Histopathological regression predicts treatment outcome in locally advanced esophagogastric adenocarcinoma.

Background: Neoadjuvant chemotherapy (neoCTx) improves survival outcomes of patients with localised esophagogastric adenocarcinoma (EGA). This analysis evaluates the predictive value of histopathological response after neoCTx.
Methods: A total of 461 patients with locally advanced EGA (≥T2 and/or N+) who received neoCTx followed by surgery were analysed: 314 (68.1%) with intestinal, 94 (20.4%) with diffuse and 53 (11.5%) with mixed histological type according to Lauren classification. Histopathological response evaluation was available for 363 patients and performed locally. This analysis evaluates the predictive value of histopathological subtype on histopathological response after neoCTx. Response was correlated with survival.
Results: Median patients' age was 63 years, 79.8% were male. Tumours were localised in the stomach in 32.5% and EG junction in 67.5% of the patients. With a median follow-up of 49.4 months, median disease-free (DFS) and overall survival (OS) were 38.0 and 66.4 months, respectively. Pathological complete response (TRG1a) was 8.8% and combined complete and subtotal regression (TRG1a/b) was 27.3% for all patients. Around 9.2% of patients with intestinal type had a TRG1a compared with 6.2% with diffuse and 10.8% with mixed type. TRG1a/b rate was higher in intestinal (31.0%) than in diffuse (15.4%) and in mixed type (21.6%). For patients with intestinal type, 3-year DFS was 78.4% with TRG1a and 54.3% with other regression grades (p = 0.031). All patients with diffuse and mixed type and TRG1a were disease free after 3 years compared with 31.1% (p = 0.056) and 47.7% (p = 0.044) with other regression grades.
Conclusion: Histopathological subtype is predictive for histopathological response and outcome after neoCTx, with the highest response rates in intestinal differentiated EGA.
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