Sinoatrial Node Toxicity after Stereotactic Ablative Radiotherapy to Lung Tumors

Publication date: Available online 13 April 2017
Source:Practical Radiation Oncology
Author(s): Yushen Qian, Han Zhu, Erqi L. Pollom, Ben Y. Durkee, Aadel A. Chaudhuri, Michael Gensheimer, Maximilian Diehn, David B. Shultz, Billy W. Loo
PurposeStereotactic ablative radiotherapy (SABR) is an established treatment for selected lung tumors. Sinoatrial node (SAN) toxicity after thoracic SABR has not been reported in the literature. We sought to understand the risk of SAN toxicity owing to incidental dose to the SAN from SABR.Materials and MethodsWe conducted a retrospective review of patients with early-stage lung cancer or limited pulmonary metastases who underwent thoracic SABR to a right-sided central lung tumor (within 2cm of the mainstem bronchus or other mediastinal structures) between January 2008 and December 2014, analyzed a subset whose treatment imparted dose to the SAN exceeding 10% of the prescription dose, and examined patient and treatment dosimetric characteristics. Mean follow-up interval was 28months. Time to toxicity was defined from start of SABR.ResultsOf 47 patients with central tumors in the right lung treated with SABR reviewed, 13 met our study criteria. A contouring atlas of regional cardiac anatomy was created. One patient treated with SABR for non-small cell lung cancer at the right hilum developed symptomatic sick sinus syndrome, requiring pacemaker placement 6months after treatment. Her acute presentation and short interval between SABR and onset of symptoms suggest that SAN toxicity was likely due to radiation induced injury. Both her age and mean dose to her SAN were the third highest in our cohort. She remained free from cancer progression at 24months follow-up. Twelve additional patients who received significant dose to the SAN from SABR did not develop toxicity.ConclusionWhile uncommon, SAN toxicity from SABR to right sided central thoracic tumors should be recognized and followed in future studies.SummaryIn this first-time clinical case series of 13 patients who received modest incidental radiation to the sinoatrial node (SAN) from SABR for lung tumors, one patient developed symptomatic sick sinus syndrome, requiring pacemaker placement 6months after treatment. Both her age and mean dose to her SAN were the third highest in our cohort. While uncommon, SAN toxicity from SABR to right sided central thoracic tumors should be recognized and followed in future studies.



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