Proton therapy for thymic malignancies: multi-institutional patterns-of-care and early clinical outcomes from the proton collaborative group and the university of Florida prospective registries

Acta Oncol. 2019 Jul;58(7):1036-1040. doi: 10.1080/0284186X.2019.1575981. Epub 2019 Feb 20.


Objective: Thymic malignancies (TM) are rare tumors with long-term survivorship, causing concerns for radiotherapy-related late side effects. Proton therapy (PT) reduces the radiation dose to organs at risk, potentially decreasing long-term toxicities while preserving disease control. We report patterns-of-care and early clinical outcomes after PT for thymoma and thymic carcinoma. Methods: Between January 2008 and March 2017, 30 patients with TMs enrolled on one of two IRB-approved prospective protocols and received postoperative or definitive PT. Clinical outcomes, pathology, treatment dose, toxicities, and follow-up information were analyzed. Results: Twenty-two thymoma patients with a median age of 52.1 years (range, 23-72) received a median RT dose of 54 Gy (RBE) (range, 45-70) either postoperatively (91%) or definitively (9%); 23% received adjuvant chemotherapy. Among eight thymic carcinoma patients, the median age was 65.5 years (range, 38-88) and median RT dose was 60 Gy (RBE) (range, 42-70) delivered postoperatively (75%) or definitively (25%); 50% received chemotherapy. Median follow-up for all patients was 13 months (range, 2-59 months). Five patients relapsed, one locally (3%). Three patients died of disease progression, including two thymomas and one thymic carcinoma patient; a fourth died of intercurrent disease. One patient with thymic carcinoma and 1 with thymoma are alive with disease. No patients treated with PT for their initial disease (de novo) experienced grade ≥3 toxicities. The most common grade 2 toxicities were dermatitis (37%), cough (13%), and esophagitis (10%). Conclusion: Adjuvant and definitive PT are being used in the treatment of TMs. Early results of the largest such cohort reported to date demonstrates an acceptable rate of recurrence with a favorable toxicity profile. Longer follow-up and a larger patient cohort are needed to confirm these findings.

Publication types

  • Multicenter Study

MeSH terms

  • Adult
  • Aged
  • Chemotherapy, Adjuvant / statistics & numerical data
  • Female
  • Florida / epidemiology
  • Follow-Up Studies
  • Humans
  • Male
  • Middle Aged
  • Neoplasm Recurrence, Local / epidemiology*
  • Neoplasm Recurrence, Local / prevention & control
  • Practice Patterns, Physicians' / statistics & numerical data*
  • Prospective Studies
  • Proton Therapy / adverse effects
  • Proton Therapy / statistics & numerical data*
  • Radiation Injuries / epidemiology*
  • Radiation Injuries / etiology
  • Radiotherapy Dosage
  • Radiotherapy, Adjuvant / adverse effects
  • Radiotherapy, Adjuvant / statistics & numerical data
  • Registries / statistics & numerical data
  • Retrospective Studies
  • Thymectomy
  • Thymus Neoplasms / mortality
  • Thymus Neoplasms / therapy*
  • Time Factors
  • Treatment Outcome
  • Young Adult