Abstract BACKGROUND: Chemotherapy-induced alopecia (CIA) is a common and quite distressing adverse effects of chemotherapy. CIA, which can occurr not only in the scalp but also in the eyebrows, eyelashes, and pubic hair, has been known to be a transient condition. However, the degree, pattern, phenotype and processes of CIA are not fully known. CIA might be influenced by many factors, such as the specific chemotherapy regimen, drug doses, the patient’s age, and hormonal statuses. There are few detailed observational studies of CIA or of the impact of age on CIA. We performed a prospective observational study to investigate the prevalence and degree of CIA, including CIA of eyebrows, eyelashes, and body, and we examined patient’s recovery from CIA, focusing on age-depending effects. METHODS: We analyzed 68 female Japanese patients with breast cancer (median age 53 years, range 29-76 yrs) who received perioperative adjuvant chemotherapy with fluorouracil/epirubicin/cyclophosphamide (FEC) and taxane. A questionnaire was administered at the point of chemotherapy completion and 6 and 12 months after chemotherapy completion. The data collected by the questionnaire were as follows: the degree of alopecia, including the eyebrows, eyelashes, and body (pubic, leg, and axillary hair), the onset of alopecia, the onset of hair regrowth, and changes in hair characteristics (color, texture, thickness, structure). RESULTS: CIA occurred in all patients, with severe hair loss irrespective of age. CIA occurred mainly in the scalp but also in the eyebrows, eyelashes, and body for most of the patients. There were significant associations between the patient’s age and the onset of hair regrowth in the eyebrows, eyelashes, and body. The onset of eyebrows, eyelash, and body hair growth were significantly shorter in the premenopausal patients. Any hair changes (e.g., thinned diameter, softer texture, curlier structure) were reported by 85.3% of the patients. The changes in hair diameter were significantly more often ‘thinner’ in the menopausal group compared to the premenopausal group, but the changes in texture, structure, and color were not significantly different between these groups. CONCLUSIONS: Our results revealed the clinical process of CIA in early breast cancer patients who received standard chemotherapy. Severe CIA occurred in all 68 patients who received FEC and taxane chemotherapy. The present findings provide the first data demonstrating that age was not associated with the degree or incidence of hair loss, but age affected the recovery from CIA. These findings are important for the provision of more accurate information to patients who may undergo chemotherapy, and our data will contribute to the optimal treatment for CIA. Citation Format: Takaaki Fujii, Kei Ichiba, Chikako Honda, Yuko Nakazawa, Misato Ogino, Sasagu Kurozumi, Sayaka Obayashi, Reina Yajima. Prospective observational study of chemotherapy-induced alopecia after sequential FEC+taxane and the effects of age in breast cancer patients [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS9-20.