Early Experience Using Proton Beam Therapy for Extremity Soft Tissue Sarcoma: A Multi-Institution Study

B. Laughlin, M. A. Golafshar, S. K. Ahmed, T. Z. Vern-Gross, M. Seetharam, K. A. Goulding, I. A. Petersen, Jonathan Ben Ashman

Research output: Contribution to journalArticlepeer-review

Abstract

PURPOSE/OBJECTIVE(S): Proton beam therapy (PBT) may provide an advantage when planning selected patients with extremity soft tissue sarcoma (STS), especially for larger and anatomically challenging cases. We analyzed our early experience with PBT on toxicity and outcomes. MATERIALS/METHODS: A retrospective study was performed of 20 consecutive patients with extremity STS treated between June 2016 and September 2020, with pencil beam scanning PBT at two institutions with a median age 51.5 years (range, 19-78 years). Demographic, tumor, treatment, and toxicity characteristics were gathered from baseline to end of follow-up or death. Surgery was performed for all patients; chemotherapy and intraoperative electron radiotherapy boost were included for selected patients. Wound complications were defined as secondary operation for wound repair (debridement, drainage, skin graft, and muscle flap) or non-operative management requiring hospitalization. Dermatitis was graded according to the CTCAE scale. Analysis was performed with statistical software. RESULTS: All patients completed the prescribed course of PBT to a median dose of 5000 cGY RBE (range: 3000 - 6600 cGY RBE). Tumor presentation was primary (n = 17) or recurrent after prior combined modality therapy (n = 3). Tumor location was either lower extremity (n = 13) or upper extremity (n = 7). Median pre-treatment tumor size was 9.2 cm (range: 1.3 - 30.0 cm). Baseline staging for patients prior to PBT follows: 2 (10%) IA, 7 (35%) IB, 4 (20%) II, 3 (15%) IIIA, 3 (15%) IIIB, and 1 (5%) IV. Radiation was delivered pre-operatively in most patients (n = 18). Median follow-up was 13.7 months (range, 1.7 - 48.1 months). Nineteen patients (90%) were alive at the end of follow-up. Locoregional control was 100%. Four patients (20%) had developed metastatic disease by end of follow-up. Acute dermatitis was maximum grade 2 (n = 8, 40%) and grade 3 (n = 3, 15 %). After pre-operative radiation and surgical resection, acute wound complications occurred in 7 patients (39%). Intraoperative debridement and I&D, unplanned skin graft, muscle flap, and IV antibiotic use requiring hospitalization was required in 5 (25%), 3 (15%), 1 (5%), and 2 (10%), respectively. Tumor size was larger in patients with wound complications compared to no complications (median 15.3 cm [range 1.6-30.0 cm] vs 6.9cm [1.3-14.4 cm], P = 0.045). Factors such as patient age, tumor location, histology, chemotherapy, or IORT were not associated with wound complications. Rates of chronic G2+ pain, neuropathy, fibrosis, and lymphedema were 25%, 15%, 5%, and 5% respectively. CONCLUSION: This early study of PBT for challenging extremity STS cases demonstrates good local control, similar acute toxicity profile, and wound complication rate comparable to photons. Long term follow-up and further dosimetric analyses will provide further insight into potential advantages of PBT in this patient population.

Original languageEnglish (US)
Pages (from-to)e317-e318
JournalInternational journal of radiation oncology, biology, physics
Volume111
Issue number3
DOIs
StatePublished - Nov 1 2021

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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