KEY POINTS
- The analysis included 50 patients with left-sided locally advanced lung cancer treated with definitive photon radiotherapy to 60 Gy in 30 fractions. Twenty-one cardiac substructures were retrospectively contoured.
- Mean whole-heart dose looked reassuring at 8.9 Gy, yet 11 cardiac substructures had cohort-average mean doses above 10 Gy.
- The highest mean exposures were the aortic arch at 38.6 Gy, pulmonary artery 33.3 Gy, pulmonary veins 28.8 Gy, and left circumflex coronary artery 27.3 Gy. Mean LAD dose was 18.8 Gy, with LAD V15 averaging 52.7%.
- Fifteen higher-exposure cases underwent strategic replanning. Their baseline mean heart dose was 13.5 Gy and LAD V15 was 83.8%.
- Replanning reduced mean heart dose to 9.7 Gy and LAD V15 to 13.7%, an absolute reduction of 70.1 percentage points. Mean dose to 13 of 14 evaluated cardiac structures fell.
- These gains did not significantly worsen conventional thoracic OAR metrics: lung V20, mean lung dose, mean esophageal dose and spinal cord D0.03cc all remained within institutional constraints, with no significant differences between original and replanned plans.
CLINICAL TAKEAWAY
Mean heart dose can hide major coronary, atrial and vascular hotspots in left-sided lung RT. This study does not establish validated substructure constraints or demonstrate fewer cardiac events, but it shows that substantial cardiac-substructure sparing may be achievable without obvious dosimetric trade-offs.