Treatment of cancer - chemotherapy and radiotherapy

Question 1

Chemotherapy treatment strategies

Answer 1

1. Curative - used to permanently cure patients e.g. acute leukaemia
2. Adjuvant - Given after a local treatment (radiotherapy or surgery) e.g. breast cancer
3. Neoadjuvant - Given prior to a local treatment such as surgery, and its designed to shrink the primary tumour e.g. bladder cancer
4. Palliative - Focusses on providing patients with relief from the symptoms, pain, physical/mental stress of a serious illness, whatever the diagnosis

Question 2

What is radiotherapy? How can it be administered?

Answer 2

Radiotherapy is the use of ionising radiation to kill cancer cells and shrink tumours.

Administered via:
1. Externally via external beam radiotherapy (EBRT) - conventional external beam radiation therapy, 3-D conformal radiotherapy

2. Internally via brachytherapy (internal radiation therapy) - delivered by placing a radiation source inside or next to the area requiring treatment, this means that the irradiation only affects a very localised area so the tumour can be treated with very high doses, however it must be accessible and well-demarcated

Question 3

Acute and late side effects of radiotherapy

Answer 3

Acute:

1. Damage to epithelial surfaces
2. Mouth, throat and stomach sores
3. Intestinal discomfort
4. Swelling of soft tissues
5. Infertility - unable to produce gametes as gonads are very sensitive to radiation

Late:

1. Fibrosis - radiated tissues become less elastic over time due to scarring process
2. Hair loss
3. Dryness - dry mouth and eyes
4. Lymphoedema

Question 4

Common side effects of chemotherapy

Answer 4

Chemotherapy affects cells with high growth fraction. Normal tissues with a high growth fraction include: bone marrow, hair follicles, GI mucosa and skin therefore the common side effects include:

1. Decreased WBC, RBC and platelets
2. Alopecia
3. Stomatitis and/or mucositis
4. Nausea and vomiting - stimulation of the vomiting centre
5. Extravasation

Question 5

How can cancers evolve resistance to anti-cancer drugs

Answer 5

1. Change in sensitivity or binding affinity of target enzymes or receptors - methotrexate & etoposide
2. Decreased drug accumulation via increased expression of glycoprotein transporters or decreased permeability - methotrexate & alkylating agents
3. Formation of drug-inactivating enzymes
   - purine and pyrimidine antimetabolites
4. Production of reactive chemicals that ‘trap’ the anticancer drug - Alkylators, cisplatin & doxorubicin
5. Increased nucleic acid repair mechanisms - alkylating agents, cisplatin
6. Reduced activation of pro-drugs - purine and pyrimidine antimetabolites