The prognosis for early stage prostate cancer is now very good, with most patients surviving for many years. Consequently much more emphasis is now given to quality of life issues when planning treatment.

The issue that most prostate cancer survivors most commonly face is impairment of sexual function, and particularly of the ability to obtain and maintain erections. However, the experiences of these men vary considerably, with some regaining sexual function almost completely and others hardly at all.

The ability to predict the likely outcome for any given patient would be very useful, but such tools that have been made available for this have proved to be of limited utility.

Now, however, a large group of US-based clinicians and researchers led by Martin G. Sanda of Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA has developed and validated such a tool based on patient characteristics and treatment options. The initial study cohort included 1027 men enrolled in the Prostate Cancer Outcomes and Satisfaction with Treatment Quality Assessment (PROSTQA) trial who were interviewed 24 months after treatment.

All subjects were diagnosed with prostate cancer of clinical stage T1 to T2 and elected to have primary treatment with prostatectomy, external beam radiotherapy or brachytherapy. Detailed demographic and clinical data were collected for all subjects, who also completed quality of life questionnaires that included questions about sexual capability before and after treatment. Multivariate analysis was performed using SAS to develop a model for predicting sexual performance and associated quality of life based on a range of variables.

The model was externally validated using 1913 patients enrolled in the community-based Cancer of the Prostate Strategic Urologic Research Endeavor [CaPSURE] study between 1995 and 2007.

Sanda and his co-workers found that erectile dysfunction increased in the whole PROSTQA cohort from 28% prior to treatment to 63% two years after treatment.

The proportion of patients who were able to maintain an erection strong enough for intercourse two years after treatment varied from 35% in the patients who chose prostatectomy to 37% after external radiotherapy and 43% after brachiotherapy. In both univariate and multivariate analysis, younger age and higher pre-treatment sexual-related quality of life scores were associated with better outcomes in all groups. Other variables associated with better outcomes in at least one of the three groups included lower PSA scores, better overall health before treatment and college education.

No use of neoadjuvant hormone therapy in patients who chose external radiotherapy and, interestingly, African-American ethnicity in those who chose brachiotherapy were also associated with improved outcomes.

The model developed from data provided by the initial PROSTQA cohort was able to predict probabilities of adequate sexual function two years after treatment ranging from 10% to at least 70%. When this was tested using the independent cohort of 1913 men from the CaPSURE study, it performed well.

The area under the receiver operating characteristic curve (AOC) – a measure of the probability of false negative and false positive outcomes, in which a value of 1.0 indicates 100% correct predictions – varied from 0.77 [95% CI, 0.74-0.80] for prostatectomy patients to 0.87 [95% CI, 0.80-0.94] for those undergoing external radiotherapy and 0.90 [95% CI, 0.85-0.95] for those undergoing brachytherapy. No reason was noted for the increased accuracy of the tool in predicting outcome after radiotherapy over that after surgery.

Despite some limitations of the study, particularly the possibility of selection bias by treatment type, the mathematical model developed by Sanda and his co-workers provides a useful tool for predicting the likelihood that individual patients will retain adequate sexual function after early stage prostate cancer treatment.

Reference

Alemozaffar, M., Regan, M.M., Cooperberg, M.R. and 18 others (2011). Prediction of Erectile Function Following Treatment for Prostate Cancer. JAMA 306(11), 1205-1214. doi: 10.1001/jama.2011.1333