Chest wall pain after single-fraction thoracic stereotactic ablative Radiotherapy: Dosimetric analysis from the iSABR trial.

BACKGROUND AND PURPOSE: Concerns over chest wall toxicity has led to debates on treating tumors adjacent to the chest wall with single-fraction stereotactic ablative radiotherapy (SABR). We performed a secondary analysis of patients treated on the prospective iSABR trial to determine the incidence and grade of chest wall pain and modeled dose-response to guide radiation planning and estimate risk. MATERIALS AND METHODS: This analysis included 99 tumors in 92 patients that were treated with 25 Gy in one fraction on the iSABR trial which individualized dose by tumor size and location. Toxicity events were prospectively collected and graded based on the CTCAE version 4. Dose-response modeling was performed using a logistic model with maximum likelihood method utilized for parameter fitting. RESULTS: There were 22 grade 1 or higher chest wall pain events, including five grade 2 events and zero grade 3 or higher events. The volume receiving at least 11 Gy (V11Gy) and the minimum dose to the hottest 2 cc (D2cc) were most highly correlated with toxicity. When dichotomized by an estimated incidence of ≥ 20 % toxicity, the D2cc > 17 Gy (36.6 % vs. 3.7 %, p < 0.01) and V11Gy > 28 cc (40.0 % vs. 8.1 %, p < 0.01) constraints were predictive of chest wall pain, including among a subset of patients with tumors abutting or adjacent to the chest wall. CONCLUSION: For small, peripheral tumors, single-fraction SABR is associated with modest rates of low-grade chest wall pain. Proximity to the chest wall may not contraindicate single fractionation when using highly conformal, image-guided techniques with sharp dose gradients.

Pulmonary Hemorrhage in Patients Treated With Thoracic Stereotactic Ablative Radiotherapy and Antiangiogenic Agents.

INTRODUCTION: Severe pulmonary hemorrhage can occur in patients treated with thoracic stereotactic ablative radiotherapy (SABR) and vascular endothelial growth factor inhibitors (VEGFis). There is limited understanding of which patients are at risk for toxicity with the combination of thoracic SABR and VEGFis or how the risk differs over either therapy alone. METHODS: We evaluated a prospectively maintained cohort of 690 patients with 818 pulmonary tumors treated with highly conformal SABR. Rates of any-grade and grade 3 plus (G3+) pulmonary hemorrhage were compared between patients treated with or without VEGFi therapy across tumor locations. Outcomes were compared between patients treated with SABR plus VEGFi and a propensity-matched cohort of those treated with VEGFi therapy alone. RESULTS: Treatment with VEGFi plus SABR was associated with higher rates of G3+ pulmonary hemorrhage compared with those treated with SABR alone for the overall cohort (3-y incidence: 7.9% versus 0.6%, p < 0.01) and those with central tumors (19.1% versus 3.3%, p = 0.04). When further subdivided, there were significantly higher toxicity rates with VEGFi for the ultracentral (9.0% versus 45.0%, p = 0.044), but not central nonabutting tumors (0.0% versus 1.3%, p = 0.69). There was an increased incidence of G3+ hemorrhage in patients treated with VEGFi plus SABR compared with VEGFi alone (9.6% versus 1.3%, p = 0.04). CONCLUSIONS: The combination of VEGFi and SABR was associated with an increased risk of high-grade pulmonary hemorrhage over either therapy alone. Low rates of toxicity were observed when excluding patients with SABR to ultracentral tumors and applying highly conformal SABR techniques.

Radiation Therapy for Primary Cutaneous Gamma Delta Lymphoma Prior to Stem Cell Transplantation.

We present a patient with widespread PCGD-TCL of the bilateral arms and legs, who underwent radiotherapy with 34 Gy in 17 fractions using circumferential VMAT and 3-D printed bolus to the four extremities prior to planned stem cell transplant, who was then found to have progression in the liver, lung, and skin, followed by drastic regression of all in and out-of-field lesions on imaging 1.5 months later. The cause of regression may be related to a radiation-induced abscopal effect from the immunomodulatory effects of radiation, or related to immune reactivation in the setting of cessation of systemic immunosuppressive agents.