Abstract
Purpose/Objective(s)Multimodality treatments together with local proton therapy (PT) are commonly used in unresectable primary bone malignancies in order to provide better tumor control rate while maintaining good feasibility. The aim of this study is to provide data on outcome of PT for the challenging cohort of pelvic and lumbar bone tumors.Methods and MaterialsThis retrospective study includes all patients with primary bone malignancy of the pelvis and lumbar spine receiving PT in our institution between May 2013 and December 2019 enrolled in the prospective registries KiProReg and ProReg collecting information on demographics, treatment, tumor characteristics, toxicities, and outcome.ResultsEighty-one patients were enrolled with a median age of 19.7 years (1.3–85.8). The median follow-up time was 27.5 months (1.2–83.2). The majority of patients was male (64.2%), ECOG status of 0–1 (75.2%), underwent only biopsy (50.6%), received chemotherapy (69.1%) and was assigned for definite PT (70.4%). The predominant tumor characteristics were as follows: Ewing’s sarcoma histology (58%), negative nodal involvement (97.5%) and no metastasis at diagnosis (81.5%). Median maximal diameter of tumor was 8 cm (1.4–20). LC, EFS and OS rate were 76.5, 60, and 88.1% at two years and 72.9, 45.7, and 68.9% at three years, respectively. Age over 20 years was a significant negative factor for LC, EFS, and OS. Metastatic disease at initial diagnosis affected OS and ECOG status of 2–4 affected EFS only. Regarding 17 relapsed cases (21%), isolated distant relapse was the most common failure (46.9%) followed by local failure (40.6%). Eleven out of 14 evaluable patients relapsed within high-dose region of radiotherapy. Acute grade 3–4 toxicity was found in 41 patients (50.6%) and all toxicities were manageable. Late grade 3 toxicity was reported in 7 patients (10.4%) without any of grade 4. Most common higher grade acute and late side effects concerned hematologic and musculoskeletal toxicity.ConclusionProton therapy resulted in good oncological outcomes when being part of the multimodality treatment for pelvic and lumbar primary bone malignancies. However, distant metastases and local failures within the high-dose region of radiotherapy are still a common issue. Acute and late toxicities of combined therapy were acceptable.
Highlights
Primary bone malignancy is a rare malignant disease [1, 2]
While clinical data on proton therapy in primary bone malignancy of the pelvic and lumbar area is still limited, this study provides clinical tumor outcome, toxicity and pattern of failure after treatment with proton therapy from our prospective registries embedded in a large interdisciplinary sarcoma center and the national study framework
Multimodality treatment of pelvic and lumbar primary bone malignancy combined with proton therapy provided high local control and overall survival rates in a high-risk population despite limited extent of surgery for most of the patients
Summary
Resection is still the main curative local treatment for bone tumors [3], but not all patients are suitable for total tumor removal with adequate margins, especially for tumors of difficult locations as pelvis and lumbar spine [4, 5]. While proton passes through the body of a patient, it releases kinetic energy in the certain depth without any dose exposure to normal tissue distal to this area. The peak of kinetic energy deposited in tissue is called Bragg peak. Due to this physical advantage, PT offers the chance to increasing RT doses while lowering the burden to the surrounding normal tissues [11, 12]
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