatic Metastasectomy in Squamous Cell Carcinoma of the Anal Canal: A Case Series of a Curative Approach

BACKGROUND

Squamous cell carcinoma of the anal canal (SCCA) is rare. Most cases are diagnosed in a localized setting. Metastatic SCCA is rare, and investigation has been limited in the past for these patients. We believe that hepatic-only metastatic disease could have a unique treatment landscape compared to diseases with diffuse metastatic involvement. Here, we describe cases at our institution.

METHODS

We reviewed eight SCCA cases with hepatic-only metastatic disease (diagnosed February 2018-January 2022). The objectives were to determine the overall survival and disease-free survival with this approach.

RESULTS

The median age was 62 years old (yo). Patients had an ECOG of 0-1. All patients received definitive chemoradiation to their primary anal tumor. A median of three months of neoadjuvant systemic therapy was provided. All patients had a response on their first scan after systemic therapy. Sixty-two percent received carboplatin + paclitaxel. A complete pathologic response was seen in 62% of patients. At their last follow-up, all patients were alive. Three patients had recurrent disease. The estimated 1-year disease-free survival probability was 56.2%.

CONCLUSION

Our report shows the feasibility of a curative-intent approach for patients with hepatic-only metastatic SCCA following the neoadjuvant application of carboplatin + paclitaxel. This approach appears promising in these select patients and warrants further investigation.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of gastrointestinal cancer

Gastrointestinal (GI) cancers, including esophageal, gastroesophageal junction, gastric, duodenal and distal small bowel, biliary tract, pancreatic, colon, rectal, and anal cancer, comprise a heterogeneous group of malignancies that impose a significant global burden. Immunotherapy has transformed the treatment landscape for several GI cancers, offering some patients durable responses and prolonged survival. Specifically, immune checkpoint inhibitors (ICIs) directed against programmed cell death protein 1 (PD-1), either as monotherapies or in combination regimens, have gained tissue site-specific regulatory approvals for the treatment of metastatic disease and in the resectable setting. Indications for ICIs in GI cancer, however, have differing biomarker and histology requirements depending on the anatomic site of origin. Furthermore, ICIs are associated with unique toxicity profiles compared with other systemic treatments that have long been the mainstay for GI cancer, such as chemotherapy. With the goal of improving patient care by providing guidance to the oncology community, the Society for Immunotherapy of Cancer (SITC) convened a panel of experts to develop this clinical practice guideline on immunotherapy for the treatment of GI cancer. Drawing from published data and clinical experience, the expert panel developed evidence- and consensus-based recommendations for healthcare professionals using ICIs to treat GI cancers, with topics including biomarker testing, therapy selection, and patient education and quality of life considerations, among others.

Prognostic and Predictive Markers for Patients With Anal Cancer

Squamous cell carcinoma of the anus and anal canal is a rare malignancy with an increasing incidence in the United States. In the past 2 decades, the proportion of Americans diagnosed with incurable, metastatic anal cancer at the time of initial presentation has increased. Most cases are linked to prior infection with HPV. Although concurrent chemoradiotherapy has been the accepted standard treatment for patients with localized anal cancer over the past half century, therapeutic advances have increased options for patients with unresectable or incurable anal cancer over the past 5 years. Specifically, combination chemotherapy and immunotherapy with anti-PD-(L)1 antibodies has demonstrated efficacy in this setting. Greater understanding of molecular drivers of this viral-associated malignancy has provided critical insight into evolving biomarkers for the clinical management of anal cancer. The pervasiveness of HPV across cases of anal cancer has been leveraged for the development of HPV-specific circulating tumor DNA assays as a sensitive biomarker for prognosticating recurrence in patients with localized anal cancer who complete chemoradiation. For patients with metastatic disease, somatic mutations, well-characterized for anal cancer, have not shown utility in identifying patients who benefit from systemic treatments. Although the overall response rate to immune checkpoint blockade therapies is low for metastatic anal cancer, high immune activation within the tumor and PD-L1 expression may identify patients more likely to experience response. These biomarkers should be incorporated into the design of future clinical trials to personalize further treatment approaches in the evolving management of anal cancer.

Oxidation of caspase-8 by hypothiocyanous acid enables TNF-mediated necroptosis

Necroptosis is a form of regulated cell death triggered by various host and pathogen-derived molecules during infection and inflammation. The essential step leading to necroptosis is phosphorylation of the mixed lineage kinase domain-like protein (MLKL) by receptor-interacting protein kinase 3 (RIPK3). Caspase 8 cleaves RIPKs to block necroptosis, so synthetic caspase inhibitors are required to study this process in experimental models. However, it is unclear how caspase-8 activity is regulated in a physiological setting. The active site cysteine of caspases is sensitive to oxidative inactivation, so we hypothesized that oxidants generated at sites of inflammation can inhibit caspase-8 and promote necroptosis. Here, we discovered that hypothiocyanous acid (HOSCN), an oxidant generated in vivo by heme peroxidases including myeloperoxidase and lactoperoxidase, is a potent caspase-8 inhibitor. We found HOSCN was able to promote necroptosis in mouse fibroblasts treated with tumor necrosis factor (TNF). We also demonstrate purified caspase-8 was inactivated by low concentrations of HOSCN, with the predominant product being a disulfide-linked dimer between Cys360 and Cys409 of the large and small catalytic subunits. We show oxidation still occurred in the presence of reducing agents, and reduction of the dimer was slow, consistent with HOSCN being a powerful physiological caspase inhibitor. While the initial oxidation product is a dimer, further modification also occurred in cells treated with HOSCN, leading to higher molecular weight caspase-8 species. Taken together, these findings indicate major disruption of caspase-8 function, and suggest a novel mechanism for the promotion of necroptosis at sites of inflammation.

Prospective Study of Perioperative Circulating Tumor DNA Dynamics in Patients Undergoing Hepatectomy for Colorectal Liver Metastases

OBJECTIVE

To evaluate the association of perioperative ctDNA dynamics on outcomes after hepatectomy for CLM.

SUMMARY BACKGROUND DATA

Prognostication is imprecise for patients undergoing hepatectomy for CLM, and ctDNA is a promising biomarker. However, clinical implications of perioperative ctDNA dynamics are not well established.

METHODS

Patients underwent curative-intent hepatectomy after preoperative chemotherapy for CLM (2013-2017) with paired prehepatectomy/postoperative ctDNA analyses via plasma-only assay. Positivity was determined using a proprietary variant classifier. Primary endpoint was recurrence-free survival (RFS). Median follow-up was 55 months.

RESULTS

Forty-eight patients were included. ctDNA was detected before and after surgery (ctDNA+/+) in 14 (29%), before but not after surgery (ctDNA+/-) in 19 (40%), and not at all (ctDNA-/-) in 11 (23%). Adverse tissue somatic mutations were detected in TP53 (n = 26; 54%), RAS (n = 23; 48%), SMAD4 (n = 5; 10%), FBXW7 (n = 3; 6%), and BRAF (n = 2; 4%). ctDNA+/+ was associated with worse RFS (median: ctDNA+/+, 6.0 months; ctDNA+/-, not reached; ctDNA-/-, 33.0 months; P = 0.001). Compared to ctDNA+/+, ctDNA+/- was associated with improved RFS [hazard ratio (HR) 0.24 (95% confidence interval (CI) 0.1-0.58)] and overall survival [HR 0.24 (95% CI 0.08-0.74)]. Adverse somatic mutations were not associated with survival. After adjustment for prehepatectomy chemotherapy, synchronous disease, and ≥2 CLM, ctDNA+/- and ctDNA-/- were independently associated with improved RFS compared to ctDNA+/+ (ctDNA+/-: HR 0.21, 95% CI 0.08-0.53; ctDNA-/-: HR 0.21, 95% CI 0.08-0.56).

CONCLUSIONS

Perioperative ctDNA dynamics are associated with survival, identify patients with high recurrence risk, and may be used to guide treatment decisions and surveillance after hepatectomy for patients with CLM.

Phase II Trial of MEDI0457 and Durvalumab for Patients With Recurrent/Metastatic Human Papillomavirus-Associated Cancers

BACKGROUND

Human papillomavirus (HPV) types 16/18 drive oncogenesis for most patients with cervical, anal, and penile cancers. MEDI0457, a therapeutic DNA vaccine containing plasmids for E6 and E7 HPV-16/18 viral oncogenes and IL-12 adjuvant, is safe and provokes an immune response against E6/E7. We tested MEDI0457 with the anti-PD-L1 antibody durvalumab for patients with HPV-associated cancers.

