Payal D. Soni, Zachary S. Zumsteg, Neil B. Desai, William C. Jackson, Ahmed E. Abugharib, Holly E. Hartman, Felix Y. Feng, Nima Aghdam, Daniel A. Hamstra, Sean P. Collins, Matthew J. Schipper, Todd M. Morgan, Simeng Suy, Daniel E. Spratt, Rohit Mehra, Robert T. Dess
Objective
To elucidate the functional erection rate after prostate stereotactic body radiotherapy (SBRT) and to develop a comprehensive prognostic model of outcomes after treatment.
Patients and Methods
Between 2008 and 2013, 373 consecutive men with localized prostate cancer were treated with SBRT at a single academic institution as part of a prospective clinical trial or prospective registry. Prospective longitudinal patient-reported health-related quality of life (HRQoL) data was collected using the Expanded Prostate Cancer Index Composite (EPIC)-26 instrument. Functional erections were strictly defined as ‘firm enough for intercourse’ according to EPIC-26. Detailed comorbidity data were also collected. Logistic regression models were used to predict 24- and 60-month functional erection rates. Observed erection rates after SBRT were compared with those after other radiation therapies (external beam radiation therapy [EBRT] and brachytherapy) using prospectively validated models.
Results
The median (interquartile range) follow-up was 56 (37–73) months and the response rate at 2 years was 84%. For those with functional erections at baseline, 57% and 45% retained function at 24 and 60 months, respectively. On multivariable analysis for 24-month erectile function, significant variables included higher baseline sexual HRQoL (adjusted odds ratio [aOR] 1.55 per 10 points, 95% confidence interval [CI] 1.37–1.74; P < 0.001) and older age (aOR 0.66 per 10 years, 95% CI 0.43–1.00; P = 0.05). At 60 months, baseline HRQoL and age remained associated with erectile function, along with body mass index (aOR 0.45, 95% CI 0.26–0.78; P < 0.001). The 24- and 60-month models had excellent discrimination (c-index 0.81 and 0.84, respectively). Erection rates after SBRT were not statistically different from model-predicted rates after EBRT or brachytherapy for the whole cohort and the cohort with baseline erectile function.
Conclusions
Intermediate- to long-term post-SBRT erectile function results are promising and not significantly different from other radiotherapy techniques. Clinicians can use our prognostic model to counsel patients regarding expected erectile function after SBRT.
