Sexual quality of life for localized prostate cancer: a cross‐cultural study between Japanese and American men

Abstract

Introduction

Race and ethnicity are important factors in health‐related quality of life (QOL) because of racial differences in preferences for, and trust in, health systems. Such factors are likely to affect QOL and patient satisfaction with care.

Results

Using a self‐reported questionnaire, Japanese men with prostate cancer reported lower sexual function scores at baseline. In detail, Japanese men were more likely than American men to report poor sexual desire, poor erection ability, poor overall ability to function sexually, poor ability to attain orgasm, poor quality of erections, infrequency of erections, infrequency of morning erections, and intercourse in the previous 4 weeks. However, Japanese men were less likely than American men to be concerned about their sexual function. Two years after surgery, American patients were more likely than Japanese patients to regain their baseline sexual function. The use of phosphodiesterase‐5 (PDE‐5) inhibitors has been widely publicized as the solution to erectile dysfunction after prostate cancer treatment. Although PDE‐5 inhibitors have been available in Japan since 1999, it is striking that Japanese men with localized prostate cancer are much less likely (only 10%) to use PDE‐5 inhibitors than American men.

Conclusion

Japanese patients with localized prostate cancer report worse sexual function but are less concerned about their reduced function. In the absence of a biological explanation for such differences, however, we suspect that cultural differences may explain the differences between QOL survey results from Japanese or American men with prostate cancer.

Introduction

Prostate cancer is the most commonly diagnosed type of cancer in Western countries [1]. However, the incidence of prostate cancer varies markedly among different races and countries. For Asians, especially Japanese and Chinese, incidence is lower than for Caucasians [2]. Traditional definitions of success in prostate cancer therapy have focused primarily on overall and disease‐free survival and biochemical recurrence, as evidenced by prostate‐specific antigen (PSA). The stage at diagnosis among men with prostate cancer has shifted dramatically during the last 20 years. From 1973 to 1979 and 1985, 73% of prostate cancer diagnoses were localized or regional cancer. In the period from 1995 to 2001, 91% of diagnoses were localized or regional. During the same periods, the percentage with distant disease at diagnosis decreased from 20 to 5%, respectively [3]. Survival has also increased during the past few decades. For the period from 1995 to 2000, 5‐year survival improved to 100 and 96% for white and black men, respectively. Nearly all contemporary men diagnosed with local/regional prostate cancer can expect to survive at least 5 years from the time of diagnosis. Given the favorable survival outcomes associated with the stage migration that occurred in recent years, patients often select primary therapy based on health‐related quality of life (QOL) considerations [4]. Assessment of QOL for prostate cancer is a rapidly evolving field. Because most men with prostate cancer are asymptomatic, it is not surprising that they are often unprepared for the diagnosis and difficult treatment decisions they face. As treatment objectives have widened to include not only survival but also better QOL, a body of research has grown on sexual function outcomes after different treatment modalities [5, 6].

Race and ethnicity are important factors in QOL because of racial differences in preferences for, and trust in, health systems, factors that are likely to affect QOL scores and patient satisfaction with care [7]. Most ethnicity‐based comparisons of QOL after prostate cancer treatment have been limited to studies of non‐Hispanic whites, African–Americans, and Hispanics in the US [8]. QOL articles have been published in 22 countries, with the US producing the maximum (47%), followed by the UK (8%), Canada (8%), and Japan (6%) [9]. Thus, there is insufficient information regarding QOL of Japanese men diagnosed with prostate cancer, and most QOL information has come from the experience of well educated white men.

Sexual function is broadly defined as including the quality and frequency of erections, strength of libido, and the ability to be physically and sexually intimate; sexual concern refers to the extent of interference or annoyance caused by any limitations of sexual function. Sexual behavior can be affected by physiologic and psychological and sociocultural factors [10, 11]. Nonetheless, erectile dysfunction (ED), which is the most common long‐term side effect of prostate cancer treatment, significantly affects martial relationships [12]. Several cross‐national surveys have suggested that ED is more prevalent in Japanese men than in men from other countries, suggesting cultural differences in the perception and/or reporting of sexual function and associated distress [13], but no plausible biological explanation has been proposed. This review introduces the assessment of QOL, gives guidelines for selecting sexual QOL instruments, and summarizes the contemporary literature related to racial differences in sexual QOL for patients with localized prostate cancer.

