Phase II study of pembrolizumab plus capecitabine and bevacizumab in microsatellite stable (MSS) metastatic colorectal cancer (mCRC)

3565

Background: MSS mCRC rarely responds to pembrolizumab monotherapy, but capecitabine and bevacizumab may induce immune-stimulatory effects. This study evaluates the safety, tolerability and preliminary efficacy of pembrolizumab in combination with capecitabine and bevacizumab in MSS mCRC. Methods: Single-center, phase 2 trial with safety lead-in to confirm the recommended phase 2 dose (RP2D) for capecitabine and expansion cohorts (NCT03396926). Key eligibility: MSS mCRC with stable disease (SD) or progressive disease (PD) on prior fluoropyrimidine-based therapy. Treatment: Capecitabine 1000 mg/m2 PO BID D1-14 Q21 days (confirmed RP2D) plus pembrolizumab 200 mg IV D1 Q21 days and bevacizumab 7.5 mg/kg IV D1 Q21 days. Endpoints: Primary: Objective response rate (ORR) by RECIST 1.1. Key secondary: Safety, duration of response (DOR), progression-free survival (PFS), overall survival (OS). Results: From 04/2018-10/2021, 44 patients (pts) were enrolled. Overall: Median age 53 years (range 28-79); female 50%; Caucasian 61%. Liver metastases at enrollment 80%. Prior therapies: median prior lines of therapy 2 (range 1-5); PD on fluoropyrimidine-containing regimens 91%; prior exposure to bevacizumab 86%. Complete toxicity data are available for 36 off-treatment pts. Grade ≥ 3 treatment-related (tr)AEs occurred in 10 (28%) pts, including grade 3 immune-related AEs in 4 (11%) pts. All-cause serious (s)AEs occurred in 13 (36%) pts and trSAEs in 5 (14%) pts. (tr)AEs leading to dose interruptions, reductions, or delays occurred in 21 (58%) pts, most commonly palmar-plantar erythrodysesthesia syndrome in 17 (47%) pts. Disposition: of 44 pts enrolled, 35 were removed for PD and 1 was removed for treatment noncompliance; 8 treatment ongoing. ORR in 40 evaluable pts was 5% (95% CI: 0.6,16.9). Best response by RECIST 1.1: partial response (PR) in 2 (5%); SD in 26 (65%); PD in 12 (30%). 2 responders: DOR 12 and 15 months, both with liver metastases. Median follow up was 7 months (range 1-45), with median PFS 4.3 months (95% CI: 3.9, 6.1), PFS at 6 months 31.1% (95% CI: 19.2%, 50.4%), and median OS 9.6 months (95% CI: 6.2, 13). Median time on treatment was 5 months (range 1-26). Single cell RNA sequencing on a subset of paired pre- and on-treatment biopsies demonstrated changes in the frequency of dendritic cells. Conclusions: The combination of pembrolizumab with capecitabine and bevacizumab was found to be tolerable with an expected toxicity profile in MSS mCRC pts. The ORR of 5% did not meet the prespecified target of ≥ 15%, however nearly a third of pts had PFS > 6 months. Immune profiling of tumor biopsies and peripheral blood is ongoing. Clinical trial information: NCT03396926.

The marginal diagnostic benefit of pancreatic cancer molecular profiling after germline testing

