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EUROPEAN UROLOGY 70 (2016) e17 available at www.sciencedirect.com journal homepage: www.europeanurology.com Letter to the Editor Re: Christopher J.D. Wallis, Refik Saskin, Richard Choo, et al. Surgery Versus Radiotherapy for Clinically-localized Prostate Cancer: A Systematic Review and Meta-analysis. Eur Urol 2016;70:21–30 Wallis et al compared the outcomes of very large cohorts of patients treated with either surgery or radiotherapy (RT) for prostate cancer [1]; however, a flawed analysis remains flawed, no matter how large. While nonrandomised comparisons can control for known confounders (eg, age, smoking), it is not possible to control for unknown confounders. Patients treated with RT are very different from those treated with surgery, and residual confounding cannot be excluded. Examining the data for low-risk prostate cancer clearly indicates that the analysis is not a fair comparison between two well-matched groups. The authors report excess overall mortality for patients treated with RT rather than surgery, with a hazard ratio of 1.47 (95% confidence interval, 1.19–1.83); however, low-risk prostate cancer is almost never lethal within 10–15 yr, with cause-specific survival of up to 99.9% even without any immediate treatment [2]. If mortality among RT patients is 47% higher than among surgical patients, it is not because they are dying from prostate cancer; rather, it is because RT patients are less healthy than surgical patients and are more likely to die from other causes. Conflicts of interest: The author has nothing to disclose. References [1] Wallis CJ, Saskin R, Choo R, et al. Surgery versus radiotherapy for clinically-localized prostate cancer: a systematic review and metaanalysis. Eur Urol 2016;70:21–30. [2] Tosoian JJ, Mamawala M, Epstein JI, et al. Intermediate and longerterm outcomes from a prospective active-surveillance program for favorable-risk prostate cancer. J Clin Oncol 2015;33:3379–85. Chris Parker* Royal Marsden Hospital, Academic Urology Unit, Sutton, UK *Royal Marsden Hospital, Academic Urology Unit, Downs Road, Sutton, DOI of original article: http://dx.doi.org/10.1016/j.eururo.2015.11.010. http://dx.doi.org/10.1016/j.eururo.2016.02.039 0302-2838/# 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved. SM2 5PT, UK. E-mail address: [email protected]. February 12, 2016