Osteosarcoma is the most common bone malignancy or bone cancer (tumours that start in the bone) in adolescents and young adults. Osteosarcoma affects about 100 to 150 new patients per year in France. The majority of these osteosarcomas (70%) occur in young people aged 10 to 25 years. There is a male predominance (1 girl affected for 1.4 boys).

Localized osteosarcomas are limited to the bone, the site of the original tumor development. Half of these tumors occur on the femur and 80% around the knee, either on the upper end of the tibia or the lower end of the femur. Other sites are possible.

In 10-20% of cases, metastases are present upon diagnosis. These metastases are located 85 to 90% of them in the lungs. Then come the metastases on another bone.

1. Definition of osteosarcoma

Osteosarcoma is a cancer of bone tissue. The Gustave-Roussy Institute provides the following epidemiological data: osteosarcoma affects young people aged between 10 and 25 years in 70% of cases and affects more boys than girls (it affects 1.4 boys for every girl). This cancer of bone tissue can be localised to the bone (stage 1 to 3 cancer) and in this case, it mainly affects the femur (lower extremity) and the knee (upper extremity of the tibia). However, it can also be located in other bones: shoulder, pelvis, jaw, skull, hip, and vertebrae. According to the Gustave-Roussy Institute, in 10 to 20% of cases, metastases are already present at the time of diagnosis, which increases the risk of recurrence. In the most frequent cases (80 to 90% of cases), these metastases have spread to the lungs. If not, they are found on a bone other than the original tumour site. Finally, the last observation is that this type of cancer affects more men of African-American origin. The management of osteosarcoma is usually a combination of surgery and chemotherapy.

2. Symptoms of osteosarcoma

The main symptoms of osteosarcoma are:

Pain at the site of the bone tumour: the pain can be moderate or intense, very localised or diffuse, constant or transient. It can be felt during the day or at night. It is often the first noticeable sign of osteosarcoma.
A swelling: a swelling or a ball can be felt in the bone tissue. This can sometimes be seen early if the tumour has swollen rapidly. However, if the tumour is located in deep bones, such as the pelvis or a vertebra, the swelling may not be visible until later.
Pathological fracture: osteosarcoma can lead to bone fragility, therefore, to spontaneous fracture or fracture after a very slight impact.
Difficulty in moving the affected joint, resulting in lameness or difficulty in walking.

3. Causes of osteosarcoma

The Canadian Cancer Society reports that the risk of developing osteosarcoma increases during the adolescent growth phase. Factors identified as being at risk include:

Genetic factors: several inherited genetic diseases can promote the development of osteosarcoma. These include familial retinoblastoma (eye cancer), Rothmund-Thomson syndrome (bone and skin problems), Werner syndrome (accelerated ageing of the body) and Bloom syndrome. But also Li-Fraumeni syndrome, neurofibromatosis type 1 (a disorder of the nervous system) or Diamond-Blackfan anaemia (a disorder of the bone marrow).
Previous radiotherapy or chemotherapy: Children who have undergone radiotherapy or chemotherapy at a very young age are more likely to develop osteosarcoma in the next 5 to 20 years.
A history of bone diseases such as Paget's disease: Paget's disease is a chronic skeletal disease in which the bones become brittle and grow enlarged. Scientists have found that Paget's disease favours the subsequent development of osteosarcoma.

4. Osteosarcoma: when to consult?

In the event of unexplained and persistent bone pain or swelling, it is essential to consult your doctor urgently. Indeed, the chances of recovery for a patient suffering from osteosarcoma are greater the earlier it is diagnosed. If the cancer is diagnosed before stage 4, which corresponds to the presence of metastases, it will be localised. And treatment is more likely to achieve remission, limit recurrence, and lead to a cure or reduced sequelae.

