Radiotherapy increases risk of thoracic STS in breast cancer survivors

Amongst 2 cohorts of US breast cancer survivors, radiotherapy was found to be the strongest risk factor for developing thoracic soft tissue sarcoma (STS), according to a study. In addition, researchers noted that a history of hypertension and diabetes were each associated with an increased risk of angiosarcoma.

The study included cohorts of women from Kaiser Permanente (KP cohort) and 15,940 women from the SEER registry (SEER cohort) diagnosed with breast cancer.

In the KP cohort, 19 of 15,940 eligible, evaluable women developed a thoracic STS, including 11 angiosarcomas, during a median of 9.3 years follow-up. Approximately 95% of thoracic STS developed in women treated with radiotherapy. No association was found with prescribed dose, fractionation, or boost.

Alkylating agents were associated with an increased risk of developing other sarcomas, and a history of hypertension and diabetes (were each associated with around a 5-times increased risk of angiosarcoma.

In the SEER cohort, 430 of 457,300 eligible, evaluable women developed a thoracic STS, including 268 angiosarcomas, during a median of 8.3 years follow-up. Approximately 78% of thoracic STS developed in women treated with radiotherapy.

At 10 years after radiotherapy, the cumulative incidence of thoracic STS was 0.21% and 0.15% in the KP cohort and SEER cohort, respectively.

Reference
Veiga LHS, Vo JB, Curtis RE, et al. Treatment-related thoracic soft tissue sarcomas in US breast cancer survivors: a retrospective cohort study. Lancet Oncol. 2022;S1470-2045(22)00561-7. doi: 10.1016/S1470-2045(22)00561-7. Epub ahead of print. PMID: 36240805.