Vitamin B12 for Aromatase Inhibitors Associated Musculoskeletal Symptoms in Breast Cancer

According to the American Cancer Society, there were more than 250,000 new breast cancer cases in 2017. Incidence of breast cancer increases with age, with more than 75% of patients being postmenopausal at the time of diagnosis. In addition, hormone receptors (HR) are over expressed in the majority of breast cancer tumors in postmenopausal women. Two classes of anti-endocrine therapies are used for treatment of HR-positive breast cancer: tamoxifen and the AIs, which can only be used to treat postmenopausal women because they are ineffective in women with functional ovaries. Joint pain is a significant AI-associated toxicity, affecting as many as 50% of patients. No factors associated with breast cancer treatment (such as chemotherapy) or co-morbid conditions (such as diabetes or body mass index) have been clearly shown to be predictive of the development of joint pain. The cause of AI-associated musculoskeletal symptoms remains elusive but some think it is associated with the direct effects of estrogen deprivation on bone, neurohormonal changes which result in change in pain sensitivity, and immune system changes that alter the circulating or local inflammatory cytokine concentrations. Some studies report more than 20% of patients are no longer taking their AI chemotherapy regimen because of AI-associated joint pain. As many as 40,000 women are affected by this toxicity in the United States annually and up to 20,000 women discontinue AI therapy because of intolerable joint pain and muscle aches. The current treatment for AI associated musculoskeletal symptoms is limited to oral pain medications and exercise, but, neither intervention has optimal effects, and the long term use of oral pain medication is problematic. Improvement in the treatment of AI associated musculoskeletal symptoms is needed to improve compliance with therapy, and thereby lead to improved breast cancer outcomes and survivorship. The study team conducted a pilot study (Campbell et al. Breast J, 2018) which suggested that vitamin B12 reduces pain and improves quality of life for participants taking aromatase inhibitors (AIs) who experienced AI-related musculoskeletal symptoms. This study aims to confirm these results in a phase III randomized prospective trial. If confirmed, Vitamin B12 would become a safe and cost-effective option for the treatment of AI-related musculoskeletal symptoms, leading to improved cancer outcomes and survivorship.