Background: Although patient-driven second opinions are increasingly sought in oncology, the desirability of this trend remains unknown. Therefore, this systematic review assesses evidence on the motivation for and frequency of requests for second opinions and examines how they evolve and their consequences for oncological practice. Materials and Methods: Relevant databases were sought using the terms “cancer,” “second opinion,” and “self-initiated.” Included were peer-reviewed articles that reported on patient-initiated second opinions within oncology. Selection, data extraction, and quality assessment were performed and discussed by two researchers. Results: Of the 25 included studies, the methodological designs were qualitative (n = 4), mixed (n = 1), or quantitative (n = 20). Study quality was rated high for 10 studies, moderate for eight, and low for seven studies. Reported rates of second opinion seeking ranged from 1%–88%. Higher education was most consistently related to seeking a second opinion. Patients’ primary motivations were a perceived need for certainty or confirmation, a lack of trust, dissatisfaction with communication, and/or a need for more (personalized) information. Reported rates of diagnostic or therapeutic discrepancies between the first and second opinions ranged from 2%–51%. Discussion: Additional studies are required to further examine the medical, practical, and psychological consequences of second opinions for patients and oncologists. Future studies could compare the potential advantages and disadvantages of second opinion seeking, and might offer guidance to patients and physicians to better facilitate the second opinion process. Some practical recommendations are provided for oncologists to optimally discuss and conduct second opinions with their patients. The Oncologist 2017;22:1197–1211

Cancer patients need to trust their oncologist to embark in the process of oncologic treatment. Yet, it is unclear how oncologist communication contributes to such trust. The aim of this study was to investigate the effect of three elements of oncologists' communication on cancer patients' trust: conferring competence, honesty, and caring. Eight videotaped consultations, ‘vignettes’, were created, reflecting an encounter between an oncologist and a patient with colorectal cancer. All vignettes were identical, except for small variations in the oncologist's verbal communication. Cancer patients (n = 345) were randomly assigned to viewing two vignettes, asked to identify with the patient and afterwards to rate their trust in the observed oncologist. The effects of competence, honesty, and caring on trust were established with multilevel analysis. Oncologist's enhanced expression of competence (β = 0.17, 95% CI 0.08, 0.27; P < 0.001), honesty (β = 0.30, 95% CI 0.20, 0.40; P < 0.001), as well as caring (β = 0.36, 95% CI 0.26, 0.46; P < 0.001) resulted in significantly increased trust. Communication of honesty and caring also increased patients' expectation of operation success and reported willingness to recommend the oncologist. As hypothesized, oncologists can influence their patients' trust by enhanced conveyance of their level of competence, honesty, and caring. Caring behavior has the strongest impact on trust. These findings can be translated directly into daily clinical practice as well as in communication skills training.