Abstract
Background: In RAS wild-type (WT) metastatic colorectal cancer (mCRC), preliminary data have suggested that circulating tumor DNA (ctDNA) may select patients for anti-EGFR rechallenge therapy.
Methods: RASINTRO is a prospective nonrandomized study evaluating anti-EGFR rechallenge strategy in third and later line treatment in RAS/BRAF WT mCRC. Liquid biopsies for ctDNA analysis were collected before the first (C1) and second (C2) cycles of anti-EGFR rechallenge therapy. The primary endpoint was the progression-free survival (PFS) according to RAS/BRAF mutational status on ctDNA at C1.
Results: Among 74 patients screened between November 2017 and March 2020, 62 were enrolled: median age, 66.1 years; median number of previous lines of therapy, 3; panitumumab or cetuximab rechallenge alone (66.2%) or with chemotherapy (33.8%); ctDNA RAS/BRAF status at C1, 42 WT (67.7%) and 20 mutated (32.3%). Median PFS (3.3 vs 1.9 months: hazard ratio (HR) = 0.43; P <.01) and overall survival (OS) (7.9 vs 4.9 months; HR = 0.46; P =.01) were significantly longer for patients with ctDNA RAS/BRAF WT vs mutated at C1. Among the 32 patients with ctDNA RAS/BRAF WT at C1 and available blood samples at C2, those who have experienced an early decrease of >50% in ctDNA concentration (n = 15) had a significantly longer median PFS (4.2 vs 2.8 months; HR = 0.39; P =.01) and OS (10.2 vs 4.2 months; HR = 0.39; P =.02).
Conclusion: This study showed that anti-EGFR rechallenge therapy in refractory disease is more effective in patients with RAS/BRAF WT on ctDNA, and in those who experienced an early decrease of >50% in ctDNA concentration.
