Boland, Patrick M.

11586 Background: Hand-foot skin reaction (HFSR) is the most common regorafenib adverse event. However, no intervention has demonstrated efficacy in preventing or palliating this adverse event, short of modulating the regorafenib dose. Methods: The Regorafenib Dose Optimization Study (ReDOS) was a randomized trial ( https://clinicaltrials.gov/ct2/show/NCT02368886 ); here we describe an a priori secondary analysis of ReDOS with the goal of assessing whether clobetasol 0.05% cream (a potent corticosteroid) applied to the palms and soles twice per day is more effective when prescribed pre-emptively (before the development of HFSR) versus reactively (after the development of HFSR). Patients were assessed during the 1st 2 cycles of regorafenib. Results: Among 116 evaluable patients, 61 received pre-emptive clobetasol, and 55 reactive clobetasol. Baseline demographics were comparable between groups. During the 1st regorafenib cycle, 46% and 52% of patients developed HFSR with pre-emptive and reactive clobetasol, respectively (p = 0.52). However, during the 2nd cycle, 56% (of 47 total patients) and 80% (of 41 total patients), developed this toxicity with pre-emptive and reactive clobetasol, respectively (p = 0.02). Of note, during the 2nd cycle, rates of grade 1,2, and 3 HFSR were 40%, 11%, and 4% (pre-emptive) and 45%, 25%, and 10% (reactive) (p = 0.07). A sensitivity analysis to examine rates of no HFSR over all 2 regorafenib cycles showed that no HFSR occurred in 33% (of 61 total patients) with pre-emptive clobetasol versus 15% (of 55 total patients) with reactive clobetasol (p = 0.02). Patient-reported outcomes showed HFSR compromised activities of daily living, including getting dressed, preparing meals, walking, and even driving, with seemingly worse descriptive outcomes in patients who received reactive therapy. No adverse events from clobetasol were reported. Conclusions: Compared to reactive therapy, pre-emptive topical clobetasol might lessen regorafenib-induced HFSR. Clinical trial information: NCT02368886.

TPS873 Background: Initial treatment of metastatic colorectal cancer (mCRC) involves a 5-fluorouracil based chemotherapy regimen, often in combination with anti-VEGF therapy. Upon disease progression, multiple studies have suggested a benefit for continued anti-VEGF therapy. There is increasing evidence that VEGF plays a role in cancer immune evasion. Targeting of inflammatory and immune checkpoints are attractive approaches to enhance the benefits of anti-VEGF therapy. The safety and activity of the anti-PD-L1 antibody atezolizumab with bevacizumab and with 5-FU, oxaliplatin, and bevacizumab have been recently reported; the combinations were well-tolerated and suggested clinical activity. Therefore, bevacizumab may increase the immunogenicity of colorectal cancers, and the combination of atezolizumab plus bevacizumab may be associated with clinically meaningful response rates and disease control. Furthermore, there may be candidate biomarkers that may identify those patients most likely to benefit from this combination. Methods: In this randomized, double-blind, multicenter, placebo-controlled phase II study, 135 patients with mCRC will be randomized 2:1 to receive capecitabine/bevacizumab/atezolizumab or capecitabine/bevacizumab/placebo. Patients with prior PD-L1/PD-1 therapy are ineligible. Primary and secondary efficacy will be conducted using ITT analysis. Safety analyses will include all randomized patients who receive at least one dose of study treatment. The primary objective is PFS. The secondary objectives are ORR, OS, safety, and tolerability. The primary comparison will be superiority of the active treatment for the PFS endpoint, atezolizumab versus placebo testing at 1-sided α = 0.1 (log rank test). A PFS hazard ratio of 0.618 (active treatment versus placebo) is detectable with 86% power (1 sided α = 0.1). No interim analyses for futility or efficacy will be conducted. A subset analysis will be performed in the microsatellite-high patients looking at potential differences in PFS and OS. Trial is active and currently recruiting patients. Clinical trial information: NCT02873195.

TPS535 Background: Small bowel adenocarcinoma (SBA) is a rare malignancy, possibly because of the high rate of immunosurveillance in baseline small bowel function, and is frequently diagnosed in late stages. Due to these factors, there is no consistent standard of care for metastatic disease beyond first-line where several prospective studies have confirmed activity of FOLFOX/CAPOX. Historically, second-line treatment of SBA has been extrapolated from colon/gastric cancer. Recent studies suggest that SBA has a distinct genomic profile, including higher incidence of microsatellite instability, compared to gastric and colon cancers. Additionally, the tumor microenvironment reflects a greater degree of PD-L1 expression and infiltration by lymphocytes. Immune checkpoint inhibitors have not previously been tested in SBA unselected for MSI status. Methods: The study is a phase 2, multicenter, single-arm clinical trial of pembrolizumab (200 mg IV every 3 weeks) for patients with unresectable or metastatic SBA refractory to first-line chemotherapy. Forty patients with any tumor mismatch repair status will be enrolled at 8 US sites as part of the ACCRU network and International Rare Cancer Initiative (IRCI) with a primary objective to assess the confirmed response rate (H0 p < 10%, HA: p > 30%) to pembrolizumab. Secondary endpoints include PFS, OS, and adverse events. Correlative aims include assessing blood and tissue biomarkers (i.e. PD-L1, MSI-H/MSS status, cfDNA, mutation burden, etc.) for association with clinical benefit. An interim analysis will be performed to assess efficacy after 18 patients become evaluable. The study is open with 16 patients enrolled at time of submission. Clinical trial information: NCT02949219.

