Breast Cancer : The Price of a "CURE"

Breast Ca: The Price of a 'Cure'

Published: Nov 1, 2014

By Charles Shapiro, MD

The majority of women with newly diagnosed invasive breast cancer will experience "personal cures." This means they will live out their lives without recurrent breast cancer. There are certain consequences of treatment that women should be aware of, however, and among them is bone loss that may lead to greater risks of subsequent osteoporosis.

Osteoporosis is a major worldwide health problem, and the resultant hip and spine fractures cause significant morbidity, mortality, and healthcare expenditures. The estimated 1-year mortality after a hip fracture is 25%.

One can think about osteoporosis as an equation. On one side is the bone mass you start with that peaks around age 35. The other side of the equation is the bone loss that occurs normally over time. The bone mass you start with versus the extent of bone you lose over a lifetime determines whether osteoporosis will develop and the risk of fractures.

Having a mother who had an osteoporotic fracture is the strongest risk factor for osteoporosis, implying that the genes you are born with play a large role is this disease. Indeed, the genetics of osteoporosis is complicated and not fully understood. Lifestyle factors such as smoking or drinking alcohol, the use of chronic steroids, and certain diseases such as rheumatoid arthritis all increase the risk of osteoporosis, but do so to a lesser extent than genetics.

After age 35 everyone, men included, experiences age-related bone loss. In addition to age-related bone loss, women experience bone loss due to the decreased estrogen levels of menopause. This explains why osteoporosis is more prevalent in women than men.

Why is estrogen so important for bones? Although bone is hard and very strong, at the cellular level it is undergoing constant bone breakdown and new bone formation in a process called bone remodeling. Bone breakdown is the job of the osteoclast cells and new bone formation is the job of the osteoblasts. There is an exquisite balance between these cells to maintain bone strength and structural integrity of bone, and one of the key factors in regulating this balance is estrogen. The hormone favors new bone formation, whereas when estrogen levels are low, as is the case in postmenopausal women, bone breakdown occurs.

Premenopausal women have about one hundred times higher blood levels of estrogen than postmenopausal women, and the main source of estrogen varies according to menopausal status. The ovaries are the source of estrogens in premenopausal women. In postmenopausal women, when the ovaries cease to produce estrogen, the adrenal glands become the major source. The adrenal glands produce androgens that get converted to estrogens by the protein aromatase located in tissues in the body.

Breast cancer treatments in pre- and postmenopausal women cause bone loss because they lower estrogen. For example, chemotherapy-induced ovarian failure, or early menopause, is a common side effect in premenopausal women receiving adjuvant chemotherapy for early stage breast cancer. When this occurs, the bone loss that ensues occurs rapidly, over 6 to 12 months, and is approximately the same magnitude as having the ovaries removed.

This relatively rapid drop in estrogen levels is in contrast to natural menopause, where the estrogen levels decrease gradually over several years. In postmenopausal women with estrogen receptor positive breast cancers, the most common form of breast cancer, the routine use of aromatase inhibitors lowers estrogen by inhibiting the function of aromatase.

Fortunately, osteoporosis is preventable and treatable. The approach to treatment and prevention of osteoporosis is generally the same in women with breast cancer as it is in all women. Periodic screening with bone density exams, encouraging healthy lifestyles by smoking cessation and reducing alcohol consumption, daily calcium intake and vitamin D supplements, and, if indicated, by guideline-defined use of drugs, such as oral and IV bisphosphonates or RANK ligand inhibitors to inhibit bone breakdown.

The key to managing bone health in breast cancer is the awareness that common breast cancer treatments cause bone loss by decreasing estrogen, and women should ask whether they are at risk for bone loss and subsequent osteoporosis. Equally important is that among all the healthcare providers, a woman should know who is responsible for bone health. Is it the oncologist, primary care physician, gynecologist, or an endocrinologist? This will vary depending on the expertise and practice patterns in the local community. The treatment summary and care plan that every individual should receive after cancer treatment should facilitate these discussions.

In observance of National Breast Cancer Awareness Month, MedPage Today has invited guest contributions that address various aspects of the disease and the month-long awareness campaign. The following contribution is by Charles Shapiro, MD, co-director of the Dubin Breast Center and director of translational breast cancer research, both at Mount Sinai Health System, and director of cancer survivorship programs at the Tisch Cancer Institute in New York City.