Introduction Breast cancer is the most common cancer that affects women in the United States (excluding the skin cancers). One out of every 8 women will develop breast cancer in their lifetime.1 Many women are diagnosed each year with breast cancer. In 2008 alone, it was estimated that 182,460 new cases of breast cancer were diagnosed.1 Commercials and billboards inundate women with thoughts of yearly mammograms and monthly self-breast exams. These methods of detection are excellent in finding early stage cancer of the breast, but what if medical science was able to prevent the onset of breast cancer rather than just treat it? Recent press has indicated that the so-called “sunshine vitamin” (vitamin D) may have a role in preventing breast cancer. Prevention of breast cancer would save patients as well as medical assistance programs such as Medicare, thousands of dollars. Cost reduction for patients and insurance alike in itself gives this topic value to review in depth. In June of 2008, the Journal of the National Cancer Institute published a study evaluating Medicare’s cancer treatment costs from 1991 to 2002. Breast cancer costs were found to have substantially increased from $4,189 to $20,964.2 This study also noted that treatment of breast cancer with Avastin costs $55,000 per year for Medicare patients with a 20% copay. This would equal an $11,000 copay for the patient if they have no private insurance to cover the cost.2 Although breast cancer does occur in men and tends to be more aggressive, this review will focus on women only. Many risk factors for the development of breast cancer exist; however, this review will focus solely on women who are vitamin D deficient in comparison with those who have adequate serum storage. Cases included in the review will only include invasive ductal carcinoma of the breast and ductal carcinoma in situ. Rarer forms of breast cancer such as Paget’s Disease and Inflammatory Carcinoma will be excluded. This evidenced-based medicine paper will discuss the proposed mechanism of action as well as recent studies evaluating the validity and role of vitamin D in prevention of breast cancer. Background In 2007, the American Cancer Society estimated that 178,480 women were diagnosed with breast cancer and 40,460 more women died of this disease.1 The chances of developing breast cancer increases with age to a lifetime risk of 1 out of every 8 women being diagnosed with this disease (Figure 1).1 In addition, Caucasian and African American women have a higher rate of cancer when compared with other ethnicities.1 Figure 1: A women’s probability increases over a lifetime to a 1 in 8 chance of developing an invasive breast cancer.1
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