Long-term mortality from cardiac causes after adjuvant hypofractionated vs. conventional radiotherapy for localized left-sided breast cancer.

Background And Purpose: Ongoing concern remains regarding cardiac injury with hypofractionated whole breast/chest-wall radiotherapy (HF-WBI) compared to conventional radiotherapy (CF-WBI) in left-sided breast cancer patients. The purpose was to determine if cardiac mortality increases with HF-WBI relative to CF-WBI.

Materials And Methods: Between 1990 and 1998, 5334 women with early-stage breast cancer received post-operative radiotherapy to the breast/chest wall alone. A population-based database recorded baseline patient, tumor and treatment factors. Baseline cardiovascular risk factors were identified from hospital administrative records. A propensity-score model balanced risk factors between radiotherapy groups. Cause of death was coded as breast cancer, cardiac or other cause. Cumulative mortality from each cause after radiotherapy was estimated using a competing risk approach.

Results: For left-sided cases, median follow-up was 14.2 years. 485 women received CF-WBI, 2221 women received HF-WBI. There was no difference in 15-year mortality from cardiac causes: 4.8% with HF-WBI and 4.2% with CF-WBI (p=0.74), even after propensity-score adjustment (p=0.45). There was no difference in breast cancer mortality or other cause mortality. For right-sided cases, there was no difference in mortality for the three causes of death.

Conclusions: At 15-years follow-up, cardiac mortality is not statistically different among left-sided breast cancer patients treated with HF-WBI or CF-WBI.