Validation of the German prostate-specific module
Theoretically, all patients newly diagnosed with prostate cancer are faced with a choice of treatment options: radical prostatectomy or radio therapy. Although these different treatments may have no differences in terms of survival, they may have very different consequences on the subsequent quality of life (QoL). Prerequisite to analyze QoL is a reliable and valid instrument to assess these differences not only in terms of general QoL (EORTC QLQ-C30) but prostate specific symptoms with a prostate specific module as well. Therefore, the aim of this study was a psychometric evaluation (validation) of the prostate-specific module (PSM). Five historical cohort studies were put together for an empirical meta-analysis. The main objective was to analyze the module’s psychometric properties. The total sample consisted of 1,185 patients, of whom 950 completed the QoL questionnaires (EORTC QLQ-C30 and a prostate specific module developed by Kuechler et al.). First step of analysis was a principal component analysis that revealed the following scales: urinary problems, incontinence, erectile dysfunction, sexual problems, problems with partner, pain, heat, nutrition, and psychic strain. The module showed good reliability and concurrent validity and very good construct validity, since the module is able to discriminate between different treatment regimes, tumor stages and age. The German PSM is a reliable, valid and applicable tool for QoL in patients with prostate cancer.