Abstract 347P
Background
Rarely, colorectal cancers (CRC) comprise signet ring cells (SRC) made of cytoplasmic mucin and responsible for a poor prognosis. The pathologic classification considers a primary tumor as a SRC tumor when the SRC component (SRCc) represent more than half of the cells. However, the prognostic impact of lower SRCc in CRC patients with peritoneal metastases (pmCRC), candidate for cytoreductive surgery, remains unclear, jeopardizing a proper selection.
Methods
A retrospective analysis of a bicentric database was performed to assess the impact of the SRCc by comparison to classical adenocarcinoma (cADK) (non SRC non mucinous) regarding oncologic outcomes. Appendiceal cancers were excluded. The SRCc was reviewed by an expert pathologist.Univariate and multivariate analyses were conducted with Cox model regression. Missing data was dealt with imputation using the mice package. Survival rates were estimated using the Kaplan-Meier method and compared with the log-rank test.
Results
Overall, 59 (25 from Sydney, 34 from Lyon) pmCRC patients with a SRCc were included (15 patients with SRCc >50%) and compared to 647 cADK patients with peritoneal metastases. Thirty-seven patients (63%) had a complete resection, all but one followed by Hyperthermic IntraPeritoneal Chemotherapy. Except one patient, all patients had systemic chemotherapy, perioperatively in 46% of cases. When compared to cADK, the SRC patients were younger, more often with right-sided tumors, with pN2 status and with higher peritoneal carcinomatosis index (median 16.0 vs 8.6, respectively). After a median follow-up of 40 months [IC95%, 36-45], the median overall survival was 16, 20 and 42 months in patients with ≤50% SRC, >50% SRC and cADK respectively (p<0.001). In multivariate analysis SRCc ≤50% (HR1.81, [IC95%, 1.11-2.97], p<0.018) and SRCc >50% (HR2.09, [1.35-2.26], p<0.001), incomplete cytoreduction and severe postoperative complications were associated with a poorer survival. After matching 3:1, lymph node invasion, PCI>15 and SRCc >50% (HR2.11, [1.25-3.60], p=0.005) were predictive of poor survival.
Conclusions
A component of SRC in pmCRC patients candidate for cytoreduction appeared as a strong negative prognosis factor, even when the SRCc was lower than 50%.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
S. Valle: Financial Interests, Personal, Ownership Interest: MUCPHARM. D. Morris: Financial Interests, Personal, Ownership Interest: MUCPHARM. All other authors have declared no conflicts of interest.