The significance of relative dose intensity of CAPOX therapy in epidemiological evaluation of gastric cancer outcomes.

e16081 Background: Epidemiological studies on drug therapy outcomes in specific populations are crucial for post-marketing surveillance (PMS), especially in cancer treatment due to their toxicity and ethnic/interpersonal variability in therapy response. Relative Dose Intensity (RDI), the ratio of administered to standard dose per m² BSA per week, measures chemotherapy tolerance. This study evaluates RDI of capecitabine+oxaliplatin (CAPOX) therapy and its correlation with overall survival (OS) in the genetically diverse Indian gastric cancer population. Methods: This pilot-retrospective study analysed 30 patients (18–60 years) with Stage II/III gastric cancer who underwent D2 lymph node dissection (2015–2018). Data from medical records evaluated toxicities graded per CTCAE v5.0. RDI, calculated as administered dose intensity relative to the standard (mg/m²/week), was assessed. OS, the primary endpoint, measured survival from CAPOX initiation to death. Kaplan–Meier analysis estimated OS, with log-rank tests evaluated age, gender, stage, and mean RDI against median OS (P &lt; 0.05). SPSS 23 was used for descriptive and survival analysis. Results: The mean follow-up was 5 years, with a median OS of 29.8 ± 11.5 months. The mean RDI of Capecitabine (54.30% ± 14.8) was notably lower than Oxaliplatin (85.60% ± 21.9). Half the patients (n = 15) failed to complete 6 cycles, among them 60% (n = 9) received below-mean RDI due to intolerance. Patients with Capecitabine RDI &lt; 54.30% had significantly higher OS (37.61 ± 9.80 months, p = 0.005) than those &gt; 54.30% (8.58 ± 2.18 months). Similarly, Oxaliplatin RDI &lt; 85.6% reported 37.61 ± 8.28 months OS, compared to 10.95 ± 2.57 months &gt; 85.6% (p = 0.005). Survival differences by age or stage were insignificant. Toxicities included fatigue (n = 6), neuropathy (n = 4), and hand-foot syndrome (n = 3). Conclusions: Our study reveals that reduced RDI for Capecitabine and Oxaliplatin, compared to standard CAPOX dosing, improved overall survival in Stage II/III gastric cancer patients within the Indian population. As a pilot study, these findings emphasize the need for larger studies to explore dose modifications for safe and effective drug therapy in specific population and highlights RDI’s value as a marker in region-specific post-marketing surveillance. Characteristics versus median survival. Parameters 95%CI (Range) N (%) Median Survival ± SD(months) 95%CI (Range) P value Age (mean ± SD) 65 ±9.75 43-78 &gt;60 yrs 16 43.8 35.1±15.6 0.23 &lt;60 yrs 8 25 29.9±8.2 Tumour stage Stage 2 10 33.3 29.9±12.6 0.58 Stage 3 13 43.3 20.5±12.6 Capecitabine RDI(mean ± SD) 54.30±14.8 18.39-56.83 RDI&lt;54.3% 12 40 37.6±9.8 18.4-56.8 0.005 RDI&gt;54.3% 12 40 8.6±2.2 4.5–12.9 Oxaliplatin RDI (mean ± SD) 85.60±21.9 37.6-133.5 &lt;85.6% 11 36.6 37.6±8.3 21.4-53.9 0.005 &gt;85.6% 13 43.3 10.9±2.6 5.9–16 <jats:fn id=