• Chemotherapy

    by  • 27/05/2013 • Oncology

    Chemotherapy:

    1. Should be given by specialist only
    2. Modes of administration:
      1. o ‘Neoadjuvant’: to shrink tumour before surgical intervention
      2. o ‘Adjuvant’: to control ‘micro-mets’ after post-operatively
      3. o Sole ‘primary therapy’ in some cancers (=haematological)
      4. o Palliative therapy: to provide relief from symptomatic metastatic disease. May prolong survival
    3. Important classes of CT (class, examples, mechanism of action, side effects):
    4. Alkylating agents
      1. o E.g.: cyclophosphamide, chlorambucil, bulsulfan, ifosfamide
      2. o All form covalent bonds between bases of DNA and interfere with replication
      3. o Potentially carcinogenic

     

    1. DNA damaging agents (platinum derivatives)
      1. o E.g. cisplatin and carboplatin
      2. o Adducts with DNA leading strand, breaks and = cell death

     

    1. Anti-tumour antibiotics:
      1. o E.g. Actinomycin D, doxrubicin and epirubicin
      2. o Intercalate in the DNA molecule and block the action of topoisomerase enzyme which unwinds DNA prior to replication

     

    1. Antimetabolites:
      1. o E.g. Flurouracil, methotrexate
      2. o F = Interferes with synthesis of thymidine (DNA base) and is incorporated into RNA
      3. o M = Inhibits a key enzyme in the metabolism of folates, which are necessary for production of purine bases

     

    1. Antimicrotubule agents:
      1. o E.g. paclitaxel, docetacel
      2. o Interfere with polymerization/depolymerization of tubulin taxanes

     

    1. Vinca alkaloids
      1. o E.g. vincristine and vinblastine
    1. Monoclonal antibodies:
      1. o (=panitumumab and cetuximab)

     

    Side effects: depends on the type of drugs used

    1. Vomiting: cause of anxiety. Avoid anticipatory vomiting with dexamethasone 4mg/12h, metoclopramide 10-20mg/8h and ondansetron 4-8mg/8h can be effective
    2. Alopecia: can have a profound on QoL
    3. Neutropaenia: seen at day 10-14 after CT commences. May start from day 7 in taxanes. Neutropaenic sepsis requires immediate attention.

     

    Imaging techniques in cancer:

    1. CT: extensive use in most cancers
    2. MRI: used for staging in areas occult to CT (bone marrow, CNS)
    3. Bone scan: used for staging/follow-up of prostate, breast, lung cancer
    4. Sestamibi scan: used for localizing active disease in breast cancer and thyroid. Like bone scans – it uses technetium (99mTc).
    5. Thalium scan: used to localize viable tissue, e.g. in brain tumours
    6. Gallium scan: used for staging and following up in lymphoma
    7. Octreotide scan: used to demonstrate cancers with somatostatin receptors (e.g pancreas, medullary thyroid, neuroblastoma, and carcinoid cancers)
    8. Monoclonal antibodies: 99mTc-labelled tumour antibodies are used in staging by detecting tumour antigens (e.g: lung, colon, prostate)
    9. FDG PET: 2[18F] fluoro-2-deoxy-D-glucose positron emission tomography detects high rates of aerobic metabolism (e.g in lung, colon, breast, testis).
    10. MIBG scan: (131I): used to localize noradrenaline production (e.g in phaechromocytoma).  
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