Discussion
Taken as a group, these studies have produced mixed results. While there are clearly significant findings reported, many of the primary hypotheses were not achieved, and at times mediator or moderator analyses were needed to demonstrate effectiveness. Additionally, only two of the six studies (Northouse and Chambers) were large randomized controlled studies. To organize the summary of results, the manuscripts can be grouped loosely into two types of studies. First, the Canada, Schover, Chambers and Walker studies all focused on sexuality and ED treatments. These studies addressed: (I) educating participants about ED treatments; (II) educating participants about how to initiate sexual activity; or (III) managing side effects of PC treatment, with a focus on engaging in sexual relations. Although the results from these studies indicated an increase in the utilization of ED treatments, the primary aim of improved EF was generally not sustained. When significant results were reported, the effect of the intervention was not encouraging as the mean Erectile Function Domain of the IIEF improved but stayed within the "moderate" ED range. Additionally, these studies generally did not find significant outcomes for the partners. The second group of studies utilized couple's interventions that primarily addressed relationship aspects. The Manne and Northouse studies addressed a variety of concerns regarding relationship variables such as communication and intimacy. The results from these studies were mixed but suggest better relationship outcomes and reduced distress for the partners. There were not many significant outcomes for the patients, suggesting that partners benefit more from relational aspects of interventions.
When this literature is considered as a whole, it is clear that future studies are needed. Since no one study stood out, using the lessons learned from these studies, and assessing their strengths and limitations, can provide valuable guidance for the next generation of interventions in this area. We outline what we believe to be important methodological and intervention considerations that when addressed, may help to produce more effective interventions for these men and their partners.
First, innovative theoretical approaches are needed to continue to push this literature forward. While the above literature has provided a sound foundation of intervention content and techniques, the studies have tested standard educational interventions, sex therapies techniques, and couples therapy strategies with only marginal success. According to the Complex Intervention Framework outlined by the Medical Research Council, in order to produce an effective intervention, the intervention must be grounded by a strong theoretical base. Therefore, changes that are expected, or changes that are likely to be achieved will have been tailored by the specific needs of the population. For example, in a recent qualitative study, Nelson et al. (in press) develop a theoretical argument that avoidance of sexual situations is an important construct to address with new interventions. The authors outline a theoretical justification to using Acceptance and Commitment Therapy techniques as the main intervention component to help men utilize ED treatments. A similar approach related to preventing avoidance of sexual situations is also being tested by Wooten and colleagues. Developing more specific interventions, based on sound theoretical foundations, would also have the benefit of helping us understand which components of the interventions are most effective for both the patients and the partners. Conducting qualitative research prior to intervention development is one way to understand which theoretical framework may be most useful. The studies reviewed above relied on previous research to guide their interventions; however, they did not conduct their own qualitative research before running their RCTs. Interviewing men with PC and their partners would have given the authors an opportunity to explore theoretical frameworks, develop a better understanding of the needs of men and their partners, and address any potential study barriers.
A second consideration is the selection of outcome measures. The assessment of sexual function is well defined in the field. The IIEF for men and the FSFI for women are gold standard measures. However, assessing secondary distress variables can be a challenge. Many of these studies used relatively general assessments of "distress", depression, or relationship functioning, and found no change on these variables. More focused assessments targeting specific constructs related to sexuality may be needed to see beneficial effects. Examples of more specific outcomes are constructs such as sexual bother, sexual self-esteem, or sexual relationships.
These studies also prove that greater attention needs to be paid to assessing the level of distress of the patients/couples prior to entry into the study. Canada et al. found no changes in marital adjustment on the A-DAS most likely because the couples were not distressed at baseline. Similarly, Schover et al. found no change in marital happiness or overall distress because there was high marital happiness and there were low-distress levels at entry into the study. Even more discouraging was the outcome that intervening on these low-distress couples can actually have unintended negative effects. Manne et al. found couples with low distress levels at baseline, after the intervention to have an increase in distress, lower intimacy levels, and poorer communication. The intervention may have been making couples more aware of problems, thus heightening their distress. Additionally, future studies should take into account the individual couples' needs in order to focus on important issues for that couple. A study protocol by Robertson et al. addresses this issue by including a qualitative interview to get an in-depth understanding of the specific challenges of each couple and what they would hope to gain from the intervention.
Other patient selection criteria, beyond levels of distress, are also important. It is essential to distinguish eligibility criteria related to such variables, such as: type of treatment for PC, the amount of time following treatment, and stage of disease. The distinction between men who were treated with surgery compared to men treated with RT can be very important for research in this area. These men differ on the trajectory of EF following treatment, types of ED treatments that will be effective at different time points following treatment, and important patient characteristics such as age and co-morbidities. Many of these studies discussed above grouped men who had surgery and men who had RT together, without addressing the distinct needs between these two groups. This limits the effectiveness of interventions and may dissipate their treatment results. Second, the length of time following treatment should be addressed as patient and partner concerns may differ based on this time frame. In the Canada study, participants were eligible if they had received treatment between three months and five years prior to entry into the study. This gap in time is especially important when addressing the individual needs of each participant, as sexual side effects of PC treatment may vary largely depending on the length of time post-treatment. The distress level within a couple may also be related to time following treatment. Clinical observation suggests that couple distress may be lower following the completion of early stage treatment when support related to the diagnosis/treatment is high and the couple is relieved with the completion of treatment, yet there is no current data available tracking the level of the couples' distress following treatment. It may not be until several months following PC treatment that the impact of ED and frustration of loss of intimacy is felt by the couple.
The largest complication of these interventions appears to be that men and women may need different types of interventions to see benefits. The six studies illuminate the fact that men who have undergone treatment for PC may benefit from education about treatment options for ED and avoidance of sexual situations, whereas their partners may gain more from interventions focused on relationship issues. In the interventions where sexual functioning was the main concern—Canada et al., Schover et al., Chambers et al., and Walker et al.—patients were more likely to report benefit and sustained increases in ED treatment use. However, the partners in these studies did not see many benefits and neither patient nor partner saw gains on measures of marital satisfaction. Conversely, in the interventions focusing on intimacy support for couples after PC treatment—Northouse et al., and Manne et al.—the patients reported far fewer benefits, if any, as compared to their partners, while the partners reported gains. Taken altogether, this suggests that interventions in the future should be developed to target the patient and partner separately, as well as together, so that the couple receives the intervention necessary to improve its sexual functioning and intimacy. Addressing the needs of the partner and the patient as individuals, as well as together, will be vital in successfully giving support to patients and their partners after treatment for PC.
While the six RCTs intended to address relational and sexual intimacy following PC treatment, the methodological limitations of these studies reduce the effectiveness of these interventions. If the aforementioned areas of concern are considered and individual needs of participants are taken into account, interventions in the future have the potential to be more effective Appendix 1.