Erectile dysfunction after radiotherapy for prostate cancer: a model assessing the conflicting literature on dose-volume effects.

Studies assessing the relationship between dose to the penile bulb (PB) and risk of ED in men treated for prostate cancer with external beam radiation therapy (EBRT) have been critically scored. A review of published literature examining dose received by the PB and clinical erectile function outcomes for patients receiving EBRT was performed. Of 146 retrieved articles, 8 evaluated EBRT-induced ED in relation to PB dose. Half of these articles showed a relationship between dose to PB and ED, and the other half did not. A reliability score (RS) was constructed to more uniformly evaluate strengths and weaknesses of these eight articles. Subsequently, they were scored by two independent reviewers. An average of both scores was calculated. A close consensus was found (identical RS for six of the eight studies; kappa statistic: P=0.97). The studies with highest RS consistently support a relationship between ED and PB doses, whereas those with low scores did not. The RS-based analysis supports the recommended dose-volume limits specified in the Quantitative Analysis of Normal Tissue Effects in the Clinic review, maintaining the mean dose to 95% of the PB<50 Gy, although the target organ at risk is not likely to be the PB.