TO THE EDITOR: Fung et al compared the risks of secondary malignancies among patients treated with chemotherapy or surgery alone for testicular nonseminoma. Utilizing the population-based SEER cohort, Fung et al found that chemotherapy-treated men had a 40% increased risk of developing secondary malignancies after initial diagnosis. Although the study is without doubt an important assessment given the rising incidence of testicular cancer in the last decades, several limitations should be raised, which may weaken the clinical applicability of their findings in the contemporary era. First, since the study span covered diagnoses from 1980 to 2008, Fung et al could not account for the variable chemotherapy regimens that were introduced over time. Patients diagnosed and treated in more recent years with newer and less toxic chemotherapy regimens might be at considerably lower risk of secondary malignancies compared to historical chemotherapy regimens used 30 years ago. Second, the lack of consideration for disease stage in the calculation of standardized incidence ratios for secondary malignancies further augments the heterogeneity of the studied population. Of note, 34% of patients treated with chemotherapy harbored metastatic disease versus 1.7% in the surgery group. Given the prevalence of metastatic patients in the chemotherapy group, Fung et al are unable to rule out the confounding effect of biologic mechanisms. Specifically, inheritance of both rare genetic variants and polygenic trait predisposing to the development of advanced disease, may ultimately increase the risks of a new onset of secondary malignancies. Third, the number of cycles and dosage received is equally unknown. For example, metastatic patients are likely to be exposed to significantly higher cumulative doses of chemotherapeutic agents compared to individuals with stage I testicular nonseminoma. Thus, the current study is not able to provide insight into the dose-response relationship between chemotherapy and the subsequent risk of solid malignancies. In conclusion, the evaluation of the potential role of chemotherapy on the development of secondary malignancies relative to surgery in patients with testicular nonseminoma is highly relevant. However several other important aspects—improvements in chemotherapy regimens used in contemporary years, a better defined population according to disease stage, better knowledge of dosage and cycles used—need to be factored in the assessment of this association to avoid over-attributing the long-term adverse effects of chemotherapy.