24 January 2022, Monday

Bone Sarcoma: Overview, Causes, Symptoms & Treatment

Overview of Sarcoma:

Sarcoma is a class of cancer arising from connective tissue, which includes bone, muscle, fat tissue, etc. The other major classes of cancer are carcinoma, lymphoma, leukaemia, etc. Almost all primary bone cancers are sarcomas.

Further Reads:

1. What is the role of surgery in the treatment of bone sarcoma?

What causes bone sarcoma?

There is no known cause for bone sarcoma and consequently, there is no general preventive precaution that can be taken or advised. It can affect anybody.

Unlike some cancers like lung cancer (which has been related to smoking), and mouth cancer (which has been related to the use of tobacco), etc., where some significant causative influence is known, there is no known cause for bone sarcoma and consequently, there is no general preventive precaution that can be taken or advised.

It can affect anybody. Therefore, the emphasis is on early detection, correct diagnosis and right treatment.

One specific precaution that can be advised is to avoid radiotherapy of any benign bone tumor (especially GCT of bone), unless all other options have been exhausted, as it is associated with a risk of formation of bone sarcoma in the treated area.

There are certain rare syndromes and familial genetic disorders, which have been associated with an increased risk of bone sarcomas. They are discussed in more detail in a subsequent section.

What are the symptoms of bone sarcoma?

The most common symptoms are pain and/or swelling. Some patients may present with a pathological fracture. A bone tumour in the region of a joint often causes a restriction in the range of movement and function of the joint, either due to a mechanical obstruction caused by the swelling or due to the pain.

When a sarcoma affects a vertebra, it can cause pain in the back, and if it compresses the spinal cord, it can cause weakness and numbness in the distal part of the body.

The most common symptoms are pain and/or swelling in the affected area. The pain initially may be felt only on activity, i.e. on using the affected part of the body, e.g. walking may cause/aggravate pain in the lower limbs and lifting or throwing may trigger pain in the upper limbs.

Soon, the pain may become more persistent and remain present even at rest, and eventually may become continuous and affect sleep.

In some patients, pain may be felt at rest, right from the beginning. The pain may be relieved initially, with painkillers. However, the pain often returns within a short time after stopping the medication.

Swelling may become noticeable in the painful area at the same time as the pain, or sometime later. Often, the swelling may appear before any pain or discomfort is felt. Sometimes, especially in children, the disease can present as a limp while walking, or difficulty in using the upper limb for routine activity.

When present around a joint, a bone tumour can cause restriction in the range of movement and function of that joint, either due to a mechanical obstruction caused by the swelling or due to the pain.

Rarely, the first sign of trouble may be a fracture of the affected bone. This is called a pathological fracture or pathologic fracture. The hallmark of this kind of fracture is that, it occurs without a significant cause.

It may occur while standing up or walking, or with a trivial fall, or even with a sudden jolt experienced while travelling in a vehicle.

However, it is important to know that pathological fracture can be caused by many conditions, other than bone tumors. One of the commonest causes of pathological fracture is osteoporosis.

Sometimes, the disease may affect a vertebra (one of the series of bones that form the backbone/spine, which houses the spinal cord in a hollow canal within) and may present with pain in the back.

If the tumour grows out of the confines of the bone and exerts pressure on the spinal cord, it may cause weakness and/or numbness in the distal part of the body, a problem which is noticed earliest, and most often, in the legs. This may sometimes also result in the loss of voluntary control over the passing of urine and stools.

Which bones can be affected by sarcoma?

Sarcoma can affect any bone in the human body. However, some regions are more commonly affected than the rest. The most commonly affected are the bones around the knee, hip and shoulder joints and the pelvic bones.

When is the treatment for bone sarcoma started?

Treatment for a bone sarcoma is started after the diagnosis is established and the staging investigations are completed. If treatment for a malignant tumor is started without staging the disease, it may result in improper therapy as vital information regarding the extent of the disease in the patient would not have been considered in the planning of that treatment.

Treatment for a bone sarcoma is started after the diagnosis is established and the staging investigations are completed. Armed with the information regarding the nature of the disease, its location and size, the extent of its presence in the patient, the general health of the patient etc. a treatment strategy is planned to give maximum benefit to the patient in terms of recovering from the disease and preservation of useful function.

If treatment for a malignant tumour is started without staging the disease, it may result in improper therapy as vital information regarding the extent of the disease in the patient would not have been considered in the planning of that treatment.

It is important that staging is done before beginning the treatment because treatment can lower the stage of the disease. Let us, for example, consider the situation of a patient with High-Grade Osteosarcoma of the femur bone, who also has lung metastasis, i.e. he has ‘Stage IV’ disease.

By doing the staging before starting the treatment, the most appropriate treatment strategy for this patient can be employed, which also includes the treatment of the metastasis.

But if the treatment is started before staging the disease, the initial treatment with neoadjuvant chemotherapy would shrink the primary tumour and the tumor metastases. In many cases it can cause the metastasis to disappear.

If this patient is staged now, no metastasis will be found, and one would erroneously consider him to be at a lower stage (e.g. ‘Stage II’), which would advocate the use of a different, less aggressive, treatment strategy than what was actually needed for this patient.

Thus, staging the patient after starting the treatment could completely change the disease picture and might result in sub-optimal treatment. It is therefore, important to remember that the real value of staging is only when it is at diagnosis, and not after starting of treatment.