How is osteosarcoma diagnosed?

Dr Cathryn Walton helps us understand the diagnostic process of osteosarcoma and treatment options thereof.

You can listen to this article below, or by using your favourite podcast player at pod.link/oncologybuddies

Osteosarcoma is a rare malignant tumour of bone that comprises 1% of all cancers diagnosed. Of all the new diagnoses of osteosarcomas, 50% of those are diagnosed in children younger than 20 years of age.

It’s characterised by the production of immature bone and the most common areas for development are the growth areas of the bones in the leg (femur and tibia).

Osteosarcoma typically develops in the growth spurt ages in adolescents (13 – 18 years) but it’s characterised by a bimodal age distribution. For example, either the young (13 – 18) or elderly (> 65 years of age). When diagnosed in the elderly, it’s often associated with Paget’s disease (a disease characterised by an accelerated rate of bone turnover).

Symptoms

Pain is the most common symptom. It’s often intermittent and can easily be misdiagnosed as growing pains in children. Pain often commences after an injury and progresses and becomes worse. 

About 12% of patients already have a fracture of bone underlying the tumour at the time of diagnosis.  

Swelling develops over the site of the tumour, over the bone. This swelling may also be tender to touch.

Redness of the skin overlying the mass owing to increased vascularity of the disease and surrounding tissues. 

Osteosarcoma does spread easily. The most common site of spread is to the lungs, which can present as a chronic cough.  

Tests for diagnosis

X-ray: This is usually diagnostic for suspected osteosarcoma. There is bone destruction in the bone underlying the tumour. The margins of the bone are indistinct, with the cortex of the bone being destroyed. There are both radiodense and radiolucent areas with intermittent periosteal new bone formation.  

MRI scan: This is usually done after an X-ray. This shows the full extent of the bone involvement as well as involvement of the surrounding structures like the soft tissue and neurovascular bundles. 

Bone scan: This is done to evaluate the full extent of bone involvement. We can see if there are any other bones involved and local spread of disease can be evaluated.

Biopsy: This is done to confirm tissue (histological) diagnosis and typing of osteosarcoma. Typing is done based on the cellular structure as seen under the microscope. Different types of osteosarcoma have different risk stratifications, resulting in different rates of risk for spread of disease. 

CT scan: This is done to evaluate the lungs. 

Once diagnosis is confirmed with the tests as described, treatment can be decided upon. The results of the tests guide the treatment options and decisions. Repeated tests are done to evaluate response to treatment.

Treatment options 

Options are discussed in a multi-disciplinary team comprising orthopaedic surgeons, radiologists, and clinical oncologists, and then full discussion with the patient and family members will be done.  

This is most often a combination of surgery, chemotherapy, and radiation therapy. Treatment will depend on final imaging and staging options as well as final histology. The aim of treatment is always to maintain limb functioning as much as possible.  

Definitive treatment is surgery with radiation and chemotherapy being given either prior to or after the surgery, depending on the extent of the initial disease as well as the results after surgery.  

If you are diagnosed with metastatic (spread) of disease at the outset, the option is to excise the disease as well as administration of chemotherapy to prevent further spread of disease. 

MEET THE EXPERT  – Dr Cathryn Walton

Dr Cathryn Walton first practiced as a GP for 10 years; she then qualified as clinical oncologist in 2015 and was in a group practice. In 2023, she opened her own practice, Bay Oncology, in Gqeberha, Eastern Cape with primary focus on breast cancer, melanoma and other skin cancers, sarcoma, CNS malignancies, paediatric radiation, and radiation of benign conditions.

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