Main Session
Sep 27
PQA 02 - Pediatric Cancer, Sarcoma and Cutaneous Tumors, Medical Education & Professional Development, and Health Services Research

2319 - Patterns of Care and Outcomes of Palliative Radiation Therapy to Mesothelial Thoracic Metastases in Children and Young Adults with Osteosarcoma

04:00pm - 05:00pm ET
Poster Hall - Exhibit Hall A
Screen: 13
POSTER

Presenter(s)

Ahmed Elmotayam, MD Headshot
Ahmed Elmotayam, MD - Brigham and Women's Hospital/Dana Farber Cancer Institute, Boston, MA

A. Elmotayam1, D. Sebastian2, K. Wong3, R. Sanjeev4, D. A. Haas-Kogan5, K. X. Liu6, T. Yock7, K. Marcus7, S. G. Dubois8, D. S. Shulman9, S. Forrest10, A. Li11, J. Morrow10, B. Weil10, K. Ecklund10, S. Voss10, C. Heincelman10, M. Anderson10, K. A. Janeway12, and H. Elhalawani6; 1Brigham and Women's Hospital/Dana Farber Cancer Institute, Boston, MA, United States, 2Northeastern University, Boston, MA, 3University Of Rochester, Rochester, NY, 4Dartmouth college, Hanover, NH, 5Department of Radiation Oncology, Mass General Brigham, Boston, MA, 6Brigham and Women's Hospital, Boston, MA, 7Mass General Brigham, Boston, MA, 8Dana-Farber/Boston Children's Cancer and Blood Disorders Center, Boston, MA, 9Department of Medical Oncology, Dana Farber Cancer Institute, Boston, MA, 10Boston Children's Hospital, Boston, MA, 11Dana-Farber Cancer Institute, Boston, MA, 12Dana-Farber/Boston Children?s Cancer and Blood Disorders Center, Boston, MA

Purpose/Objective(s): Data on the management of mesothelial thoracic metastases (MTMs) in osteosarcoma are scarce. We report outcomes and treatment characteristics of osteosarcoma patients who received palliative radiotherapy (RT) for MTMs.

Materials/Methods: We conducted an IRB-approved single-institution retrospective chart review of children, adolescents, and young adults (AYAs) =40 years old diagnosed with osteosarcoma between 2005 and 2023, with mesothelial metastatic disease to the pleura and/or pericardium treated with photon RT. We outlined patient, disease, and treatment characteristics. We report outcomes, including MTM local control (LC) and overall survival (OS), using JMP 19.0.

Results: 17 patients were identified, 11 males, median age at initial diagnosis: 16.7 (IQR: 12.7-19.1) with 25 metachronous MTMs (19 pleural, 6 pericardial; 16 with calcifications). 10 MTMs were symptomatic; median volume 63.2 ml (IQR: 6.5 -148.5) and max dimension 3.9 cm (IQR: 2.3 - 7.8). All primary tumors arose from the appendicular skeleton; median size 12cm (IQR, 7.9–16.5), and 76.5% were metastatic at presentation. Most frequently used MTM RT dose fractionations were 30Gy/10fx (n=6), 40Gy/10fx (n=3), and 56Gy/8fx (n=3). Median RT equivalent dose in 2Gy fractions (EQD2) at alpha/beta of 10 was 46.7Gy (IQR: 32.5-70); two courses were delivered in the postoperative setting. Three patients developed symptoms during RT, which were resolved in 66.7% of the cases within 6 months post-RT. Concurrent therapies were administered during 15 RT courses, most commonly multi-target tyrosine kinase inhibitors (n=10). Median change in max. Dimension at 1st follow-up was –1.4% (IQR: -29.2 to 24.6). On a univariable analysis, higher RT EQD2 was associated with better MTM LC [HR= 0.06 (95% CI 0.003-0.52; p=0.009)]. The 6-month MTM LC rate was 64%. Median OS was 3.5 years (IQR: 2.5-8).

Conclusion: RT has been used in the management of children and AYAs with osteosarcoma MTMs with varying outcomes. Our data suggest that higher radiation doses may result in better MTM LC. Larger studies are needed to better characterize the safety, efficacy, and optimal use of various treatment strategies.