Sarcoma and Cutaneous Tumors
PV QA 2 - Poster Viewing Q&A 2
MO_22_2762 - Prospective Phase II Study of Scanned Beam Proton Therapy for Spine Sarcomas
Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3
Prospective Phase II Study of Scanned Beam Proton Therapy for Spine Sarcomas
D. J. Konieczkowski1,2, Y. L. E. Chen2, K. D. Bernstein2, B. Y. Yeap3, M. C. DiMaria4, W. Jiang5, N. Thomas2, S. L. McGovern6, J. T. Mullen7, J. H. Schwab8, F. J. Hornicek9, and T. F. DeLaney2; 1Harvard Radiation Oncology Program, Boston, MA, 2Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA, 3Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, 4Cancer Center Protocol Office, Massachusetts General Hospital, Boston, MA, 5Biostatistics Center, Massachusetts General Hospital, Boston, MA, 6The University of Texas MD Anderson Cancer Center, Houston, TX, 7Department of Surgical Oncology, Massachusetts General Hospital, Boston, MA, 8Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA, 9Department of Orthopaedic Surgery, University of California Los Angeles, Los Angeles, CA
Purpose/Objective(s): Pre- and/or post-operative radiation therapy (RT) may improve local control in patients undergoing surgery for spine sarcomas. In addition, definitive-intent RT may have a role in patients who do not undergo surgery. However, delivery of adequate RT doses is challenging due to proximity of normal structures. We previously reported a Phase II trial of passively scattered proton therapy for spine sarcoma. Here, we hypothesized that scanned beam proton therapy would allow high local control with acceptable toxicity.
Materials/Methods: We conducted a Phase II, NCI-sponsored clinical trial of scanned beam proton therapy for primary or recurrent chordomas and chondrosarcomas of the spine or sacrum. In patients undergoing surgery, CTV1 (encompassing pre-operative gross tumor plus a microscopic margin) was treated pre-or post-operatively to 45-50.4 GyE, CTV2 (encompassing pre-operative gross tumor) post-operatively to a total of 64.8-70.2 GyE, and GTV (only if residual gross disease) post-operatively to a total of 77.4-79.2 GyE. Surgery consisted of en bloc resection with the goal of R0 margins, although in some cases a microscopic positive margin (R1) was planned with the goal of preserving nerve function. In patients not receiving surgery, the same CTV1 and GTV dose levels were used.
Results: 60 patients (51 chordoma, 9 chondrosarcoma) were enrolled between February 2011 and March 2017. 63% were male, with a median age of 59 (range 18-89). All but one had primary tumors. Tumors were predominantly sacral/coccygeal (n=35, 58.3%). 51 patients (85%) underwent surgery, of whom 65% had R0, 29% R1, and 6% R2 resections (all at outside institutions prior to trial enrollment). In surgical patients, RT was most often delivered both pre- and post-operatively (32 patients, 63%; median total dose 68.7 GyE), and less often pre-operatively only (7 patients, 12%; median 50.4 GyE) or post-operatively only (12 patients, 20%; median 70.8 GyE). 9 patients (15%) underwent definitive RT without surgery (median 77.4 GyE). With a median follow-up of 28.3 months among 55 patients still alive, two-year local control was 92%, recurrence-free survival (RFS) 85%, and overall survival 94%. On univariate analysis, post-operative only RT (vs both pre- and post-operative) was associated with shorter RFS (62.9% vs 90.8% at two years, HR 5.86 [1.75-19.7], p=0.005); there was also a trend towards shorter RFS in non-R0 resections (71.6% vs 89.1% at two years, HR 2.65 [0.87-8.01], p=0.074). No local or distant recurrences were observed in the definitive RT arm. Acute and chronic toxicities were mild (3.4% grade 3-4, each); one patient experienced a late grade 2 sacral insufficiency fracture, and two patients experienced late grade 1 hardware failures. No RT-associated myelopathies were observed.
Conclusion: Scanned beam proton therapy can be given safely for spine chordomas and chondrosarcomas. Although follow-up is limited, initial results suggest promising outcomes in both the peri-operative and definitive settings.
Author Disclosure: D.J. Konieczkowski: None. Y.E. Chen: Employee; Beth Israel Deaconess Medical Center. K.D. Bernstein: None. B.Y. Yeap: None. M.C. DiMaria: None. W. Jiang: None. S.L. McGovern: Independent Contractor; MD Anderson Physicians Network. Honoraria; American College of Radiology. Travel Expenses; American College of Radiology. J.T. Mullen: None. F.J. Hornicek: None.