When cancer puts your bones at risk

Health Monitor Staff
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A diagnosis of cancer is difficult enough, yet many people battling the disease will face another challenge: bone metastasis. That’s when cells travel away from the initial tumor and settle in bone. While doctors can’t predict who will get metastases (aka “bone mets”), they are able to offer new hope in treating them. “Treatments have traditionally included hormone therapy, chemotherapy, targeted therapy, as well as radiation and even surgery in some instances,” notes Marc B. Garnick, MD, Gorman Brothers Professor of Medicine, Harvard Medical School. “Today’s bone-targeting agents can strengthen bones, reduce the number of fractures and even help prevent further cancer spread.”
What is metastasis?
Bone metastasis occurs when cancer cells break away from a primary
tumor and enter the blood and lymph vessels. From there, they may travel to distant parts of the body. How long the process of metastasis takes can vary greatly. Sometimes bone mets are a patient’s first sign of cancer; other times, they occur years after initial treatment.

Certain cancers—most notably prostate, breast, lung, thyroid and kidney—are more likely to spread to bone. In fact, prostate and breast cancers account for about 80% of cases. Between 65% and 75% of patients with advanced prostate or breast cancer develop bone mets, while about 40% of advanced lung cancer patients do.

When patients develop bone metastases, it is crucial to determine which bones are affected, says Dr. Garnick. “Metastases in the weight-bearing areas, such as the hips and femur (the long bone of the leg), can result in fractures, while those in the vertebrae can affect the spinal cord.”

How bones are affected
Bones are constantly renewing and rebuilding themselves, thanks to osteoblasts, which create new bone, and osteoclasts, which break down old bone. Cancer cells can send both types of cells into overdrive, causing either an abnormal buildup of bone or small holes that weaken bones. Doctors use imaging tests, such as X-rays or MRIs, and blood tests to confirm metastasis.

It’s important to note that bone metastasis is different from bone cancer: Bone mets are made of cells from the original cancer site. So prostate cancer that has spread to the bones is known as metastatic prostate cancer.

Hope for the future
While bone mets are usually incurable, current treatments can shrink or stop the growth of tumors. And new therapies in development may soon offer more hope. “Several new classes of drugs can strengthen weakened bones and help prevent them from fracturing. This is an exciting development, as some of the disability caused by bone metastases can now be lessened or even eliminated,” says Dr. Garnick. “Right now treatment is focused on both shrinking tumors and preventing complications, with a hope of preventing bone metastases from occurring at all.”

November 2014