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- MATERIALS AND METHODS
- FUNDING SOURCES
Female sexual dysfunction (FSD) is quite common among women who have survived cancer,1-5 and the most commonly used measure to assess sexual functioning in this population is the Female Sexual Function Index (FSFI).6 However, the FSFI originally was developed and validated in healthy women, and the validity and reliability of the FSFI in cancer populations has not been established.
FSD resulting from cancer may differ qualitatively and quantitatively from FSD experienced in otherwise healthy women. Cancer treatments, including surgery, chemotherapy, radiotherapy, and hormone therapy, can directly affect sexual organs and hormone levels,1 resulting in vaginal shortening and stenosis, decreased vaginal lubrication and elasticity, as well as disruption of the sexual response cycle.2 A survey of long-term vaginal and cervical cancer survivors reported rates of FSD well over twice those of matched healthy controls; in particular, survivors had >14 times the odds of dyspareunia compared with controls.4 FSD also has been identified as a primary source of psychological distress after cervical cancer treatment7 and as an independent predictor of depressive symptoms.8 FSD can contribute to poor body image, reinforce stigma felt by those with a cancer diagnosis, and disrupt relationship closeness and intimacy.5 Indeed, some studies have demonstrated that up to one-third of relationships were ended within 1 year after completing cancer treatment.9, 10 Collectively, these studies highlight the necessity of integrating sexual function assessment into routine oncologic clinical care and the importance of identifying FSD for early intervention.
Unfortunately, few psychometrically sound measures of sexual function have been used consistently in female cancer populations.5 The exception is the FSFI, a 19-item instrument assessing 6 domains of sexual function: Desire, Arousal, Lubrication, Orgasm, Satisfaction, and Pain. The original validation study6 established the FSFI's reliability and construct validity in women diagnosed with sexual arousal disorder and in women without sexual difficulties. Later studies demonstrated its validity in women diagnosed with the other major categories of FSD.11, 12 Recently, validation of the FSFI was extended further to women with vulvar intraepithelial neoplasia, a preinvasive skin lesion of the vulva that can become cancerous if left untreated.13 In all these studies, the FSFI total and domain scores displayed excellent internal consistency reliability coefficients (ie, Cronbach α>.80) as well as the ability to differentiate between clinical and nonclinical samples.
The FSFI items and domains were developed to reflect the key features of the major categories of FSD6 as defined by the current diagnostic classification systems in the United States14 and internationally.15 This correspondence with well established theories and diagnostic systems of sexual dysfunction is likely why the FSFI is 1 of the most widely administered measures of female sexual function. It is noteworthy that the FSFI has been cited in studies with gynecologic,16-22 breast,23, 24 rectal,25, 26 and urologic27 cancer patients/survivors, although other specialized questionnaires exist addressing sexual and vaginal problems specific to certain types of cancer and/or treatment.28-30 Despite its widespread use among cancer survivors, it is concerning that no studies to date have empirically evaluated and documented the reliability and validity of the FSFI in female cancer populations. The etiology of sexual dysfunction and symptoms in cancer survivors differs from that experienced by women in the general population; therefore, it is imperative to carefully examine the psychometric properties of the FSFI for use among cancer survivors. The objective of this study was to provide the first systematic evaluation of the factor structure, reliability, and construct validity of the FSFI for measuring the sexual functioning of female survivors.
- Top of page
- MATERIALS AND METHODS
- FUNDING SOURCES
The objective of the current study was to perform the first empirical validation of the FSFI in female cancer survivors. Our results indicate that the FSFI is a reliable and valid instrument for measuring levels of sexual functioning and cancer-related FSD in this population. The psychometric properties obtained in this study are very similar to those reported in the initial FSFI validation. Specifically, the original FSFI factor structure, on which the domain subscales are based, was replicated in this group of cancer survivors, as were the reliability coefficients of the total and domain scores. The FSFI demonstrated convergent validity by correlating strongly with validated measures of menopausal symptoms, reproductive concerns, QOL, and depression. Finally, the FSFI exhibited preliminary evidence of discriminative validity, in that marginally significantly (P < .10) higher proportions of survivors who had received chemotherapy and/or radiation were classified as having FSD by the FSFI diagnostic cutoff compared with survivors who did not receive those treatments. In addition, the chemotherapy/radiation-treated patients tended to have lower mean FSFI scores than the untreated patients, particularly in the Lubrication and Pain domains.
