PATHOLOGICAL COMPLETE RESPONSE TO NEOADJUVANT CHEMORADIOTHERAPY IN PATIENTS WITH LOCALLY ADVANCED GASTRIC CANCER

Abstract

The impact of pathological complete response (pCR) on long-term treatment outcomes was analyzed in patients with locally advanced gastric cancer, who received prolonged neoadjuvant chemoradiotherapy.Material and Methods. The study included 45 patients with locally advanced gastric cancer. Neoadjuvant hyperfractionated accelerated radiotherapy at a total dose of 45 Gy was given concurrently with capecitabine and oxaliplatin chemotherapy. There were more men than women. The median age of the patients was 62 years. Tumors were most commonly located in the upper (46 %) and middle (38 %) thirds of the stomach. Low-grade adenocarcinoma and signet-ring cell carcinoma were the most common (65 %). According to a comprehensive examination, including CT and laparoscopy, tumors which invaded the subserous layer of the stomach wall were diagnosed in 17 (37.8 %) patients, and tumors which penetrated the serous layer or surrounding structures were found in 28 (62.2 %) patients. Regional lymph node metastases were detected in 38 (84.4 %) cases.Results. The absolute majority of patients underwent gastrectomy (43 patients, 96 %). Grade IaIb pathological response occurred in almost half of the patients (45.4 % of cases). Peritoneal metastases were found to be the most common mode of cancer dissemination; they were mostly observed in patients with poorly differentiated gastric cancer. Multivariate analysis revealed no effect of any of the factors characterizing the patient, tumor and completeness of treatment on the pathological response grade. However, a correlation between the clinical and morphological assessments of tumor regression was observed. In cases with complete or partial responses of the primary tumor and regional lymph nodes to chemoradiotherapy, 1aIb grades of pathological response were more frequently observed. It was also demonstrated a direct correlation between the pathological response grade and pathomorphological stage of the tumor (yp), as well as ypT and ypN categories. Analysis of long-term treatment outcomes showed that the overall and relapse-free 5-year survival rates were significantly higher in patients with 1a and Ib grades of pathological response. The overall 3-year survival rates were 70 ± 10 % and 41 ± 11 %, respectively (p=0.003). Multivariate analysis using the Cox regression model confirmed a statistically significant independent effect of the pathological response grade on the overall survival (p=0.015).Conclusion. Grade IaIb pathological response was observed in almost half of the patients, who received neoadjuvant chemoradiotherapy for locally advanced gastric cancer. No clinical and morphological factors influencing the pathological response grade were found. A correlation between the clinical and morphological assessments of tumor regression was observed. Patients with Ia-Ib pathological response had significantly higher overall and disease-free survival rates.