Dear Sir,
I read with interest the article by Engels and Pfeiffer. 1 The authors have provided the first true population-based study on the demographic patterns of thymoma incidence and for this they should be commended. The study is limited, however, and some of the conclusions are thus questionable. Specifically, the authors contend that second cancers associated with thymoma are more restricted in type and less common than reported in previous studies. 2,3 They have attributed this to the fact that the other studies have overestimated the risk of second cancers as they were based at tertiary-referral centers. I doubt this explains the discrepancy and propose an alternative solution.
Any radiation oncologist would find it unusual that 70.1% of the patients in the study received radiotherapy. In typical practice, only about a third of thymoma patients ever are treated with radiation. This is because Masaoka stage I patients are typically treated and cured of their disease with surgery alone. Roughly two-thirds of all thymoma patients fall into this category. 4 Clearly, the population studied by Engels and Pfeiffer 1 is different from the populations examined in other series. Engels and Pfeiffer 1 used SEER data to collect cases of thymoma, but as they have mentioned, SEER only collects data