Survival Impact of Extracolorectal Malignancies in Colorectal Cancer Patients

Colorectal cancer (CRC) patients are at high risk for developing extracolorectal malignancies (EMs). Although development of a second primary cancer and deaths thereof are included as events of disease-free survival (DFS) and overall survival (OS), the role of EMs in these survival end points has not been fully investigated.

A total of 1,625 CRC patients who underwent surgery from April 2004 to March 2014 were retrospectively evaluated. EMs were classified as preoperative metachronous EMs (pre-MEMs), synchronous EMs (SEMs) and postoperative metachronous EMs (post-MEMs).

A total of 145 pre-MEMs (134 patients), 132 SEMs (125 patients) and 97 post-MEMs (89 patients) were observed. The incidence of SEM correlated with male sex, age >70 years and absence of distant metastasis. In patients undergoing curative surgery (n = 1,550), the 5-year CRC- and EM-related death, CRC-specific recurrence and post-MEM development rates were 10.4, 2.6, 27.9 and 7.3%, respectively. SEM strongly and independently correlated with shorter OS and DFS (hazard ratios, 2.52 and 1.54, respectively). Moreover, patients with SEM or those aged >70 years were at high risk for developing post-MEM.

Because the presence of SEM strongly indicates shorter DFS and OS, exploration of EMs prior to colorectal surgery is important.