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Purpose: There is very little information detailing outcomes and toxicity following reirradiation for ultracentrally located thoracic tumors, and detailed dosimetric data are nonexistent. These data are critical for the safe management of these extremely difficult cases. Methods and Materials: The records of 15 individuals undergoing 10-fraction hypofractionated stereotactic body radiation therapy for the management of ultracentrally located thoracic tumors between 2009 and 2020 at a single institution were retrospectively reviewed. Treatment outcomes and toxicity were analyzed. A detailed dosimetric analysis of treatment plans and centrally located organs at risk (OARs) from the initial reirradiation and cumulative radiation therapy courses were presented. Results: At a median follow up of 10 months, the 1- and 3-year overall survival, progression-free survival, and local control were 52% and 28%, 33% and 28%, and 76% and 61%, respectively. Treatment-related adverse events were low, with 5 individuals (33%) developing ≥grade 2 pneumonitis (grade 2 = 4, grade 3 = 1). Dosimetric parameters were not associated with the development of clinically relevant pneumonitis. No adverse events involving central OARs (esophagus, great vessels, and primary bronchial tree) were identified. The median cumulative mean lung dose was 24 Gy equivalent total doses in 2 Gy fractions (EQD2) (range, 10-33 Gy), with a volume receiving 20 G (V20) of 33% (range, 11%-51%). The median esophageal, primary bronchial tree, and great vessel maximum doses (Dmax) were 93.2 Gy (EQD2) (range, 50-148 Gy), 163 Gy (range, 77-204 Gy), and 191 Gy (range, 129-262 Gy), respectively. Conclusions: The current investigation is the first to provide detailed cumulative dosimetric data from a cohort of patients comprised entirely of ultracentrally located thoracic tumors. Despite unfavorable anatomic tumor location, given an intimate association with critical OARs, delivering an ablative dose with a 10-fraction hypofractionated stereotactic body radiation therapy course can serve as a feasible option for these challenging cases.

Purpose: The treatment of apical lung tumors with stereotactic body radiation therapy (SBRT) is challenging due to the proximity of the brachial plexus and the concern for nerve damage. Methods and materials: Between June 2009 and February 2017, a total of 75 consecutive patients underwent SBRT for T1-T3N0 non-small cell lung cancer involving the upper lobe of the lung. All patients were treated with 4-dimensional computed tomography (CT)-based image guided SBRT to a dose of 40 to 60 Gy in 3 to 5 fractions. For dosimetric analysis, only apical tumors as defined by the location of the tumor epicenter superior to the aortic arch were included. The anatomical brachial plexus was delineated using the Radiation Therapy Oncology Group atlas. Results: Thirty-one patients with 31 apical lung tumors satisfied the anatomical criteria for inclusion. The median age was 73 years (range, 58-89). The median planning target volume was 26.5 cc (range, 8.2-81.4 cc). The median brachial plexus, brachial plexus maximum dose (Dmax), Dmax per fraction, V22 (cc, 3-4 fractions), V30 (cc, 5 fractions), and biologically effective dose 3 Gy were 15.8 Gy (range, 1.7-66.5 Gy), 3.4 Gy (range, 0.6-14.7 Gy), 0.0 cc (range, 0-0.9 cc), 0.06 cc (range, 0-2.5 cc), and 31.5 Gy (range, 3.3-133.1 Gy), respectively. At a median follow-up of 17 months, the observed incidence of brachial plexopathy was 0%. Conclusions: There is significant variation in dose to the brachial plexus for patients treated with SBRT for apical lung tumors. Although the incidence of neuropathic symptoms in this series was zero, further attention should be focused on the clinical implications of these findings.