Osteolytic Lesions Due to Cancer

Osteolytic lesions, also called osteoclastic or lytic lesions, are areas of damaged bone that most often occur in people with certain cancers, such as multiple myeloma and breast cancer. On an X-ray, osteolytic lesions appear as tiny holes, giving the bone a "moth-eaten" or "punched-out" appearance.

Osteolytic lesions weaken bone, leading to pain, bone fractures, and other potentially serious complications. Treatment is necessary to ease symptoms and stave off further bone deterioration.

This article discusses osteolytic lesions, the symptoms they cause, and why they occur. It also explains how lytic lesions are diagnosed and treated.

Symptoms and Complications

Osteolytic lesions can cause a range of symptoms and complications whether they are cancerous or not.

Some of the symptoms and conditions that arise from lytic lesions include:

• Bone pain that is common, can be severe, and is often accompanied by nerve damage from bone compression
• Osteoporosis, a progressive weakening of the bone
• Pathological fractures caused by bones which have been weakened by cancer
• Hypercalcemia of malignancy, when bone releases excessive calcium into the bloodstream, causing a range of symptoms such as nausea, confusion, myalgia (muscle pain) and arrhythmias (irregular heart rates)

What Causes Osteolytic Lesions?

Osteolytic lesions occur when the biological process that breaks down and replaces old cells in bone with new ones becomes imbalanced.

Known as bone remodeling, this cycle involves two types of cells:

• Osteoclasts, which release substances to break down bone so it can be replaced
• Osteoblasts, which are responsible for building bone
  

Certain types of cancer can disrupt the production of new cells. For example, when myeloma invades bone tissue, it inhibits the osteoblasts from forming new bone while, at the same time, stimulating osteoclasts to increase cell breakdown.

Osteolytic lesions are also common in metastatic cancers that have spread beyond the site of the original tumor, including:

• Prostate cancer
• Thyroid cancer
• Lung cancer
• Renal (kidney) cancer
• Breast cancer

In cases of metastatic (spreading) cancer, the osteolytic lesions are most often found in larger bones, such as the skull, spine, pelvis, ribcage, and long bones of the legs.

Osteolytic vs. Osteoblastic Lesions

Osteolytic lesions are not the same as osteoblastic lesions. Both terms describe the cellular pathways that lead to bone issues, but they are opposites of one another.

A cancer usually results in one or the other, and certain lesions are more common with particular cancers than others. Though not as common, some cancers can even cause both types of lesions.

Diagnosis

Healthcare providers will monitor patients with cancer, especially multiple myeloma, for signs and symptoms of bone damage. Multiple myeloma is the most common cancer affecting bone, with 70% of people having bone lesions at diagnosis.

There are a few different types of tests used to detect bone changes with cancer, including:

• Blood tests to check calcium levels
• A bone scan using radiotracers to assess bone density
• X-ray imaging to look for areas of damaged or weakened bone
• Computed tomography (CT) scans or magnetic resonance imaging (MRI) to see if cancer has spread to other areas of the body, including the skeletal bone frame and nervous system

Because your blood cells are formed in the bone marrow, this tissue is involved with myelomas and blood-related cancers, like leukemia.

A bone marrow biopsy is used to diagnose and monitor these cancers. Osteolytic lesions in bone marrow are common with myeloma but less often may be found in other conditions, including lymphoma and certain leukemias.

Treatment of Osteolytic Lesions

Treatment of lytic lesions depends on their cause and whether or not they are benign.

Many osteolytic lesions are cancer-related and treated with a combination of low-dose radiation and bisphosphonates, a class of drug commonly used in people with osteoporosis.

Radiation therapy is often used to treat many types of cancer and has been shown to help control pain caused by osteolytic lesions.

Bisphosphonates are given intravenously approximately every four weeks. The medication is often given alongside cancer treatment such as chemotherapy. Bisphosphonates can have potentially serious side effects, including reduced kidney function and, in rare cases, osteonecrosis of the jaw (where the bone of the jaw begins to deteriorate).

Patients with cancer may also be prescribed medications such as Reclast (zoledronic acid) to prevent worsening of bone lesions or XGEVA (denosumab) to inhibit the protein that tells osteoclasts to destroy bone.

Other medications or treatments may be recommended depending on the cause of the osteolytic lesions and a person's symptoms, as well as the stage of cancer and goals of the treatment.