611 Background: Regorafenib is an oral multikinase inhibitor with survival benefit in refractory mCRC patients (pts). Toxicities such as Palmar-plantar erythrodysesthesia syndrome (PPES), fatigue and hypertension (HTN) have limited its use. Despite absence of supportive data, various dosing or interval scheduling have been implemented into clinical practice. Methods: A randomized phase II study of regorafenib dose-escalation (Arm A: 80 mg/day, weekly dose escalation if no significant drug-related toxicities, up to 160 mg/day) vs. standard dose (Arm B: 160 mg/day) in pts with mCRC for 21 days of a 28-day cycle. Pts were randomized 1:1:1:1 to arms A1 and B1 (Pre-emptive Clobetasol for PPES); A2 and B2 (Reactive Clobetasol). The primary endpoint was the proportion of patients who completed 2 cycles of treatment and initiated the 3rd in Arm A (Pooled A1 + A2) vs. Arm B (Pooled B1 + B2). Superiority for Arm A was to be declared if the one-sided p-value calculated using Fisher’s exact method was less than 0.2. Results: From June 2015 to June 2017, 123 pts were randomized with 116 (A = 54, B = 62) evaluable for the primary endpoint. Demographic data were well balanced with overall median age of 61yrs (range: 29-81), M/F (61/39%) and ECOG PS 0/1 (37/63%) and KRAS MT/WT/UNK (47/44/9%).The study met its primary endpoint with 43% of pts on Arm A initiating the 3rd vs. only 25% of pts Arm B [one-sided p-value 0.028]. Median Overall Survival (OS) was improved in Arm A vs. Arm B (9.0 mos vs. 5.9 mos; p = 0.094). Median Progression Free Survival (PFS) was 2.5 mos for Arm A vs. 2.0 mos for Arm B (p=0.553). Overall rates of grade 3/4 toxicity were more favorable for Arm A vs. Arm B (% PPES 15 vs. 16, HTN 7 vs. 15 and fatigue 13 vs. 18, respectively). Multiple QOL parameters were improved in A vs. B primarily at week 2 of the first cycle. Conclusion: A strategy with weekly dose escalation of regorafenib from 80 mg to 160 mg/day was found to be superior to a starting dose of 160 mg/day. These results establish a new standard for optimizing regorafenib dosing. Further data on outcomes of preemptive vs. reactive clobetasol strategies are undergoing analysis and will be presented later. Clinical trial information: NCT02368886.

Objectives: Preclinical studies demonstrated antitumor activity of dovitinib in pancreatic cancer models. This phase Ib study aimed to determine the maximum tolerated dose (MTD) of dovitinib in combination with gemcitabine and capecitabine and to characterize the safety and pharmacokinetic profile in patients with advanced pancreatic and biliary tract cancers and solid malignancies. Materials and Methods: Patients received gemcitabine 1000 mg/m² intravenously on days 1 and 8, capecitabine 1300 mg/m² oral daily from day 1 to 14, and dovitinib oral daily 5 days on and 2 days off, every 21-day cycle. The standard 3+3 dose escalation design was utilized and the study expanded to treat an additional 20 advanced pancreatic and biliary tract cancers patients at MTD. Results: A total of 29 patients were enrolled. One patient experienced dose-limiting grade 3 colitis. Two patients developed clinically significant neuropathy after the first cycle requiring dose reduction. The MTD was not reached and dovitinib 300 mg was declared the recommended dose for expansion. The most frequent grade 2 or worse adverse events were fatigue (45%), neutropenia (41%), thrombocytopenia (34%), anemia (24%), nausea (24%), and palmer-plantar erythrodysaesthesia syndrome (21%). Partial responses were observed in 5 patients. Pharmacokinetic studies showed no drug-drug interaction between dovitinib, capecitabine and gemcitabine. Fibroblast growth factor 23 plasma level increased in 4 of 5 patients during the first cycle of treatment. Conclusions: Dovitinib 300 mg daily is the recommended dose when combined with gemcitabine and capecitabine, achieving clinically relevant plasma concentrations. The study combination demonstrated encouraging efficacy signals in advanced pancreatic cancer.

The recent success of anti-PD1 drugs in metastatic colorectal cancer patients with mismatch repair deficiency generated overwhelming enthusiasm for immunotherapy in the disease. However, patients with mismatch repair deficient colorectal cancer represent only a small subset of the metastatic population. Current research focuses on advancing immunotherapy to earlier stages of the disease including adjuvant and first-line metastatic settings, and on inducing sensitivity to immune checkpoint inhibitor therapy through a combinatorial approach. Here, we review the contemporary understanding of the immune and molecular landscape in colorectal cancer and discuss ongoing clinical trials evaluating novel combination regimens based on immune checkpoint inhibitors.