Define tumour lysis syndrome. List the risk factors associated with its development. Outline measures to prevent it and provide a rationale for the use of each of those measures.

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College Answer

Definition:
Tumor lysis syndrome (TLS) is an oncologic emergency that is caused by massive tumor cell lysis
with the release of large amounts of potassium, phosphate, and nucleic acids into the systemic circulation

Risk factors

Tumour-related factors

•    High tumour cell proliferation rate
•    Chemo sensitivity of the malignancy
•    Large tumour burden

Patient factors

•    Pre-treatment hyperuricemia or hyperphosphatemia
•    A pre-existing reduction in renal function
•    Volume depletion

Prevention measures

a) Fluids and hydration to achieve a urine output of at least 1 – 1.5 ml/kg (80 to 100 mL/m2) per hour.

Justification:  minimize the likelihood of uric acid precipitation in the tubules. b) Avoid fluids containing potassium and calcium
Justification: Minimize risk of hyperkalemia and calcium deposits

c) Alkalinization of urine

Justification: convert uric acid to the more soluble urate salt, thereby diminishing the likelihood of uric acid precipitation in the tubules. However, there are no data demonstrating the efficacy of this approach.

d) Allopurinol: decreasing uric acid formation by blocking xanthine oxidase.,

e) Rasburicase: Decreases uric acid levels by converting uric acid to allantoin.Justification: Thus, for patients with preexisting hyperuricemia rasburicase is the preferred hypouricemic agent

f) Role of dialysis if there is pre-existing renal dysfunction g) Posttreatment monitoring

•    uric acid, phosphate, potassium, creatinine, calcium and LDH
•    Fluid input and urine output should be assessed four to six hours after the initial administration of chemotherapy.
•    Evidence of TLS or a rising level of uric acid should prompt immediate therapeutic intervention.

Discussion

This question is identical to Question 27 from the first paper of 2013.