Chemotherapy is the use of drugs to destroy cancer cells. These drugs are called as antineoplastic agents or anticancer drugs. Normal cells grow and die in a controlled way. When cancer occurs, cells in the body that are not normal keep dividing and forming more cells without control. Anticancer drugs destroy cancer cells by stopping them from growing or multiplying. Because some drugs work better together than alone, often two or more drugs are given at the same time. This is called combination chemotherapy. Usually the three main modalities of cancer treatment i.e. surgery, radiotherapy and chemotherapy are used in different combinations and sequences
When chemotherapy is used as the only curative treatment of a particular cancer it is known as definitive chemotherapy. The hematolymphoid malignancies like blood cancer, lymphoma, and multiple myelomas are the examples where definitive chemotherapy is the administered to cure the cancer
When the chemotherapy is used before surgery or radiotherapy it is known as neoadjuvant chemotherapy. The aim of the neoadjuvant chemotherapy is to reduce the tumor burden and make the tumor either operable or curable by radiotherapy. Another aim of the neoadjuvant chemotherapy is “organ preservation”. In early days the treatment for locally advanced breast cancers used to be mastectomy. However now, with recent advances in the field of medical oncology, neoadjuvant chemotherapy is administered first enabling the surgeon to operate only the tumor and hence conserving the breast and the cosmesis, self image and confidence of the women. The locally advanced head and neck malignancies often used to be radically operated with loss of voice, swallowing functions. However with neoadjuvant chemotherapy and advance radiotherapy the function of larynx and pharynx is preserved without need of surgery for this subset of patients.
The chemotherapy which is administered after the surgery is known as adjuvant chemotherapy. Successful cancer surgery conducted by adhering to oncological principles brings good outcome and immediate satisfaction to a cancer patient. However the natural history of most of the cancer predisposes the patient for recurrence and distance metastasis. This recurrence is delayed and avoided in several cases with the adjuvant chemotherapy. Colon cancer is a good example of where adjuvant chemotherapy is given after surgery to give the survival advantage to the patients.
The chemotherapy which is administered along with the radiotherapy course is known as concomitant chemotherapy. The aim of such type of chemotherapy is to enhance the effect of radiotherapy. Head and neck cancers, cancer of cervix are most frequently used examples where chemotherapy is administered concomitantly with radiotherapy.
Most advanced and end stage cancers are incurable. The only aim of treatment becomes to relieve the symptoms of the patient. Palliative chemotherapy provides very important role at this stage. The aim of palliative chemotherapy is not to cure the disease but to restrict the spread and to relieve the symptoms of the existing cancer.
General condition the patient is assessed objectively by the Oncologist using different scores and the decision for chemotherapy agents and their doses is taken. Blood parameters like CBC, renal function tests, liver function tests are essential to assess as most of the drugs are excreted through renal or hepatic pathways. There are specific drugs which affect specific body systems and hence they are used cautiously after evaluating that particular body system. For example; adriamycin is cardiotoxic and hence pretreatment cardiac evaluation becomes part of routine workup for the chemotherapy fitness.
Routes of chemotherapy administration
Most agents are administered via intravenous route. The importance of patent IV line, avoiding extravasation needs to be stressed during the IV administration. The patient who requires prolonged IV access for chemotherapy is advised to get a PICC [Peripherally Inserted Central Catheter] or chemotherapy Ports. This not only becomes convenient to patient but also avoids repeated IV puncture attempts. The other routes used for chemotherapy administration are oral, subcutaneous, intramuscular, intra-thecal, intra-arterial, intra-peritoneal and intra-vasical. This route is determined by the pharmacokinetic properties of the particular drug and clinical presentation of the cancer
Most chemotherapy drugs cause nausea, vomiting and myelosuppression. While some drugs causing specific effects on particular body systems like blomycin causes peumotoxicity. The drawback of such side effects is gap or delay in administration of the subsequent chemotherapy cycles. With advancement in the pharmaceuticals the newer and more potent anti emetics are widely available. The artificially prepared growth factors counteract very effectively against the myelosuppression. The potent antibiotics are effective against the chemotherapy induced infections.
This is the recent advancement in the field of Medical Oncology and now more and more new agents are coming up in the armamentarium of oncologist. The traditional chemotherapy agents used to harm cancer cells as well as normal cells as they could not differentiated between the two. But the targeted therapy agents have specific design to identify the targets on the cancer cells and thus sparing the normal cells from the side effects. This has revolutionized the field of medical oncology with more customized approach to the cancer treatment rather than blanket treatment to all. Trastuzumab is an excellent example of targeted agent specifically acting on Her2Neu receptor positive breast cancer patients
The way ahead…
The future of cancer management is now going to be personalized treatment for the individual depending on his cancer biology map and targeted agents suitable for him. The advances in the field of histo-pathology, immunohistochemistry, molecular pathology has lead to categorizing the same cancer into different subtypes and allocating different prognostic values and therapies.
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