Bone cancers and sarcomas are rare and heterogeneous group of tumors that arise predominantly from the connective tissues. Globally, they account for less than 1% of all cancers. These cancers usually affect children and young adults more than the older population. According to the National Cancer Registry Programme of the India Council of Medical Research (ICMR), the incidence of bone cancer is below 2 % of all cancers among Indian population, while sarcomas are the fifth most common solid tumors in children, and account for about 6-7% of all childhood malignancies.
Bones and Soft tissues
Bones are the supporting framework of our body which facilitates movement, protection of internal organs and hematopoiesis (formation of blood cellular components). Soft tissues are the extra-skeletal tissues of the body that surround organs and other anatomic structures like tendons, lining of the joints, muscles, fats and blood vessels.
Sarcoma and bone cancers arise from the embryonic mesenchymal cells that mature into muscles, adipose tissue, bone and cartilage among other tissues.
Bone cancer develops when the healthy cells in the bone grow uncontrollably and form a mass called tumor. As the tumor develops, abnormal cells crowd out the healthy ones. These tumors weaken the bone and make it vulnerable to fracture. The tumors can be malignant (cancerous, spread to other parts of the body) or benign (non-cancerous, do not spread to nearby tissues).
Types of bone cancer
There are mainly two types of bone cancer:
- Primary bone cancer- cancer that starts in the bone.
- Secondary bone cancer- cancer that starts in another part of the body and spreads to the bone (metastatic bone cancer).
Primary cancers are the true bone cancers; the different kinds of primary bone cancers are:
- Osteosarcoma: Originates from the bone-forming cells called osteoblasts in the osteoid tissue (immature bone tissue). They occur most often in the arms, legs, and pelvis.
- Chondrosarcoma: Originates in the cartilage and mainly affects the pelvis, legs, and arms. Middle-aged and older adults are more likely to develop this cancer.
- Ewing's sarcoma: Occur mostly in the bones of pelvis, legs, or ribs. These are aggressive in nature and spread to other parts of body, including lungs.
- Chordoma: Usually seen in the spine and base of the skull. They tend to grow slowly and rarely spread to other parts of the body.
Signs and Symptoms
People with bone cancer may experience the following signs and symptoms:
- Dull aching pain that worsens at night and with activity
- Joint swelling and stiffness
- Bone fracture
Other less common symptoms are fever, a feeling of being unwell, unintentional weight loss, and anemia (low level of red blood cells).
Causes and Risk factors
The exact cause of bone tumor is unknown. Researchers believe that bone cancer may develop due to sudden changes in the cells of bone. Additionally, there are some factors that may increase the risk of bone cancer, and include:
- A prior history of other cancers like breast, lung, prostate, kidney, or thyroid cancer
- Paget's disease (a noncancerous bone condition)
- Injury to a bone causing chronic infection
- Some inherited conditions such as retinoblastoma (eye cancer that begins in the retina) , Li-Fraumeni syndrome (inherited familial disorder)
- History of radiation therapy
- Exposure to certain chemicals
If any sign or symptom in a patient raises the suspicion of bone cancer, the following tests are recommended:
- Blood tests: Presence of certain markers such as alkaline phosphatase and lactate dehydrogenase in the blood indicates cancer.
- Imaging studies: These tests help to determine the location, size of bone tumors, and the extent of tumor, and include:
- X-ray: X-rays create picture of the dense structures like bones inside the body. Cancer may make the bone appear different from a healthy bone on an X-ray.
- Bone scan: This uses radioactive tracers to view insides of the bones. These traces get accumulated in areas of the bone and show the changes or abnormalities in the bones.
- Other imaging studies: In some cases, magnetic resonance imaging (MRI), computerized tomography (CT), or positron emission tomography (PET) scan are performed to help evaluate the tumor further.
- Biopsy: A biopsy involves collected a sample tissue from the suspected area and examining it in the laboratory to determine any abnormalities. A needle biopsy or incisional biopsy is performed depending on the location of tumor.
Stages of bone cancer
The cancer staging is done followed the TNM staging system. It provides detailed information about:
- Tumour (T): Size and extent of tumor
- Node (N): Whether the cancer has spread to the surrounding lymph nodes
- Metastasis (M): Whether the cancer has spread to distant parts of the body
Based on TNM staging, a bone cancer can be in any of the following stages:
- Stage I: The cancer is low-grade and is either smaller or larger than 8cm. The tumor is limited to the bone and has not spread to the surrounding tissue of the bone.
- Stage II: The cancer is medium or high-grade and is either smaller or larger than 8cm. It has not spread to the surrounding tissue of the bone.
- Stage III: The cancer is medium or high-grade and is found in more than one place on the same bone. It has not spread to any lymph node or to other parts of the body.
- Stage IV: Cancer cells are of any size or grade and have spread to the lymph nodes and distant parts of the body like brain, liver, or lungs.
Treatment options for bone cancer usually depend on several factors, including the type, stage of cancer, possible side effects and the overall health of the patient.
Treatment modalities available for bone cancer are:
Surgery: Surgery is an appropriate treatment option for all types of bone cancer. It involves the removal of the tumor and some surrounding healthy tissues. The common types of surgeries include:
- Limb salvage surgery: In this method, the cancerous section of the bone is removed while leaving the nearby muscles, tendons, nerves, and blood vessels intact.
- Amputation: In this method, a part or the entire affected limb (arm or leg) is removed.
- Cryosurgery: It is a type of ablation to destroy the cancerous tissues using cold temperature. During the procedure, a very cold metal probe is placed directly on the site of tumor to kill the abnormal cells.
