Cancers usually begin when the growth cycle of a cell is abnormal. Normal cells have genetic blue prints or guidelines that regulate their growth, attainment of maturity, reproduction and functions and ultimately death. The DNA provides these basic information and instructions.

If there is a change in the DNA at a point it is called a mutation. This change may alter the instructions that control cell growth. This ultimately may lead to the death of the cells or even to an uncontrolled growth of the cells.

The cells continue to grow without stopping or dying and also reproduce uncontrollably. This leads to formation of a lump of tissue called a tumour. 1-8

In some cases this tumor may be harmless or slow growing and is termed benign. This tumor, apart from pressing on the surrounding tissues may not affect the person. In some cases the mutation of the DNA may lead to cancer.

Left untreated or unchecked the cancer cells may spread to other organs from the affected area of the bone. The spread may affect the bone marrow that lies within the inner core of the bone and is responsible for formation of blood cells or into other organs via blood vessels.

Who does bone cancer usually affect?

Most primary bone cancers affect children and young people in whom there is a growth spurt and rapid bone growth.

Bone cancers commonly affect the fast growing ends of the bones. The ends of the bones are the fastest growing sites of the bone where the osteoblasts are most active.

Risk factors for bone cancer

The exact cause of bone cancers that originate from the bone (Primary bone cancers) is not known. It is speculated that some risk factors may raise the chance of getting bone cancers. It must be remembered that primary bone cancers are very rare.

These risk factors include:

• Age - The risk of osteosarcoma is highest during the teenage growth spurts

• Height – There may be link between tall children and osteosarcoma.

• Sex - Osteosarcoma is more common in males than in females.

• Ethnicity - Osteosarcoma is slightly more common in African Americans than in whites.

• Those who have been exposed to radiation or radiation therapy previously are at a higher risk of bone cancers.

• Those with Paget’s disease of the bone are also at risk of bone cancers. However, the risk of bone cancers in individuals with Paget’s disease is less than 1%. Chondroma also increases the risk of osteosarcoma.

• There is a rare genetic condition called Li-Fraumeni syndrome. This affects 1 in every 142,000 people and may raise the risk of bone cancers. Hereditary multiple exostoses (HME) and inherited breast cancer may also raise the risk of bone cancers.

• Babies with a rare type of childhood cancer which develops in the eye called retinoblastoma have a higher risk of bone cancers.

• Ewing’s sarcoma has been seen three times more commonly in babies who are born with an umbilical hernia. The cause of this association is as yet unknown. Umbilical hernia occurs in some babies at birth when their abdominal contents like intestines tend to protrude out from their navel that refuses to close. The risk of Ewing’s sarcoma in these babies however is very small with only one in 110,000 children with an umbilical hernia going on to develop Ewing’s sarcoma.

• Bone cancer has often been linked to injuries to a limb but this association is not proven.

Symptoms of bone cancer

The most common symptom of bone cancer is bone pain. The affected area is tender to touch and the child is often seen avoiding the use of the joint or limb with the affected bone. The pain becomes chronic and may worsen during the night and affect sleep.

Ewing sarcoma patients complain of rapidly worsening bone pain. This bone pain may be mistaken for arthritis in older adults and “growing pains” in children and teenagers.

Apart from pain and tenderness there may be swelling and redness and a noticeable lump over the affected area. If the affected area is near the joint, movement at the joint may be stiff or restricted.

Bones affected with cancer are also weak and brittle and may fracture or break easily with minor injuries or trauma.

Other less common but more serious symptoms include:

• high temperature (fever) of 38C (100.4F) or above

• sweating, usually at night

• weakness

• fatigue

• anemia

• unexplained weight loss etc.