Cancer outcomes and cardiopulmonary toxicities for black patients with breast cancer treated with proton therapy.

Background: Black women have a 40% higher breast cancer (BC) mortality rate than White women and are at a higher risk of acquiring cardiovascular disease. Proton therapy (PT) can be used to mitigate cardiac radiation exposure; however, PT remains a scarce resource in the United States. We report on the cardiovascular profiles of patients undergoing PT to determine the potential benefit of PT for Black women when compared to non-Black patients.

Methods: We retrospectively analyzed 599 BC patients who received PT from June 2016 to December 2021 at the Maryland Proton Treatment Center. A variety of sociodemographic, disease, and treatment variables were analyzed using descriptive statistics.

Results: With a median follow-up of 26 months (range: 0.47-90 months), Black patients comprised 31.6% of the population and presented with higher rates of hypertension (p < .001), cardiopulmonary conditions (p < .001), and a larger median BMI (p = .015) when compared to the other cohort, a trend that persisted at time of post-PT follow-up. Black women had higher rates of triple negative disease (p < .001) with subsequent greater receipt of neoadjuvant chemotherapy (p = .039). Pulmonary events were 2.6-times more likely to occur in Black patients vs the non-Black cohort after PT (OR : 2.60; CI: 1.39-4.88; p = .003).

Conclusions: Black women presenting for PT had higher baseline risks of cardiovascular co-morbidities combined with more aggressive BC biology and a subsequent 2.6-fold increased risk of pulmonary events after PT. Our findings support the use of advanced radiation techniques as means to spare important organs-at-risk, especially in historically marginalized populations.