METHODS

Patients with recurrent/metastatic, treatment-refractory HPV-16/18 cervical cancer, or rare HPV-associated (anal and penile) cancers were eligible. Prior immune checkpoint inhibition was not permitted. Patients received MEDI0457 7 mg intramuscularly (weeks 1, 3, 7, 12, and every 8 weeks thereafter) and durvalumab 1500 mg intravenously every 4 weeks. The primary endpoint was overall response (RECIST 1.1). In this Simon two-stage phase 2 trial (Ho: p < 0.15; Ha: p ≥ 0.35), ≥2 responses were needed in both cervical and non-cervical cohorts during the first stage for the trial to proceed to stage 2 with an additional 25 patients (34 total) enrolled.

RESULTS

Twenty-one patients (12 cervical, 7 anal, and 2 penile) were evaluable for toxicity and 19 for response Overall response rate was 21% (95% CI, 6%-46%) among evaluable patients. Disease control rate was 37% (95% CI, 16%-62%). Median duration of response among responders was 21.8 months (95% CI, 9.7%-not estimable). Median progression-free survival was 4.6 months (95% CI, 2.8%-7.2%). Median overall survival was 17.7 months (95% CI, 7.6%-not estimable). Grades 3-4 treatment-related adverse events occurred in 6 (23%) participants.

CONCLUSIONS

The combination of MEDI0457 and durvalumab demonstrated acceptable safety and tolerability in patients with advanced HPV-16/18 cancers. The low ORR among patients with cervical cancer led to study discontinuation despite a clinically meaningful disease control rate.

HPV-related anal cancer is associated with changes in the anorectal microbiome during cancer development

Background

Squamous cell carcinoma of the anus (SCCA) is a rare gastrointestinal cancer. Factors associated with progression of HPV infection to anal dysplasia and cancer are unclear and screening guidelines and approaches for anal dysplasia are less clear than for cervical dysplasia. One potential contributing factor is the anorectal microbiome. In this study, we aimed to identify differences in anal microbiome composition in the settings of HPV infection, anal dysplasia, and anal cancer in this rare disease.

Methods

Patients were enrolled in two prospective studies. Patients with anal dysplasia were part of a cross-sectional cohort that enrolled women with high-grade lower genital tract dysplasia. Anorectal tumor swabs were prospectively collected from patients with biopsy-confirmed locally advanced SCCA prior to receiving standard-of-care chemoradiotherapy (CRT). Patients with high-grade lower genital tract dysplasia without anal dysplasia were considered high-risk (HR Normal). 16S V4 rRNA Microbiome sequencing was performed for anal swabs. Alpha and Beta Diversity and composition were compared for HR Normal, anal dysplasia, and anal cancer.

Results

60 patients with high-grade lower genital tract dysplasia were initially enrolled. Seven patients had concurrent anal dysplasia and 44 patients were considered HR Normal. Anorectal swabs from 21 patients with localized SCCA were included, sequenced, and analyzed in the study. Analysis of weighted and unweighted UniFrac distances demonstrated significant differences in microbial community composition between anal cancer and HR normal (p=0.018). LEfSe identified that all three groups exhibited differential enrichment of specific taxa. Peptoniphilus (p=0.028), Fusobacteria (p=0.0295), Porphyromonas (p=0.034), and Prevotella (p=0.029) were enriched in anal cancer specimens when compared to HR normal.

Conclusion

Although alpha diversity was similar between HR Normal, dysplasia and cancer patients, composition differed significantly between the three groups. Increased anorectal Peptoniphilus, Fusobacteria, Porphyromonas, and Prevotella abundance were associated with anal cancer. These organisms have been reported in various gastrointestinal cancers with roles in facilitating the proinflammatory microenvironment and neoplasia progression. Future work should investigate a potential role of microbiome analysis in screening for anal dysplasia and investigation into potential mechanisms of how these microbial imbalances influence the immune system and anal carcinogenesis.

Differential Spatial Gene and Protein Expression Associated with Recurrence Following Chemoradiation for Localized Anal Squamous Cell Cancer

The identification of transcriptomic and protein biomarkers prognosticating recurrence risk after chemoradiation of localized squamous cell carcinoma of the anus (SCCA) has been limited by a lack of available fresh tissue at initial presentation. We analyzed archival FFPE SCCA specimens from pretreatment biopsies prior to chemoradiation for protein and RNA biomarkers from patients with localized SCCA who recurred (N = 23) and who did not recur (N = 25). Tumor cells and the tumor microenvironment (TME) were analyzed separately to identify biomarkers with significantly different expression between the recurrent and non-recurrent groups. Recurrent patients had higher mean protein expression of FoxP3, MAPK-activation markers (BRAF, p38-MAPK) and PI3K/Akt activation (phospho-Akt) within the tumor regions. The TME was characterized by the higher protein expression of immune checkpoint biomarkers such as PD-1, OX40L and LAG3. For patients with recurrent SCCA, the higher mean protein expression of fibronectin was observed in the tumor and TME compartments. No significant differences in RNA expression were observed. The higher baseline expression of immune checkpoint biomarkers, together with markers of MAPK and PI3K/Akt signaling, are associated with recurrence following chemoradiation for patients with localized SCCA. These data provide a rationale towards the application of immune-based therapeutic strategies to improve curative-intent outcomes beyond conventional therapies for patients with SCCA.

Patient-reported Bowel Function and Bowel-related Quality of Life After Pelvic Radiation for Rectal Adenocarcinoma: The Impact of Radiation Fractionation and Surgical Resection

INTRODUCTION

Multimodality treatment for locally advanced rectal cancer (LARC) can include long-course radiotherapy (LCRT) or short course radiotherapy (SCRT). Nonoperative management is increasingly pursued for those achieving a complete clinical response. Data regarding long-term function and quality-of-life (QOL) are limited.

METHODS

Patients with LARC treated with radiotherapy from 2016 to 2020 completed the Functional Assessment of Cancer Therapy- General (FACT-G7), the Low Anterior Resection Syndrome Score (LARS) and the Fecal Incontinence QOL Scale (FIQOL). Univariate and multivariable linear regression analyses identified associations between clinical variables including radiation fractionation and the use of surgery versus non-operative management.

RESULTS

Of 204 patients surveyed, 124 (60.8%) responded. Median (interquartile range) time from radiation to survey completion was 30.1 (18.3-43) months. Seventy-nine (63.7%) respondents received LCRT, and 45 (36.3%) received SCRT; 101 (81.5%) respondents underwent surgery, and 23 (18.5%) pursued nonoperative management. There were no differences in LARS, FIQoL or FACT-G7 between patients receiving LCRT versus SCRT. On multivariable analysis, only nonoperative management was associated with lower LARS score signifying less bowel dysfunction. Nonoperative management and female sex were associated with a higher FIQoL score signifying less disruption and distress from fecal incontinence issues. Finally, lower BMI at the time of radiation, female sex, and higher FIQoL score were associated with higher FACT-G7 scores signifying better overall QOL.

CONCLUSIONS

These results suggest long-term patient-reported bowel function and QOL may be similar for individuals receiving SCRT and LCRT for the treatment of LARC, but nonoperative management may lead to improved bowel function and QOL.

Survival improvement for patients with metastatic colorectal cancer over twenty years

Over the past two decades of successive clinical trials in metastatic colorectal cancer (CRC), the median overall survival of both control and experimental arms has steadily improved. However, the incremental change in survival for metastatic CRC patients not treated on trial has not yet been quantified. We performed a retrospective review of 1420 patients with de novo metastatic CRC who received their primary treatment at the University of Texas M.D. Anderson Cancer Center (UTMDACC) from 2004 through 2019. Median OS was roughly stable for patients diagnosed between 2004 and 2012 (22.6 months) but since has steadily improved for those diagnosed in 2013 to 2015 (28.8 months), and 2016 to 2019 (32.4 months). Likewise, 5-year survival rate has increased from 15.7% for patients diagnosed from 2004 to 2006 to 26% for those diagnosed from 2013 to 2015. Notably, survival improved for patients with BRAFV600E mutant as well as microsatellite unstable (MSI-H) tumors. Multivariate regression analysis identified surgical resection of liver metastasis (HR = 0.26, 95% CI, 0.19-0.37), use of immunotherapy (HR = 0.44, 95% CI, 0.29-0.67) and use of third line chemotherapy (regorafenib or trifluridine/tipiracil, HR = 0.74, 95% CI, 0.58-0.95), but not year of diagnosis (HR = 0.99, 95% CI, 0.98-1), as associated with better survival, suggesting that increased use of these therapies are the drivers of the observed improvement in survival.

