10.1 cancer chemotherapy

Question 1

how do alkylating agents help with tumour cell death?

Answer 1

forms a bound between two strands of DNA in helix

= can’t unwind for DNA replicating = cell dies

Question 2

how do platinum compounds help with tumour cell death?

Answer 2

inhibit DNA synthesis

Question 3

how does methotrexate help in chemotherapy ?

Answer 3

it inhibits dihydrofolate reductase
= folate cycle won’t work
= can’t make purines e.g adenine and guanine
= no DNA synthesis and tumour growth stopped

Question 4

how does 5- fluororouracil help in chemotherapy?

Answer 4

affects thymidylate synthase
= folate cycle can’t work
= cant make purines e.g adenine and guanine
= no DNA synthesis and tumour growth stopped

Question 5

how do spindle poisons help in chemotherapy?

Answer 5

In mitosis, when chromosomes are lined up at metaphase plate, spindle microtubules depolymerise and move sister chromatids to opposite poles

microtubule binding agents affect tubule in 2 ways

• inhibit polymerisation
• stimulate polymerisation and inhibit depolymerisation

Question 6

how do alkylating agents help In chemotherapy?

Answer 6

1. decrease entry or increase exit of chemotherapy entry
2. inactivate agent in cell
3. enhance repair of DNA lesions produced by alkylation

Question 7

what chemotherapy agents affect DNA synthesis?

Answer 7

anti metabolites

Question 8

what chemotherapy agents act on DNA?

Answer 8

alkylating agents

Question 9

what chemotherapy agent affects mitosis?

Answer 9

spindle poisons

Question 10

what chemotherapy agent affects DNA replication?

Answer 10

intercalating agents

Question 11

what are the routes of chemotherapy administration?

Answer 11

• IV is most common
• PO = for convenience, depends on oral bioavailability
• SC = good in community setting
• Into body cavity e.g bladder

Question 12

what are some side effects of chemotherapy?

Answer 12

• mucositis (inflammation and ulcers in mouth) due to GI epithelial damage. Present with sore throat, diarrhoea and GI bleed. Can get oral candida.
• alopecia, hair things at 2-3 weeks. may be total, may regrow.
• nausea/vomiting due to action on chemoreceptor trigger zone
• cystitis
• myalgia
• renal failure = hyperuricaemia caused by rapid tumour lysis = precipitation of urate crystals in renal tubules (pretreat)
• skin toxicity. Local = thrombophlebitis and irritation of veins. General = hyper pigmentation and ulcerated sores.
• cardio toxicity e.g myopathy and arrhythmia.
• lung toxicity e.g pulmonary fibrosis

NB: DUE TO SIDE EFFECTS PROFILE NEW TARGETED DUGS ARE BEING DEVELOPED

Question 13

why do you need to take care with chemotherapy prescribing?

Answer 13

they’re cytotoxic drugs so have

• narrow therapeutic windows
• significant side effects
• dose needs to e altered for individual patient based on BMI, general wellbeing and drug handling ability
• treatment phasing needs to be considered e.g GI and marrow recovery etc.

Question 14

what causes variability in how chemotherapy is received?

Answer 14

• abnormalities in absorption e.g compliance and gut problems
• abnormalities in distribution e.g weight loss and reduced body fat
• abnormal elimination e.g liver and renal dysfunction, other meds
• abnormal protein binding e.g low albumin, other drugs

Question 15

what are the important drug interactions of chemotherapy drugs?

Answer 15

other drugs may increase plasma levels of chemotherapy drug and therefore side effects

• vincristine and itraconazole lead to more neuropathy
• methotrexate, caution with penicillins and NSAIDs

Question 16

how do you monitor chemotherapy during treatment?

Answer 16

• response of cancer e.g radiological imaging, tumour marker blood test and bone marrow
• drug level e.g methotrexate drug assays to ensure clearance from blood after folic acid rescue
• check for organ damage e.g creatinine clearance and echocardiogram