Top Line: The clinical significance of heart dosimetry is quite difficult to tease out among patients receiving radiation for locally-advanced lung cancer.
The Study: The first, perhaps most obvious, reason is the latency of most radiation-induced cardiotoxicity (established by experiences of long term survivors of lymphoma and breast cancer survivors) frankly hasn’t been of historic concern for these patients with extremely limited life expectancies. A second is the struggle to tease out any potential badness of heart dosimetry from the well-known badness of large and/or centrally-located tumors. A 2018 analysis demonstrated that treatment volume shifts in the direction of the heart, while not intrinsically linked to bad anatomy, was significantly associated with worse survival. This similar study aimed to externally validate that heart dosimetry is a causal factor in survival outcomes. Looking back at the heart position on daily treatment cone beam CTs relative to position at planning for 489 patients receiving definitive radiation for locally-advanced non-small cell lung cancer. On multivariate analysis, a shift in heart position toward the treatment volume was indeed associated with worse overall survival approximately 50 months after treatment. What’s more, this was most pronounced among those with the lowest clinical features who presumably had the most to lose.
TBL: More data suggests “heart irradiation is a causal factor impacting the survival of lung cancer patients treated with radiotherapy.” | Brink, Radiother Oncol 2022