Chemotherapy is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells.
Various roles of chemotherapy are

• Primary Treatment
• Neo adjuvant Treatment
• Adjuvant Treatment
• Regional Treatment
• Induction Treatment
• Palliation

Combination Chemotherapy is better because

• It provides maximal cell kill with minimal toxicity
• It provides a broader range of interaction between drugs & tumour cells in heteogenous tumour population
• It may slow the subsequent development of drug resistance