Multicenter cohort retrospective clinical study assessing the impact of complete pathological tumor response on survival rates in patients with locally advanced gastric and esophagogastric junction cancer: demographic and clinical-morphological characteristics, treatment options and immediate results (report 2)

Background. Gastric cancer remains one of the leading causes of cancer-related mortality globally and ranks second in Russia. Pathological complete response (pCR, ypT0N0M0) is a significant surrogate marker for the efficacy of neoadjuvant therapy and disease prognosis. Despite accumulating data, the demographic and clinical-morphological characteristics of this patient category, as well as the dependence of pCR on the neoadjuvant therapy regimen, remain insufficiently studied. Aim : to characterize the demographic and clinical-morphological characteristics, methods and tolerability of perioperative therapy, and features of surgical treatment in a multicenter retrospective cohort of patients with locally advanced gastric and esophagogastric junction cancer, who achieved pCR after neoadjuvant therapy. Material and Methods. Data from 221 patients with histologically confirmed gastric or esophagogastric junction adenocarcinoma (cT2-4N0-3M0) who achieved pCR (ypT0N0M0) confirmed by pathomorphological examination of the resected specimen were retrospectively analyzed. Results. The median age was 65 years (range 24-89). Men (52.5 %) and patients with clinical stage iii (48.0 %) and IIB (30.8 %) predominated. Poorly differentiated adenocarcinoma was detected in 124 (56.1 %) patients, and signet ring cell carcinoma in 35 (15.8 %). Lymph node metastasis (cN+) at the time of diagnosis was found in 124 (56.1 %) patients. The completion rate of neoadjuvant chemotherapy was 96.6 %. Grade >3 adverse events were registered in 17 (8.3 %) patients receiving chemotherapy and in 3 (17.6 %) receiving chemoradiotherapy. According to follow-up examination, a complete clinical response was detected in 2 (0.9 %) patients, a partial response in 57 (25.8 %), and disease stabilization in 162 (73.3 %). Adjuvant chemotherapy was administered to 132 (59.7 %) patients (including the FLOT regimen in 75.0 %). The predominant method of surgical treatment was gastrectomy (59.3 %). Postoperative complications occurred in 47 (21.3 %) patients, including Clavien-Dindo grade >iii in 24 (10.9 %); the 30-day postoperative mortality rate was 1.4 %. Conclusion. Within the clinical study, the largest sample of the Russian population of gastric cancer patients with a registered pathological complete response after neoadjuvant therapy was collected - 221 patients. This cohort is dominated by features associated with aggressive gastric cancer: diffuse and mixed Lauren types; poorly differentiated adenocarcinoma, including signet ring cell carcinoma; clinical categories cT3-4 and cN+. in patients with pCR, the completion rate of neoadjuvant therapy was 96.6 %, with the FLOT regimen being the most frequently used. Routine CT scanning does not reliably diagnose pCR; thus, searching for and validating new standardized biomarkers for the objective assessment of tumor response to neoadjuvant therapy is highly relevant.