Defining sexual QOL: validated instruments

Historically, the study of ED has primarily been reported in the psychiatric literature [14]. A comprehensive collection of means of assessing ED in the setting of psychiatric disease [15, 16, 17] have proved to be too long and detailed to be efficiently used for the evaluation of urological patients [18]. Despite limited application of the psychiatric questionnaire for urological patients, two important fundamental principles were established:

1. sexual performance and satisfaction are best measured by patient and partner self‐reporting; and

2. differentiation among various domains of sexuality is essential.

The introduction of the self‐administered questionnaire provided a means to critically evaluate patients in respect of erectile/ejaculatory function, desire, satisfaction, and concern (distress). The validated instruments used in the psychiatric literature were tailored for urological patients, and efforts were made to create concise, efficient methods to evaluate all aspects of male sexual dysfunction. Disorders of sexual function can be subclassified into those related to erectile function, ejaculatory function, orgasmic function, and failure of detumescence (priapism). In addition to these disorders, consideration is given to patients’ satisfaction and concern.

Validated instruments

A number of validated questionnaires have been developed for evaluation of sexual dysfunction in urological patients. Recently, validated, patient‐completed questionnaires for measurement of sexual function have emerged. Several are in common use, including the International Index of Erectile Function (IIEF, or IIEF‐15) [19] and its derivatives (Sexual Health Inventory for Men, SHIM); Functional Assessment of Cancer Therapy‐Prostate (FACT‐P) [20]; University of California Los Angeles Prostate Cancer Index (UCLA‐PCI) [21]; Expanded Prostate Cancer Index Composite (EPIC) [22], and others [23, 24, 25, 26]. Few direct comparisons of these have been reported [27, 28, 29, 30]. The SHIM was designed as a brief yet powerful, relatively narrow questionnaire for assessment of ED. The EPIC and UCLA‐PCI were designed as comprehensive means of measuring QOL, including sexual function, especially in men with prostate cancer. In a recent review, the developers of the SHIM examined the strengths and limitations of their abridged version of the IIEF, and surveyed the many published uses and misuses [31].

Comparative analyses among questionnaires are rare. In small cohorts, the SHIM has been compared with single item assessments of ED, and with IIEF‐6 and the complete IIEF [32, 33, 34]. Both the IIEF and SHIM have also been compared with the less used, non‐prostate cancer specific, ED questionnaires [35]. In a single patient cohort, the UCLA‐PCI was used to define the single‐question assessment of ED and to compare them with the surgeon‐reported frequency of ED, although the actual subscales and indices of the UCLA‐PCI questionnaire were not used [36]. The first was the only other study to directly compare UCLA‐PCI sexual function and EPIC sexual function, done in an interesting linking analysis on a cohort of Japanese men with prostate cancer [37]. In a cross‐sectional analysis, 385 men at varying stages of recovery from multiple prostate cancer therapy were simultaneously administered both the EPIC and UCLA‐PCI. Levinson et al. [38] reported that the EPIC sexual function and the UCLA‐PCI sexual function captured gradations of both sexual and erectile and function for men with prostate cancer and could be used to define potency more comprehensively than other questionnaires.

Sexual QOL between Japanese and American men with localized prostate cancer

Ethnic comparisons of sexuality after prostate cancer treatment have been limited to studies of non‐Hispanic whites, African‐Americans, and Hispanics in the US [39]. Disparities in sexual function among Asian men treated for prostate cancer have not been fully explored. Namiki et al. [40] assessed differences in self‐reported sexual function and concern between American and Japanese men with newly diagnosed prostate cancer. A total of 447 Japanese men and 427 American men with clinically localized prostate cancer were enrolled in separate studies of QOL outcomes. Sexual function and sexual concern (distress resulting from sexual dysfunction) were measured with the UCLA‐PCI. Each UCLA‐PCI domain is scored from 0 to 100 points, with higher scores representing better outcomes. Hence, a higher sexual function score indicates better function, and a higher sexual concern score indicates less concern. In the UCLA‐PCI, sexual function is measured with eight items, and sexual concern is measured with a single item. The UCLA‐PCI has been shown to perform well not only for men with prostate cancer but also for healthy older men without prostate cancer [41] and men presenting for evaluation for ED [42]. A validated Japanese version is available [43].

