Chemotherapy - Indications, Administration + MoA

Question 1

How do most chemotherapies work?

Answer 1

-Most target DNA (directly or indirectly)
-Preferentially toxic towards actively proliferating cells, so tumours which divide rapidly respond best to chemo

Question 2

When is neoadjuvant chemotherapy used?

Answer 2

-Pre-operatively before intervention
-Aiming to make tumour smaller, allow less radical surgery, and treating occult micro-metastases
-Used for osteosarcoma, trialled for breast cancer
-Aims to cure patients

Question 3

When is primary chemotherapy used?

Answer 3

-Initially used for a tumour that is inoperable / of uncertain operability, where a reduction in tumour size may make surgery more feasible
-Aims to increase cure rates

Question 4

When is adjuvant chemotherapy used?

Answer 4

-Given following complete macroscopic clearance from surgery
-Treats occult microscopic mets in lymph-node positive disease to prevent relapse
-Aims to increase cure rates

Question 5

When is palliative chemotherapy used?

Answer 5

-Given to alleviate symptoms or prolong life in patients that cannot be cured
-Must be balanced with QoL

Question 6

When is curative chemotherapy used?

Answer 6

-Often more intensive treatment in cases of significant chances of cure
-Often more toxic

Question 7

When is prophylactic chemotherapy used?

Answer 7

-Hormonal treatments given before overt malignancy is found eg tamoxifen for in-situ breast cancer before invasive carcinoma is recognised

Question 8

Why does chemotherapy involve a combo of different drugs?

Answer 8

-Different classes have different actions so work synergistically to kill more cells
-Reduces chance of drug-resistant malignant cells emerging
-Can maintain dose with drugs that have different toxicity sites

Question 9

How is chemotherapy administered?

Answer 9

Cyclically every 3-4 weeks
Maximum response seen after a 6-month course

Question 10

What routes of administration are there for chemotherapy drugs?

Answer 10

ORAL
-Reduces hospital visits / no invasive procedure required
-Only a minority of drugs are available to be taken PO (tamoxifen, cyclophosphamide)
SYSTEMICALLY
-ie IV via blogs injection or short infusion
-Some may be given continuously via a central line
REGIONALLY
-Intra-vesical - superficial bladder cancer
-Intra-peritoneal - trans-coelomic tumours eg spread from ovarian cancer
-Intra-arterial - any tumour that has a well-defined blood supply eg liver mets

Question 11

How is the appropriate dose of chemotherapy calculated?

Answer 11

-Using patient’s body surface area (BSA)
-Exception = carboplatin dose is calculated directly according to the renal function