A new study found that two patient-reported measures of sexual function following radical prostatectomy are valid and important tools in prostate cancer survivorship. Experts note, though, that without comparators such analyses of patient-reported outcomes (PROs) can be difficult to interpret.
“Sexual dysfunction after radical prostatectomy is directly related to treatment regret, feelings of loss, and distress in relationships,” wrote study authors led by Nnenaya Q. Agochukwu, MD, MS, of the University of Michigan Health System in Ann Arbor. “The importance of sexuality in prostate cancer care is evidenced by the fact that some patients are willing to sacrifice survival to preserve potency.”
The focus of post-prostatectomy sexual function has traditionally been on erectile function, but this may not fully capture patient experiences. The Patient-Reported Outcomes Measurement Information System (PROMIS) includes the Interest in Sexual Activity and Satisfaction With Sex Life measures in an attempt to move beyond these limitations.
The new study included a total of 1,604 men who underwent radical prostatectomy between 2014 and 2016. The participants were asked one item from each of the two PROMIS domains: “When you have had sexual activity, how satisfying has it been?” and “How interested have you been in sexual activity?” Both were rated on a 5-point Likert scale ranging from “not at all” to “very much.” The results of the analysis were published in the Journal of Clinical Oncology.
The average age in the study was 63.2 years, and most patients were white (84.1%); most of the cohort was married (80.6%).
The two PROMIS measures were found to have “moderate to large” correlations with other measures of sexual satisfaction and interest, supporting their convergent validity. They had very little or no correlation with measures of bowel function and general quality of life, supporting their discriminant validity.
For the interest measure, there was a decrease in mean score from baseline to 3 months (P = .001), followed by an increase from 3 months to 24 months (P < .001). Interest scores were higher at 24 months than at baseline.
For the PROMIS satisfaction measure, a similar pattern was observed, with a decrease from baseline to 3 months (P < .001) followed by an increase from 3 months to 24 months (P = .002). In this case, the 24-month scores did not return to baseline levels.
“When combined with tools to measure symptom burden, these PROMIS measures can give survivors of prostate cancer hope that, although they may have functional losses, they can still maintain sexual relationships and recover sexuality,” the authors concluded.
In an accompanying editorial, Andrew J. Vickers, PhD, of Memorial Sloan Kettering Cancer Center in New York, noted some serious potential issues with this method of validating PROs. “These positive findings seem to give a green light to any researcher wishing to use the PROMIS measures in a study or a clinician wishing to implement them in routine practice,” he wrote. “However, a study with a positive result can only be a useful guide to action if the result could have been negative. A methodology that only gives one type of result is not much of a methodology at all.”
Most published studies aiming to validate PRO instruments tend to be positive, he wrote, because they are non-comparative, and they have no formal criteria for success, among other reasons. In the current study’s case, it did not compare with other possible wordings of questions regarding sexual interest or satisfaction. “This is not unlike deeming a drug to be effective because patients on the drug seemed to do well, rather than because the drug was demonstrated to be superior to a placebo or existing standard of care,” Vickers wrote. He added that the work is “not a bad start,” but that questions remain whether the tools could be modified to perform even better, both for research and for the benefit of patients.