Purpose: Primary staging of prostate cancer relies on modalities, which are limited. We evaluate simultaneous [68Ga]Ga-PSMA-11 PET (PSMA-PET)/MRI as a new diagnostic method for primary tumor–node–metastasis staging compared with histology and its impact on therapeutic decisions. Experimental Design: We investigated 122 patients with PSMA-PET/MRI prior to planned radical prostatectomy (RP). Primary endpoint was the accuracy of PSMA-PET/MRI in tumor staging as compared with staging-relevant histology. In addition, a multidisciplinary team reassessed the initial therapeutic approach to evaluate its impact on the therapeutic management. Results: PSMA-PET/MRI correctly identified prostate cancer in 119 of 122 patients (97.5%). Eighty-one patients were treated with RP and pelvic lymphadenectomy. The accuracy for T staging was 82.5% [95% confidence interval (CI), 73–90; P < 0.001], for T2 stage was 85% (95% CI, 71–94; P < 0.001), for T3a stage was 79% (95% CI, 43–85; P < 0.001), for T3b stage was 94% (95% CI, 73–100; P < 0.001), and for N1 stage was 93% (95% CI, 84–98; P < 0.001). PSMA-PET/MRI changed the therapeutic strategy in 28.7% of the patients with either the onset of systemic therapy/radiotherapy (n = 16) or active surveillance (n = 19). Conclusions: PSMA-PET/MRI can provide an accurate staging of newly diagnosed prostate cancer. In addition, treatment strategies were changed in almost a third of the patients due to the information of this hybrid imaging technique.

Reflecting one's mental self is a fundamental process for evaluating the personal relevance of life events and for moral decision making and future envisioning. Although the corresponding network has been receiving growing attention, the driving neurochemical mechanisms of the default mode network (DMN) remain unknown. Here we combined positron emission tomography and functional magnetic resonance imaging to investigate modulations of the DMN via serotonin-1A receptors (5-HT_1A), separated for 5-HT autoinhibition (dorsal raphe nucleus) and local inhibition (heteroreceptors in projection areas). Using two independent approaches, regional 5-HT_1Abinding consistently predicted DMN activity in the retrosplenial cortex for resting-state functional magnetic resonance imaging and the Tower of London task. On the other hand, both local and autoinhibitory 5-HT_1Abinding inversely modulated the posterior cingulate cortex, the strongest hub in the resting human brain. In the frontal part of the DMN, a negative association was found between the dorsal medial prefrontal cortex and local 5-HT_1Ainhibition. Our results indicate a modulation of key areas involved in self-referential processing by serotonergic neurotransmission, whereas variations in 5-HT_1Abinding explained a considerable amount of the individual variability in the DMN. Moreover, the brain regions associated with distinct introspective functions seem to be specifically regulated by the different 5-HT_1Abinding sites. Together with previously reported modulations of dopamine and GABA, this regional specialization suggests complex interactions of several neurotransmitters driving the default mode network.