Maintenance therapy after induction chemotherapy with anti-EGFR–antibody and survival in metastatic colorectal cancer: A retrospective real-world study.

e15613 Background: Maintenance therapy (MT) after induction chemotherapy in metastatic colorectal cancer remains clinically uncertain, as its benefit has been demonstrated primarily for progression-free survival (PFS), whereas a consistent impact on overall survival (OS) has not been unequivocally established. Methods: We retrospectively analyzed patients with RAS-wild-type metastatic colorectal cancer treated at Moscow City Oncology Hospital No. 62 between 2009 and 2024 with anti-EGFR therapy. OS and PFS were evaluated according to receipt of MT. Survival outcomes were estimated using the Kaplan–Meier method and compared with the log-rank test. Multivariable Cox models were used with adjustment for sex, age, metastatic burden, anti-EGFR treatment category, ECOG performance status at first line, and year of treatment initiation. Results: We identified 781 patients who received anti-EGFR therapy; 355 (46%) were treated in the first line, 380 (50%) in the second or third line, and 30 (3.9%) in the fourth or later lines. Among patients receiving MT, regimens included fluoropyrimidine monotherapy (26.8%), anti-EGFR monotherapy (10.7%), fluoropyrimidines plus anti-EGFR (31.8%), fluoropyrimidines plus anti-VEGF (25.1%), and FOLFIRI plus bevacizumab (5.7%). Compared with observation, MT was independently associated with improved median OS (36.1 vs 30.5 months; unadjusted HR = 0.82, 95% CI 0.68–0.99, p = 0.042; adjusted HR = 0.69, 95% CI 0.56–0.85, p < 0.001). MT was also associated with improved PFS in line-specific analyses. In the first line, median PFS was 13.8 months (n = 295) versus 9.6 months (n = 441) (crude HR = 0.62, 95% CI 0.53–0.73; p < 0.001; adjusted HR = 0.58, 95% CI 0.49–0.69; p < 0.001). In the second line, median PFS was 13.1 months (n = 144) versus 6.1 months (n = 452) (crude HR = 0.53, 95% CI 0.43–0.65; p < 0.001; adjusted HR = 0.52, 95% CI 0.42–0.65; p < 0.001). In the third line, median PFS was 11.1 months (n = 68) versus 4.5 months (n = 323) (crude HR = 0.47, 95% CI 0.35–0.63; p < 0.001; adjusted HR = 0.52, 95% CI 0.38–0.70; p < 0.001). Conclusions: In this large real-world cohort of patients with RAS wild-type mCRC treated with anti-EGFR–based therapy, MT was independently associated with clinically meaningful improvements in OS and PFS across multiple lines of treatment. These findings should be interpreted with caution, as MT was preferentially administered to patients with objective response and preserved performance status, potentially introducing selection bias and confounding the observed OS benefit. As a non-randomized retrospective analysis, the study remains vulnerable to residual confounding from unmeasured or incompletely captured factors.