Anticancer Drugs

ANTICANCER DRUGS

The anticancer drugs either kill cancer cells or modify their growth. However, selectivity of majority of drugs is limited and they are one of the most toxic drugs used in therapy.

Treatment of malignant diseases with drugs is a rather recent development—started after 1940 when nitrogen mustard was used, but progress has been rapid, both in revealing patho-biology of the diseases and in discovery of new drugs. In addition, attempts have been made to define optimal combinations, treatment strategies and patient support measures. Cancer chemotherapy is now of established value and a highly specialized field; only the general principles and an outline will be presented here.

In addition to their prominent role in leukaemias and lymphomas, drugs are used in conjunction with surgery, radiotherapy and immunotherapy in the combined modality approach for many solid tumours, especially metastatic. In malignant diseases, drugs are used with the aim of:

1. Cure Or Prolonged Remission Chemotherapy is the primary treatment modality that can achieve cure or prolonged remission in:

In Children

Acute leukemias

Wilm’s tumour

Ewing’s sarcoma

Retinoblastoma

Rhabdomyosarcoma

Other Ages

Choriocarcinoma

Hodgkin’s disease

Lymphosarcoma

Burkitt’s lymphoma

Testicular teratomas

Seminoma

Mycosis fungoides

2. Palliation Gratifying results are obtained (shrinkage of evident tumour, alleviation of symptoms) and life is prolonged by chemotherapy in:

Breast cancer    

Chronic lymphatic leukemia

Ovarian carcinoma                                                                          

Chronic myeloid leukemia

Endometrial carcinoma

Non-Hodgkin lymphomas

Myeloma          

Head and neck cancers

Prostatic  carcinoma

Lung (small cell) cancer

Many other malignant tumours are less sensitive to drugs—life may or may not be prolonged by chemotherapy. Tumours that are largely refractory to presently available drugs are:

Colorectal carcinoma

Malignant melanomas

Carcinoma pancreas

Bronchogenic carcinoma

Carcinoma stomach

Carcinoma esophagus

Hepatoma

Renal carcinoma

Sarcoma

3. Adjuvant Chemotherapy Drugs are used to mop up any residual malignant cells (micro metastases) after surgery or radiotherapy. This is routinely employed now.

Classification

A.Drugs acting directly on cells (Cytotoxic drugs)

1. Alkylating agents

Nitrogen mustards:

Mechlorethamine

(Mustine HCl)

Cyclophosphamide,

Ifosfamide,

Chlorambucil,

Melphalan

Ethylenimine: Thio-TEPA

Alkyl sulfonate: Busulfan

Nitrosoureas: Carmustine (BCNU), Lomustine (CCNU), Triazine Dacarbazine (DTIC)

2. Antimetabolites

Folate antagonist: Methotrexate (Mtx)

Purine antagonist: 6-Mercaptopurine (6-MP), 6-Thioguanine (6-TG), Azathioprine, Fludarabine

Pyrimidine antagonist: 5-Fluorouracil (5-FU), Cytarabine (cytosine arabinoside)

3. Vinca alkaloids: Vincristine (Oncovin), Vinblastine

4. Taxanes: Paclitaxel, Docetaxel

5. Epipodophyllotoxin: Etoposide

6. Camptothecin analogues: Topotecan, Irinotecan

7. Antibiotics:  Actinomycin D (Dactinomycin), Doxorubicin, Daunorubicin (Rubidomycin), Mitoxantrone, Bleomycins, Mitomycin C

8. Miscellaneous: Hydroxyurea, Procarbazine, L-Asparaginase,Cisplatin, Carboplatin, Imatinib

B. Drugs altering hormonal milieu

1. Glucocorticoids: Prednisolone and others

2. Estrogens: Fosfestrol, Ethinylestradiol

3. Selective estrogen receptor modulators: Tamoxifen, Toremifene

4. Selective estrogen receptor down regulators: Fulvestrant

5. Aromatase inhibitors:  Letrozole, Anastrozole, Exemestane

6. Antiandrogen: Flutamide, Bicalutamide

7. 5-α reductase: Finasteride, inhibitor Dutasteride

8. GnRH analogues: Nafarelin, Triptorelin

9. Progestins: Hydroxyprogesterone acetate, etc.