Top Line: Does radiation dose to the sinoatrial node increase the risk of atrial fibrillation?
The Study: There is an ever-growing list of cardiac substructures that have been dosimetrically associated with adverse cardiac events after radiation for NSCLC. The most frequently studied events are ischemic events, but what about atrial fibrillation? This retrospective study of 560 patients treated for NSCLC (57%) or SCLC (43%) sought to determine whether dose to the atria, ventricles, coronary arteries, and conduction nodes was associated with developing AF. During a median follow up of 36 months for NSCLC patients and 26 months for SCLC patients, 4.6% developed new onset AF while 2% developed non-AF cardiac events. While heart substructure dose was similar between the SCLC and NSCLC cohorts, almost twice as many NSCLC patients developed AF. Among cardiac substructures, maximum dose to the sinoatrial node (SAN) was the strongest predictor of developing AF followed by SAN V15Gy. SAN Dmax was also associated with overall survival. The optimal SAN Dmax cutoff was much higher in the SCLC cohort (53.5Gy) than the NSCLC cohort (20Gy). Given similar heart dosimetry in each cohort, it is unclear why this difference was seen, but one possibility is that there were simply more events to analyze in the NSCLC cohort. Regardless, shooting for a more conservative SAN Dmax during optimization may help reduce the risk of AF. Don’t forget to also optimize LAD V15 in addition to overall heart dose.
TBL: Higher maximum dose to the SA node is associated with an increased risk of AF and mortality among patients receiving radiation for SCLC and NSCLC. | Kim, JAMA Oncol 2022