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.
Two large series have reported outcomes. In the first study, 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 III thymoma underwent surgery and additional radiation therapy. Patients with stage IV thymoma were treated with radiation therapy or chemotherapy. For patients with stage III or stage IV thymoma, the 5-year survival rates were 93% for patients treated with total resection, 64% for patients treated with subtotal resection, and 36% for patients whose disease was inoperable. Prophylactic mediastinal radiation therapy did not appear to prevent local recurrences effectively in patients with totally resected stage III thymoma. Adjuvant therapy including radiation or chemotherapy did not appear to improve the prognosis in patients with totally resected stage III or stage IV thymoma.
In the second study, 1,334 patients diagnosed and treated between 1973 and 2005 were identified in a SEER database. At a relatively short median follow-up of 65 months, radiation therapy did not appear to increase the risk of cardiac mortality or secondary malignancy. Routine use of PORT did not appear to improve long-term survival.
Most invasive thymomas have been found to be relatively sensitive to cisplatin-based combination chemotherapy regimens. The combinations that follow have reported objective response rates from 79% to 100% with subsequent resectability rates ranging between 36% and 69%:[13,14,15,16,17,18,19,21]