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 .

ctDNA-based fusion detection for advanced colorectal cancer with a partner-agnostic assay

186

Background: Actionable mutations can predict therapeutic benefit in patients with advanced malignancies, though clinical relevance of fusion testing for advanced colorectal cancer (aCRC) remains undefined. Identification of fusions from circulating tumor DNA (ctDNA) has previously been restricted to defined oncogenic fusion partners. To improve the sensitivity for fusion detection, we evaluated a partner-agnostic fusion analysis from ctDNA of patients with aCRC. Methods: De-identified data from Guardant Health was reviewed for 18,558 patients with aCRC who underwent ctDNA NGS testing by Guardant360 (Redwood City, CA) between 2017-2022. Fusion results were analyzed with a partner-agnostic bioinformatic approach. A fusion was defined as “clonal” if the variant allele frequency (VAF) ratio exceed ≥50% of highest somatic VAF, and “subclonal” if < 50% maxVAF. Microsatellite instability (MSI) status [MSI-high (bMSI-H) or microsatellite stable (bMSS)] and anti-EGFR exposure signature were determined using prior methods. Associations between fusion occurrence and coexisting alterations were performed using Fisher’s exact test. Results: Fusions were detected in 221 (1.2%) of patients with aCRC. 258 activating fusions were detected in 187 patients; FGFR3 (N = 59, 23%), RET N = 55, 21%), BRAF (N = 43, 17%), and ALK (N = 41, 16%) were most frequent. There were 71 previously unreported fusions in 28 additional patients; RET (N = 16; 23%), MET (N = 15, 21%), and BRAF (N = 11; 15%) were most prevalent. Clonal fusions occurred in 7% (18/258) of all activating fusions; RET (5/18, 28%) and FGFR3 (3/18, 17%) were most common and associated with bMSI-H status relative to bMSS (27% vs 4%, OR 8.165, 95% CI 2.332-33.99; p = 0.0076). Clonal fusions occurred less commonly in samples with a prior EGFR signature (OR 0.22, 95% CI 0.05-0.997, p = 0.049). Most detected fusions were subclonal including ALK, FGFR1-3, MET, RET and ROS1. Conclusions: Highly specific partner-agnostic fusion detection is feasible to increase sensitivity of ctDNA assay performance. Oncogenic fusions occurred in ~1% of all patients with aCRC. Clonal fusions as oncogenic drivers were infrequent and associated with bMSI-H status. Subclonal fusions were more common and occur in a setting consistent with prior exposure to anti-EGFR therapies. Reporting fusion partners and clonality from ctDNA may guide oncologists on the appropriate context for consideration of fusion-directed treatments.

Randomized phase II trial of encorafenib and cetuximab with or without nivolumab for patients with previously treated, microsatellite stable, BRAFV600E metastatic and/or unresectable colorectal cancer: SWOG S2107

TPS265

Background: Patients with microsatellite stable (MSS), BRAFV600E metastatic colorectal cancer (mCRC) experience poor survival outcomes. Treatment with the BRAF inhibitor encorafenib (E) and anti-EGFR antibody cetuximab (C) is an approved treatment combination, with a reported overall response rate (ORR) of 20% and median progression-free survival (PFS) of 4.1 months. Anti-PD-1 antibodies like nivolumab (N) are ineffective as monotherapy for patients with MSS, BRAFV600E mCRC. In preclinical models of MSS, BRAFV600E CRC, inhibition of BRAF and EGFR induces a loss of expression of mismatch repair genes and promotes a microsatellite instability-high phenotype, which may prime these tumors for response to immunotherapy. In support of these findings, a single-institution clinical trial of E + C + N for 26 patients with MSS, BRAFV600E mCRC reported an ORR of 50% and median PFS of 7.2 months. We hypothesize that the addition of N to E + C will improve median PFS for patients with MSS, BRAFV600E mCRC. Methods: In this prospective phase II clinical trial (N = 75), patients with previously treated MSS, BRAFV600E mCRC will be randomized 2:1 into 2 arms, respectively: experimental treatment (E + C + N) or standard treatment (E + C). No prior BRAF, EGFR, or immunotherapy agents are allowed. All patients will receive E (300 mg PO daily) and C (500 mg/m2 IV every 14 days), and patients in the experimental arm will receive N (480 mg IV every 28 days). The primary endpoint is PFS. Secondary endpoints include overall survival, best overall response, duration of response, and safety/tolerability. Using a one-sided α = .10 and power 80%, we target an improvement in median PFS from 4.2 to 7.3 months and a hazard ratio of 0.57. Additional patient specimens will be collected for exploratory correlative research. The study activated across the United States in June 2022 and as of September 2022 has enrolled 2 of 75 planned participants. Funding: NIH/National Cancer Institute grants U10CA180888, U10CA180819, U10CA180820, U10CA180821, U10CA180868; and in part by The Hope Foundation for Cancer Research STrS award. Clinical trial information: NCT05308446 .

Survival benefit to immunotherapy according to site of organ involvement in metastatic anal cancer

3

Background: For patients with metastatic anal cancer, demonstration of anti-tumor activity by anti-PD-(L)1 antibodies has expanded the treatment landscape. To date, there are no predictive biomarkers associated with clinical benefit to immunotherapy in this setting. In the absence of clinical trials directly comparing chemotherapy and immunotherapy for metastatic anal cancer, the optimal sequencing of therapeutic lines remains undefined because historical series have been limited to cytotoxic chemotherapy. We evaluated the survival outcomes of patients with metastatic anal cancer following treatment with immunotherapy and with chemotherapy. Methods: We reviewed retrospectively the MD Anderson Cancer Center database for patients with unresectable and/or metastatic anal cancer diagnosed between 6/2014 and 11/2021. Median survival was estimated using the Kaplan-Meier method and compared between subpopulations of interest with a log-rank test. Results: Among 82 patients with metastatic anal cancer, 68 (83%) were female, and the median age was 60 years (range, 39-81). With a median follow-up time of 24.6 months, the median lines of systemic therapy were 2 (range, 1-5). 58 (71%) received anti-PD-(L)1 immunotherapy, either alone (N=51) or in combination with bevacizumab or with MEDI-0457 on a clinical trial (N=7). Median progression-free survival times (PFS) for lines 1, 2, and 3 of systemic therapy were 7.2 months (95% CI (Confidence Interval) 5.3-9.1; N=82), 3.6 months (95% CI 2.4-4.8; N=58), and 4.1 months (95% CI 2.8-5.4; N=34), respectively. In the treatment-refractory setting, no difference in median PFS between chemotherapy and immunotherapy was observed (4.7 months vs 2.9 months, respectively; hazard ratio (HR) 0.9, 95% CI 0.5-1.4); p=.17). Median overall survival (OS) was estimated at 33.9 months (95% CI, 24.0-34.8). For patients with metastatic anal cancer treated with immunotherapy, involvement of only distant lymph nodes (N=10/58, 17%) was associated with improved median PFS (11.3 months vs 2.8 months; HR 3.5, 95% CI 1.8-6.6; p=.002) and median OS (45.2 months vs 27.1 months; HR 2.9, 95% CI 1.3-6.5, p=.02) than other sites of distant organ involvement (N=48/58, 83%). Conclusions: In this single-institution retrospective study at a large academic referral center, both chemotherapy and immune checkpoint blockade were effective treatment options for patients with metastatic anal cancer. These data provide historical context in estimating median PFS necessary for future trial design in patients with metastatic anal cancer. Lymph node-only distribution of distant metastatic disease was predictive for improved survival with immunotherapy. Pending further validation, these data provide novel identification of a potential predictive factor associated with benefit to immunotherapy in patients with metastatic anal cancer.

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.

Resistance Mechanisms to Anti-Epidermal Growth Factor Receptor Therapy in RAS/RAF Wild-Type Colorectal Cancer Vary by Regimen and Line of Therapy

PURPOSE

Acquired resistance to anti-epidermal growth factor receptor (EGFR) inhibitor (EGFRi) therapy in colorectal cancer (CRC) has previously been explained by the model of acquiring new mutations in KRAS/NRAS/EGFR, among other MAPK-pathway members. However, this was primarily on the basis of single-agent EGFRi trials and little is known about the resistance mechanisms of EGFRi combined with effective cytotoxic chemotherapy in previously untreated patients.

METHODS

We analyzed paired plasma samples from patients with RAS/BRAF/EGFR wild-type metastatic CRC enrolled in three large randomized trials evaluating EGFRi in the first line in combination with chemotherapy and as a single agent in third line. The mutational signature of the alterations acquired with therapy was evaluated. CRC cell lines with resistance to cetuximab, infusional fluorouracil, leucovorin, and oxaliplatin, and SN38 were developed, and transcriptional changes profiled.

