Background: Age- and cancer-related sarcopenia and malnutrition are common in older patients with colorectal cancer (CRC) and may negatively influence treatment tolerance and prognosis. However, the comparative prognostic value of post-chemotherapy changes in CT-based body composition parameters at the third lumbar vertebra (L3) and the twelfth thoracic vertebra (T12) levels, and their associations with nutritional indices, remain unclear. This study aimed to examine and compare the prognostic relevance of post-chemotherapy body composition changes at L3 and T12 and to assess their relationship with nutritional indices in older patients with metastatic CRC (mCRC). Methods: This retrospective study included 87 older patients with mCRC. Baseline and ~3-month follow-up CT scans were analyzed at L3 and T12 using 3D Slicer to quantify skeletal muscle index (SMI), subcutaneous adipose tissue index (SATI), visceral adipose tissue index (VATI), visceral-to-subcutaneous fat ratio (VSR), and intramuscular adipose tissue index (IMATI). Changes (Δ) in CT-derived body composition after chemotherapy were calculated as percentage change using ((follow-up − baseline)/baseline) × 100. Prognostic Nutritional Index (PNI) and Geriatric Nutritional Index (GNRI), which are established nutritional assessment tools, were calculated from baseline laboratory/anthropometric data. Agreement between T12 and L3 was assessed, and associations with grade ≥ 3 toxicity, progression-free survival (PFS), and overall survival (OS) were evaluated using multivariable models and ROC analyses. Results: Mean age was 69.0 ± 4.5 years (59 male/28 female), and 26.4% developed grade ≥ 3 adverse events. Over 3 months, mean SMI declined significantly at both L3 (46.7 ± 8.8 → 42.8 ± 9.8 cm²/m²) and T12 (34.6 ± 8.2 → 31.6 ± 8.1 cm²/m²) (p < 0.001 for both), accompanied by decreases in VATI and VSR; T12-IMATI increased significantly. Baseline PNI showed a weak positive correlation with L3-SMI (r = 0.302, p = 0.033), whereas GNRI showed moderate correlations with SMI at L3 (r = 0.502, p < 0.001) and T12 (r = 0.317, p = 0.025) and was associated with longitudinal changes in muscle metrics. T12-SMI consistently yielded lower values than L3-SMI, and agreement varied by compartment (best for SATI; weakest for VSR). Lower GNRI and greater L3-SMI loss were independently associated with grade ≥ 3 toxicity; ΔL3-SMI showed the highest discrimination (AUC = 0.79, 95% CI = 0.69–0.87, p < 0.001; cut-off >5.1% loss). All patients progressed (median PFS 7.6 months); mortality was 82.8% (median follow-up: 25 months). In multivariable analysis, PFS, CRP, GNRI, and ΔL3-SMI remained independently associated with OS. ΔL3-SMI provided the strongest mortality discrimination (AUC = 0.85, 95% CI = 0.74–0.94, p < 0.001; cut-off >10.4% loss), while ΔIMATI was also informative (AUC = 0.71, 95% CI = 0.59–0.82, p = 0.023). Conclusions: In older patients with mCRC, early post-chemotherapy skeletal muscle loss—particularly at the L3 level—showed the strongest prognostic association with severe toxicity and mortality. GNRI provided complementary prognostic information as a marker of baseline immunonutritional reserve. Although T12-derived measurements were correlated with L3-derived values, systematic bias suggests that they should not be interpreted interchangeably for longitudinal risk stratification.

Objective: This study aimed to evaluate the impact of anti-epidermal growth factor receptor (anti-EGFR)–based maintenance therapy administered after first-line chemotherapy combined with anti-EGFR treatment on progression-free survival (PFS) and overall survival (OS) in patients with RAS wild-type metastatic colorectal cancer (mCRC), using real-world data. Methods: Patients followed at a single center between 2015 and 2025 were retrospectively analyzed. A total of 37 RAS wild-type patients who achieved disease control after first-line chemotherapy combined with anti-EGFR therapy were included. Patients were divided into a maintenance therapy group (n = 19) and an active surveillance group (n = 18). Survival analyses were performed using the Kaplan–Meier method, groups were compared using the log-rank test, and a landmark approach was applied to minimize immortal time bias. Results: At a median follow-up of 27.4 months, median PFS was 11.4 months in the maintenance group and 5.4 months in the surveillance group, without reaching statistical significance (P = .133). In contrast, median OS was significantly longer in the maintenance group (56.9 months vs. 9.6 months; P = .041). Additionally, higher rates of transition to subsequent lines of therapy were observed in patients receiving maintenance therapy. Conclusion: Anti-EGFR–based maintenance therapy was associated with numerically prolonged PFS and improved treatment continuity in patients with RAS wild-type mCRC. Although a significant difference in OS was observed, this finding should be interpreted cautiously given the limited sample size, retrospective design, and potential influence of selection bias and subsequent therapies. Larger prospective studies are warranted to better define the role of anti-EGFR maintenance therapy in clinical practice. Cite this article as: Çokgezer S, Artan S, Topuz S, et al. Effect of maintenance anti-EGFR therapy on survival in RAS wild-type metastatic colorectal cancer: real-world data. Cerrahpaşa Med J 2026, 50, 0069, doi: 10.5152/cjm.2026.26069.