Cancer refers to cells in the body that grow out of control. Because they continue to grow and divide, they are quite different from normal cells. Normal cells are programmed to die in the body, while cancer cells outlive normal cells and continue to form new abnormal cells. Cancer usually forms a tumour. The type of cells found in a tumour determines the kind of cancer. There are two main types of lung cancer; small cell and non-small cell lung cancer (NSCLC). NSCLC accounts for about 75 per cent of all lung cancer cases. Non-small cell lung cancer include carcinoma, adenocarcinoma, and large cell carcinoma. The way NSCLC spreads is different to that of small cell cancers. Treatment options for NSCLC include surgery, chemotherapy and radiation and biologic therapies. Unfortunately, not all patients are candidates for surgery as most often the cancer is detected late. The majority of patient will undergo some sort of chemotherapy or radiotherapy to try to cure the cancer or manage the disease. Chemotherapy makes use of drugs to kill cancer cells so they may cure the cancer or control the growth of the cancer. Radiation therapy uses high-does x-rays or other high-energy rays to kill the cancer cells. Unfortunately, chemotherapy and radiation therapy give disappointing results in terms of the survival of patients. There are also side-effects from chemotherapy and radiation therapy. Hence treatment and management of cancer should aim not only to control the cancer but reduce symptoms or side-effects and therefore improve the quality of life of patients. Biologic therapy, sometimes called immunotherapy, uses drugs called biological response modifiers or immunomodulatory drugs. These have been shown to be effective in treating certain cancers and lessen the side-effects from other cancer treatments. Dr Alfred Rudolph, medical director and chief operating office of SciClone Pharmaceuticals USA, says: 'The goals of adding a biological response modifier such as thymosin-alpha 1 to cancer treatment are to improve the effectiveness of chemotherapy, increase survival, reduce side-effects, perhaps improve the ability to increase chemotherapy doses, and to enhance the quality of life.' Thymosin-alpha 1 is a biological response modifier or immunomodulatory drug. Thymosin-alpha 1, originally isolated from the thymus gland, has been shown to have a dual mechanism of action; it has an anticancer action and it boosts the immune system. Animal studies have shown that thymosin-alpha 1 not only stimulates the immune cells but also prevents the growth of the cancer cells themselves. In trials in patients with advanced lung cancers, thymosin-alpha 1 has been shown, after radiotherapy, to improve survival, restore immune function and decrease the incidence of severe, life-threatening respiratory infections.