RESULTS

Patients whose tumors were treated with and responded to EGFRi alone were more likely to develop acquired mutations (46%) compared with those treated in combination with cytotoxic chemotherapy (9%). Furthermore, contrary to the generally accepted hypothesis of the clonal evolution of acquired resistance, we demonstrate that baseline resistant subclonal mutations rarely expanded to become clonal at progression, and most remained subclonal or disappeared. Consistent with this clinical finding, preclinical models with acquired resistance to either cetuximab or chemotherapy were cross-resistant to the alternate agents, with transcriptomic profiles consistent with epithelial-to-mesenchymal transition. By contrast, commonly acquired resistance alterations in the MAPK pathway do not affect sensitivity to cytotoxic chemotherapy.

CONCLUSION

These findings support a model of resistance whereby transcriptomic mechanisms of resistance predominate in the presence of active cytotoxic chemotherapy combined with EGFRi, with a greater predominance of acquired MAPK mutations after single-agent EGFRi. The proposed model has implications for prospective studies evaluating EGFRi rechallenge strategies guided by acquired MAPK mutations, and highlights the need to address transcriptional mechanisms of resistance.

Antibiotic Exposure Does Not Impact Immune Checkpoint Blockade Response in MSI-H/dMMR Metastatic Colorectal Cancer: A Single-Center Experience

BACKGROUND

Immune checkpoint blockade (ICB) has improved outcomes for patients with microsatellite instability high (MSI-H)/deficient mismatch repair (dMMR) tumors. However, not all MSI-H/dMMR patients will exhibit the same ICB efficacy. Previous studies suggest that concomitant antibiotic use while receiving ICB may result in poorer outcomes. We aimed to evaluate this association in patients with MSI-H/dMMR metastatic colorectal cancer (mCRC).

MATERIALS AND METHODS

A single-site, retrospective review of 57 patients with MSI-H/dMMR mCRC that received ICB was completed. Data collected included patient demographics, ICB information, and antibiotic use. Antibiotic exposure was considered from 90 days prior to ICB through 6 weeks after initiation. Primary endpoint was overall response rate (ORR).

RESULTS

The majority of patients received pembrolizumab (27 [47%]) or nivolumab (17 [30%]) monotherapy as their ICB agent. Of the 57 patients, 19 (33.3%) had antibiotic exposure from 90 days prior to ICB initiation through 6 weeks after initiation with most (13 [68%]) having antibiotic use in the 30 days preceding ICB initiation. Similar ORRs were seen in both groups (P-value > .99). No difference was observed in OS (P-value .29) or PFS (P-value .36) between groups.

CONCLUSION

Our data show no association of lower response rates or survival in those MSI-H/dMMR patients with mCRC who receive antibiotics around the initiation of ICB. This information needs to be confirmed in a larger prospective cohort.

Targeting RAS Mutant Colorectal Cancer with Dual Inhibition of MEK and CDK4/6

KRAS and NRAS mutations occur in 45% of colorectal cancers, with combined MAPK pathway and CDK4/6 inhibition identified as a potential therapeutic strategy. In the current study, this combinatorial treatment approach was evaluated in a co-clinical trial in patient-derived xenografts (PDX), and safety was established in a clinical trial of binimetinib and palbociclib in patients with metastatic colorectal cancer with RAS mutations. Across 18 PDX models undergoing dual inhibition of MEK and CDK4/6, 60% of tumors regressed, meeting the co-clinical trial primary endpoint. Prolonged duration of response occurred predominantly in TP53 wild-type models. Clinical evaluation of binimetinib and palbociclib in a safety lead-in confirmed safety and provided preliminary evidence of activity. Prolonged treatment in PDX models resulted in feedback activation of receptor tyrosine kinases and acquired resistance, which was reversed with a SHP2 inhibitor. These results highlight the clinical potential of this combination in colorectal cancer, along with the utility of PDX-based co-clinical trial platforms for drug development.

SIGNIFICANCE

This co-clinical trial of combined MEK-CDK4/6 inhibition in RAS mutant colorectal cancer demonstrates therapeutic efficacy in patient-derived xenografts and safety in patients, identifies biomarkers of response, and uncovers targetable mechanisms of resistance.

Bintrafusp alfa, an anti-PD-L1:TGF-β trap fusion protein, in patients with ctDNA-positive, liver-limited metastatic colorectal cancer

BACKGROUND

Identification of circulating tumor DNA (ctDNA) following curative intent therapies is a surrogate for microscopic residual disease for patients with metastatic colorectal cancer (mCRC). Preclinically, in micrometastatic microsatellite stable (MSS) CRC, increased TGF-β signaling results in exclusion of anti-tumor cytotoxic T cells from the tumor microenvironment. Bintrafusp alfa (BA) is a bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor ("TGF-β trap") and anti-PD-L1 antibody.

METHODS

Patients with liver-limited, MSS mCRC and with detected ctDNA after complete resection of all known tumors and standard-of-care therapy were treated with 1200 mg of BA intravenously every 14 days for six doses. The primary endpoint was ctDNA clearance. Radiographic characteristics at recurrence were compared using independent t-tests to historical data from a similar cohort of patients with liver-limited mCRC who underwent observation.

RESULTS

Only 4 of 15 planned patients received BA before the study was stopped early for loss of equipoise. There was no grade ≥3 AE. None of the patients cleared ctDNA. All patients developed radiographic recurrence by the first planned restaging. Although not detectable at prior to treatment, TGFβ3 was found in circulation in all patients at cycle 2 day 1. Compared to a historical cohort, patients administered BA developed more metastases (15 versus 2, p=0.005) and greater tumor volumes (9 cm vs 2 cm, p=0.05).

CONCLUSIONS

Treatment with BA in patients with ctDNA-detected, liver-limited mCRC did not clear ctDNA and was associated with large-volume recurrence, highlighting the potential context-specific complexity of dual TGF-β and PD-L1 inhibition.

Phase II study of durvalumab (anti-PD-L1) and trametinib (MEKi) in microsatellite stable (MSS) metastatic colorectal cancer (mCRC)

Background

Monotherapy with immune checkpoint blockade is ineffective for patients (pts) with microsatellite stable (MSS) metastatic colorectal cancer (mCRC). This study investigates whether the combination of trametinib (T) with durvalumab (D) can alter the immune tumor microenvironment (TME) by successfully priming and activating T-cells.

Methods

Open-label, single-center, phase II trial with primary endpoint of immune-related response rate for combination of T+D in refractory MSS mCRC pts (NCT03428126). T is 2 mg/day orally starting 1 week prior to D, which is given 1500 mg intravenously every 4 weeks. Simon 2-stage design used to enroll 29 pts into first stage, requiring a response in two or more pts to proceed to stage 2. Tumor biopsies were collected at baseline (BL) and early on-treatment (OT) at week 4.

Results

Twenty nine treated pts include 48% females, median age 48 years (range 28–75), and median prior therapies 2 (range 1–5). No grade (G) 4 or 5 treatment-related adverse events (TRAE). The most common TRAE of any grade was acneiform rash, 17% being G3. One of 29 pts had confirmed partial response (PR) lasting 9.3 months (mo) for an overall response rate of 3.4%. Seven pts had stable disease (SD) and five pts (1 PR, 4 SD) demonstrated decrease in total carcinoembryonic antigen ng/mL (best percentage reduction: 94%, 95%, 42%, 34%, and 22%, respectively). Median progression-free survival was 3.2 mo (range 1.1–9.3 months). Three pts with both liver and lung metastases demonstrated discrepant responses in which clinical benefit was present in the lung metastases but not liver metastases. Comparison of BL and 4-week OT tumor tissue flow cytometry demonstrated no changes in T-cell infiltration but upregulation expression of PD-1 and Tim3 on CD8 T cells. However, expression of PD-1 and Tim3 as single markers and as coexpressed markers was observed to increase OT relative to BL (p=0.03, p=0.06 and p=0.06, respectively).

Conclusions

T+D demonstrated acceptable tolerability in pts with refractory MSS mCRC. The response rate in the first stage of the study did not meet efficacy criteria to proceed to the second stage. Specific site of metastatic disease may impact outcomes in novel immunotherapy combination trials.

Trial registration number

NCT03428126.

