A Case of Aromatase Inhibitor-Induced Alopecia Successfully Treated with Low-Dose Oral Minoxidil.

Breast cancer is the most common malignant neoplasm among women worldwide. Adjuvant hormonal therapy (HT) is used for hormone receptor-positive breast cancer. Patients undergoing HT often show a progressive recession of the frontal-temporal hairline with hair miniaturization. The treatment options for endocrine therapy-induced alopecia (EIA) are limited and described in few studies.1-3 Most of these studies have analyzed the safety and efficacy of topical minoxidil treatment.2, 3 As alopecia affects the quality of life (QoL) in females, topical minoxidil has been used for EIA. However, some patients do not respond to topical minoxidil. A 52-year-old female patient receiving letrozole as adjuvant HT for hormone receptor-positive breast cancer visited the clinic with recession of the frontal-temporal hairline and diffuse hair loss. Before HT initiation, she had no medical history of hair loss. After 6 months of HT, she noticed diffuse thinning of the hair on her scalp and loss of pubic hair. The phototrichogram revealed a decrease in both the hair density and thickness in the crown area (hair density: 85 hairs/cm2; hair thickness: 50 μm) (Figure 1A). We prescribed 5% topical minoxidil; however, there was no improvement even after 12 months. Therefore, discontinuing the topical minoxidil, we initiated treatment of low-dose oral minoxidil (1.25 mg once daily). After 10 months of oral minoxidil treatment, the patient showed a significant clinical improvement (hair density: 135 hairs/cm2; hair thickness: 65 μm) (Figure 1B) and did not experience any adverse effects. Adjuvant HT has been the emerging cornerstone in managing hormone receptor-positive breast cancer, including selective estrogen modulators, and aromatase inhibitors (AI).1-3 Aromatase inhibitors, including anastrozole, letrozole, and exemestane, suppress the plasma estrogen levels by inhibiting aromatase.2, 3 Blocking the conversion of testosterone to estradiol, AI increases the activity of 5α-reductase, leading to a higher production of dihydrotestosterone around hair follicles.1, 3 Additionally, AI shortens the anagen phase, contributing to the induction of male-pattern hair loss in susceptible women undergoing HT.1, 2 In patients treated with HT, a progressive recession of the frontal-temporal hairline has often been reported with hair miniaturization in the frontal-temporal and central areas of the scalp.1-3 Among 236 patients treated with AI, 8% discontinued treatment owing to EIA.4 Nevertheless, there have been few case reports and review articles on treating EIA.1-3 Considering the negative impacts of EIA on QoL in patients, low-dose oral minoxidil (LDOM) may be a useful treatment for patients with EIA not responding to topical minoxidil. Minoxidil induces arteriolar vasodilatation by opening the potassium channels and stimulates prostaglandin E2 production, which may result in entry and prolonging the hair follicle cycle into the anagen phase.1, 2 Recently, a multicenter study demonstrated that LDOM had a favorable safety profile in treating diverse forms of alopecia, including telogen effluvium and alopecia areata.5 Oral minoxidil has dose-dependent adverse effects such as hypertrichosis, postural hypotension, headache, and fluid retention.5 However, all systemic adverse effects are resolved on dose adjustment or withdrawal.5 As a pro-drug, minoxidil requires bio-activation into minoxidil sulfate by sulfotransferase.5, 6 Although sulfotransferase is expressed in hair follicle, its expression levels are extensively higher in the liver.6 Moreover, oral minoxidil administration has a higher follicular accumulation of minoxidil than topical minoxidil administration.6 These findings might explain why our patient responded well to oral minoxidil administration. As alopecia is a traumatizing and distressing experience for patients, supportive care for EIA is critical for breast cancer survivors. This case shows the possibility of using LDOM in patients with EIA refractory to topical minoxidil treatment. In the future, more prospective, controlled studies are needed to evaluate the safety and efficacy of low-dose oral minoxidil for EIA in patients with breast cancer. Young Lee: Conception and planning of the study, Interpretation of the data, and Supervised and critical review of the manuscript. Young Yoon Lee: Writing and critical review of the manuscript, and submitting the paper. Yeoun Kuk Sung: Collation and interpretation of the data. Dongkyun Hong and Kyung Eun Jung: Interpretation of the result and critical review of the manuscript. Young-Joon Seo: Supervised the final manuscript. None to declare. Written consent was obtained from the patient for the publication of this case report and for any accompanying images. The case was presented in accordance with ethical principles.