Colon cancer as a subsequent malignant neoplasm in young adults

The incidence of colon cancer (CC) is rising in younger adults and can occur de novo or in patients previously treated for another cancer. To the authors' knowledge, the impact on survival of CC occurring as a subsequent malignant neoplasm (SMN) has not been described for younger patients, which the authors anticipate to be lower with SMNs than that of primary CC.

Patients aged <50 years with CC in the 2004 through 2014 National Cancer Data Base were identified. Patients were stratified by primary or subsequent occurrence. The impact of SMN status on overall survival (OS) was evaluated.

Of 41,915 patients, 2852 (6.8%) had colon SMNs. More patients with colon SMNs were aged 40 to 49 years compared with patients with primary CC (83% vs 77%; P < .001). Patients with colon SMNs presented with earlier clinical and pathological T, N, and M classifications (all P < .001). Colon SMNs more commonly occurred in the right colon, whereas primary CC was found to have a higher prevalence in the sigmoid colon (P < .001). Patients with colon SMNs more frequently underwent total colectomy (17% vs 5%; P < .001), but received less chemotherapy (53% vs 65%; P < .001). When adjusted for demographic, tumor, and treatment characteristics, SMN status was associated with a 23% decreased OS compared with primary CC (95% CI, 1.14-1.31; P < .001). Chemotherapy offered a 33% improvement in OS (95% CI, 0.56-0.8; P < .001).

Colon SMNs in younger patients present at an earlier stage and are treated more aggressively surgically compared with primary CCs. Patients with SMNs of the colon have decreased survival, although chemotherapy offers a survival advantage. Further investigation is warranted to determine whether these disparities are due to the effects of cancer treatment or differences in tumor biology.