Excellent long-term survival can be obtained following complete surgical excision for a pathologic stage I thymoma. There appears to be no benefit to adjuvant radiation therapy following complete resection of encapsulated noninvasive tumors.[1,2] For patients with stage II thymomas with pathologically demonstrated capsular invasion, adjuvant radiation therapy following complete surgical excision has been considered a standard of care despite the lack of prospective clinical trials.[3,4]
Note: Some citations in the text of this section are followed by a level of evidence. The PDQ editorial boards use a formal ranking system to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for more information.)
Incidence and Mortality
Note: Estimated new cases and deaths from testicular cancer in the United States in 2012:
New cases: 8,590.
Most studies use 40 Gy to 70 Gy with standard fractionation scheme (1.8–2.0 Gy/fraction). Some, but not all, retrospective clinical studies show improved local control and survival with the addition of postoperative radiation therapy (PORT).[5,6,7,8][Level of evidence: 3iiiDiv] More recent retrospective studies have found no outcome difference in patients treated with or without PORT following complete resection of the thymic tumor.[8,9,10,11,12]
In the largest series reported to date, data was obtained from 1,320 Japanese patients. The Masaoka clinical stage was found to correlate well with prognosis of thymoma and thymic carcinoma. Patients with stage I thymoma were treated with surgery only, and patients with stage II thymoma underwent surgery and additional radiation therapy. Prophylactic mediastinal radiation therapy did not appear to prevent local recurrences effectively in patients with totally resected stage II thymoma.
The role and risks of adjuvant radiation therapy for patients with completely resected stage II thymomas need further study. To avoid the potential morbidity and costs associated with thoracic radiation, PORT may be reserved for stage II patients where adjacent organs are within a few millimeters or involve of the surgical margin as determined by both pathological and intraoperative findings.
Current Clinical Trials
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with stage I thymoma and stage II thymoma. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
General information about clinical trials is also available from the NCI Web site.
Operable or Potentially Operable Stage III and Stage IVA Thymoma
Stage III thymoma may be difficult to identify prior to surgery as invasion of adjacent subtle invasion to the adjacent organs may only be identified at the time of mediastinal exploration. Such patients often receive aggressive surgical resection including wide surgical margins with consideration of adjuvant radiation therapy. Invasion of local organs can be apparent on pretreatment computed tomographic imaging. Such patients may be offered combined modality treatment with chemotherapy followed by surgery and/or radiation therapy.[13,14,15,16,17,18,19,20] The optimal strategy for induction therapy, which minimizes operative morbidity and mortality and optimizes resectability rates and ultimately survival, currently remains unknown.