Abstract
BACKGROUND: Mycosis fungoides (MF) is associated with increased risk of second primary hematologic malignancies, but its association with second primary solid tumors is less well characterized. OBJECTIVE: This retrospective analysis seeks to assess the risk of being diagnosed with a second primary hematologic or solid malignancy in patients with MF. DESIGN: We performed an analysis of patients diagnosed with MF from 2000 through 2015 in the United States cancer registries of SEER-18 (N = 6742). RESULTS: Relative risks were estimated by using standardized incidence ratios (SIRs). Among 6742 patients, there were 511 (7.5%) second cancer events (SIR, 10.15; 95% confidence interval [CI], 9.29-11.07). These included 184 (36.0%) hematologic malignancies (SIR, 39.71; 95% CI, 34.05-46.05) and 327 (64.0%) solid tumor malignancies (SIR, 7.33; 95% CI, 6.56-8.17). Patients with MF were at increased risk for non-Hodgkin lymphoma; Hodgkin lymphoma; melanoma; and lung, female breast, prostate, colon, and renal cancers. Females were at higher risk than males (P < .05). All ethnic groups showed a statistically significant elevation in SIRs. Elevation of SIRs was observed across all stages of MF. CONCLUSIONS AND RELEVANCE: Patients with MF are at increased risk for diagnosis of second primary malignancies and should be carefully screened for discernable signs and symptoms of second malignancies.