Specialist oncology pharmacists are being trained in Japan to assist cancer treatment teams. These specialized pharmacists address patients' physical and mental problems in pharmacist-managed cancer care clinics, actively participate in formulating treatment policies, and are beneficial in offering qualitative improvements to patient services and team medical care. However, the effect of outpatient treatment by oncology pharmacists on therapeutic outcomes and medical costs is still unknown. A retroactive comparative analysis of the treatment details and clinical course was conducted among three groups of patients: patients who underwent adjuvant chemotherapy managed by a gynecologic oncologist only (S arm), patients managed by a non-oncologist (general practice gynecologist) only (NS arm), and patients managed by both a nononcologist and a specialist oncology pharmacist (NS Ph arm). The medical cost per course was significantly lower for patients in the NS Ph arm than for those in the other two arms. Surprisingly, the outpatient treatment rate in the NS Ph arm was overwhelmingly high. The involvement of an oncology pharmacist did not make a significant difference in therapeutic outcomes such as recurrence rate and survival. The participation of oncology pharmacists in the management of cancer patients undergoing chemotherapy enables safe outpatient treatment and also reduces medical costs.Key words oncology pharmacist; pharmacist-managed clinic; cancer chemotherapy; cost; outpatient treatment The development of drug therapies for cancer has resulted in improved therapeutic outcomes; these drugs play an important role in cancer treatment. However, unfortunately, cancer drugs always cause side effects, including hematological adverse events such as neutropenia and thrombocytopenia and non-hematological adverse events such as nausea, vomiting, and skin disorders. Such side effects not only diminish a patient's quality of life but may also make it difficult for the patient to continue treatment; dose adjustment, decisions on implementation, and supportive care all become important. In recent years, a policy designed to encourage outpatient treatment of cancer patients was introduced in Japan. However, satisfactory management of treatment in the outpatient setting, where there are few points of contact with patients, has been difficult, and structuring an efficient medical system is important. We established the collaborative drug therapy management (CDTM) care framework in 2008 as a method for managing joint care provided to cancer patients by physicians and specialist oncology pharmacists who address the physicians' requests. 1) In the CDTM workflow, specialist oncology pharmacists examine cancer patients at a pharmacist-managed cancer care clinic before they are seen by their attending physician, and offer proposals to the physician regarding chemotherapy management. Specialist oncology pharmacists play a major role in cancer drug therapy management, and a very high proportion of their proposals are ultimately ado...