According to the survey, Japanese men were much more likely than American men to report low sexual desire (odds ratio (OR) = 21.2; 95% confidence interval (CI) = 12.2–37.0), poor erections (OR = 16.2; 95% CI = 9.7–27.1), and poor overall sexual function (OR = 16.7; 95% CI = 9.7–28.9). Japanese men were more likely to report difficulty with orgasms (OR = 1.7; 95% CI = 1.3–2.3), and low quality (OR = 2.5; 95% CI = 1.9–3.5) and frequency (OR = 2.3; 95% CI = 1.7–3.1) of erections. Japanese men were more likely to report not having morning erections (OR = 2.7; 95% CI = 1.8–4.2), and to report having had no intercourse in the previous 4 weeks (OR = 2.7; 95% CI = 1.9–3.8). However, despite reporting worse sexual function for all eight items, the Japanese men were significantly less likely to report sexual concern (OR = 0.36; 95% CI = 0.24–0.54) (Table 1). Using a self‐reported questionnaire, Japanese men reported less sexual activity than did American men, even after adjustment for age. This finding is consistent with other reports in which ED and reduced libido were noted in a greater proportion of Japanese than American men [44]. Population‐based data from Japan indicate that the proportion of ED is 20, 42, and 64% for ages 50–59, 60–69, and 70–79, respectively, all higher than in other countries [45, 46]. The relationship between sexual function and serum testosterone level has been controversial. In the Japanese male population, however, no continuous decline in testosterone levels has been noted after age 40 as it has in other countries [47].

Table 1.

Proportions and odds ratios of men reporting poor sexual function, by ethnicity

	Japanese	American	Odds ratio a
	n = 412	n = 427	OR (95% CI)
	% (n)	% (n)	American as referent
1. Level of sexual desire	96% (394)	51% (214)	21.2 (12.2–37.0)
2. Ability to have erection	95% (386)	49% (204)	16.2 (9.7–27.1)
3. Ability to orgasm	62% (246)	40% (167)	1.7 (1.3–2.3)
4. Quality of erections	64% (258)	33% (137)	2.5 (1.9–3.5)
5. Frequency of erections	61% (246)	32% (135)	2.3 (1.7–3.1)
6. Awakened with erection	91% (367)	72% (303)	2.7 (1.8–4.2)
7. Intercourse	83% (335)	56% (238)	2.7 (1.9–3.8)
8. Overall ability to function sexually	96% (387)	52% (216)	16.7 (9.7–28.9)
9. Problem with sexual function	11% (47)	25% (97)	0.36 (0.24–0.54)

^aAll models were controlled for patient age

Reprinted with permission from Namiki et al. [40]

In Japan, physician consultation time in outpatient clinics is much shorter than that in the US. Moreover, conditions in the clinical setting in Japanese hospitals may reduce patient motivation: some patients are asked to wait outside the consultation room where they might overhear conversations between the doctor and other patients, which may in turn cause them to be self‐conscious about discussing sensitive issues with the doctor during their own consultations. These factors in the clinical setting could discourage patients from raising complicated psychological issues such as sensitive sexual aspects of their treatment and force them to focus on the general physical aspects. A safer and more private atmosphere might encourage more open dialogue about sexual function. Nonetheless, it would be valuable to distinguish between the patients who do not give high priority to their sexual function from those who are hesitant to raise the topic with their medical providers. Conversely, while male erectile rigidity contributes to the frequency of sexual intercourse, it is not necessarily associated with a satisfactory sexual life in the Japanese men's partners [48]. The discrepancy between Japanese males and their partners’ responses might be explained by discordant views of what constitutes a satisfactory sexual life (e.g., non‐coital, intimate activities). While a lack of privacy during consultations might inhibit frank personal discussions, there might be less than complete candor in written self‐reports of sexual function.

