The Relationship Between Osteoporosis (Bone Loss) and Cancer

Bone health is fundamental to health and directly affects quality of life. Osteoporosis, commonly referred to as bone loss, affects millions worldwide and can substantially reduce quality of life through fractures. Its relationship with cancer, another condition affecting millions, is complex and important. Reduced bone density during cancer treatment can adversely affect treatment and general health. This article examines the connection, why it matters and how that knowledge can be used. Understanding these issues is important for their management.

• What Is Osteoporosis (Bone Loss)? Symptoms and Prevention

The Connection Between Osteoporosis and Cancer

Both conditions are associated with aging, which underlies their relationship. Osteoporosis commonly occurs in older people and can develop without cancer. Cancer is also more frequent in older people. The link is therefore closely connected to aging.

Below is a mind map of the relationship between osteoporosis and cancer :

How Do Osteoporosis and Cancer Risks Increase with Age?

1. Sex hormone levels tend to decline with age in both sexes. Estrogen protects against bone loss, but women's levels may fall by approximately 90% as menopause approaches, weakening bones. Some research links men's bone density with declining sex hormones. Estrogen generally decreases by 47% and testosterone by 64%. Less active estrogen also means lower bone mineral density. 
2. Cancer can also affect bones. Even if a cancer has not metastasized , it can still affect bone through increased inflammation at the cancer site and throughout the body. Bones are also a common metastatic site, affecting the skeletal system.
3. Some cancer treatments improve survival while weakening bones. Others, particularly for breast or prostate cancer, lower estrogen or testosterone to slow cancer growth. Blocking these hormones can also weaken bone.

Treatments that may increase osteoporosis risk include:

• Femara (letrozole), Arimidex (anastrozole) and Aromasin (exemestane):  aromatase inhibitors
• Zoladex (goserelin) and Eligard (leuprorelin): gonadotropin-releasing hormone agonists
• Surgical removal of the ovaries or testes
• Casodex (bicalutamide): androgen deprivation therapies
• Prednisone and cortisone:  steroids
• Some chemotherapy drugs
• Methotrexate: immunosuppressive drugs

Fractures from Bone Metastases and Osteoporosis

Metastatic and osteoporotic fractures are common complications in cancer, but their frequency varies with cancer type, general health, age and treatment. An overview follows:

1. Fractures from Bone Metastases: Bone metastases are particularly common in cancers such as breast, prostate and lung cancer. These tend to spread to bone and can cause fractures. Bone metastases may occur in 65-75% of breast cancer cases, while fracture frequency associated with metastatic bone disease may range from 10% to 30%.

2. Osteoporotic Fractures: Treatments such as chemotherapy and radiotherapy can put patients at risk of osteoporosis, reducing bone density and causing fractures. Rates vary by cancer and treatment. Annual osteoporotic fracture incidence is approximately 2% in the general population and may be higher with some cancer treatments.

These rates are important in understanding the relationship and planning treatment. Early diagnosis and appropriate management are essential to preserve quality of life and prevent fractures.

What Are the Risk Factors for Osteoporosis?

People with cancer may face greater osteoporosis risk not only from treatment or cancer's direct effects but also from other cancer-related factors.

Cancers that may adversely affect bones include:

• Primary cancer arising in bone
• Breast cancer
• Prostate cancer
• Lung cancer
• Multiple myeloma (a cancer affecting plasma cells)

Patients with primary bone cancer or breast cancer are particularly at higher risk of osteoporosis. 

Specific treatments may add risk. Cancer treatment-related bone loss may be seven times faster and more severe than normal age-related loss. Treatment can worsen existing osteoporosis.

Treating and Managing Osteoporosis Alongside Cancer

Both osteoporosis and its increased risk may affect cancer management. Doctors assess the risk of weakened bones and fractures.

Noncancer risk factors include:

• Age
• Postmenopausal status
• Smoking
• Alcohol
• Any fracture in adulthood
• Insufficient sex hormone production
• Low body weight 
• A parental history of hip fracture

A person with cancer and at least one other osteoporosis risk factor may be offered a bone mineral density test (DEXA). If cancer medication that can cause bone loss is prescribed, DEXA should also be repeated at least every two years.

For existing osteoporosis or high risk, bisphosphonates such as zoledronic acid (Zometa) may be prescribed to reduce fracture risk. 

In hormone-sensitive cancer, bone-protective hormone replacement, such as estrogen replacement, is generally avoided because it may stimulate cancer growth.

Can People with Cancer Prevent Osteoporosis?

Not everyone diagnosed with cancer will develop osteoporosis. Recommendations to help prevent it include:

• Increasing calcium and vitamin D intake. In general, at least 1000 – 1200 milligrams of calcium and 800 – 1000 milligrams of vitamin D daily are recommended.
• Stopping smoking can affect bone quality; continued smoking may increase fracture risk.
• Avoiding alcohol, which can affect balance and increase falls. 
• To improve balance, strength and flexibility and help reduce falls, exercise regularly.

The Connection Between Cancer and Osteoporosis: A Summary

Osteoporosis occurs naturally with age, but cancer can also trigger it. Cancer may weaken bones, and treatment that kills cancer cells can do the same.

Falling estrogen levels, whether natural or treatment-induced, can cause bone thinning in people of any sex. Estrogen is often blocked to prevent estrogen-sensitive tumors from spreading.

Bone density is usually monitored during cancer treatment. Lifestyle measures and medicines may be recommended to help prevent bone loss.

If you have osteoporosis and are concerned about a cancer diagnosis, remember that preventive measures and medicines can make a difference. Monitoring and treating osteoporosis will form part of your care plan.