In reference to Sexual problems after total or partial laryngectomy

Singer et al. conducted a cross-sectional study to assess the extent and predictors of sexual problems among postoperative laryngeal and hypopharyngeal cancer patients. In unadjusted analyses, they reported significantly higher levels of sexual difficulties among the 88 patients who underwent total laryngectomy compared to the 118 patients who underwent partial laryngectomy (P < .01) and in the 105 patients who underwent radiotherapy compared to the 101 patients who did not (P 1⁄4 .02). Results from the multivariate analysis presented in Table IV, however, indicated that only high levels of distress (F 1⁄4 50.03, P < .01) and advanced tumor stages (F 1⁄4 4.07, P 1⁄4 .04), but not radiotherapy or type of surgery, were independently associated with sexual problems. Results from the same analysis were presented in the abstract with slightly different results. In the abstract, Singer et al. indicated that only psychological distress (F 1⁄4 46.27, P < .001), stage of disease (F 1⁄4 4.50, P < .05), and age (F 1⁄4 4.79, P < .05) were significant independent predictors of sexual problems. Based on these results, Singer et al. claimed that type of cancer treatment (mode of surgery, radiotherapy) had ‘‘no impact on the sexual difficulties of the patients’’ and, without reservation, stated that ‘‘laryngeal and hypopharyngeal cancer patients can be reassured that it is unlikely that any given specific treatment option will have a severe negative impact on their sexual relationship. ’’ The boldness of this unqualified assertion is surprising for several reasons. First, Singer et al. did not assess patients who underwent all ‘‘specific treatment options,’’ because all patients in their study had either partial or total laryngectomy, and none had radiotherapy alone. Second, this reassurance is not consistent with an earlier study, which found that patients who underwent laryngectomies had a substantially lower rate of sexual contacts than patients who underwent radiotherapy alone. Finally, the discrepancy between unadjusted and adjusted results for cancer treatments on sexual function may have been caused by methodological flaws in the analyses they conducted. The extremely large association reported by Singer et al. in multivariate analysis between psychological distress and sexual problems, and the concomitant reduction in the association between radiotherapy and total laryngectomy with sexual problems, raises the question of whether the psychological distress variable was appropriately used as a covariate/confounder. Singer et al. note that psychological distress may have been the cause of sexual problems or the consequence of the sexual problems. If the latter were true, then using psychological distress as a covariate in the multivariate analysis would have inappropriately removed variance in sexual problems that may have been causally explained by treatment variables. On the other hand, if psychological distress led to sexual problems causally, it is almost certainly the case that psychological distress was ‘‘downstream’’ from cancer and its treatment. That is, psychological distress was on the causal pathway between cancer and its treatments and sexual problems. In this case, a mediation model should have been specified. Doing so would have provided evidence on the degree to which the relationship between type of surgery or radiotherapy may have been mediated by psychological distress. Failure to attend to the nature of the relationship between cancer, its treatment, psychological distress, and sexual problems, however, would have resulted in the allocation of an inappropriate amount of variance in sexual problems to psychological distress instead of to treatment variables. A second potential problem in the multivariate analysis presented by Singer et al. relates to multicollinearity. Multicollinearity occurs when sets of highly correlated predictors, effectively measuring the same or similar constructs, are included in the same model. In Singer et al., operation mode, radiotherapy, and tumor stage were highly correlated, particularly for dichotomously measured variables; 77% of patients with total laryngectomies had radiotherapy treatment compared to 31% of patients with partial laryngectomies (r 1⁄4 .57); 78% of patients with advanced cancer stages (stage III or IV) had total laryngectomies versus 16% of patients with stage I or II cancer (r 1⁄4 .62); and 71% of patients who received radiotherapy had advanced cancer versus 15% of patients who did not receive radiotherapy (r1⁄4 .45). Since the authors presented results in an ANCOVA format, which is less transparent than multiple regression, it is not possible to determine definitively the degree to which multicollinearity may have been present. Nonetheless, the high intercorrelations between cancer and treatment variables and the disappearance of their effects between unadjusted and adjusted analyses suggest that concern is warranted. In sum, it is certainly possible that type of cancer treatment may not impact sexual problems. However, the results presented by Singer et al. did not demonstrate this convincingly. Demonstrating nonharm from medical interventions requires studies with methods specifically designed for this purpose. Until rigorous