Prognostic factors for gastric cancer patients with positive peritoneal cytology who underwent upfront surgery.

400 Background: Positive peritoneal cytology (CY1) is classified as Stage IV disease, the standard treatment for which is systemic chemotherapy. However, CY1 is often diagnosed after surgery in patients for whom staging laparoscopy is not indicated. In addition, the treatment strategy for patients with CY1 diagnosed during surgery is controversial. The Japanese guidelines recommend upfront surgery followed by adjuvant chemotherapy for patients diagnosed with CY1 during surgery. To identify patients with CY1 who are most likely to benefit from upfront surgery, we investigated prognostic factors in patients with CY1 who underwent upfront surgery. Methods: A total of 169 gastric cancer patients diagnosed as P0CY1 during or after surgery who underwent R1 resection other than positive resection margins were included. The diagnosis of CY1 was obtained by staging laparoscopy or during laparotomy in 69 patients and after surgery in 87 patients. Fourteen patients were initially diagnosed as CY0 by staging laparoscopy but were rediagnosed as CY1 after surgery. The clinicopathological factors of overall survival (OS) and progression-free survival (PFS) were investigated. Prognostic factors were identified using Cox regression models. Results: The median patient age was 72 years, and there were 108 males. The histological type was undifferentiated type in all of 102 patients. The macroscopic types were 0 in 10) patients 1 in 3, 2 in 27 3 in 84 and 4 in 45). cT grades and cN grades were cT1 in 3, cT2 in 7, cT3 in 12, cT4 in 147, cN0 in 65cN1 in 30), cN2 in 46 and cN3 in 28. The median OS and PFS were 25.1 months and 14.6 months, with 5-year OS rate and PFS rate of 30% and 23%, respectively. A multivariate analysis for OS identified macroscopic type 0-2, Charlson Comorbidity Index<3, and adjuvant chemotherapy as independent prognostic factors. Similarly, macroscopic type 0-2, tumor size <80 mm, and adjuvant chemotherapy were identified as independent prognostic factors for PFS. In a subgroup analysis of patients who received adjuvant chemotherapy, macroscopic type 0-2 was the only independent prognostic factor for PFS. The 5-year PFS rate in patients with macroscopic type 0-2 was 42%. Conclusions: Patients with macroscopic type 0-2 who are suitable for adjuvant chemotherapy may have benefit from upfront surgery, even if peritoneal cytology is positive.