Association of adjuvant chemotherapy initiation timing with recurrence-free survival in patients with completely resected non-small cell lung cancer: a single-center retrospective cohort study

Adjuvant platinum-based chemotherapy is the standard of care after complete resection of non-small cell lung cancer (NSCLC), yet the impact of initiation timing on recurrence-free survival (RFS) remains insufficiently characterised, particularly in Chinese patient cohorts. This single-center retrospective cohort study enrolled 250 patients with completely resected NSCLC who received platinum-based adjuvant chemotherapy between September 2021 and September 2024 at The Second Affiliated Hospital of Tianjin University of Traditional Chinese Medicine. Patients were classified as timely (time to adjuvant chemotherapy [TTAC] ≤ 56 days; n = 160) or delayed (TTAC > 56 days; n = 90). The primary outcome was RFS and the secondary outcome was overall survival (OS). Cox regression was used to estimate the association between initiation timing and survival outcomes; independent predictors of delayed initiation were identified by multivariable binary logistic regression. The median TTAC was 47 days (timely group: 39 days; delayed group: 84 days). Over a median follow-up of 22.6 months, 108 RFS events were recorded. Delayed initiation was independently associated with inferior RFS after multivariable adjustment (aHR 1.69, 95% CI 1.14–2.49; P = 0.008). Estimated 12-month RFS rates were 76.9% vs. 63.3%, and 24-month rates 56.4% vs. 48.1%, in the timely and delayed groups, respectively. The association with OS did not meet the prespecified threshold for statistical significance (aHR 1.89, 95% CI 1.00–3.59; P = 0.050) at current follow-up. Independent predictors of delayed initiation were postoperative complications (adjusted odds ratio [aOR] 3.28, 95% CI 1.66–6.47; P < 0.001) and older age (aOR per year 1.04, 95% CI 1.01–1.07; P = 0.022). Delayed initiation beyond eight weeks was associated with inferior RFS in the primary analysis; however, this finding requires confirmation in analyses specifically designed to address treatment-timing bias, as the landmark sensitivity analysis was directionally consistent but not statistically significant. Postoperative complications and older age were the principal independent predictors of delayed initiation.