Timing Of Chemotherapy:
The role of chemotherapy can be divided into several different clinical settings.
Induction Chemotherapy
Induction chemotherapy is the use of drugs given as primary treatment when no alternative viable treatment modalities exist. An example would be the use of anthracyclines and cytosine arabinoside in the treatment of acute myeloid leukemia to induce a complete remission.
Neoadjuvant (primary) Chemotherapy
Neoadjuvant (primary) chemotherapy is the use of chemotherapy as the initial treatment and given in the hope of reducing the extent of local treatment needed or to increase its effectiveness. This would also address micrometastases and be an effective bioassay to assess responsiveness of the tumor to chemotherapy. An example would be the use of chemotherapy to decrease the extent of surgical resection in breast cancer or along with radiation in other malignancies to deem a tumor surgically resectable.
Adjuvant Chemotherapy
Adjuvant chemotherapy is used after eradication of all measurable disease with local treatment (surgery and/or radiation). The rationale is to treat microscopic disease to prohibit local or distant relapse. This is used after optimal local treatment so that tumor mass would be at a minimum, enhancing the efficacy of antineoplastic agents. This is used commonly in numerous different malignancies including breast cancer and ovarian cancer.
Maintenance Chemotherapy
Maintenance chemotherapy is used usually at lower doses to prolong the duration of remission achieved with more aggressive treatment. This is used in acute lymphocytic leukemia and is being tested in clinical trials in other diseases like ovarian cancer, lymphoma, and others.
Palliative Chemotherapy
Palliative chemotherapy is used solely in the hope of palliating symptoms of the patient when the cancer is deemed incurable by any modality or combination. It does not require symptoms to be present; it is used with the hope of preventing symptoms from appearing or reoccurring or to prolong life if possible. This has been used in varying combinations with radiation, surgery, or as a single modality in cancers such as lung, prostate, and several others.