Randomized intermittent or continuous panitumumab plus FOLFIRI (FOLFIRI/PANI) for first-line treatment of patients (pts) with RAS/BRAF wild-type (wt) metastatic colorectal cancer (mCRC): The IMPROVE study.

Abstract

3503 Background: Continuous anti-EGFR-based FOLFIRI is a first-line standard of care in pts with RAS/BRAF wt mCRC. The emergence of resistance and treatment-related toxicity limit the efficacy of continuous treatment. Thus, an intermittent strategy could reduce both toxicity and resistance. Methods: This is a prospective, randomized, non-comparative, open-label, multicenter phase II study. Unresectable, previously untreated RAS/BRAF wt mCRC pts, were randomized to a control arm (A) receiving FOLFIRI/PANI continuously until progression or to the experimental arm (B), receiving 8 cycles of the same regimen followed by a treatment free interval. This lasted untill progressive disease, when another treatment period of up to 8 cycles was restarted. This intermittent strategy was continued until progression occurred on treatment. Tumor assessment was always done every 8 weeks in both arms. Pts were stratified for center, ECOG PS (0-1 vs 2), previous adjuvant therapy (yes or no), sidedness (right vs left) and metastatic sites (1 vs ≥ 2). The primary endpoint was the progression-free survival on treatment (PFSOT) at 1 year. Assuming p1=43% PFSOT at 1 year, corresponding to an expected median PFSOT time ≥ 10 months in the experimental arm, and a 5% drop-out rate, a sample size of 68 pts in each arm granted the study a power of 80%, with a type I error of 10% (binomial test) for rejecting the null hypothesis, p0=30%, corresponding to a median PFSOT time of ≤ 7 months. Secondary endpoints were safety, quality of life, OS and response rate (ORR); ctDNA samples were also collected. No formal comparison between the two arms was planned. Results: From May 2018 to June 2021, 137 pts were randomized (69 arm A/68 arm B). Main pts’ characteristics were (arm A/B): males 59/61%; median age 62/66yrs; PS 0 84/72%; right colon 17/15%; previous adjuvant therapy 22/29%; single metastatic site 33/26%. At a median follow-up of 18 months (IQR: 10-26), median PFS OT was 12.6 months (95% CI: 9.0-16.1) in arm A and 17.6 months (95% CI: 7.5-27.8) in arm B with a 1 year PFSOT rate of 51.7% and 61.3%, respectively. ORR (arm A/B) was 64/56%. Median number of FOLFIRI/PANI cycles administered per patient were (arm A/B) 13/12. Main grade 3-4 toxicities were (arm A/B): skin 27/13%, neutropenia 23/22%; diarrhea 13/15%. Conclusions: The primary endpoint of the study was met with the intermittent FOLFIRI-PANI strategy producing a long PFS with a reduced skin toxicity. These data deserve further investigations in a phase III trial. Clinical trial information: NCT04425239.