Although Japanese men reported less sexual activity than did American men, Japanese men were less likely to be concerned. Other studies show that, unlike their American counterparts, older Japanese men do not report dissatisfaction with their sexual life [49, 50]. The pattern of help‐seeking behavior differs substantially between Japan and US. In Japan most men take no action whereas in America men may seek help from the partner, family members, or other sources of social support. Among those who do not seek treatment, younger men seem to believe that their ED would resolve spontaneously whereas older men resisted seeking treatment because they felt ED was a natural part of aging.

Whereas Japanese beliefs regarding sexual dysfunction have changed substantially in recent years, discussion of sex‐related topics continues to be repressed in Japanese patient–doctor encounters. In fact, the most commonly cited reason for not self‐referring to a doctor is that sexual problems are not medical problems [51]. In Japan, it may be difficult to find medical professionals who consider it their role to deal with a patient's sexual issues. Hence, in addition to improving privacy during consultations, it is also important that providers be trained more comprehensively in male health. Such added emphasis should focus greater attention on cancer survivors’ sexual concerns, especially given the recent pharmacological advances in this discipline.

Conversely, American men tend to perceive their sexual difficulties as a serious medical issue that requires intervention. This is consistent with other reports documenting the great weight sexual dysfunction carries with many American men [52]. Being married or living with a partner might motivate American men to seek treatment for ED, which causes more distress than reduced function.

Sexual QOL after radical prostatectomy

Radical prostatectomy (RP) is a standard treatment for patients with localized prostate cancer and a life expectancy of more than 10 years who accept the risk of treatment‐related complications [53]. ED is the principal postoperative adverse effect for patients who have undergone RP. In the years after undergoing RP, patients seem to experience improvements in sexual functioning. Catalona et al. [54] reported excellent results, with overall postoperative potency rates of 68% and postoperative continence rates of 92%. However, these rates were affected by age, preoperative sexual function, and whether nerve‐sparing surgery was performed [55].

We conducted a cross‐cultural comparison of recovery of sexual function and concern during the first 2 years after radical prostatectomy (RP) between American and Japanese men [56]. The Japanese men had worse sexual function scores than the American men before RP (40 vs. 59, p < 0.01). Although both groups declined substantially at 1 month and improved over the next 24 months, both group means were lower than baseline at all postoperative time points. After 1 month the American men had better mean sexual function scores than did the Japanese men at all subsequent assessments (p < 0.01). With regard to sexual concern scores, Japanese and American men did not differ at baseline (70 vs. 68, p = 0.64). After RP, the Japanese men had equivalent or significantly better sexual concern scores (less distress) than did the American men at all postoperative time points. For both groups sexual concern scores were worse (more distress) than at baseline throughout postoperative follow‐up (Fig. 1).

Figure 1.

Longitudinal changes in sexual function and concern over time in Japanese and American men. Reprinted with permission from Namiki et al. [56]

In Fig. 2 the Kaplan–Meier curves show the proportion of men who returned to their own baseline sexual function or concern score. At two years postoperatively, 22% of Japanese men and 35% of American men had fully returned to baseline sexual function. Among those who did return to their own baseline, the adjusted mean recovery time was 9.3 months for the Japanese men and 10.3 months for the American men. American men tended to regain their baseline sexual function more rapidly than Japanese men. Older subjects were somewhat less likely than younger subjects to return to their baseline sexual function. The higher the baseline sexual function score, the less likely men were to return to their own baseline sexual function. Bilateral nerve sparing made a significant contribution to recovery of sexual function whereas baseline PSA, and unilateral nerve‐sparing did not. By 1 year postoperatively, more than 76% of Japanese men had reached their baseline sexual concern scores, but there was little additional recovery after 12 months. The adjusted mean recovery time was 3.3 months for the Japanese men and 6.5 months for the American men (p < 0.01). Multivariate modeling revealed that American men were less likely than Japanese men to return to their baseline sexual concern scores. As with sexual function, the better the baseline sexual concern score (less distress), the less likely men were to return to their own baseline. Sexual concern was not significantly associated with age, baseline PSA, or nerve‐sparing.

Figure 2.

