Abstract
BACKGROUND: Male breast cancer (MBC) as a second primary cancer (SPC) has a known association with prior MBC. However, its association with non-breast index malignancies, relative to population risk, has not been previously reported. MATERIALS AND METHODS: Using Surveillance, Epidemiology, and End Results program (9 catchment area) data, we identified MBCs diagnosed from 1973-2012 as their SPC. Information regarding the index malignancy was also obtained. Standardized incidence ratios (SIR) of MBC as SPC were estimated, along with incidence rates and trends. Kaplan-Meier curves were used to estimate survival. RESULTS: Over a 38-year period, 464 MBCs were identified as SPC. The most common index malignancies were breast (SIR 30.86, 95% confidence interval [CI] 21.50-42.92, p < .001), lymphoma (SIR 1.58, 95% CI 1.08-2.22, p = .014), melanoma (SIR 1.26, 95% CI 0.80-1.89), urinary (SIR 1.05, 95% CI 0.74-1.43), colorectal (SIR 0.94, 95% CI 0.69-1.24), and prostate (SIR 0.93 95% CI 0.81-1.07). Apart from the known association with prior breast cancer, the only significant association was with lymphoma as an index cancer, although not significant with a Bonferroni correction. From 1975-2012, incidence of breast cancer as a first cancer increased at an annual percentage change of 1.3% while breast cancer as a SPC increased at 4.7% (both p values < .001). CONCLUSION: Male breast cancer as a SPC has increased markedly over 4 decades. Men with a history of lymphoma may experience higher-than-expected rates of breast SPC. These observations warrant further research, and suggest possible etiologic connections with disease biology, prior therapy, or genetics. IMPLICATIONS FOR PRACTICE: This study reports that men are presenting more frequently to the clinic with breast cancer, both as an initial cancer and as a second cancer following an earlier malignancy. We also report the novel observation that men who survive lymphoma are at increased risk of developing a subsequent breast cancer. Further work is needed to better understand possible treatment or biologic causes of this association. More immediately, these findings suggest the need for heightened vigilance for male breast cancer overall and, in particular, for male lymphoma survivors.