Assessment of sexual function in prostate cancer patients
Assessment of sexual interest/function in prostate cancer patients An accurate assessment of the changes in sexual interest and function following the different treatment options for advanced prostate cancer and how patients feel about these changes is necessary, so that patients and their physicians may select the treatment that best meets the patients’ needs. However, the design of studies of the sexual aspects of quality of life in elderly men with a potentially life-threatening disease presents a number of difficulties.
Table 1 The effect of non-steroidal antiandrogens on serum testosterone levels in prostate cancer patients.
First, it is common for patients with advanced prostate cancer, particularly those over 75 years of age, to have relatively low levels of interest/ function before study entry. In the pivotal trials of bicalutamide 150 mg/day monotherapy, approximately 50% of patients had no sexual interest at study entry (data on file), while Boccon-Gibod and colleagues reported that they were unable to assess the impact of flutamide on sexual function because the vast majority of patients (mean age about 73 years) were impotent before the initiation of treatment. Additionally, some patients may have experienced erectile difficulties before the diagnosis of prostate cancer or following previous therapy (prostatectomy or radiotherapy).
Second, sexual function is a difficult parameter to assess in clinical trials owing to the lack of a clear definition of erectile functioning45 and the lack of standardized methodology. Although the measurement of nocturnal penile tumescence (NPT) and rigidity, a widely accepted method of differentiating between organic and psychogenic
sexual dysfunction, correlates well with actual functioning in small studies in prostate cancer patients, it is not practical for use in large trials. Furthermore, sexual function should not be assessed only objectively; patients’ feelings about changes in function also need to be examined. 
A further problem in assessing both sexual function and interest is that many elderly men find it difficult to discuss sexual issues with their physician. For example, 22% of patients enrolled in one of the phase III trials of bicalutamide 150 mg/day versus CAB refused to respond directly to physician questioning. Finally, as castration is currently the standard therapy for advanced prostate cancer, studies of new therapies tend to have an open design. There are, however, difficulties in interpreting data on sexual interest/function obtained from such open trials, as patients, informed that regimens containing castration are likely to result in loss of sexual activity, will consider these events less severe or report them less frequently, as they were expected.
The problems inherent to assessing sexual function in prostate cancer patients are illustrated by the failure of a study specifically designed to compare bicalutamide 150 mg/day with medical castration with goserelin acetate (Zoladex®) to draw definitive conclusions on the relative effects of the two treatments on sexual interest and function. This was due to the large proportion of patients who were protocol violations (68% of patients), that is they were thought not to demonstrate sufficient evidence of sexual function at entry to the trial as they did not have at least one qualifying episode of NPT (a rigidity of >60% for at least 10 min) per night (data on file).
Such a large proportion of protocol violations may have affected the power of the trial analyses. Data from the Derogatis Interview of Sexual Functioning-Male (DISF-M) questionnaire used in this trial did not give consistent evidence of the level of sexual function of patients at entry to the trial (data on file). Thirty-eight men with locally advanced prostate cancer and aged between 46 and 73 years were recruited to this double-blind study and randomized to bicalutamide 150 mg/day (n=17) or goserelin acetate 3.6 mg every 28 days (n=21).
The primary end-points were mean penile rigidity assessed by NPT, and sexual function and interest assessed by the DISF-M questionnaire. There were no significant differences in either treatment group in the change from baseline in mean penile rigidity. Results from the DISF-M questionnaire showed that patients who received bicalutamide 150 mg/day had less change from baseline in sexual function on all dimensions of the questionnaire than that of patients who received goserelin acetate 3.6 mg. However, the difference between the two groups did not reach statistical significance.
