Reducing Bone Loss Caused by Prostate Cancer Treatment
Experts recommend the following treatment guidelines from the National Osteoporosis Foundation (NOF). According to these guidelines, doctors should consider drug treatment to halt bone loss if your T-score is -2.5 or lower or you have already had a hip or vertebral fracture. Also consider drug treatment if your T-score is between -1 and -2.5 and you meet one of the following two criteria:
- your 10-year probability of experiencing a hip fracture is 3 percent or more
- your 10-year probability of experiencing a major osteoporosis-related fracture is 20 percent or more
To determine these probabilities, your doctor is likely to use a tool called FRAX, which assesses your risk of a fracture based not only on your BMD but also on a number of other factors such as your age, weight and alcohol intake. You can access the tool at www.shef.ac.uk/FRAX. Click on "Calculation Tool" and choose your country and race. If you are on ADT for prostate cancer, select yes for item number 10 (secondary osteoporosis).
Drug Treatment Options
When medication is required to halt bone loss in ADT users with prostate cancer, bisphosphonates are the first-choice treatment. Selective estrogen receptor modulators (SERMs) offer a second-line option, and a new alternative, a monoclonal antibody called denosumab (Prolia), holds great promise.
Bisphosphonates. These drugs work by slowing the rate of bone breakdown, helping to preserve existing bone mass. Studies in men taking ADT for prostate cancer show that the bisphosphonates alendronate (Fosamax), pamidronate (Aredia), and zoledronic acid (Reclast) can improve BMD in the spine and hip.
To date, none of these medications has been approved by the U.S. Food and Drug Administration (FDA) specifically for the treatment of ADT-induced osteoporosis. However, alendronate and Reclast have been approved to increase bone mass in men with osteoporosis. Research is still needed to determine whether bisphosphonates can reduce fracture risk in men taking ADT for prostate cancer.
Side effects associated with bisphosphonates include flu-like symptoms (muscle aches and pains and fever), nausea, fatigue and kidney damage. Rare instances of osteonecrosis of the jaw (a serious bone disease that affects the jaw) have been reported, particularly after use of intravenously administered bisphosphonates. As a precaution, the American Dental Association and the American Association of Oral and Maxillofacial Surgeons recommend having major dental work performed at least two weeks before the initiation of treatment with a bisphosphonate.
SERMs. These medications mimic some of the actions of estrogen, a hormone that can help stimulate bone-building osteoblasts and shut down bone-destroying osteoclasts. Studies show that the SERMs raloxifene (Evista) and toremifene (Fareston) can increase both spine and hip BMD in ADT users with prostate cancer. A clinical trial is now under way to assess the effect of Fareston on fracture risk; however, the results have not yet been published.
A major concern with SERMs is that they increase the risk of blood clots. If you already have an increased risk of blood clots (for example, you are older than age 80 or have had a previous blood clot, recent surgery, a recent bone fracture; or are immobile), treatment with a SERM is not recommended.
The new drug on the block. The Hormone Ablation Bone Loss Trial (HALT), which began in 2004, followed 1,468 men being treated with ADT for prostate cancer to determine whether a new osteoporosis drug, denosumab (Prolia), might help prevent bone loss and fracture. Prolia is a monoclonal antibody that blocks the formation of a protein known as RANK ligand, which is required for bone breakdown.
The results of the HALT trial, published in The New England Journal of Medicine in 2009, showed that Prolia is indeed an effective and swift treatment for bone loss associated with ADT. Specifically, when injected once every six months, Prolia improved bone density of the lumbar spine by nearly 6 percent, compared with a 1 percent loss of bone density in the placebo group. Prolia increased bone density in as quickly as one month, and the effects lasted throughout the 36 months of the study. The researchers also noted increases in bone density at the hip and forearm. Most important, however, Prolia also reduced the risk of new vertebral fractures by 62 percent.
Prolia was approved in 2010 by the FDA to treat women with osteoporosis who are at high risk for experiencing a fracture. Although an FDA advisory committee had recommended that it also be approved to treat prostate cancer patients with ADT-induced bone loss, the drug has not yet been given the green light for that indication.
What Else Can You Do to Prevent Bone Loss?
Here are more steps you can take to preserve your bone health:
- Exercise. An exercise program that includes weight-bearing aerobic exercise, resistance training, and balance exercises can help preserve your bone density.
- Get enough calcium. Calcium is a key mineral that strengthens bone, and a calcium deficiency can lead to osteoporosis and a risk of fracture. The NOF recommends that adults over age 50 get at least 1,200 mg of calcium a day.
- Get enough vitamin D. Vitamin D contributes to bone health by helping to absorb calcium. The NOF recommends that people over age 50 get between 800 and 1,000 IU of vitamin D each day.
- Don't smoke. Smokingand perhaps even exposure to secondhand smokeis linked to an increased risk of osteoporosis and bone fracture. Quitting can reduce your risk of further bone loss and fracture. If you need help quitting, talk to your doctor. Counseling, nicotine replacement therapy, and prescription medication can help.
- Limit alcohol consumption. Chronic alcohol use can disrupt calcium and hormone levels in your body and can increase your risk of falls that could lead to a fracture. If you drink, it's best to do so in moderation. The usual recommendation for men is no more than two drinks a day.