Chemotherapy

Terminology

Adjuvant therapy - given in addition to standard therapy

Consolidation therapy - given after induction therapy with multidrug regimens to further reduce tumor burden

Induction therapy - initial dose of treatment to rapidly kill tumor cells and send the patient into remission

Maintenance therapy - given after induction and consolidation therapies or after the initial standard therapy to kill any residual tumor cells and keep the patient in remission

Neoadjuvant therapy - given before the standard therapy for a particular disease

Remission - less than 5% tumor burden

Salvage therapy - given when standard therapy fails

Adjuvant therapies in various cancers

Metastasis to bone - bisphosphonates (e.g. zoledronic acid) are given to prevent lytic lesions and pathologic fractures as well as malignant hypercalcemia. Bisphosphonates work by inhibiting osteoclasts and thereby preventing bone breakdown.

Breast cancer
Tamoxifen, a selective estrogen receptor modulators (SERM) is used as adjuvant therapy for estrogen receptor positive (ER+) breast cancer. Tamoxifen works to reduce the risk of recurrence and prevent occurrence in the other breast. Adverse effects of tamoxifen include hot flashes.
Trastuzumab, a monoclonal antibody, is used in human epidural growth receptor 2 positive (HER2+) breast cancer. Adverse effects include cardiotoxicity, therefore a baseline echocardiogram is done before starting trastuzumab, and the drug is stopped if ejection fraction falls 16% or more, or if symptoms of heart failure.
Aromatase inhibitors (anastrozole, letrozole), are used in postmenopausal ER+ breast cancer. Adverse effects include increased risk of osteoporosis, therefore, baseline bone density scan is done.

Adverse effects of chemotherapy

Nausea & Vomiting
Chemotherapy induced nausea is common and is treated with serotonin (5HT) receptor 3 antagonists (5HT3) such as ondansetron. They have few adverse effects and work well, and may be given as prophylaxis or as acute therapy.

Tumor lysis syndrome (TLS)
Increased risk of developing this if given cytotoxic chemotherapy for a hematologic cancer. The death of many cells in a short interval leads to release of large amounts of uric acid, potassium, phosphate (phosphate binds calcium leading to hypocalcemia). This leads to damage to various tissues including the kidneys (uric acid and calcium-phosphate damage tubules) and heart (arrhythmias from hyperkalemia). Giving IV fluids and allopurinol/ rasburicase before starting chemotherapy (i.e. prophylactic therapy) can reduce the risk of tissue damage (especially the uric-acid induced kidney damage). Once TLS develops, supportive therapy with continuous telemetry and aggressive electrolyte monitoring and management is indicated.

Ototoxicity
Baseline audiometry should be done before starting agents that are known to cause ototoxicity. These include platinum-based chemotherapy agents (cisplatin, carboplatin).

Myelosuppression
Baseline bone marrow biopsy is not routinely done, but bone marrow evaluation may be done during therapy to check for any myelosuppression. Chemotherapy agents that can cause myelosuppression include 5-fluorouracil, methotrexate.

Pulmonary fibrosis
Baseline pulmonary function tests (PFTs) are needed along with regular interval PFTs when using agents known to cause pulmonary fibrosis. For example, bleomycin.




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