Phase 2 study of anti-EGFR rechallenge therapy with panitumumab with or without trametinib in advanced colorectal cancer

3520

Background: In RAS/RAF WT colorectal cancer (CRC), rechallenge with anti-EGFR therapy (EGFRi) in patients (pts) with prior response leads to clinical benefit, with response rates up to 30% in prior trials. However, secondary MTs in the MAPK signaling pathway have been implicated in resistance to EGFRi. We designed a phase 2 trial to evaluate the efficacy of EGFRi rechallenge +/- a MEK inhibitor (trametinib) based on pre-treatment ctDNA MTs. Methods: This trial evaluated the efficacy and safety of EGFRi rechallenge +/- trametinib in pts with RAS/BRAF WT, MSS, treatment refractory mCRC who achieved clinical benefit with prior EGFRi based therapy for ≥16 weeks with subsequent progression. Pre study ctDNA was used to enroll in one of 3 arms: Arm A: Pts with an acquired EGFR ECD MT but absence of RAS/BRAF/MAP2K1 or with absence of any acquired resistance MT (Arm C) at time of study initiation received panitumumab 6 mg/kg IV Q2 wks. Arm B: Pts with an acquired RAS/BRAF/MAP2K1 MT received panitumumab 4.8 mg/kg plus trametinib 1.5 mg PO daily. Pts in Arms A and C were allowed to cross over on progression. The primary endpoint was ORR by RECIST v1.1. Results: 54 pts were enrolled, with 52 evaluable for efficacy. Median age is 59 yrs (range, 37-78), and 23 (46%) are female. Median number of prior therapies was 3. Three, 20, and 31 pts were enrolled in Arms A, B, C, respectively. Grade 3 TREAs occurred in 29 (54%) pts (all receiving the doublet regimen) and included acneiform rash in 17 (31%) and others occurring in < 5% of pts. There were no grade 4 TRAEs. In pts with no acquired MTs (Arm C), ORR was 20% (6/30) (95% CI, 0.07-0.37), DCR 67% (20/30) (95% CI, 0.45- 0.81), and median PFS and OS 4.1 mo and 11.2 mo, respectively. The median DOR was 5.5 mo. 22 patients crossed over to add trametinib at time of progression, without any responses. In contrast, in pts with acquired RAS/RAF/MAP2K1 MTs (Arm B), there were no responses, with DCR of 63% (12/19) (95% CI, 0.36-0.81), and median PFS and OS 2.1 mo and 5.9 mo, respectively. Only 3 pts were identified with EGFR ECD MTs (Arm A), and ORR is 0% (0/3) in this cohort, with DCR 67% (2/3) (95% CI, 0.09-0.99). Pts with PR had a longer median interval from prior EGFRi and longer time on prior EGFRi than those with SD+PD (5.5 vs 3.6 mo; p = 0.03, and 9.5 vs. 8.8 mo; p = 0.03, respectively). Conclusions: CtDNA guided rechallenge leads to responses in 20% of pts without acquired resistance MTs, with DCR of 67%. This exceeds current third line standard options. While panitumumab has the potential to block EGFR ECD mutations arising from cetuximab, these mutations in isolation were uncommon and there were no signals of efficacy. Although the acneiform rash induced by the combination of MEK and EGFR inhibition was manageable with close dermatologic management, the combination failed to improve outcomes for pts with acquired resistance. Alternative approaches to downstream MAPK blockade should be explored to improve outcomes. Clinical trial information: NCT03087071.

RAS co-mutation and early onset disease represent an aggressive phenotype of atypical (non-V600) BRAF mutant metastatic colorectal cancer

3592

Background: While BRAFV600E accounts for the majority of BRAF mutations in mCRC, non-V600 BRAF variants (a BRAF) have emerged in recent years as a distinct molecular subtype. There are no consensus recommendations regarding management. This study provides a comprehensive profile of a BRAF, their clonalities and co-mutations in mCRC using a large genomic database as well as a prospective treatment cohort of patients with a BRAF and mCRC managed at a single center. Methods: A systematic analysis was performed of patients with mCRC who underwent ctDNA testing (Guardant360 platform, Guardant Health) from September 2014 to May 2021. A variant was defined as clonal if the mutant allele frequency (MAF) was greater than 50% of the highest somatic MAF in the sample; otherwise it was defined as subclonal. Co-mutation analysis was conducted with BRAF, KRAS, NRAS, NF1, ERBB2, PIK3CA and SMAD4. Treatment history and overall survival (OS) for patients with a BRAF mCRC from MD Anderson Cancer Center were included. Results: 1,733 out of 14,742 mCRC patients had at least one BRAF variant, including 6.5% of patients with BRAFV600E variants and 6.2% with a BRAF variants (1.1% with class II, 1.9% with class III, and 3.2% with unclassified variants). 431 unique BRAF variants were identified in a total of 1,905 BRAF variants. BRAF class II and III variants showed a higher rate of co-occurring KRAS mutations (25.6% and 21.5%) and co-occurring NRAS mutations (5.8% and 2.7%) compared with BRAFV600E variants (2.4% for KRAS and 0.1% for NRAS); however, co-occurring KRAS G12C was only noted in one patient. In our MDACC cohort, 38 patients were included in the analysis. The median age was 55, 81% were Caucasian, and 74 % had left sided primary tumors (45% rectal, 24% sigmoid) with 37% being exposed to at least 2 lines of therapy. The most common mutations in clinical practice were class III, D594G (39%), followed by class II G469A (10%), & class III G466E (7%). The median follow-up time was 23.8 months (mo). While there were no survival differences between a BRAF classes II and III, there was a significant difference in OS in patients with RAS co-mutation (28.3 mo vs not reached [NR], p = 0.05) or liver involvement (28.8 mo vs NR, p = 0.02). Patients < 50 years of age had extremely poor survival with OS of 16.3 mo (vs. NR) and HR 7.51 (95% CI 1.82-31.0, p = 0.005). Treatment with anti-EGFR or use of metastasectomy was not associated with improved survival. Conclusions: a BRAF mutations have historically been considered a favorable prognostic marker in mCRC. Co-mutation with RAS is frequent for both classes and portends poor survival in our real-world cohort. Furthermore, early onset a BRAF mCRC is associated with more aggressive disease. These factors highlight the need for dedicated clinical trials for this unique subset of mCRC and may represent an opportunity to improve management in early onset colorectal cancer.

A multi-arm, phase 2, open-label study to assess the efficacy of RXC004 as monotherapy and in combination with nivolumab in patients with ring finger protein 43 (RNF43) or R-spondin (RSPO) aberrated, metastatic, microsatellite stable colorectal cancer following standard treatments

TPS3637

Background: The Wnt pathway is a critical driver of cancer. RXC004 is a potent, selective, orally active inhibitor of the key Wnt pathway regulator, Porcupine. Inhibition of Porcupine blocks the release of all Wnt ligands from cells, preventing both tumour growth and tumour immune evasion. Wnt pathway alterations, including loss-of-function (LoF) RNF43 mutations and RSPO gene fusions, increase expression of the Wnt receptor Frizzled (Fzd) on the tumour cell surface, driving Wnt-ligand signalling. These alterations are present in ̃8% (Gao, 2013; Cerami, 2012; Shesagiri, 2012; Shinmura, 2014; Kleeman, 2019) of colorectal cancers (CRC). LoF RNF43 mutations are associated with poor prognosis in MSS CRC (Yaeger, 2018 ). Preclinical genetically selected CRC models showed disease stabilisation, differentiation towards a normal colonic phenotype with increased mucin secretion, and reduced metabolic activity on FDG-PET. In a Phase 1 study in patients with advanced solid tumours (NCT03447470), RXC004 was safe and tolerated at doses up to 2mg QD, the recommended phase 2 dose (RP2D), and showed a differentiated efficacy signal in Wnt-ligand dependent tumours (Cook, 2021 ). Methods: The PORCUPINE (NCT04907539) trial is a 2-arm Phase 2 trial of RXC004 monotherapy (Arm A) and RXC004 in combination with nivolumab (Arm B). 20 evaluable patients will be enrolled into each Arm. The study initially opened with Arm A; Arm B will be opened once the RP2D for RXC004 in combination with nivolumab is established in a separate phase 1 study. Once Arm B is opened, patients in Arm A may be treated with RXC004 + nivolumab if they have progressive disease on the first RECIST assessment scan. To be eligible for this study, patients must have metastatic microsatellite stable (MSS) CRC that has progressed following standard therapies. Tumours must have a LoF RNF43 mutation, or an RSPO2/3 fusion. As Wnt inhibition can affect bone metabolism, patients undergo a screening DEXA scan and receive prophylactic denosumab throughout the treatment period. The primary endpoint for Arm A is the disease control rate (DCR= CR+PR+SD at 16 wks), and for Arm B is objective response rate (ORR). Secondary endpoints are Safety and PK. Exploratory endpoints include FDG-PET changes and on-treatment changes in protein and gene expression in tumour biopsies. For Arm A, a target value (TV) of 60% DCR is considered a clinically significant improvement over standard of care against a lower reference value (LRV) of 40% DCR (Grothey, 2013; Mayer, 2015 ). For Arm B, a TV of 30% ORR is considered clinically significant against a LRV of 10% ORR (Eng, 201 9). RXC004 is also being investigated in a second Phase 2 trial, PORCUPINE 2 (NCT04907851), in Biliary Tract Cancers and RNF-43 mutated Pancreatic Cancers. Clinical trial information: NCT04907539.