On the other hand, late management of bone cancer can lead to complications such as metastatic osteosarcoma, with a high risk of amputation or death. Metastases may have developed to organs (frequently the lungs) or to another bone. Treatment in the latter case will require higher doses of radiotherapy, a dose level not always feasible if the metastases are located close to organs. Furthermore, while recurrence of osteosarcoma at the original tumour site is rare, this is not the case for metastatic osteosarcoma. In this case, the patient must undergo re-operation and, if the metastases can be removed, further radiotherapy or even amputation of the affected limb. It is therefore easy to understand why it is absolutely necessary not to delay consulting a doctor in case of doubt, as the consequences of an extensive osteosarcoma are serious, even lethal.

5. Examinations and diagnosis of osteosarcoma

The diagnosis of osteosarcoma is based on various elements:

A clinical examination: by examining the patient, he or she looks for any swelling and locates the pain. The doctor also checks the mobility of the joint, feels the lymph nodes, listens to the lungs, etc.
Questioning of the patient: the doctor asks questions about any previous pathologies (bone pathology, radiotherapy or chemotherapy, hereditary genetic diseases mentioned above), the context of the appearance of the symptoms, and the factors that aggravate or relieve the symptoms...
Medical imaging tests such as X-rays to detect possible bone cancer. Then a CT scan, an MRI or scintigraphy to orientate toward the diagnosis of bone cancer and to check whether it has spread to other parts of the body.
A biopsy is the only test that confirms the diagnosis: removal of bone tissue for analysis.
A full blood test.

6. Treatments for osteosarcoma

The treatment plan will depend on several factors: the stage of development of the osteosarcoma (stage 1, 2, 3 or 4), the patient's general health and the location of the tumour. There are several stages of care.

Chemotherapy: Whether the osteosarcoma is localised or metastatic, the first step is neo-adjuvant chemotherapy. The products used are generally cisplatin and doxorubicin, methotrexate or ifosfamide. The aim is to reduce the size of the tumour and treat any metastatic sites, stop the progression of the disease and reduce pain. This stage prepares the patient for surgery.
Surgery: After chemotherapy, surgery is performed. The type of surgery considered depends on both the size of the tumour, its location and its response to pre-operative chemotherapy. It may be a wide excision, i.e. Removal of the tumour and a large part of the surrounding bone and soft tissue. On the other hand, it can be a conservative surgery, i.e. The removal of the diseased part of the bone and its reconstruction (bone graft, Endoprosthesis...) during the same operation. In 10% of cases, according to the Gustave-Roussy Institute, amputation is necessary (because the tumour is infected, too large, the osteosarcoma has affected the nerves and blood vessels, there is too little healthy tissue, etc.).
Post-operative adjuvant chemotherapy: this chemotherapy is considered in specific cases of risk of recurrence. In other words, if metastases have been observed, if cancer has not responded well to pre-operative chemotherapy treatment if the tumour could not be removed at all or not entirely.

Scientists are continuing to explore ways of treating and preventing this type of cancer. One of the avenues being pursued is that of immunotherapy, developed in particular at Inserm over the last ten years. The principle of immunotherapy is to strengthen the immune system, so that it recognises cancer cells more easily and fights them better, rather than seeking a treatment that will attack the cancer cells themselves. This involves research into vaccines, monoclonal antibodies and immunomodulatory drugs (drugs that stimulate the immune system).

7. How can osteosarcoma be prevented?

As the causes of osteosarcoma can be multiple and are not all understood at this time, it is difficult to prevent this disease. However, it is advisable to adopt a healthy lifestyle, with a balanced and varied diet, regular physical activity, limiting alcohol consumption and stopping smoking. In this way, the risk of cancer and, more generally, health problems are limited to a minimum. Finally, as previously mentioned, it is essential to consult one's doctor quickly at the slightest doubt, especially if the patient is at risk: between 10 and 25 years of age, in the middle of a growth spurt, with a history of radiotherapy or bone disease, etc. The faster osteosarcoma is treated, the greater the chance of recovery and the lower the risk of sequelae.