When renal cell carcinoma (RCC) spreads beyond its original location in the kidneys, it often travels to the bones. Bone is the second most common site of RCC metastasis — between 35 percent and 40 percent of people with advanced RCC will experience bone metastasis.

When cancer spreads to the bone, the symptoms can be difficult to manage. Bone pain, fractures, and high blood calcium levels can all worsen your quality of life. However, new treatment strategies can help improve life and outlook with bone metastasis.

In this article, we’ll cover how RCC metastasizes to bones, what symptoms this might cause, and what treatments doctors generally recommend for bone metastasis.

How Does Bone Metastasis Happen?

When kidney cancer spreads to other parts of the body, it’s referred to as metastatic RCC, which is classified as stage 4. When kidney cancer grows past its initial location within the kidney, it first begins to spread into the tissues, blood vessels, or lymph nodes around the organ. From there, cancer cells can detach from the tumor and enter your bloodstream. Cancer cells that reach the bone can stick and form new tumors. These are bone metastases.

In RCC, the common sites of bone metastasis are the:

• Pelvis
• Spine
• Sacrum
• Ribs
• Skull
• Long bones of the upper arms and legs

Once in the bone, the RCC cells affect how the bone grows and maintains itself. Normally, two different types of bone cells work together to balance the amount of bone broken down with the creation of new bone. This makes sure that your bones stay strong and intact. Tumor cells from kidney cancer tend to interfere with the cells that break down old and damaged bone sections. This means that too much bone is broken down, leading to bone pain, breaks, and fractures. As bone is dissolved, the calcium within it is released into the blood. The result is a high blood calcium level, known as hypercalcemia. Hypercalcemia causes its own set of symptoms.

Risk Factors for Bone Metastasis

A few different risk factors have been found to increase the chance of developing bone metastases with RCC. These include:

• Older age
• Higher grade of tumor cells
• Metastatic cancer in the lung, brain, and liver

Diagnosis of Bone Metastasis

Bone metastatic RCC is usually diagnosed through imaging. The different scans that can pick up bone tumors include bone scintigraphy or bone scan, CT scans, X-rays, and MRI scans.

What Are the Symptoms of Bone Metastasis in RCC?

About three-quarters of people with metastatic RCC in the bones will have symptoms or will need bone-specific cancer treatment. The most common symptoms caused by bone metastasis are described below.

Pain

One of the earliest symptoms of bone metastasis is pain. This pain might come and go at first, but it often becomes constant. The pain could be an ache, or it could be sharp and sudden. Sharp, sudden pain can mean that a bone has broken. Some people have described pain from bone metastasis as the worst pain they have experienced in their lives.

Bone Fractures

Studies estimate that about 13 percent of people with RCC bone metastasis experience broken bones. This happens because the bone is weakened by too much breakdown. Fractures can happen during falls, but sometimes the bone is so weak that it breaks on its own or from a minor injury or movement.

Spinal Cord Compression

When cancer cells grow in the spine, they can press on the spinal cord. If this pressure isn’t treated, it can cause paralysis, which means losing the ability to move part of the body. It can also lead to problems with going to the bathroom, like losing control of urination or bowel movements. Early signs that tumors are pressing on the spinal cord are pain in the back or neck, or numbness in the hands, arms, feet, and legs. Around 8 percent to 28 percent of people with bone-metastasized RCC develop spinal cord compression.

Effects of Hypercalcemia

High blood calcium levels from bone breakdown can cause symptoms including:

• Muscle weakness or aching
• Feeling thirsty all the time
• Peeing often
• Feeling sleepy or confused
• Constipation

How Is Bone Metastasis Treated?

Treatment can help manage symptoms of bone metastasis. If you have any of the symptoms mentioned above, talk to your cancer care team about ways they can help.

Treatment for bone metastasis in RCC often involves multiple approaches. Treatment is focused on reducing the severity of the symptoms and improving quality of life. This is called palliative care. Your oncology team might recommend one or more of the following treatments.

Surgery

Surgical procedures can fix bone fractures, remove bone tumors causing spinal cord compression, and reduce pain. In certain cases, when there’s one single bone tumor, surgery to remove the tumor can cure the symptoms. In general, surgery to remove bone metastases — even if there are many — can improve the survival rate. However, this is not usually done because of the extensive surgery needed to remove most metastases, which can lead to major complications and disability.

Radiation Therapy

This approach uses high-energy beams to kill cancer cells. Radiation therapy (also called radiotherapy) is used to control bone pain and to control cancer spread. Between 60 percent and 80 percent of people with RCC bone metastasis receive radiation therapy.

Medications

Systemic therapies are medications that work throughout the whole body. Many types of systemic therapies are approved or in clinical trials to treat bone metastases. These include bisphosphonates, drugs that slow the breakdown of bone. Some bisphosphonates are given as an infusion (into a vein) or an injection, while others can be taken by mouth. Some targeted therapies, which block molecules cancer cells need for tumor growth, may also help.

Clinical Trials

Clinical trials — research studies that test new drugs or treatments — are ongoing to determine the best drug and treatment combinations for RCC bone metastasis. If you’re interested in joining one, ask your oncology team if there are any studies near you for which you may be eligible.

How Does Bone Metastasis Affect Outlook With RCC?

Several factors can affect the outlook for RCC with bone metastasis. In general, having more bone tumors is linked to shorter survival. For example, one study reported that people with one bone tumor lived for an average of 28 months, while those with more than five tumors had an average survival of nine months.

On the other hand, having a long time interval between your initial RCC diagnosis and the beginning of bone metastasis was associated with longer average survival. Finally, people whose RCC metastasized only to the bone (and not to other common sites, like the lung) and who had a single bone tumor had a relatively good prognosis. One study found that the overall survival in this group was about 60 months.

Living with bone metastasis can be difficult, so it’s important to get support and focus on feeling as well as you can. If you’ve been diagnosed with renal cell cancer and are concerned about possible bone metastasis, follow up with your oncology team about any symptoms. They can work with you to recommend the best tests and treatment options for your situation. Remember, you’re not alone — your healthcare team is there to support you every step of the way.

Talk With Others Who Understand

On MyKidneyCancerTeam, the social network for people with kidney cancer and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with kidney cancer.

Have you or a loved one been diagnosed with bone metastatic kidney cancer? Have any treatments worked to help you feel better? Share your experiences in the comments below, or start a conversation by posting to your Activities page.