The role of radiation therapy in malignant thymoma: a Surveillance, Epidemiology, and End Results database analysis.

INTRODUCTION: The potential benefits and long-term complications of radiotherapy treatment for malignant thymoma are unclear. This is a retrospective analysis of outcome in patients with malignant thymoma from the Surveillance, Epidemiology, and End Results database between 1973 and 2005.
METHODS: Of the 1987 patients identified, 1334 were analyzed. Patients were categorized according to the Masaoka staging system as stage I to IIA, IIB or III to IV. The primary end points were overall survival, cardiac mortality, and the development of secondary malignancies.
RESULTS: Patients received surgery and radiation (50%), surgery alone (26%), radiation alone (12%), or no treatment (12%). The median follow-up time for survivors was 65 months (range, 1-361 months). There was no significant increase in the 12-year cumulative incidence rate of death from heart disease (10.2% radiation versus 7.5% no radiation, p = 0.83) or incidence of secondary malignancies (11.7% versus 12.4%, p = 0.70) with radiation. Compared with surgery alone, adjuvant radiation significantly improved overall survival in patients with stage III to IV disease (p = 0.04) and demonstrated a nonsignificant trend in patients with stage IIB disease (p = 0.09). However, after excluding patients surviving less than 4 months to account for surgical mortality, the benefit with radiation was no longer significant (stage IIB: p = 0.45, stage III-IV: p = 0.44).
CONCLUSIONS: Radiation does not seem to increase the risk of cardiac mortality or secondary malignancy in patients with malignant thymoma. Although the routine use of postoperative radiotherapy in malignant thymoma does not appear warranted, high-risk patients may benefit from adjuvant radiation. This study can help to design prospective trials to further establish the role of radiotherapy in malignant thymoma.