Background
Previous studies with the majority of breast cancer (BC)
patients treated up to 2000 provided evidence that radiation dose to the heart
from radiotherapy (RT) was linearly associated with increasing risk for
long-term cardiac disease. RT techniques changed substantially over time. This
study aimed to investigate the dose-dependent cardiac risk in German BC
patients treated with more contemporary RT.
Methods
In a cohort of 11,982 BC patients diagnosed in 1998–2008, we
identified 494 women treated with 3D-conformal RT who subsequently developed a
cardiac event. Within a nested case-control approach, these cases were matched
to 988 controls. Controls were patients without a cardiac event after RT until
the index date of the corresponding case. Separate multivariable conditional
logistic regression models were used to assess the association of radiation to
the complete heart and to the left anterior heart wall (LAHW) with cardiac
events.
Results
Mean dose to the heart for cases with left-sided BC was
4.27 Gy and 1.64 Gy for cases with right-sided BC. For controls,
corresponding values were 4.31 Gy and 1.66 Gy, respectively. The odds
ratio (OR) per 1 Gy increase in dose to the complete heart was 0.99 (95%
confidence interval (CI): 0.94–1.05, P = .72). The OR per
1 Gy increase in LAHW dose was 1.00 (95% CI: 0.98–1.01, P = .68).
Conclusions
Contrary to previous studies, our study provided no evidence
that radiation dose to the heart from 3D-conformal RT for BC patients treated
between 1998 and 2008 was associated with risk of cardiac events.