The sound psychometric properties of the FSFI among cancer survivors were clearly evident in this study. More subtly, however, the results suggest that emotional intimacy with a partner may play an important role in the sexual functioning of cancer survivors that is conceptually distinct from overall satisfaction with sexual life. Although only 32% of survivors endorsed strong sexual desire (Table 4), and only 50% were very satisfied overall with their sexual life, 72% reported being very satisfied with their emotional closeness with partners during sexual activity. In addition, this “emotional closeness” item had the lowest and second lowest corrected item-total correlations in the domain-specific analysis and the FSFI total score, respectively. Although these properties are within acceptable ranges for a psychometric scale, the findings seem to suggest that this item is measuring a facet of satisfaction that may be particularly salient among cancer survivors and is somewhat distinct from overall satisfaction. This is consistent with a recent qualitative study in which, although survivors reported mainly negative effects of cancer on sexual functioning, many indicated improvements in intimacy after their cancer diagnosis, highlighting the complex relations among overall satisfaction with sex life, intimacy, and sexual functioning among cancer survivors.44
Although these results support the continued use of the FSFI among cancer survivors, clinicians and researchers should be acutely aware of the threat to the validity of the instrument's scores when administered to women with little or no recent sexual activity. In general, the FSFI scores are not valid measures of sexual functioning for sexually inactive women, because of 15 of the 19 items that have response options of “no sexual activity” or “did not attempt intercourse” are assigned a score of zero by the FSFI scoring algorithm. From a psychometric viewpoint, treating these responses as the lowest possible level of functioning on the ordinal response scale is justifiable only when it is explicitly known that a given respondent avoided sexual activity specifically because of extreme dysfunctions in the symptoms assessed by these items. Even in these instances, however, it is possible that women who attribute their avoidance of sexual activity to sexual dysfunction represent a qualitatively distinct clinical subgroup in need of more in-depth sexual rehabilitation and should not have their sexual functioning measured on the same metric as survivors who are not avoidant of sexual activity. More clearly, the FSFI is not a valid measure of sexual functioning for female survivors who are sexually inactive because of lack of a partner, poor relationship quality, or other reasons unrelated to changes secondary to cancer treatment (eg, estrogen deprivation).
It is likely that many studies reporting FSFI scores, particularly those focused on cancer populations, have inflated prevalence estimates of FSD because of this eccentricity in the scoring of the instrument. For example, if we had not excluded women with ≥8 zero-scored responses, then our FSFI-based estimate of FSD would have been 60%, instead of 52%. Clinical experience with cancer survivors, particularly those still in treatment, suggests that women often indicate very low sexual activity levels in the months after cancer diagnosis and treatment not because of dysfunctions in the domains assessed by the FSFI but because they are mentally and physically focused on the impact of the disease in their lives and on their recovery, and they often are preoccupied with concerns about their cancer recurring. Studies that do not omit sexually inactive women from analysis of the FSFI also will tend to have downward biased mean and median FSFI scores as well as inflated score standard deviations. In an illuminating critique of the FSFI, Meyer-Bahlburg & Dolezal41 note the effect these biases can have on group comparisons. For example, a study comparing women treated for vulvar intraepithelial neoplasia (VIN) with matched controls revealed that the women with VIN had significantly lower FSFI total scores and had lower scores on 4 of the 6 domains.13 However, women in the control group were required to be sexually active, but the women with VIN were not. Indeed, greater than 25% of the women with VIN reported no sexual activity in the 4 weeks before completing the FSFI.