Chemotherapy: It involves the use of drugs to destroy rapidly growing cancer cells in the body. These drugs interfere with the process of cell division and promote cancer cell death. For bone cancer, the chemotherapy is administered along with the radiation therapy or after surgical procedures to enhance its effect. It is an important part of treatment for osteosarcoma and Ewing’s sarcoma.
Some side effects of chemotherapy are nausea, hair loss, weight loss, and extreme fatigue.
Radiation Therapy: It involves using high energy beams like X-rays, gamma rays, and electron beams to shrink and destroy the tumors. For bone cancer, the radiation therapy can be given alone or in combination with chemotherapy or after surgery to ease the symptoms and to prevent the recurrence of cancer.
Side effects from radiation therapy may include mild skin reactions, fatigue, nausea and vomiting, diarrhea and weight loss.
Targeted Therapy: This therapy involves the use of drugs that interfere with genes or proteins that contribute to the growth and survival of cancer cells, thereby destroying the cancer cells. These are different from the chemo drugs and have minimal side effects.
A sarcoma occurs when healthy cells in the soft tissues and other locations undergo a change and start to grow out of control, which slowly forms a mass or lump called a tumor. The tumors can be benign (non-cancerous, do not spread to nearby tissues) or malignant (cancerous, spread to other parts of the body).
The tumors that originate within the soft tissues are called as primary cancers while those cancers that start in another part of the body and spread to the soft tissues are called as secondary tumors.
Signs and Symptoms
Sarcomas are usually asymptomatic during the early stage. As the sarcomas originate in different locations, the signs and symptoms vary depending on the location of tumor. A lump or swelling which may or may not cause pain is usually the first sign of sarcoma.
Other possible symptoms include:
- Abdominal pain that worsens
- Blood in stool or vomit
- Bone fracture and pain
- Skin lesions
- Abnormal vaginal bleeding
Causes and Risk factors
The exact cause of soft tissue sarcoma is not clear. Generally, errors in the DNA cause the cell to divide in an uncontrollable rate, forming tumors.
Other risk factors that can increase the risk of sarcoma include:
- Specific inherited disorders such as Von Recklinghausen’s disease, Li-Fraumeni syndrome or retinoblastoma
- Being exposed to the chemicals
- History of radiation therapy
- Having a weak immune system
- Damaged lymph system( lymphedema)
There are no screening tests that can detect sarcomas in its early stages. If a person experiences any possible sign or symptom of sarcoma, following tests are recommended.
- Imaging tests: Tests such as computerized tomography (CT), magnetic resonance imaging (MRI) scan, chest X-ray, bone scan and angiography are done to examine any suspicious area to learn how far the cancer may have spread.
- Biopsy: Biopsy can help make a definite diagnosis of sarcoma. It involves removal of some tumor tissues from the suspicious area using a needle guided by CT or MRI scanning. The sample is analyzed under a microscope to determine if it is cancerous or benign.
- Tissue testing of the tumor: These laboratory tests will help to identify specific genes, proteins, and other factors unique to the tumor.
Stages of sarcoma
Sarcomas are also staged based on the TNM staging system. Based on this system, the sarcomas can be in the following stages:
- Stage I: The cancer is low-grade and is either less than or larger than 5 cm across. It has not spread to the lymph nodes or other parts of the body.
- Stage II: The cancer is medium or high-grade and is either 5 cm or larger than 5 cm across. It has not spread to the lymph nodes or other parts of the body.
- Stage III: The cancer is high-grade and larger than 5 cm across and has not spread to the lymph nodes; OR the cancer is of any size or grade, but it has spread to the lymph nodes and not to other parts of the body.
- Stage IV: The cancer is any size or grade and may have spread to the lymph nodes and distant parts of the body like lungs and liver.
The treatment method for soft tissue cancer is based on the location, type and stage of sarcoma, possible side effects and overall health of patient. The major treatment modalities include:
Surgery: Surgery is the mainstay and involves the surgical removal of the entire tumor. In rare cases, where the tumor is large and involves major blood vessels and nerves, the whole tumor is removed to control its spread (amputation). This is common in arms and limbs.
Radiation therapy: Radiation therapy may be used before the surgery (neoadjuvant therapy) to shrink the tumor or after the surgery (adjuvant therapy) to destroy any remaining cancer cells.
Radiations can be given through an external machine or can be delivered by placing a radiation source near the site of tumour (internally). In some cases, intraoperative radiation is perfomed during surgery to protect the nearby healthy tissues.
Common side effects of radiation therapy include fatigue, headaches, memory loss and scalp irritation.
Chemotherapy: Chemotherapy is the usage of drugs to destroy rapidly growing cancer cells in the body. Chemo drugs are injected into a vein (IV) or given orally. For sarcomas, chemotherapy is given as a main treatment or after the surgical procedures to enhance its effect.
Common side effects of chemotherapy include nausea, vomiting, fatigue and hair loss.
Targeted therapy: It involves the use of specific drugs to identify and destroy the specific cancer cells without harming the normal cells. The targeted drugs work differently from standard chemo drugs and offer minimal side effects.
Although there is no way to prevent bone cancer and sarcomas, early diagnosis and timely treatment can help improved mortality and morbidity. For those with a known risk factor, a regular checkup can help in the early detection of cancer. Patients with early-stage tumors have the best chance of long-term survival. Once the active treatment is completed, regular checkups and medications are needed to manage the side effects and maintain overall well-being.
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