Chapter 1: Radiobiology of Radiotherapy

Cancer is a non-communicable disease. In simple words cancer occurs due to uncontrolled growth of cells. The cancer cells can spread to different organs of the body via blood vessels and arteries and refereed as metastasis. According to world health organization (WHO) nearly 10 million people died in 2020. Breast in female and lung in male are the most common cancer found. The other common cancers are cancers are colon, cervix, rectum and prostate. There are multiple risk factors responsible for cancer, but around one third of death happen from tobacco chewing. High body mass index, alcohol consumption, unhealthy diet and carcinogens. There are number of categories and types of cancers, mainly divided on the basis of histopathology of cancer cells. Examples are carcinoma, sarcoma, leukemia, lymphoma and multiple myelomas etc. depending upon cancer staging, site and histopathology different types of treatment modalities are available. These treatment modalities are surgery, chemotherapy and radiotherapy. Treatment of cancer can be possible by all these three modalities or combination of any two depends on type of cancer. Surgery is a standard treatment modality in many solid tumors in which tumor is surgically removed from cancer site. Chemotherapy is a kind of systemic treatment where cytotoxic drugs are administered through intravenously. The third treatment modality is a radiation therapy which we will discuss in this chapter in detail.