Kaplan–Meier analysis of the proportion of subjects returning to baseline over time. Reprinted with permission from Namiki et al. [56]

Factors affecting postoperative sexual function after RP have been studied extensively [57, 58, 59, 60, 61]. They include patient age, PSA, Gleason grade, neurovascular bundle preservation, surgeon experience, disease stage, and data collection methodology. Overall, patient age was regarded as the most significant predicting factor for postoperative erectile function. The Japanese data on sexual function revealed that the score was substantially lower just after RP than thereafter. At 60 months after RP, the sexual function of only 34% of subjects had fully returned to the baseline level. The mean recovery time of the subjects whose sexual function returned to their own baseline level was 13.2 months. Bilateral nerve sparing (BNS) contributed to the recovery of urinary and sexual function after RP [62]. Recently, there has been concern that the differences are related to data collection method and definition of postoperative potency [63]. Because the cause of ED after RP is complicated and probably multifocal, psychological factors may also have a significant role. Partner characteristics might also be considered a psychological factor. Several studies reported that the return to normal sexual activity depends on partner motivation, age, and health status [64, 65]. The post‐treatment change in sexual ability may have an effect on the partner and cause increased emotional distance, which in turn is deleterious for sexual activities [66, 67]. As demonstrated in these studies, although it is obviously not the only factor, partner age is an easily defined criterion that may affect sexual function preservation, because a younger partner and/or a patient may be more motivated to engage in sexual activity. Thus, it was suggested that the mean age difference between the patient and partner or the marriage status should be reported in RP outcomes series. Although Japanese beliefs regarding sexual dysfunction have changed substantially in recent years, discussion of sexually‐related topics continues to be uncommon in Japanese patient–doctor encounters. Japanese patients, unlike their American counterparts, do not report dissatisfaction with their sexual life, even when reporting erectile dysfunction and decreased libido [40, 56].

The effect of sexual QOL on PDE‐5 inhibitors after radical prostatectomy

The use of phosphodiesterase‐5 (PDE‐5) inhibitors (for example sildenafil, tadalafil, and vardenafil) has been widely publicized as a solution for ED. Studies have suggested that PDE‐5 inhibitors can be at least partially effective in restoring erectile function after prostate cancer treatment [68, 69, 70]. Based on cohort of Prostate Cancer Outcome Study data used ED treatment following prostate cancer diagnosis, approximately half of the patients with localized prostate cancer [71]. In multivariate analysis, medication use was significantly more common among RP patients than among men treated with brachytherapy or external beam radiotherapy [72]. Although PDE‐5 inhibitors have been available in Japan since 1999, it is striking that Japanese men with localized prostate cancer are much less likely (only 10%) to use PDE‐5 inhibitors than American men [73]. However, the Japanese men who used PDE‐5 inhibitors reported better sexual function than those who did not, both before and after RP. In contrast with Japanese men, American men who took PDE‐5 inhibitors after RP reported lower sexual function than those who did not. This finding may reflect the differences between Japanese and American men with regard to their sexual motivation (Table 2). Conversely, American men are more proactive than Japanese men in seeking care for ED after prostate cancer treatment [74]. Most Japanese men might not take any action whereas American men may seek support from their partners, family members, or other sources of social support. Another explanation is that Japanese urologists’ attitudes toward their patients’ sexual problems may compound the hesitation to talk about sexual issues; they may, therefore, seem less active in dealing with ED in cancer patients, choosing to focus more on outcomes such as laboratory test results. This is consistent with previous studies. In a nationwide survey in Japan on the attitudes of breast cancer surgeons, one‐third reported addressing “nothing in particular” about their patients’ sexuality after surgery [75]. Furthermore, the lack of privacy in Japanese hospitals often limits confidentiality, perhaps reducing motivation to discuss such sensitive issues. American urologists tend to prescribe therapy for their patients with post‐prostatectomy ED in part because of theories that early sexual rehabilitation may promote post‐surgical recovery of erectile function [76].

Table 2.

