Chemotherapy works by stopping or blocking cancer cells from growing and immunotherapy works by boosting up a patient's immune system to find and then attack cancer. Though immunotherapy is gaining popularity but still it is in growing stage. 

Chemotherapies have been key to cancer treatment from a very long time with all established and compiled data regarding the effects and side effects thus making doctors more confident about it in comparison to immunotherapy which is still newer. But gradually it is proving itself in some cancers as preferred line of treatment. Consult an oncologist for clear understanding.

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