Distribution of side effects of anti-EGFR treatments in patients with metastatic colorectal cancer and evaluation of their relationship with survival.

Many previous studies have investigated cetuximab and panitumumab's efficacy, safety, and side effects. Only a few studies have evaluated the relationship between toxicity and survival. Therefore, we conducted this study to examine the relationship between the side effects of anti-EGFR agents and survival in metastatic colorectal cancer patients. Our study is a single-center retrospective analysis of the medical records of 100 metastatic colorectal cancer patients between September 2014 and September 2023. Overall survival (OS) was found to be statistically significantly longer in patients who developed skin toxicity during anti-EGFR treatment (26.0 vs. 70.0 months) (P < 0.001). Similarly, OS was significantly better in patients with hypomagnesemia (P < 0.001) and constipation (P < 0.001) side effects. In contrast, OS was significantly worse in patients with lung toxicity (P = 0.016). Ocular side effects during anti-EGFR treatment did not affect OS statistically significantly (P = 0.268). The median PFS of patients with skin toxicity with anti-EGFR agents and hypomagnesemia in first-line treatment was 22.0 months (19.4-24.5) and 21.0 months (18.2-23.8), respectively (P = 0.002, P = 0.022). In the second line, the median PFS of patients with skin toxicity and patients with hypomagnesemia who received anti-EGFR therapy was 19.0 months (6.2-31.8) and 17.0 months (8.4-25.6), respectively (P = 0.013, P = 0.037). In our study, it was found that skin toxicity and hypomagnesemia positively affected both OS and PFS. OS was longer in patients with constipation, and OS was shorter in patients with lung toxicity. We suggest that survival might be predicted by monitoring side effects of these therapeutics; therefore, studies with larger cohorts are required.