Sexual function and concern scores, by country and PDE‐5 inhibitor use

PDE‐5 inhibitors	Japan (N = 168)				p value	USA (N = 205)				p value
	Yes (n = 17)		No (n = 151)			Yes (n = 140)		No (n = 65)
	Mean	SD	Mean	SD		Mean	SD	Mean	SD
Baseline
Sexual function	41	(22)	29	(21)	0.0278	59	(27)	77	(19)	<0.0001
Sexual concern	81	(27)	74	(28)	0.3369	67	(36)	77	(32)	0.0758
Follow‐up
Early (1, 3, or 6 months)
Sexual function	30	(25)	9	(11)	0.0457	18	(20)	38	(21)	<0.0001
Sexual concern	47	(43)	57	(36)	0.4633	33	(36)	30	(25)	0.6744
Late (12, 18, or 24 months)
Sexual function	31	(28)	9	(12)	0.0399	33	(27)	54	(21)	0.0006
Sexual concern	42	(28)	56	(36)	0.2412	49	(35)	53	(33)	0.6650

Bold values indicate significant differences between users (yes) and non‐users (no)

Follow‐up was stratified into early (1, 3, 6 months) and late (12, 18, 24 months)

Reprinted with permission from Namiki et al. [62]

In Japan, those who took PDE‐5 inhibitors reported better sexual function than those who did not (both before and after RP). Those who took PDE‐5 inhibitors may have been more motivated to maintain their baseline sexual function. This is consistent with other reports in which baseline sexual function and the use of sexual aids correlated with worsening sexual concern after RP [77]. Conversely, Japanese men who did not take PDE‐5 inhibitors may have viewed ED as a natural part of aging and a normal side effect of cancer treatment. Thus, they were more accepting of their deterioration and less motivated to seek help. In this study, however, we did not assess the extent of usage or dosage of these medications (nightly or on demand) between both countries. The wording relating to PDE‐5 inhibitors is not exactly the same in that the Japanese version mentions PDF‐5 inhibitors as “medical treatment”. However, even if Japanese include herbals, their numbers are still less than in the US. Moreover, health insurance systems differ between the US and Japan in the comprehensiveness of pharmaceutical coverage; most US insurance companies cover at least some PDE‐5 inhibitors, but the Japanese system generally does not cover the cost of PDE‐5 inhibitors. Hence, differences in patterns of PDE‐5 inhibitor use may reflect financial barriers more than patient preferences for some men.

In contrast with Japanese men, the American users of PDE‐5 inhibitors reported worse sexual function than non‐users both before and after RP. This result suggests that ED is a more substantial problem for American men, and this is a group (younger, bilateral nerve sparing, less disease) for whom sexual function is more important than in Japanese men with poor sexual function before RP. The lower the sexual function score, the more likely the American men were to use PDE‐5 inhibitors. This is consistent with other reports documenting the great importance of sexual dysfunction to many American men [78, 79]. Our data also emphasize the basic importance of sexuality in American men as a main factor driving the motivation to remain sexually active after prostate cancer treatment. Indeed, prostate cancer survivors are highly likely to seek treatment for their ED [80].

Future perspectives

There is insufficient information regarding QOL of Asian men, including Japanese men, diagnosed with prostate cancer. In the absence of a biological explanation for cross‐national differences, however, we suspect there are cultural differences between QOL survey results from Japanese and American men with prostate cancer. Different cultures have different concepts of health, well‐being, and illness, and health insurance systems. A concept that is well developed in one country may not even exist in another. Even if we use QOL studies with validated survey instruments in English, we need to be aware that these multicultural issues may introduce a significant bias in the collection of data and reflect not only the men's preferences but also the medical care they received.

Conclusions

The maintenance of a satisfactory QOL is recognized as a principal concern for most men. Because men with prostate cancer are being diagnosed at a younger age and are observed to live longer, it is critical that we obtain a better understanding of all the factors that could affect short‐term and long‐term functional states and QOL in prostate cancer patients.

Race and ethnicity are important factors that affect QOL because the patient's preferences for, and trust in, health systems are likely to affect QOL and patients’ satisfaction with care. In patient‐reported questionnaires Japanese men with localized prostate cancer report worse sexual function and less concern about the reduced function than do American men. It is striking that Japanese men with localized prostate cancer are much less likely to use PDE‐5 inhibitors than American men. Cultural differences seem to be important in the reporting of sexual activity and the perception of related distress. Accordingly, healthcare providers should assertively discuss and thoroughly understand patient expectations of sexual performance after prostate cancer treatment.