Reply to K. P. Dieckmann

Abstract

We thank Dr Dieckmann for his letter 1 in response to our recently published article. 2 Our study showed a higher absolute excess risk for developing a contralateral testicular germ cell tumor (CTGCT) in primary seminoma compared with primary nonseminoma. 2 This is in line with the main result of our study, namely, that receipt of platinum-based chemotherapy is associated with a dose-dependent decrease in the risk of developing a CTGCT, and the fact that platinum-based chemotherapy is offered in a higher proportion to patients with nonseminoma, to which Dr Dieckmann also alludes. 1 Our multivariable (cause-specific) analysis, however, also suggested that seminoma histology was associated independently with the development of CTGCT, mainly because of a somewhat higher risk of CTGCT in patients with chemotherapy-naive seminoma. This was also to some extent reflected by the 10-year cumulative incidence of CTGCT in patients without chemotherapy-naive seminoma, which was 2.5% compared with 3.6% in patients with chemotherapy-naive seminoma. We agree that this finding should be treated with some caution, as a biological explanation is not clear. Contralateral testicular biopsies are infrequently performed in the Netherlands, so we have no information on the presence of contralateral germ cell neoplasia in situ (GCNis) before treatment. Nonetheless, the 20-year cumulative incidence of CTGCT in chemotherapy-naive patients (3.9% in patients with nonseminoma v 4.6% in patients with seminoma) agrees well with a 5%-6% prevalence of GCNis in contralateral testicular biopsies of patients with unilateral testicular germ cell tumor. The distribution of the tumor histology of the CTGCT did not differ in patients with chemotherapy-naive nonseminoma (77.3% seminoma) compared with patients with chemotherapy-naive seminoma (76.9% seminoma, P 5 .97). In contrast, the CTGCT among chemotherapytreated patients with nonseminoma was predominantly of nonseminoma histology (63.2%) and CTGCT histology differed significantly between patients with chemotherapynaive and chemotherapy-treated nonseminoma. The overrepresentation of seminoma CTGCT among patients with a nonseminoma germ cell tumor primary is interesting. As stated by Dieckmann, 1 it is known that patients with nonseminoma are usually several years younger than their seminoma counterparts. Could our data show that when our patients with nonseminoma age, they do tend to develop more often CTGCT with a seminoma origin as do their peers in the general population, while GCNis with nonseminoma delineation does develop into CTGCT less