Real-world data (RWD) reveals benefit for adjuvant chemotherapy with docetaxel, oxaliplatin and fluorouracil/leucovorin (FLOT) is limited to those with tumour regression grade (TRG) >= 3 in oesophago-gastric cancer (OGC).

4039 Background: Despite potentially curative surgery, long-term survival from OGC remains poor due to high relapse rate. Neoadjuvant (naFLOT) and adjuvant (aFLOT) FLOT is currently standard treatment for resectable OGC based on data from the FLOT-4 trial. We explored whether TRG was associated with FLOT-outcome using RWD. Methods: Pts with OGC treated with naFLOT +/- aFLOT at a tertiary UK centre were identified following institutional board approval. Clinical and laboratory data were extracted from the patient record. TRG was evaluated by a histopathologist. Median overall survival (OS) and median progression-free survival (PFS) were evaluated using Kaplan-Meier and Log-rank tests; time taken from start of naFLOT, and associations between factors with Fisher’s exact (FE) test. Results: 171 pts were identified, median FU 30 mths. 144 (84%) male; median age 66 (32-84); oesophagus 66 (38%), junctional (GOJ) 73 (43%), gastric 32 (19%); stage IB 3 (2%), stage IIB 26 (15%), stage III 91 (53%), stage IVA 47 (28%) and unknown 4 (2%). Pts had median of 2 comorbidities (range 0-6); performance status (PS) 0: 95 (56%), PS 1: 71 (41%), PS 2: 3 (2%) and PS unknown 2 (1%). 132/171 pts completed 4 cycles of naFLOT and this was significantly associated with undergoing surgery (p = 0.02). Those who had surgery (140/171) had significantly improved PFS (not reached (NR) vs. 6 mths; 95% CI 2-10; p < 0.001) and OS (NR vs. 12 mths; 95% CI 6-18; p < 0.001). TRG was reported for 126/140 patients who underwent surgery. TRG 1/2 (42/126) vs. TRG ≥3 was significantly associated with improved PFS (NR vs. 35 mths; 95% CI NR; p < 0.001) and OS (median NR either group; p < 0.001). Pts with TRG 1/2 who commenced aFLOT (≥1 cycle; n = 31/42) or completed 4 cycles of aFLOT (17/31) did not have improved PFS or OS vs. those who did not. Those with TRG ≥3 who commenced aFLOT (≥1 cycle; n = 62/85) had improved PFS (median NR vs. 22 mths; 95% CI 13-31 p = 0.006) and OS (median NR vs. 25 mths; 95% CI 18-32 p = 0.019). Those with TRG ≥3 who completed 4 cycles of aFLOT (n = 38/62) had significantly improved PFS (median NR vs. 25 mths; 95% CI 14-36 p = 0.016) and OS (median NR vs. 36 mths; 95% CI 16-55 p = 0.012). There was no difference in PFS or OS in pts with TRG ≥3 who had a dose reduction at any time during aFLOT. Conclusions: TRG is a predictor of outcome following naFLOT + surgery with superior outcomes in those with TRG 1/2. Our analyses suggest that only pts with TRG >3 following naFLOT + surgery benefit from adjuvant FLOT. Prospective randomised studies are required to confirm whether pts with TRG 1/2 require treatment with aFLOT.