Real-world outcomes of anthracycline and taxane-based perioperative breast cancer therapy using the Japanese electronic medical record database.

[BACKGROUND] Anthracycline (A) and taxane (T)-based therapies improve breast cancer survival, with guidelines strongly recommending these regimens and dose-dense approaches. However, the real-world maintenance of optimal dose intensity, a critical prognostic factor, remains unclear. We aimed to clarify the current treatment situation regarding relative dose intensity (RDI), with a secondary focus on safety.

[METHODS] In this retrospective observational study, we analyzed big data from the DATuM IDEA® electronic medical record database of the Japan Medical Association Medical Information Management Organization, collected from 1 206 955 individuals across 53 medical institutions throughout Japan over 57 months since 2019. We focused on women with primary breast cancer receiving adriamycin/cyclophosphamide (AC), epirubicin/cyclophosphamide (EC), or docetaxel/cyclophosphamide chemotherapy (TC).

[RESULTS] Analysis included 1989 women who received at least two courses of AC, EC, or TC perioperatively. Patients received 2-weekly adriamycin/cyclophosphamide (ddAC) (n = 207), 3-weekly AC (AC q3w) (n = 177), 2-weekly epirubicin/cyclophosphamide (ddEC) (n = 269), 3-weekly EC (EC q3w) (n = 684), and TC (n = 652). Pegfilgrastim was administered to 98% of ddAC/ddEC, 38% of AC q3w, 42% of EC q3w, and 74% of TC patients. Grade 4 neutropenia (incidences >20%) was observed in AC q3w patients aged ≥65 years (22.6%) and in TC patients of any age (27.6%). RDI remained >95% in all groups.

[CONCLUSIONS] RDI was high in all groups. Clinicians should be cautious when administering AC q3w therapy owing to the high likelihood of patients developing Grade 4 neutropenia. For TC, a slightly lower pegfilgrastim administration rate and >20% Grade 4 neutropenia suggest the need for appropriate pegfilgrastim use.