Hair regrowth in endocrine therapy alopecia with dutasteride treatment in woman with estrogen positive breast cancer

Introduction

Women with estrogen receptor-positive breast cancer are treated with systemic therapies that include selective estrogen receptor modulators (SERMs) and aromatase inhibitors (AIs). These treatments work with incredible efficacy to improve life expectancy in women with breast cancer by reducing estrogen levels in the body. This estrogen reduction is necessary for treating certain breast cancers; however, it is associated with adverse events, one of which is alopecia or endocrine therapy-induced alopecia (EIA), seen in approximately 15% to 25% of women.¹ Alopecia in this population is likened to female androgenic alopecia with involvement of the frontoparietal and vertex regions of the scalp. The condition notably impacts quality of life in these patients, causing some to discontinue their breast cancer treatment.² Despite the impact on quality of life, there is no therapy approved by the Food and Drug Administration (FDA) for EIA in women with breast cancer.

Herein, we describe a case of EIA in which daily oral dutasteride, a potent 5-α reductase inhibitor used widely for treating male pattern hair loss, improved the alopecia when taken in conjunction with topical minoxidil 5%. Hair regrowth was seen in this patient after 3 months of daily use of 0.5 mg of dutasteride. This finding supports the administration of oral dutasteride with adjunctive topical minoxidil for EIA in women on SERMs for breast cancer treatment.

Case Report

A 70-year-old woman was diagnosed with stage IA, estrogen-positive, progesterone-negative, and HER2-negative breast cancer in September 2019. She underwent a bilateral total mastectomy in October 2019. In early 2020, she initiated AI treatment with anastrozole; however, she discontinued use in October 2020 due to joint pain and osteoporosis, and initiated tamoxifen treatment. In April 2021, 7 months after initiating tamoxifen treatment for breast cancer, she presented with diffuse hair thinning and hair loss in clumps (Fig 1, A) and initiated treatment with once-daily dutasteride 0.5 mg and topical minoxidil 5%. Since then, she has consistently taken dutasteride daily and used topical minoxidil on most days. Despite her continued use of tamoxifen, she has experienced notable hair regrowth and stabilization of her hair loss. On examination, her hair density markedly improved (Fig 1, B) from the time of dutasteride and topical minoxidil initiation, with a noticeable improvement compared to baseline clinical photographs (Fig 1, A and B), representing a period of 18 months. She has not reported any significant side effects from dutasteride throughout her treatment.

Fig 1.

A, Scalp crown with decreased hair density prior to dutasteride treatment. B, Scalp crown with increased hair growth after 18 months of dutasteride treatment.

Discussion

There is a great need to find safe and effective treatments for endocrine therapy alopecia in women undergoing estrogen-inhibiting therapies for breast cancer. These therapies are long in duration, often taken for 5 to 10 years, and the diffuse hair loss associated with their use can be distressing. The only larger-scale study on endocrine therapy alopecia in this population evaluated the use of 3 to 6 months of topical minoxidil 5% monotherapy for treating EIA, contributing to its establishment as a mainstay treatment for women with breast cancer on SERM or AI treatment.¹ Topical minoxidil monotherapy has also been used in several case reports to treat EIA and is the only treatment approved by the FDA for female androgenic alopecia.^3,4 However, true compliance with topical minoxidil as monotherapy is often too difficult and burdensome for patients as it requires careful and consistent topical application twice daily and has been associated with some adverse effects, including but not limited to hypertrichosis, dermatitis, and temporarily increased hair shedding.

This being considered, there is a need to explore novel treatment options for EIA in women that are safe, effective, well-tolerated, and easy to take. Dutasteride, an inhibitor of both type I and type II isoforms of the 5-α reductase enzyme, has been used off-label and in case reports to treat female androgenic alopecia.^5,6 However, larger-scale studies of dutasteride for female hair loss are currently lacking. Dutasteride interrupts a key factor in the development of androgenetic alopecia, that is, dihydrotestosterone levels, which can contribute to hair loss in women when increased. Dihydrotestosterone levels increase in women when endocrine receptor pathway activation and signaling are blocked by endocrine therapy, including both SERMs and AIs that suppress systemic estrogen levels.⁷

Our reported case demonstrates the efficacy and tolerability of dutasteride in treating EIA alongside topical minoxidil 5% in a woman with a history of breast cancer on estrogen-inhibiting treatment. In this patient, EIA was reported after 6 months of estrogen-inhibiting therapy; consistent daily oral therapy with 0.5 mg dutasteride, and adjunctive topical minoxidil led to hair regrowth with no adverse effects. Further, we believe that dutasteride can be safely given in this population without clinically significant changes in the efficacy and activity of tamoxifen. However, we suggest implementing regular tamoxifen level monitoring in larger scale studies to track the interaction between the two medications in this population. Current research on male patients also suggests no association between rates of breast cancer and dutasteride use, though this may be limited given the lack of studies as well as the lack of existing research on female patients on dutasteride.^8,9 We recommend that future controlled studies evaluate the efficacy and safety of dutasteride treatment, both with adjunctive topical minoxidil and as a monotherapy, for EIA in women with breast cancer.

Conflicts of interest

None disclosed.