Synchronous/metachronous endometrial and colorectal malignancies in Taiwanese women: a population-based nationwide study

Endometrial cancer (EC) and colorectal cancer (CRC) may share a common genetic background. In a subset of patients, the two malignancies can coexist either at the time of diagnosis (synchronous) or develop consequently (metachronous). The purpose of this nationwide, population-based study was to investigate the occurrence and clinical outcomes of synchronous/metachronous EC/CRC in Taiwanese women. Data for women diagnosed with EC and/or CRC between 2007 and 2015 were retrospectively retrieved from the nationwide Taiwan Cancer Registry. Mortality data were obtained from the National Death Registry. Women with synchronous/metachronous EC/CRC versus EC or CRC were compared in terms of clinical characteristics and outcomes. Of the 62,764 Taiwanese women diagnosed with EC and/or CRC during the study period, 167 (0.3%) had synchronous/metachronous EC/CRC. Among them, 72 cases (43.1%) presented with EC followed by CRC, 66 (39.5%) with CRC followed by EC, and 29 (17.4%) with synchronous EC/CRC. Kaplan–Meier estimates for time-to-event data revealed that the 2-year risk rates of developing a metachronous tumor of interest (CRC or EC) in women diagnosed with an initial EC and CRC were 39.6% and 42.1%, respectively. The 5-year overall survival rates of women with metachronous EC/CRC who had an initial diagnosis of EC, CRC, and synchronous EC/CRC were 73.9%, 70.9%, and 37.0%, respectively. Endometrial cancer is the most common first tumor in Taiwanese women with metachronous EC/CRC. The 2-year risk rates of developing a metachronous tumor of interest (CRC or EC) in women diagnosed with an initial EC and CRC are not negligible. Surveillance for CRC is recommended for all women diagnosed with EC. The clinical outcomes of synchronous EC/CRC are markedly less favorable.