Lavage cytology diagnosed by immunostaining may be a poor prognostic factor in pathological stage III colorectal cancer

Abstract

AimTo clarify the prognostic impact of positive lavage cytology diagnosed by immunostaining on long‐term outcomes following curative resection for pathological stage III colorectal cancer (CRC).MethodWe retrospectively investigated patients who underwent radical resection and intraoperative lavage cytology (LCY) simultaneously for pathological stage III primary CRC between 2005 and 2017. All LCY specimens were evaluated by Papanicolaou staining and immunostaining for carcinoembryonic antigen and Ber‐EP4. Only Class V diagnosed by either staining method was defined as positive LCY, and patients were classified into two groups: a positive lavage cytology (LCY+) group; and a negative lavage cytology (LCY−) group. Overall survival (OS) and relapse‐free survival (RFS) were compared between groups. Multivariate analysis was performed to identify clinicopathological factors affecting OS and RFS.ResultsAmong 708 patients with pathological stage III CRC, 30 patients (4.2%) showed positive LCY. OS and RFS were significantly lower in the LCY(+) group than in the LCY(−) group. Five‐y OS rates in the LCY(+) and LCY(−) groups were 58.7% and 91.0%, respectively, and 5‐y RFS rates were 28.8% and 76.6%, respectively. Multivariate analysis revealed that positive LCY was independently associated with lower OS and RFS. In the LCY(+) group, the proportion of patients with negative Papanicolaou staining but positive immunostaining was 20.0% (6 of 30). No significant differences in OS and RFS were evident between those patients and patients with positive results for both Papanicolaou staining and immunostaining.ConclusionPositive LCY as diagnosed by immunostaining may represent a poor prognostic factor for pathological stage III CRC.