Table 1.
Multivariable Logistic Regression Models Predicting Functional Erections Suitable for Intercourse at 2 Years After Treatment, According to Planned Primary Prostate Cancer Treatment in the PROSTQA Cohorta
| Treatment, Variable | Parameter Estimate (SE) |
OR (95% CI) | Wald χ2 P Value |
Bootstrap Parameter Estimate (SE) |
||
|---|---|---|---|---|---|---|
| Prostatectomy | ||||||
| Intercept | −2.96 (1.38) | −3.00 (1.42) | ||||
| Pretreatment sexual HRQOL score (per 10 points) | 0.45 (0.07) | 1.6 (1.4–1.8) | <.001 | 0.45 (0.07) | ||
| Age (per 10 y) | −0.56 (0.16) | 0.6 (0.4–0.8) | <.001 | −0.58 (0.16) | ||
| Nerve-sparing | 1.29 (0.52) | 3.6 (1.3–10.1) | .01 | 1.39 (0.57) | ||
| PSA ≤10 ng/mL | 0.85 (0.36) | 2.3 (1.2–4.7) | .02 | 0.88 (0.37) | ||
| External radiotherapy | ||||||
| Intercept | −5.22 (0.76) | −5.37 (0.79) | ||||
| Pretreatment sexual HRQOL score (per 10 points) | 0.54 (0.08) | 1.7 (1.4–2.0) | <.001 | 0.55 (0.09) | ||
| No neoadjuvant hormone therapy | 1.18 (0.39) | 3.3 (1.5–7.0) | .003 | 1.24 (0.41) | ||
| PSA <4 ng/mL | 1.17 (0.46) | 3.2 (1.3–8.0) | .01 | 1.24 (0.48) | ||
| Brachytherapy | ||||||
| Intercept | −3.13 (2.21) | −3.40 (2.34) | ||||
| Pretreatment sexual HRQOL score (per 10 points) | 0.72 (0.11) | 2.1 (1.7–2.5) | <.001 | 0.75 (0.11) | ||
| Age (per 10 y) | −0.63 (0.28) | 0.5 (0.3–0.9) | .03 | −0.64 (0.30) | ||
| African American race/ethnicity | 1.13 (0.60) | 3.1 (0.9–10.0) | .06 | 1.18 (0.64) | ||
| BMIb | ||||||
| <25 | 2.22 (0.86) | 9.2 (1.7–50.0) | .01 | 2.30 (0.94) | ||
| 25–34.9 | 1.40 (0.77) | 4.0 (0.9–18.4) | .07 | 1.45 (0.85) | ||
| ≥35 | 0 | 1 [Reference] | ||||
Abbreviations: BMI, body mass index; CI, confidence interval; HRQOL, health-related quality of life; OR, odds ratio; PROSTQA, Prostate Cancer Outcomes and Satisfaction With Treatment Quality Assessment; PSA, prostate-specific antigen.
Model areas under the receiver operating characteristic curve were 0.77 (95% CI, 0.72–0.82) for prostatectomy, 0.83 (95% CI, 0.78–0.88) for external radiotherapy, and 0.89 (95% CI, 0.85–0.94) for brachytherapy. Individual predicted probabilities of functional erections suitable for intercourse at 2 years can be calculated using the inverse logistic function {exp[X′ β]/[1 + exp(X′ β)]}, where X′ β is the sum with X representing individual characteristics observed and β representing the associated model parameter estimates for the individual characteristics.
Calculated as weight in kilograms divided by height in meters squared.