Risk of nonkeratinocyte skin cancers postradiotherapy high among breast cancer patients

Patients with breast cancer appear to be at increased risk of melanoma and hemangiosarcoma after treatment with radiation therapy, as shown in a study.

For the study, researcher used longitudinal data from the Surveillance, Epidemiology, and End Results (SEER) Program and identified 875,880 patients with newly diagnosed breast cancer (51.6 percent older than 60 years, 99.3 percent women, 69.5 percent non-Hispanic White).

Of the patients, 50.3 percent received radiation therapy and 41.2 percent received chemotherapy. The most common surgical intervention was partial mastectomy (52.7 percent).

Over a 10-year period, 3,839 patients had incident nonkeratinocyte skin cancer, including melanoma (89.1 percent), Merkel cell carcinoma (3.2 percent), hemangiosarcoma (2.7 percent), and 32 other nonkeratinocyte skin cancers (5.1 percent), with the malignancies documented to occur after breast cancer treatment.

Compared with the general population, breast cancer patients had a 57-percent higher risk of nonkeratinocyte skin cancer diagnosis after treatment with radiation (standardized incidence ratio [SIR], 1.57, 95 percent confidence interval [CI], 1.45–1.7) when considering the most relevant site: the skin of the breast or trunk.

When the risk of nonkeratinocyte skin cancer at the breast or trunk was stratified by skin cancer subtype, the SIRs were pronounced for melanoma (SIR, 1.37, 95 percent CI, 1.25–1.49) and hemangiosarcoma (SIR, 27.11, 95 percent CI, 21.6–33.61).

Receipt of radiation therapy was a significant risk factor for nonkeratinocyte skin cancer relative to chemotherapy and surgical interventions.

The findings suggest that although occurrences of nonkeratinocyte skin cancers are rare, clinicians should be aware of this elevated risk to help inform follow-up care.