Cardiac Dose and Survival After Stereotactic Body Radiotherapy for Early-stage Non–Small-cell Lung Cancer
Cardiac dose is a predictor of survival after chemoradiation for locally advanced lung cancer; however, its effect on survival after stereotactic body radiotherapy has not been adequately studied. We analyzed the cardiac dose–volume metrics and survival for 102 patients who had undergone lung stereotactic body radiotherapy. No cardiac dose metric was associated with survival, and no acute cardiac toxicity was identified, despite extremely high doses to small volumes of the heart in some cases.Introduction:
Recent analyses have identified cardiac dose as an important predictor of overall survival (OS) after chemoradiation for locally advanced non–small-cell lung cancer (NSCLC). However, the survival influence of the cardiac dose after stereotactic body radiotherapy (SBRT) is unknown. We performed a dose–volume histogram (DVH) analysis of patients treated with SBRT for early stage NSCLC to examine survival and cardiac toxicity.Materials and Methods:
We reviewed the medical records of patients who had undergone SBRT for early-stage NSCLC from June 2007 to June 2015 and documented the cardiac DVH parameters, including the maximum and mean dose and percentage of volume receiving >5, >10, >20, and >30 Gy (V5, V10, V20, and V30, respectively). The biologically effective doses and 2-Gy equivalent doses were also calculated. The DVH parameters were assessed as predictors of OS using Cox regression analysis.Results:
We identified 102 patients with 118 treated tumors. At a median follow-up period of 27.2 months (range, 9.8-72.5 months), the 2-year OS estimate was 70.4%. The cardiac DVH parameters were as follows: maximum dose, median, 14.2 Gy (range, 0.3-77.8 Gy); mean dose, median, 1.6 Gy (range, 0-12.6 Gy); and V5, median, 8.7% (range, 0%-96.4%). We identified no correlation between OS and any cardiac dose parameter. No patient developed acute (within 3 months) cardiac toxicity. Four patients died of cardiac causes; all had had preexisting heart disease.Conclusion:
In our cohort, cardiac dose was not a predictor of OS after lung SBRT, despite a subset of patients receiving high maximum cardiac doses. The findings from our limited cohort showed that high doses to small volumes of the heart appear safe. Analyses of larger patient cohorts with longer follow-up durations are needed to better delineate the safe cardiac DVH constraints for SBRT.