Phase I/II trial of encorafenib, cetuximab, and nivolumab in patients with microsatellite stable (MSS), BRAFV600E metastatic colorectal cancer

3598

Background: Treatment with encorafenib (E) and cetuximab (C) offers response and survival benefit for patients (pts) with MSS, BRAFV600E metastatic colorectal cancer (CRC). BRAF + EGFR inhibition induced a transient MSI-H phenotype in preclinical models of MSS, BRAFV600E CRC and may prime these tumors for response to immunotherapy with anti-PD-1 antibodies like nivolumab (N). Methods: In this single-arm, single-institution, phase I/II clinical trial, pts with treatment-refractory MSS, BRAFV600E metastatic CRC were eligible. No prior BRAF, MEK, or ERK inhibitors, anti-EGFR antibody, or immunotherapy was permitted. Pts received E (300 mg PO daily), C (500 mg/m2 IV q14 days), and N (480 mg IV q28 days). The primary endpoints were best overall response (RECIST 1.1) and safety/tolerability (CTCAE v5). A Simon two-stage design (H0: p≤.22; Ha: p≥.45, where p = percentage of pts with radiographic response) was employed using a one-sided α =.05 and β =.20. Median progression-free survival (PFS) and overall survival (OS) were estimated via Kaplan-Meier. To measure ex vivo treatment responses with an E-slice assay (EMPIRI), 300 µm fresh tissue slices from core biopsies were generated and cultured in serum-free media with E, C, and N. Longitudinal changes in viability were measured at days 4, 8, and 12 and compared to baseline viability in each tissue. Ex vivo “response” was defined if < 1X baseline tumor cell viability. Results: With a data cutoff of 2/8/2022, all pts are enrolled: 26 evaluable for toxicity and 23 for response. Median age is 60 years (range, 32-85), and 16 (62%) are female. Grade 3-4 treatment-related adverse events (AE) have occurred in 5/26 (19%) patients: colitis, maculopapular rash, leukocytosis, and myositis/myocarditis (all N = 1); asymptomatic elevated amylase/lipase (N = 2). Overall response rate is 48% (95% CI, 27-69), and disease control rate is 96% (95% CI, 78-100). Median PFS is 7.4 months (95% CI, 5.6-NA). For the 11 pts with responses, median duration of response is 7.7 months (95% CI, 4.5-NA). Median OS is 15.1 months (95% CI, 7.7-NA). E-slices showed concordance between pts with radiographic responses and reduction in cell viability, and between non-responders and increase in cell viability. Final results will be presented. Conclusions: E + C + N appears to be effective and well-tolerated for pts with MSS, BRAFV600E metastatic CRC. Ex vivo analysis of pretreatment tissue predicted eventual clinical response in matched patients. A follow-up randomized phase II trial (SWOG 2107) to evaluate encorafenib/cetuximab with or without nivolumab in pts with MSS, BRAFV600E metastatic CRC will activate in 2022. Clinical trial information: NCT04017650.

HER3 expression in metastatic colorectal cancer: Defining the clinicomolecular profile of an emerging target

3588

Background: The success of tailored systemic therapies in treating distinct molecular subsets of patients (e.g., deficient mismatch repair, BRAF mutant, HER2 amplified) has spurred further exploration of novel targetable subsets within the heterogeneous landscape of metastatic colorectal cancer (mCRC). Human epidermal growth factor receptor 3 [HER3 (ErbB3)], a member of the HER (ErbB) receptor tyrosine kinase family, plays an important role in tumorigenesis and metastases and has emerged as a promising therapeutic target in a diverse array of cancers. For example, patritumab deruxtecan (U3-1402; HER3-DXd) is a HER3-directed antibody drug conjugate that has demonstrated clinically meaningful antitumor activity and acceptable safety profiles in metastatic breast cancer and EGFR-mutated non-small cell lung cancer. There is limited data, however, on the clinicopathological characterization of HER3 expression in mCRC. Methods: Tissue samples (surgical-metastatectomy) (N = 115) were obtained from a clinical cohort of patients (N = 99) with histologically proven mCRC and liver metastases who underwent liver resection with/without perioperative systemic chemotherapy. HER3 expression was analyzed on whole-mount preparations by immunohistochemistry (IHC). Staining was performed and visualized using the HER3 (D22C5) XP Rabbit-mAb (Cell Signaling Technology). Patients were categorized based on membranous intensity score as follows: Low with IHC 0 (absence of staining or staining in < 10% of tumor cells), 1+ (faint/barely perceptible staining in ≥10% of tumor cells) or 2+ (weak to moderate staining in ≥10% of tumor cells), or High with IHC 3+ (strong staining in ≥10% of tumor cells). Clinicomolecular and treatment data, including gender, tumor sidedness, mutational status (RAS or BRAF), and prior chemotherapy were collected by review of patient electronic medical records. Chi-squared (or Fisher’s exact) test were used to determine associations between groups. Overall survival (OS) was calculated using Kaplan-Meier method and compared using log-rank tests. Results: Among 99 analyzed patients, 98 were evaluable for HER3 expression. Of these 25.5%, 26.5%, 40.8% and 7.2% showed HER3 IHC scores of 3+, 2+, 1+ and 0, respectively. No significant association was seen with HER3 expression and clinicopathological variables, mutational status, or prior treatment. Among patients with 2 samples analyzed from the same liver surgery, there was a moderate level of heterogeneity with concordance of 78.5% (kappa 0.43). Patients with high HER3 expression had poorer OS (5-year OS: 52%; median: 90.2 months) compared to low HER3 expression (5-year OS: 85%; median: not reached). Conclusions: In this large cohort of mCRC, HER3 expression was observed in 92.8% of patients and across diverse clinical and molecular features, supporting HER3 as a promising targetable biomarker in a large subset of mCRC.

A phase 2 multicenter, open-label, randomized, controlled trial in patients with stage II/III colorectal cancer who are ctDNA positive following resection to compare efficacy of autogene cevumeran versus watchful waiting

TPS3641

Background: Colorectal cancer (CRC) is one of the most commonly occurring cancers with high recurrence and mortality rate. Circulating tumor DNA (ctDNA) can be used as a marker of minimal residual disease after completion of surgical resection of stage II/III CRC, where detectable ctDNA levels (positive) post-AdCTx are associated with an increased risk of disease recurrence and novel therapies are needed. Autogene cevumeran is an investigational individualized neoantigen-specific immunotherapy that is designed to harness an immune response against patient-specific, tumor neoantigens. This clinical trial is in progress in patients with Stage II (high risk) / Stage III colorectal cancer who are ctDNA positive following resection. Methods: Autogene cevumeran is being evaluated in an open-label, Phase 2, randomized, controlled trial in patients with Stage II / III CRC patients who are ctDNA positive following resection. Patients are randomized to adjuvant therapy followed by autogene cevumeran compared to adjuvant therapy followed by watchful waiting. The primary endpoint is disease-free survival (DFS). The trial has a Biomarker Cohort of 15 patients who will receive autogene cevumeran irrespective of the ctDNA status to pursue exploratory objectives. The main study of the phase 2 trial consists of a randomized (1:1) design comparing the experimental arm (autogene cevumeran) with the observational arm (watchful waiting) in ctDNA positive CRC patients. A third Exploratory Cohort explores the efficacy and safety of autogene cevumeran in ctDNA positive CRC patients with early recurrence/relapse during or after completion of AdCTx. Patients enrolled onto the experimental group, the biomarker and exploratory cohorts will receive autogene cevumeran 6x q1w, followed by 2x q2w, followed by 7 “booster” doses q6w, to receive a total of 15 doses (dosed at 25μg). AEs are assessed according to CTCAE v5. DFS will be determined by an independent central radiology assessment. Key eligibility criteria include 1) Patients must have stage II/III rectal cancer or stage II (high risk)/III colon cancer that has been surgically resected (R0 confirmed by pathology report); 2) patients must be ctDNA positive following resection; and 3) at least 5 tumor neoantigens must be identified in the provided tumor sample for autogene cevumeran manufacturing (RNA lipoplex, RNA-LPX). ClinicalTrials.gov identifier: NCT04486378.

