Chemotherapy is a treatment used for some types of cancer. This section gives information about chemotherapy. We hope that it answers some of the questions you may have about the treatment and helps you to cope with any side effects it may cause. Where cancer is mentioned, this refers to cancer, leukaemia and lymphoma.
Sometimes chemotherapy is used to treat non-cancerous conditions but often the doses are lower and the side effects may be reduced.
1. Therapeutic : acute lymphatic leukaemia ( ALL ), hodgkins disease ( HD ), corio carcinoma an testicular tumor.
2.Palliative : to reduce the pressure symptoms of tumors on vital organs, lungs, osephagus,tracea, nerves etc. And reducing the size of the tumors.
3. Adjuvat : in combination with surgery and radiotherapy to eliminate any micro metastasis. Eg cancer of the breast, bone sarcoma and soft tissue sarcoma.
4. Neoadjuvant : 2 – 3 course of chemotherapy is given before radiation or surgery.
General Principles Of Chemotherapy :
1. To destroy or remove all neoplastic cells with minimal effects on normal host cells tissue.
2. Drug with different modes of actions and side effect are combined then the effect on the tumor can be increasing the severity of the side effects.
3. Chemotherapy can more effective in patient who may be at a risk of distant micro metastasis after effective treatment with radiotherapy and / or surgery. Chemotherapy offer systemic control of the disease, where as surgery and radiotherapy offer local control only.
4. Chemotherapy can also be combined with immunotherapy or hormone therapy to be more effective.
5. Chemotherapy is contraindicated in existing bone marrow depression with low white cell count and platelet count. Presence of severe infections, impaired renal or hepatic dysfunctions.
6. Chemotherapy is administered in 5 – 6 course at an interval of 3 – 4 weeks depending upon the disease and regimen being followed.
7. Side effect of chemotherapy are usually not life threatening but in case of toxic effect such as nephrotoxicity, severe bone marrow depression or anemia they may have to reduce the medications dose, postpone or discontinue the treatment.
8. The dose administered must be the maximum dose that can be tolerated by the patient.
9. Certain malignancy exhibits resistance to chemotherapeutic drugs. Resistance may be from the star treatment or after the treatment has begun.
Chemotherapy agent are classified
A. CYTOSTATIC
1. Alkalyting agent : Nitrogen mustard, chlorambucil, cyclophospamide, ifosfamde, BCNU, CCNU, DTIC, temodal, cisplatin, carboplatin, oxaliplatin
2.Antimetabolite : Methrotaxe, cytarabine, capetabine ( xeloda ), 5 flourouracil
3. Natural Product :
a. Inhibitors : vinblastine, vincristine, vinoralbine (navelbine), paclicatel (taxol), docetaxel (taxotere)
b. Topoismerase Inhibitors : etoposide (vp16), tenoposide, irinotecan (campto, CPT 11), topotecan (ycamtin)
c. ANtibiotic : bleomycine, doxorubicyne, caelyx, daunorucine, noantrone, mitomicyn, epirubicin
d. Enzym : asparaginase
B. HORMONAL ANTINEOPLASTIC AGENTS
1. Corticosteroid : dexamethasone, prednisolone, hydrocortisone, methylprednisolone, prednisolone
2. Progestins : megestrol acetate (megace), medroxyprogesteron acetate (provera)
3. Estrogen antagonist : tamoxifen (nolvade)
4. Androgen antagonist : flutamide, nilutamide
5. Aromatase inhibitors : anastrozole (arimidex), letrozole (femara), exemestane ( aromasin)
6. Luteinizing hormone-releasing hormone anatagonis : goserelin (zoladex), leuprolide ( lupron)
C. BIOLOGIC RESPONE MODIFIERS (IMMUNOTHERAPY)
1. Interferons : Interferons alpha (roferon, intron, wellferon), interferon beta, gamma -rarely used
2. interluekin-2 : proleukin
D.BILOGICAL TARGETED AGENTS
herceptine, mabthera, gleevec, iressa, erbitux, avastine, velcade, myltorag
Mechanisms of chemotherapy action
Chemotherapy drugs are effective in destroying cancer cells because they interfere directly or indirectly in with the synthesis or functions of nucleic acids. Chemotherapy also produce undesirable damage to the rapidly growing normal cells of the body such as hematologic suppression. Gastrointestinal tract lining inflammation and scalp hair loss. The highly fatal nature of the disease makes the risk of serious toxicity relatively acceptable.
CELL CYCLE :
a review of cell cycle to understand the mechanism of chemotherapeutic action
a. G1 ( gap one ) phase : 18 hours post mitotic enzymes for DNA synthetic are manufactured.
b. S ( synthesis ) phase : 20 hours synthesis of DNA takes place. The chromosome content of DNA doubles.
c. G2 ( gap two ) phase : 3 hours synthesis of RNA and format ion of mitotic spindle shapes.
d. M ( mitosis ) phase : 3 hours – the cell divides into two daughter cells which enter into G0 or G1 phase of the cell cycle.
e. G0 (gap zero ) phase : the inactive resting phase of the cell cycle.
Cell cycle specific drugs interrupt the cell cycle at one or more specific phase eg. Plant alkaloids and anti metabolites. Cell cycle nonspecific may act at all phase of the cell cycle eg. aNtibiotics and alkalyting agents.
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