Safety analysis of the randomized phase II study of FOLFOXIRI plus cetuximab versus FOLFOXIRI plus bevacizumab as the first-line treatment in metastatic colorectal cancer with RAS wild-type tumors: The DEEPER trial (JACCRO CC-13)

86 Background: Triplet regimens, FOLFOXIRI, combined with bevacizumab (bev) or panitumumab have been shown to be superior in terms of early tumor shrinkage (ETS) and depth of response (DpR) compared to doublet regimen plus bev or triplet regimen in patients with RAS wild-type metastatic colorectal cancer (mCRC), in the TRIBE trial ( N Engl J Med 2014) or VOLFI trial ( J Clin Oncol 2019), respectively. There have been few studies which directly compared cetuximab (cet) with bev when combined with triplet regimen. Therefore, we investigated the efficacy and safety of bev vs. cet in combination with FOLFOXIRI in previously untreated mCRC patients with RAS wild-type tumors. Methods: This trial was a randomized phase II trial to evaluate modified (m)-FOLFOXIRI (irinotecan 150 mg/m2, oxaliplatin 85 mg/m2, 5-FU 2400 mg/m2) plus cet vs. bev as first-line treatment in terms of the DpR during the entire course as the primary endpoint in 360 patients with RAS wild-type mCRC (ClinicalTrials.gov Identifier: NCT02515734). The experimental arm with cet was considered to be active if the difference of median DpR was over 12.5% compared with the bev arm, under the conditions of significance level of 0.05 and power of 0.85. Secondary endpoints included the ETS at week 8, progression-free survival, overall survival, secondary resection rate, and toxicity. Results: A total of 359 patients were enrolled between July 2015 and June 2019. For the safety analysis set (median age 65y, 64% male, PS0/1:91%/9%, left/right primary:83%/17%), 173 and 175 patients were randomly assigned to the cet and bev arms, respectively, some patients were excluded for the safety analysis due to the violation of inclusion criteria (6 for cet arm and 5 for bev). On the cutoff date of September 2020, median number of cycles administered was 10 (range, 1-51) for the cet arm and 12 (range, 1-51) for the bev arm. The incidence of severe adverse events (AEs) was 25.4% (44/173) for the cet arm and 25.7% (45/175) for the bev arm, respectively. The following AEs of grade 3-4 were observed more frequently in the cet arm compared to the bev arm: oral mucositis (9.2% vs. 2.3%), diarrhea (12.1% vs. 8.0%), dermatitis acneiform (12.1% vs. 0%), and hypomagnesemia (4.0% vs. 0%). The treatment-related death occurred in 2 patients of the cet arm, while no patients in the bev arm. The rate of treatment discontinuation due to AEs of any cause was comparable between the cet and bev arms (7% vs. 9%). Conclusions: This safety analysis indicated that both regimens of m-FOLFOXIRI plus cet or bev were tolerable in RAS wt mCRC patients although some frequent severe AEs were observed. Clinical trial information: UMIN000018217.