Don't blame the messenger: lessons learned for cancer mRNA vaccines during the COVID-19 pandemic

mRNA vaccines have proven safe and effective in preventing serious illness and death during the COVID-19 pandemic. In this Comment, Morris and Kopetz argue that these technologies offer a novel approach towards personalizing immune-based treatments for patients with cancer with the potential for immune activation beyond commonly utilized immunotherapies.

Prognostic role of systemic inflammatory markers in patients with metastatic MSI-h/dMMR colorectal cancer receiving immunotherapy

3524

Background: Markers of systemic inflammation including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (LMR) are prognostic in patients with metastatic colorectal cancer receiving systemic chemotherapy. The presence of liver metastases has also been hypothesized to modulate response to immunotherapy. In this study, we assess the prognostic role of these markers in patients with microsatellite high (MSI-H)/deficient mismatch repair (dMMR) tumors receiving immunotherapy for metastatic or unresectable colorectal cancer (CRC). Methods: This was a single-institution retrospective analysis of patients with dMMR/MSI-H CRC who received anti-PD-(L)1 and/or anti-CTLA-4 therapy for metastatic or unresectable disease at between 2015 and 2021 (n = 59). NLR, PLR, and LMR were calculated based on the complete blood count obtained within 1 week prior to treatment. Patient and tumor characteristics were obtained from the clinical record. Patient characteristics were compared using Fisher’s exact test and Mann-Whitney U where appropriate. Progression free survival (PFS) and overall survival (OS) were the primary endpoints and log-rank test was used for comparison of survival distribution among groups. Results: 59 patients with metastatic dMMR/MSI-H CRC were identified. Median age was 60, 53% (n = 31) had right-sided tumors, 35% (n = 35) of patients with testing available had RAS-mutated tumors, and 37% (n = 22) received prior chemotherapy. Most common sites of metastatic disease were peritoneum (n = 23, 39%) and liver (n = 17, 29%). Patients were divided into NLR-High (NLR ≥ 3, n = 20) and NLR-Low (NLR < 3, n = 39), and both groups had similar baseline characteristics. The rate of progressive disease as best response was not different in NLR-Low versus NLR-High (15% vs 30%, p = 0.3). At a median follow-up of 32 months, neither median PFS nor median OS were reached. 74% (n = 29) remained progression free at 1 year in the NLR-Low group versus 60% (n = 12) in NLR-High group which was not statistically significant (p = 0.37); 90% (n = 35) remained alive at 2 years in the NLR-low versus 80% (n = 16) in the NLR-High group (p = 0.4). Similarly, using a cut-off of 150 and 3 for PLR and LMR respectively, there was no significant difference between PFS at 1 year in the PLR-Low (n = 32) vs PLR-High (n = 27) (66% vs 74%, p = 0.58) and LMR-Low (n = 35) vs LMR-High (n = 24) (60% vs 83%, p = 0.084) groups. The presence of liver metastasis or the presence of a RAS mutation did not influence PFS at 1 year (p = 0.35 and p = 1.00, respectively). Conclusions: Markers of systemic inflammation may have a limited prognostic role for patients with dMMR/MSI-H CRC receiving immunotherapy.

Clinical outcomes following termination of immunotherapy due to long-term benefit in MSI-H colorectal cancer

3585

Background: Immune checkpoint blockade therapy improves survival in patients (pts) with microsatellite instability-high (MSI-H) advanced colorectal cancer (CRC). Oncologists often discontinue immunotherapy after 2 years of disease control based on prior trial data. Recurrence outcomes following discontinuation of immunotherapy and clinicopathologic features associated with recurrence remain underreported given the recent advent of these agents for pts with MSI-H advanced CRC. Methods: Records from pts with MSI-H CRC from MD Anderson Cancer Center who received immunotherapy between 2015-2022 and stopped after clinical benefit were reviewed. Median survival was estimated according to the Kaplan-Meier method. Associations between the event of recurrence and coexisting mutations ( KRAS, NRAS, BRAFV600E, PIK3CA, APC, TP53, POLE/POLD), metastatic site (lung, liver, lymph nodes, or peritoneum), primary tumor sidedness (right vs. left colon), and prior immunotherapy (anti-PD-(L)1 alone or with anti-CTLA-4 antibodies) were measured by Fisher’s exact tests. Results: Thirty-six pts with MSI-H CRC without progression on immunotherapy were reviewed. Of these 29 and 7 received anti-PDL1 antibody alone or in combination with anti-CTLA-4 antibody, respectively. Median exposure to prior immunotherapy was 24 months (range, 5-43). After a median follow-up of 19 months (95% CI, 14-26) after stopping immunotherapy, 30 of 36 pts (83%) remained without disease progression. For the 6 patients with progression after stopping, median time to relapse was 13 months (range, 5-31). Median disease-free survival (DFS) was not reached. The estimated 1-year, 2-year, and 3-year DFS probabilities were 90% (95% CI, 79-100), 79.1% (95% CI, 64-98), and 68% (95% CI, 47-98), respectively. Median overall survival from the time that immunotherapy was stopped was 54 months (95% CI, 47-NA). Only 1 pt died due to unrelated illness. There were no observed associations between disease recurrence and co-existing mutations, metastatic organ involvement, primary tumor sidedness, or immunotherapy used. Conclusions: Most pts with MSI-H advanced CRC who achieve initial clinical benefit and do not progress on immunotherapy do not recur after treatment is stopped. Our data suggest that favorable outcomes do occur following cessation of immunotherapy in this setting even with concomitant prognostically unfavorable clinical features (RAS, BRAFV600E mutations; liver, peritoneal metastases).

Resistance mechanisms to anti-EGFR therapy in RAS/RAF wildtype colorectal cancer varies by regimen and line of therapy

3554

Background: The conventional theory for the development of treatment resistance to anti-EGFR for metastatic colorectal cancer (mCRC) is the selective growth advantage of pre-existing therapy-resistant subclones with genomic mechanisms such as RAS mutations, leading to treatment resistance and disease progression. However, the impact of cytotoxic chemotherapy in combination with anti-EGFR on the mechanisms of resistance has not been assessed. Methods: We analyzed paired plasma samples from RAS/BRAF/EGFR wild-type mCRC patients enrolled in three large randomized phase 3 trials of anti-EGFR rechallenge in whom paired baseline and time of progression plasma samples had been collected for sequencing of ctDNA on a platform optimized for very low allele frequencies. 569 patients had paired baseline and progression ctDNA samples analyzed, including 147 in the first line study of FOLFOX +/- panitumumab, 91 patients in third line with panitumumab vs best supportive care, and 331 patients in the third line study of cetuximab vs. panitumumab. The mutational signature of the alterations acquired with therapy was evaluated. We also established colon cancer cell lines with resistance to cetuximab, FOLFOX, and SN38, and profiled transcriptional changes. Results: Using serial plasma samples, we demonstrate that patients whose tumors were treated with and responded to anti-EGFR alone were approximately 5-times more likely to develop acquired mutations at progression compared to those treated with an EGFR inhibitor in combination with cytotoxic chemotherapy (46% vs. 9%, respectively; p < 0.001). Consistent with this clinical finding, cell lines with non-genomic acquired resistance to cetuximab were cross-resistant to cytotoxic chemotherapy and vice-versa, with transcriptomic profiles consistent with epithelial to mesenchymal transition. In contrast, common acquired genomic alterations in the MAPK pathway that drive resistance to EGFR monoclonal antibodies do not impact sensitivity to cytotoxic chemotherapy. Further, contrary to the generally accepted hypothesis of clonal expansion of acquired resistance, in our work we demonstrate that baseline resistant subclonal mutations rarely expanded to become clonal at the time of progression (8%), and most remained subclonal (44%) or disappeared (49%). Conclusions: Collectively, this work outlines a model of resistance where non-genomic mechanisms of resistance common to both EGFR inhibitors and cytotoxic chemotherapy predominate in patients treated with EGFR and chemotherapy combinations. With EGFR inhibitor monotherapy, genomic acquired resistance mechanisms predominate, although only rarely through expansion of pre-existing subclones. These findings have important implications for strategies of EGFR-inhibitor rechallenge studies.

