PS02.242: SIGNET-RING CELL PERCENTAGE MAY INFLUENCE PATHOLOGICAL RESPONSE TO CHEMOTHERAPY IN ESOPHAGO-GASTRIC JUNCTION SIGNET RING CELL CARCINOMA

Abstract

Abstract Background Like in gastric cancer, the incidence of signet-ring cell carcinoma (SRCC) is rising also in esophago-gastric junction (EGJ) adenocarcinoma Siewert type I and II. SRCC is much more studied in gastric cancer and WHO classification divides poorly cohesive gastric cancer in two subtypes, depending on the percentage of signet-ring cells: real SRCC (percentage of signet-ring cell more than 50%) and poorly cohesive non-SRCC (less than 50%). Real SRCC seems to have higher chemosensitivity and better prognosis than poorly cohesive non-SRCC. Recently, a new classification for SRCC has been proposed, which subdivides SRCC based on different cut-off percentages of signet ring cells (less than or equal to 90% vs more than 90%). Aim of this study was to compare pathological response in patients with EGJ SRCC treated with neoadjuvant chemotherapy. Methods Study population comprised 11 patients with Siewert I and II EGJ SRCC treated with neoadjuvant chemotherapy and surgery. We analyzed differences in pathological response to therapy between ‘pure’-SRCC (more than 90% of SRC) and ‘non-pure’-SRCC (less than or equal to 90%). Tumor regression grade (TRG) was used to define response to treatment, with TRG 1–2 defining good response to treatment and TRG 3–5 poor or absent response to treatment. Results Among the 11 patients with EGJ SRCC, 6 had ‘pure’-SRCC histology and 5 ‘non-pure’-SRCC. Response to treatment in ‘pure’-SRCC patients was equally splint into good and poor responders: 3 had good response to treatment (TRG 1–2) and 3 poor or absent response (TRG 3–5). On the contrary most of ‘non-pure’-SRCC had poor or absent response: 4 out of 5 patients had TRG 3–5. Conclusion Although the case series was too small to perform statistical analyses, our results suggest that signet-ring cell percentage may influence the outcome of neoadjuvant therapy. Probably a larger case series would allow to better define cut-offs of percentage of signet-ring cell carcinoma of the EGJ. Moreover it would allow to inspect other factors related to response to treatment. This is only a preliminary investigation and further studies are needed to better understand the characteristics of these rising in incidence types of cancer. Disclosure All authors have declared no conflicts of interest.