This finding, the authors say, is at least partly because even without radiotherapy, their early-stage thymoma patients had good long-term outcomes after complete resection, "which made it difficult to demonstrate that postoperative radiotherapy had a further benefit on survival."

Dr. Tomoki Utsumi from Osaka University Graduate School of Medicine and colleagues investigated the impact of postoperative radiation on survival in 324 patients who underwent complete resection of a thymoma between 1970 and 2005.

The actuarial 10- and 20-year disease-specific survival rates were 92.8% and 83.5%, respectively, for patients who received postoperative radiation, the authors report, compared with 94.4% and 94.4%, respectively, for those treated without radiation therapy (P=0.2208).

Actuarial overall survival rates at 10 and 20 years were 80.7% and 56.5% for those who received postoperative radiation therapy and 86.2% and 40.4% for those who did not (P=0.0640).

In addition, radiation therapy did not impact survival in subgroups of patients stratified by disease stage or WHO cell type, the researchers note.

"Surgical resection alone is sufficient for thymoma patients with Masaoka stage I and II and those with WHO cell types A, AB, and B1," Dr. Utsumi and associates write. In these groups, 10-year disease-specific survival was 100% without radiation.

"Furthermore," they conclude, "an optimal treatment strategy should be established for patients with Masaoka stage III/IV and WHO cell type B2/B3 thymomas," whose survival - while unaffected by radiation therapy -- is reduced compared to patients with earlier stage disease.

Cancer 2009;115:5413-5420.

Last Updated: 2009-12-01 17:45:49 -0400 (Reuters Health)

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