Abstract
Aromatase inhibitors (AIs) are most commonly used for breast cancer patients with hormone receptor positive disease. Although the side effect profile of aromatase inhibitors is well known, including common side effects like arthralgia, bone pain, arthritis, hot flashes, and more serious problems like osteoporosis, we present a case of an uncommon side effect of these medications. We report the case of a postmenopausal woman on adjuvant hormonal therapy with anastrozole after completing definitive therapy for stage IIIB estrogen receptor-positive breast cancer, who was referred to hematology service for evaluation of persistent erythrocytosis. Primary and known secondary causes of polycythemia were ruled out. On further evaluation, we found that her erythrocytosis began after initiation of anastrozole and resolved after it was discontinued. We discuss the pathophysiology of aromatase inhibitor-induced erythrocytosis and reference of similar cases reported in the literature.
Highlights
An estimated 234,190 patients will be diagnosed with invasive breast cancer in 2015 and 40,730 patients will die from the disease this year, as per the American Cancer Society [1]
The most common side effects seen are related to deficiency of estrogen and include increased risk of bone loss and fractures, arthralgia and bone pain, hypercholesterolemia, vaginal dryness and atrophy, dyspareunia with decreased libido, hot flashes, night sweat, and heat intolerance [2]
Though erythrocytosis is not a major side effect reported with aromatase inhibitor use, aromatase inhibitors prevent peripheral conversion of testosterone to estradiol, leading to increased levels of testosterone, which would explain the erythrocytosis seen in our case
Summary
An estimated 234,190 patients will be diagnosed with invasive breast cancer in 2015 and 40,730 patients will die from the disease this year, as per the American Cancer Society [1]. Of these patients, those that have estrogen receptor-positive tumors receive hormonal therapy designed to suppress the tumor by reducing estrogen levels. In postmenopausal women with estrogen receptor-positive breast cancer, the hormonal therapy of choice is an aromatase inhibitor whose mechanism of action causes a reduction in estrogen production. The most common side effects of aromatase inhibitors are related to their antiestrogen effect and are widely known. Present a case of aromatase inhibitor-induced erythrocytosis, an uncommon side effect of aromatase inhibitor use
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