To the Editor Hwang et al1 must be congratulated for their great effort in putting together the data of 10 big institutions. However, given the limitations that we discuss herein, their conclusions that adjuvant radiotherapy (ART) reduces biochemical failure, distant metastases, and overall mortality may be optimistic.
Hwang et al1 argue that their report distinguishes itself from previous studies (references 4 and 22-26 in their article) by addressing overall mortality as an end point. Yet, the value of the latter in this report is limited. Specifically, the authors mention that in the propensity score–matched cohort, cancer-specific death events were 1 vs 6 in patients treated with ART vs early-salvage radiotherapy (ESRT), while overall death events were 20 vs 35 for the same groups, respectively. As such, it seems that the difference in overall death is 3 times higher than the difference in cancer-specific death. This implies that the patients receiving ESRT were less healthy than those receiving ART. Consequently, any difference in overall mortality between ART and ESRT in this report is most likely attributed to causes other than cancer and is not derived by treatment effect. The fact that the authors1 did not adjust for comorbidity increases the relevance of this point. Moreover, this unexplained difference in overall death events calls into question the robustness of the propensity score matching and undermines the validity of the other 2 examined end points, namely, biochemical failure and distant metastases, which could have been biased by a number of unbalanced and unobserved confounders.
Abdollah F, Dalela D, Menon M. Comparing Adjuvant vs Early-Salvage Radiotherapy After Radical Prostatectomy. JAMA Oncol. Published online August 23, 2018. doi:10.1001/jamaoncol.2018.3533
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