Cancer and Bone Density

by Amanpreet Buttar, MD:                                    

Osteoporosis literally means "porous" bones. It causes bones to become abnormally thin, weakened, and prone to factures. Postmenopausal women are at a higher risk for osteoporosis as the levels of estrogen, a female hormone that helps maintain bone mass, goes down. In cancer patients the risk of osteoporosis is particularly high owing to the disease itself and the treatments used.

Managing bone health has become an important part of cancer treatment, especially since most cancer patients are elderly. Along with managing other issues in cancer survivors, Oncologists need to keep abreast with the latest developments in managing bone health for their patients.

Bone physiology

In our bodies, bones are constantly being remodeled. In healthy bones with normal bone mass density there is a fine balance between bone destruction and new bone formation. Osteoclasts are the cells that cause bone destruction and osteoblasts help bone formation. Anything that tips the balance towards more osteoclast activity causes bone destruction and osteoporosis.

Risk factors for bone loss

1. Calcium deficiency:  Premenopausal women and all men should consume at least 1000 mg of calcium per day. Postmenopausal women should consume 1200 mg of calcium per day.

2. Vitamin D deficiency:  Men over 70 years and postmenopausal women should consume 800 international units (IU) of vitamin D each day.

3. Physical inactivity, alcohol, and tobacco use

4. Drugs:

Chemotherapy drugs:  Many female patients are rendered menopausal after chemotherapy. With this they lose the protective effect of estrogen on their bones.   Premenopausal females getting chemo can have as much as 7% bone loss every year.

Aromatase inhibitors can cause bone loss. These drugs are used to treat and prevent recurrence of breast cancer.

Similarly in men with prostate cancer treatment with androgen ablation increases bone loss.

Long-term steroid use, blood thinners like lovenox, or radiation treatment can also increase the risk of bone loss.

Epilepsy drugs also have a detrimental effect on bone density.

Prediction of fracture risk

Bone density scanning, or dual-energy x-ray absorptiometry (DXA) or bone densitometry, is an enhanced form of x-ray technology that is used to measure bone loss. DXA is the standard for measuring bone mineral density (BMD).

Bone density scans helps determine the risk of fractures and assess the bone density at the hip and spine.  Based on the results your physician will decide your risk of fractures.

Treatment

Bisphosphonates: Are medications that slow the breakdown and resorption of bone. These are available both by mouth and intravenous for those who cannot tolerate the medication by mouth

Alendronate (Fosamax)-It is available as a pill that is taken once per day or once per week.

Risedronate (Actonel)- It can be taken once per day, once per week, or once per month..

Ibandronate (Boniva)- It is available as a pill that is taken once per day or once per month. It is also available as an injection that is given into a vein once every three months.

Zoledronic acid -It is the intravenous bisphosphonate.. Depending on the indication it is used for, the frequency can vary from once every 4 weeks to once every year. This medication is given into a vein over 15 minutes and is usually well tolerated.

Rank Ligand Inhibitors: Denosumab is an antibody directed against a factor (RANKL) involved in the formation of cells that break down bone. It is approved for use in both osteoporosis due to ageing and in patients with spread of cancer to the bones. It is given as subcutaneous injection under the skin once every 4 weeks or once every six months depending on the indication.

One needs to be aware of the risk of osteoporosis and fractures. It could be part of ageing or acquired due to a diagnosis of cancer and the treatments used for it. Appropriate follow up with your physician and use of DEXA scan can help identify your risk. With the use of above drugs one can significantly reduce the risk of a fracture and maintain adequate bone density.

Dr. Buttar is a Medical Oncologist and Hematologist with Epic Care, a group of experts in the diagnosis and comprehensive treatment of cancer and blood disorders. www.epic-care.com

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