The aim of treatment in patients with cancer is either kill cancer cells or modify their growth. The selectivity of antitumour drugs is marginal at best. Many cancers are characterized by localized tumour masses but surgery or radiotherapy often fail to eradicate it which can become widespread.

Treatment for malignant diseases with drugs started after 1940 when nitrogen mustard was used. From then very rapid progress has been made in new drug discovery for cancer, new effective combination of drugs and pathobiology of the disease.

Drugs used to treat cancer inhibit cell proliferation by inhibiting certain mechanisms of cell proliferation. Therefore they are toxic to both tumour and other normal proliferating cells present in bone marrow, gastrointestinal epithelium and hair follicles. The malignant tumours have a higher proportion of cells undergoing division than in normal proliferating cells in the body. So, the selectivity of cytotoxic drugs occurs.

In addition to leukemias and lymphomas, drugs, are also used in conjunction with surgery, radiotherapy and immunotherapy in a combined approach for many solid tumours, like metastatic. The anticancer drugs are used with the aim of:

1. Cure or prologed remission: This is now possible in cancers like

Acute leukemias
Choriocarcinoma
Wilmis tumour
Hodgkin's disease
Ewing's sarcoma
and Mycosis fungoides

2. Palliation: In this gratifying results are obtained and life is prolonged. This is used in the following cases,

Breast cancer
Chronic lymphatic leukemia
Ovarian carcinoma
Chronic myeloid Leukemia
Prostatic carcinoma
Non Hodgkin lymphomas
Lung (small cell) cancer
Head and neck cancers

Many other malignant tumours are less sensitive to drugs - life may or not be prolonged by chemotherapy. Tumours that are largely refractory to presently available drugs are:

Colorectal carcinoma
Malignant melanomas
Carcinoma pancreas
Bronchogenic carcinoma (non small cell)

3. Adjuvant chemotherapy: Not all radiotherapy and surgery eradicate the cancer cells completely. So adjuvant chemotherapy is used to mop up any residual cancer cells. This is routinely employed now.