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Background: Germline genetic testing is now universally recommended for patients (pts) with pancreatic ductal adenocarcinoma (PDAC) for purposes of both familial screening and therapeutic guidance. Treatment selection can be further informed by tumor molecular profiling (TMP) to identify targetable somatic alterations in pts with advanced disease, but this is inconsistently applied. Determination of the rate of actionable findings identified with TMP after germline testing, which we term marginal diagnostic benefit, may inform practice patterns and workflow in this patient population. Methods: This retrospective analysis included all pts with PDAC who underwent germline testing and TMP at UCSF over a 4-yr period. Medical records were reviewed for demographics, disease-specific data, and germline testing/TMP clinical reports. Alterations classified as ‘pathogenic’ or ‘likely pathogenic’ were included, and were deemed ‘actionable’ if there was clinical or preclinical evidence of benefit from targeted therapy in any cancer, as previously described. Results: From 1/2016-1/2020, 144/738 (20%) UCSF pts with PDAC completed both germline testing and TMP. Germline testing identified actionable pathogenic alterations in 10 (7%). TMP confirmed 8/10 of these alterations and identified 3 additional therapeutic targets. Among the 134 pts without actionable germline findings, TMP identified 45 new therapeutic targets in 41 (31%) pts, increasing the overall rate of actionable findings from 7% to 35%. Most (35/58, 60%) actionable alterations involved genes associated with the Homologous Recombination DNA Damage Repair (HR-DDR) pathway (Table). 80% of pts with HR-DDR pathway alterations (9/10 germline, 19/25 somatic) received platinum-based chemotherapy. Four pts were treated with targeted therapy based on test results: PARP-inhibitor (n = 2, germline BRCA1 and PALB2 mutations), PARP-inhibitor + ATR inhibitor (n = 1, somatic ARID1A mutation) and mTOR inhibitor (n = 1, somatic STK11 deletion). Conclusions: In this analysis, PDAC TMP after germline testing increased the detection of actionable alterations (the marginal diagnostic benefit) by five-fold. As more somatic tumor alterations become actionable with the development of targeted therapeutics, TMP is a necessary complement to germline testing to fully inform personalized treatment decisions for all pts with PDAC.[Table: see text]

Investigating tumor molecular profiling as a possible contributor to racial/ethnic disparities in pancreatic cancer

6522

Background: A variety of biologic, socioeconomic, and treatment-related factors may contribute to the racial/ethnic disparities observed in pancreatic ductal adenocarcinoma (PDAC) outcomes. As tumor molecular profiling (TMP) is now recommended for patients (pts) with advanced PDAC to inform treatment selection, we hypothesized that rates of TMP, detection of actionable alterations (AA), and use of molecularly-targeted treatments differ across different racial/ethnic groups and may contribute to disparate outcomes. Methods: This retrospective analysis included all Non-Hispanic White (NWH), Asian, Hispanic/Latinx (H/L), and Black/African American (B/AfrAm) pts with PDAC who underwent TMP at UCSF over a 4-yr period. Medical records were reviewed for demographic and disease-specific data. Alterations classified as ‘pathogenic’ or ‘likely pathogenic’ in TMP clinical reports were included, and were categorized as ‘actionable’ if there was clinical or preclinical evidence of benefit from targeted therapy in any cancer. Associations between NHW and other groups were tested with Fishers exact test. Results: Between 1/2016-1/2020, 159/727 (22%) pts underwent PDAC TMP. 60 AA were detected in 54 pts. Rates of TMP or AA detection were not associated with racial/ethnic group (Table). Most AA (33/60, 55%) were associated with the Homologous Recombination DNA Damage Repair (HR-DDR) pathway ( ARID1A n = 15 , ATM n = 7 , and BRCA1 n = 5). Other common AA included PIK3CA alterations (n = 6), CDK4/6 amplifications (n = 5), AKT2 amplifications (n = 4) and KRAS G12C mutation (n = 4). Molecular targets differed between groups (HR-DDR genes comprised 55% AA in NHW vs 100% in H/L, p = 0.03). Regarding treatment, rates of platinum chemotherapy for HR-DDR gene-altered PDAC differed significantly between groups. Three NHW pts with HR-DDR alterations received a PARP-inhibitor +/- ATR inhibitor. Conclusions: To our knowledge, this is the first study to report PDAC TMP rates and therapeutic implications across racial/ethnic groups. Acknowledging the limitations of sample size and what defines AA, we observed no significant differences in rates of testing nor AA detection. Further study is needed to evaluate whether rates of molecularly-informed treatment selection contribute to racial/ethnic disparities in clinical outcomes. As therapeutic advances increase the likelihood of identifying AA, equitable access to both TMP and targeted treatments must be ensured for all pts with PDAC.[Table: see text]

Phase II study of pembrolizumab plus capecitabine and bevacizumab in microsatellite stable (MSS) metastatic colorectal cancer (mCRC): Interim analysis