Although the VIN study appears to have been biased toward identifying significant differences in FSFI scores between groups, the greater score variability and inflated SDs that result from including sexually inactive women in the analysis of group comparisons also can obscure meaningful differences that otherwise would have been statistically significant.41, 42 For example, a study comparing surgical technique for resection of rectal cancer revealed no differences in female sexual function as measured by the FSFI despite significant differences in patients' ratings of how the surgery affected their sexual functioning overall.25 This seemingly contradictory failure to identify significant FSFI differences is not surprising considering that >50% of the women reported no sexual activity.
It seems reasonable to expect that women who answer “no sexual activity” to any 1 of the 15 FSFI items with this option would indicate the same response to the other 14. In practice, however, this does not appear to be the case. In the current study, we considered women with nonzero responses to at least 8 of these 15 items (ie, more than half) to be sufficiently sexually active for the FSFI scores to be valid indicators of their sexual functioning. This threshold for sexual activity was chosen by rational means only, and future studies should attempt to evaluate this important validity issue in a more empirical manner. In particular, we strongly recommend that future studies using the FSFI in cancer survivors pay specific attention to sexual activity levels and respondents' reasons for sexual inactivity. The lack of such an assessment in the studies on which the current analysis is based was an unfortunate limitation of the design of those studies.
The current study has 2 important strengths related to the characteristics of the samples. First, 75% of the sample was ≤41 years old, an age range in which sexual functioning and reproductive issues are important components of QOL. Second, the women in this study were diverse in terms of cancer diagnosis, treatment, age at diagnosis, and time since diagnosis, all of which can vary with respect to the severity and type of sexual symptoms caused. In addition to conferring greater generalizability to the results, this kind of diversity is advantageous to psychometric studies, because it ensures that a wide range of the construct being measured is represented in the responses.
Despite this diversity, a limitation of the current study is the lack of data from breast cancer survivors. Although, ultimately, we believe that these results are generalizable to breast cancer survivors, future research is needed to establish this empirically. We also want to note the limits to the generalizability of the discriminant validity analysis. It is important to emphasize that the 4 cohorts of survivors combined for this report came from studies with different eligibility criteria. Because of this, many important characteristics, such as cancer type, treatment, and time since cancer diagnosis, are not random across this combined sample but, instead, are inextricably confounded with the study cohorts. Therefore, the analysis of discriminant validity should be considered exploratory, providing only provisional evidence that the FSFI can accurately discriminate between groups of cancer survivors with different treatment histories. Although a previous study indicated that cervical cancer survivors who received radiotherapy alone had significantly worse FSFI scores compared with those who underwent surgery alone and healthy controls,20 it is not clear how the inclusion of sexually inactive women may have influenced those results. More research is needed with sexually active female cancer survivors to determine the sensitivity of the FSFI to treatment differences.
A final aspect of validity not addressed in the current study is the sensitivity of the FSFI scores to changes over time. The longitudinal study that provided the CERV cohort data, however, indicated a significant increase in the mean FSFI total score from 16.8 at the presurgical baseline to 23.8 at 12-months postsurgery.19 Another study indicated significant FSFI improvements in patients with cervical cancer who received radiotherapy from a mean score of 17.0 at baseline to 29.4 after 3 months of using a clitoral therapy device.21 Although these studies suggest that the FSFI is sensitive to changes over time, this is another area that is ripe for future investigations.
In summary, responses given by women in the current study support the continued use of the FSFI for monitoring sexual function and cancer-related dysfunction of female cancer survivors. Researchers and clinicians should be aware that the FSFI may not provide valid assessments of sexual function among women who have not had recent sexual activity. Researchers must take this into account when designing and reporting studies using the FSFI to avoid reporting artificially low FSFI scores and estimates of FSD prevalence as well as potentially biased group comparisons. With the validity of the FSFI established among cancer survivors, in a future study, we will develop a short form of the instrument to make routine screening for sexual dysfunction more realistic and feasible in busy oncology settings.