The management (diagnostic and therapeutic) of cancer in the geriatric population involves a number of complex difficulties. The aim of this study was to assess the impact of a medical specialty on the diagnostic and therapeutic management of elderly cancer patients. Four clinical scenarios of cancer in the geriatric population, with a dedicated survey to gather information regarding each clinical case’s diagnostic and therapeutic approaches, as well as the different criteria influencing physicians’ therapeutic decisions, were exposed to geriatricians, oncologists, and radiotherapists in Saint-Etienne. The surveys were filled out by 13 geriatricians, 11 oncologists, and 7 radiotherapists. There was a homogeneity of responses regarding the confirmation of cancer diagnostics in the elderly. There were strong disparities (inter- and intra-specialties) for several clinical situations regarding the therapeutic management of cancer. There were significant disparities in terms of surgical management, the implementation of a chemotherapy protocol, and the adaptation of the chemotherapy dosage. Contrary to oncologists, who primarily consider the G8 and the Karnofsky score, geriatric autonomy scores and frailty with cognitive assessment were the key factors determining diagnostic/therapeutic therapy for geriatricians. These results raise important ethical questions, requiring specific studies in geriatric populations to provide the homogenous management of elderly patients with cancer.