Urologists’ Estimation of Online Support Group Utilization Behavior of Their Patients With Newly Diagnosed Nonmetastatic Prostate Cancer in Germany: Predefined Secondary Analysis of a Randomized Controlled Trial - Philipp Karschuck; Christer Groeben; Rainer Koch; Tanja Krones; Andreas Neisius; Sven von Ahn; Christian Peter Klopf; Steffen Weikert; Michael Siebels; Nicolas Haseke; Christian Weissflog; Martin Baunacke; et al. (Journal of Medical Internet Research)