Lung Cancer

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TU_24_3550 - Toxicities and Clinical Outcomes of Whole Pleural Intensity-Modulated Proton Therapy for Lung-Intact Malignant Pleural Mesothelioma

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Toxicities and Clinical Outcomes of Whole Pleural Intensity-Modulated Proton Therapy for Lung-Intact Malignant Pleural Mesothelioma
J. K. Molitoris1, E. Glass1, K. Miller2, M. Culligan3, J. S. Friedberg3, C. B. Simone II4, and S. N. Badiyan1; 1Maryland Proton Treatment Center, University of Maryland, Baltimore, MD, 2Division of Medical Oncology, University of Maryland, Baltimore, MD, 3Division of Thoracic Surgery, University of Maryland, Baltimore, MD, 4University of Maryland, Department of Radiation Oncology, Baltimore, MD

Purpose/Objective(s): Significant challenges impede the ability to safely deliver hemi-thoracic pleural irradiation for malignant pleural mesothelioma (MPM). Limited data currently exist on toxicities and outcomes for mesothelioma patients treated to an intact lung with proton therapy. We hypothesize that intensity-modulated proton therapy (IMPT) may facilitate safer delivery of radiotherapy in the definitive and adjuvant settings for MPM.

Materials/Methods: We assessed toxicities and early clinical outcomes of the first 10 consecutive patients treated with whole pleural (WP) IMPT for lung-intact MPM. Acute and subacute toxicities were scored based on CTCAE version 4. Kaplan-Meier was used to estimate local control, progression-free survival and overall survival.

Results: Patients were a median of 69 years old and had predominantly epithelial histology (70%), stage III (80%) and right-sided (70%) disease, and ECOG 0-1 performance status (80%). Nine (90%) had prior therapy, all receiving platinum/pemetrexed with a median of 4 cycles. They received definitive (90%) or salvage after extended pleurectomy/decortication failure (10%) WP-IMPT. Median prescribed WP dose was 45Gy (range 45.0-50.4 Gy/1.8-2.0 Gy) and median total dose was 54Gy (range 50.0-60.0 Gy/1.8-2.4 Gy). One patient discontinued WP-IMPT early due to decline of pre-existing multiple sclerosis. At a median follow-up of 6.5 months, treatment was well tolerated, with acute and subacute toxicities limited to grade 2 nausea (30%), grade 2 esophagitis (20%), and grade 2 (10%) and grade 3 (20%) pneumonitis. No other grade ≥2 toxicities were observed. Two (20%) patients had local/pleural progression occurring at 3 and 7 months post-IMPT, and 30% developed distant metastases. Six month estimated outcomes include: local control 87.5% (95% CI: 76 – 99), progression free survival 31% (95% CI: 14 - 48) and overall survival 64.3% (95% CI 48 – 81).

Conclusion: Our early experience with WP-IMPT for lung-intact mesothelioma, the largest such report to date, demonstrates that the treatment is well tolerated and can achieve excellent local control at 6 months, with continued follow-up necessary.

Author Disclosure: J.K. Molitoris: None. E. Glass: None. K. Miller: None. M. Culligan: None. C.B. Simone: Employee; Nemours/Alfred I. duPont Hospital for Children. Chair, Executive Council; Chair, Lung Committee; Proton Collaborative Group (PCG). Editor-in-Chief; Annals of Palliative Medicine. Chair, Lung Resource Panel; American Society for Radiation Oncology. S.N. Badiyan: None.

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