77

Background: MSS mCRC rarely responds to pembrolizumab monotherapy, but capecitabine and bevacizumab may induce immune-stimulatory effects. This study evaluates the safety, tolerability and preliminary efficacy of pembrolizumab in combination with capecitabine and bevacizumab in MSS mCRC. We present results at the planned interim analysis. Methods: Design:single-arm, open-label, single-site phase 2 trial with a safety lead-in to confirm the recommended phase 2 dose (RP2D) for capecitabine and expansion cohorts. Per the Simon’s 2-stage design, ≤1 response in 29 patients (pts) requires trial suspension. Key eligibility criteria: MSS mCRC with stable disease (SD) or progressive disease (PD) on prior fluoropyrimidine-based therapy. Treatment: RP2D PO capecitabine on days 1-14 plus 200 mg IV pembrolizumab and 7.5 mg/kg IV bevacizumab on day 1 in 21-day cycles. Pts are followed for toxicity and radiographic response. Results: From 04/2018-09/2020, 29 pts were enrolled, of whom 15 (52%) were female; 21 (72%) white; and median age was 55 years (range 36-77 years). Prior therapies: 2 (7%) pts had SD and 27 (93%) pts had PD on fluoropyrimidine-containing regimens; 24 (83%) pts had prior exposure to bevacizumab. The RP2D for capecitabine was 1000 mg/m2 PO BID, with no dose limiting toxicities observed. Complete toxicity data are available for 25 off-treatment pts. The most common related adverse events (AEs) were palmar-plantar erythrodysesthesia (PPE) (64%) and fatigue (68%). Grade ≥3 related AEs occurred in 9 (36%) pts, including immune-related AEs of Grade 3 dyspnea, hypophosphatemia, and pancreatitis in 1 pt each. Treatment related AEs leading to dose interruptions, reductions, or delays occurred in 15 (60%) pts, most commonly PPE in 13 (52%) pts. No pt had a related AE leading to treatment discontinuation or death. Disposition: of 29 pts enrolled, 24 were removed for PD and 1 was removed for an unrelated AE. Best response by RECIST 1.1 in 23 evaluable pts: partial response (PR) in 2 (9%); SD in 14 (61%); PD in 7 (30%). Median time on treatment was 6 months (range 2-26 months). Conclusions: Combination of pembrolizumab with capecitabine and bevacizumab was found to be tolerable with an expected toxicity profile in MSS mCRC pts. With 2 responses, the study met interim analysis criteria to continue accrual. Tissue and blood-based immune correlatives are planned. Clinical trial information: NCT03396926.

Phase I prospective trial of TAS-102 (trifluride and tipiracil) and radioembolization with 90Y resin microspheres for chemo-refractory colorectal liver metastases

110

Background: Clinical efficacy of Yttrium-90 (90Y) radioembolization (TARE) for patients with chemotherapy-refractory metastatic colorectal cancer (mCRC) is limited by extrahepatic disease progression. TAS-102 (trifluride and tipiracil) has overall survival benefit for patients with refractory mCRC and may be a radiosensitizer. We aimed to evaluate the safety of the combination of TAS-102 and 90Y resin TARE in a Phase I dose-escalation trial. Methods: Adult patients with bilobar liver-dominant chemo-refractory mCRC were treated with sequential Y90 resin TARE (body surface area dosimetry) in combination with TAS-102 (20mg/m2, 27mg/m2, and 35mg/m2) in 28-day cycles according to 3+3 dose-escalation design. Beginning with cycle 3, TAS-102 was administered as monotherapy until disease progression or development of intolerable toxicity. Primary objectives were to determine maximum tolerated dose (MTD) of TAS-102, to assess toxicity, and to establish safety of TAS-102 in combination with 90Y TARE. Results: A total of 14 patients (10 women, 4 men) have been treated to date. Among 9 patients enrolled in the dose-escalation phase, no dose limiting toxicities were observed. The MTD of TAS-102 in combination with Y90 was 35mg/m2, which was selected for the dose expansion phase. Severe adverse events (AEs) included: neutropenia (46%); anemia (23%); and thrombocytopenia (8%), which were attributed to TAS-102. All other AEs were mild and transient. At least one follow-up imaging study has been obtained for 13 patients, and 10 patients have completed trial participation. Disease control rate in the liver was 100%. Conclusions: The combination of TAS-102 and 90Y TARE for patients with liver-dominant mCRC is safe and consistently achieved disease control within the liver. Severity and incidence of AEs is within the expected range of TAS-102 and 90Y TARE monotherapy. A dose-expansion phase with planned enrollment of 12 patients is ongoing. Clinical trial information: NCT02602327.