Burnout among early-career medical oncologists: A single-institution experience

11015

Background: Burnout is a psychological syndrome defined by the Maslach Burnout Inventory (MBI) as emotional exhaustion, depersonalization, and a low sense of personal accomplishment. Risk of job-related burnout for early-career medical oncologists can significantly impact career longevity and health outcomes for providers and patients alike. Because little is known about burnout specific to early-career academic oncologists, we sought to characterize the prevalence of burnout and associated factors among Assistant Professors at MD Anderson Cancer Center (MDACC). Methods: For this IRB-approved retrospective study, an electronic survey was developed for Assistant Professors in medical oncology at MDACC. Participants were all involved directly in patient care with at least some clinical effort. Our survey included nine questions validated in the MBI addressing equally the 3 aforementioned domains of burnout. An additional 31 questions were formulated to assess personal and professional factors that may contribute to burnout at our institution (clinical workload, research expectations, communication, COVID, and home-life). Each question was scored on a scale of 1 to 5, with higher scores correlating to higher levels of burnout. Descriptive statistics were used to describe the prevalence of burnout, and logistic regression analyses were performed to identify characteristics associated with burnout. Results: Among 70 (of 86 total) Assistant Professors who responded, mean duration on faculty was 3.1 years (standard deviation +/-1.8). Mean clinical effort was 67% (range, 19-95). Gender identifications were 44% female, 54% male, and 2% non-binary. 54% of respondents reported symptoms of burnout already, including 21% endorsing severe burnout. Severe burnout was more common for solid tumor providers than liquid tumor providers (55% vs 13%, p =.03). Using the MBI, severe emotional exhaustion (25%) was more prevalent (p <.0001) than depersonalization (6%) or lack of personal accomplishment (17%). Sentiments of being “emotionally drained” (20%), fatigue to face another day on the job” (37%), and “becoming more callous” (30%) were especially concerning among early-career faculty. Emotional exhaustion was associated with a feeling of less autonomy over personal decision making (p =.03) and female gender (p =.04). Conclusions: Burnout exists with high prevalence among early-career medical oncologists in this single-institution analysis. Emotional exhaustion was the specific manifestation of burnout in this population. Further validation of these data nationwide is anticipated. Interventions focusing on reducing emotional exhaustion are under development to reduce medical oncology-specific burnout in an academic setting for faculty retention and for deliverance of optimal care to patients with cancer.

A phase 1 trial of the bifunctional EGFR/TGFβ fusion protein BCA101 alone and in combination with pembrolizumab in patients with advanced solid tumors

2513

Background: BCA101 is a first-in-class bifunctional fusion protein consisting of an anti-EGFR monoclonal antibody (mAb) and TGFβ receptor 2 extracellular domain (TGFβRII-ECD). Herein, we report the safety, pharmacokinetic (PK), pharmacodynamic (PD), and preliminary efficacy data of BCA101 as monotherapy and in combination with pembrolizumab among patients (pts) with advanced solid tumors refractory to standard therapies. Methods: Pts received BCA101 as a single agent (SA) or in combination with pembrolizumab at escalating doses in a parallel 3+3 design starting at 64 mg intravenously (IV) weekly (qw); and at 240 mg IV qw with pembrolizumab 200 mg IV q3w. Primary endpoint: safety and tolerability (CTCAE v5.0); dose limiting toxicity (DLT) period: 21 days. Secondary endpoints: overall response rate (ORR), PK/PD profile, progression-free survival (PFS), and changes in plasma and intra-tumoral TGFβ signaling assessed by SMAD2 phosphorylation. Results: As of 08-Feb-2022, 60 pts have received BCA101 (part A). Forty-five pts (colorectal, n=14; pancreatic, n=7; head and neck squamous cell carcinoma [HNSCC], n=6) received SA BCA101 at doses up to 1500 mg IV weekly. Fifteen subjects (SCC of the anal canal [SCAC], n=8; HNSCC, n=7) received BCA101 doses ranging from 240 to 1500 mg IV qw in combination with pembrolizumab. Maximum tolerated dose has not been reached. Common adverse events (AEs) attributed to BCA101 include rash (70%), fatigue (23%), pruritis and epistaxis (17% each); all grade (G)2 or less. One DLT was observed at the 1250 mg SA dose (G3 anemia, hematuria). No drug-related G4 AEs or deaths were observed. At data cutoff, best response in the SA arm was stable disease (SD) in 15/39 (39%) evaluable pts. In combination, partial response (PR) was observed in 3/11 (27%) evaluable pts (2 in SCAC, 1 in HNSCC) and a disease control rate (DCR) of 9/11 (82%). Two of 3 responders have been on study >4 months; including 1 confirmed PR in a HNSCC pt refractory to anti-PD-1 therapy and cetuximab. Saturation of the EGFR target was observed at BCA101 doses ≥750 mg. Dose proportional increase in Cmax and AUC were observed with doses of BCA101 750-1500 mg. Prolonged neutralization of plasma TGFβ1 was achieved at all doses ≥500 mg. Among paired tumor biopsies (n=23), pSMAD2 reduction up to 62% was observed at doses ≥500 mg. Conclusions: BCA101 is well tolerated and clinically active as a SA and in combination with PD-1 blockade with a predictable PK/PD profile. A recommended dose of 1500 mg both as SA and in combination has advanced to the part B expansion phase for pts with HNSCC, SCAC, and cutaneous SCC. Clinical trial information: NCT04429542.

Benchmarking Outcomes for Definitive Treatment of Young-Onset, Locally Advanced Rectal Cancer

PURPOSE

There has been an increase in the incidence of rectal cancer diagnosed in young adults (age < 50 years). We evaluated outcomes among young adults treated with pre-operative long course chemoradiation (CRT) and total mesorectal excision (TME).

METHODS

The medical records of 219 patients, age 18-49, with non-metastatic, cT3-4, or cN1-2 rectal adenocarcinoma treated from 2000 to 2017 were reviewed for demographic and treatment characteristics, as well as pathologic and oncologic outcomes. The Kaplan-Meier test, log-rank test, and Cox regression analysis were used to evaluate survival outcomes.

RESULTS

The median age at diagnosis was 44 years. CRT followed by TME and post-operative chemotherapy was the most frequent treatment sequence (n = 196), with FOLFOX (n = 115) as the predominant adjuvant chemotherapy. There was no difference in sex, stage, MSS/pMMR, or pCR by age (< 45 years [n = 111] vs. ≥ 45 years [n = 108]). The 5-year rates of DFS were 77.2% for all patients, 69.8% for age < 45 years and 84.7% for age ≥ 45 years (P = .01). The 5-year rates of OS were 89.6% for all patients, 85.1% for patients with age < 45 years and 94.3% for patients with age ≥ 45 years (P = .03). Age ≥ 45 years was associated with a lower risk of disease recurrence or death on multivariable Cox regression analysis (HR = 0.55, 95% CI 0.31-0.97, P = .04).

CONCLUSION

Among young adults, patients with age < 45 years had lower rates of DFS and OS, compared to those with age ≥ 45 years. These outcomes could serve as a benchmark by which to evaluate newer treatment approaches.

Encorafenib, cetuximab, and cytotoxic chemotherapy combinations in BRAFV600E CRC murine models

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Background: Based on promising results from latest trials, a crucial point is to evaluate whether encorafenib (E) plus cetuximab (C), alone or in combination with chemotherapy, can improve clinical outcomes relative to current standard of care in previously untreated BRAFV600E mutant mCRC. Considering the high number of BRAFV600E mutant mCRC patients who will never receive a second-line treatment, the rationale of this strategy is to maximize treatment outcome within the first-line setting. Methods: We performed an in vivo study using human BRAFV600E CRC cell line-derived xenografts in nude mice. We evaluated the efficacy of encorafenib (E) + cetuximab (C), FOLFOX, and FOLFIRI, both as individual regimens and in combinations. Mice were treated for 3 weeks and followed for an additional 8 weeks to evaluate durability of tumor control. Additionally, we validated our findings using 3 BRAFV600E mutated patient derived xenografts. Tumors progressing on single agent and combined treatment were profiled by RNA sequencing, protein extraction for RPPA/Western blot, and establishment of in vitro primary cell cultures for further analyses. Results: Our study showed across all 4 models both FOLFOX and FOLFIRI, each in combination with encorafenib plus cetuximab, having greater efficacy than encorafenib plus cetuximab or either chemotherapy alone. No significant change in toxicity was seen with the addition of chemotherapy. Interestingly, in the one model with long term treatment, FOLFOX + E +/- C performed greatest over the long-term, with significant endpoint separation against all other treatment arms (P < 0.05). Conclusions: Taken together, results from our study suggest that the addition of chemotherapy to BRAF+EGFR targeted therapy can further increase the magnitude of response in BRAFV600E mCRC and is a promising combination now being explored clinically. Additionally, this research will substantially contribute to our understanding of the genetic and molecular bases of resistance to target therapies and chemo-based approach in BRAFV600Econtext.