What can prevent tumor lysis syndrome and acute kidney injury in a patient post chemotherapy?

Allopurinol is the Correct Answer to Prevent Tumor Lysis Syndrome

The answer is B. Allopurinol - this medication should be administered prophylactically before chemotherapy in patients at risk for tumor lysis syndrome to prevent the catastrophic presentation described (hyperkalemia, hyperphosphatemia, hypocalcemia, acute kidney injury). 1, 2

Understanding the Clinical Scenario

This patient has developed tumor lysis syndrome (TLS) following B-cell lymphoma chemotherapy, evidenced by:

• Hyperkalemia (K=6)
• Hyperphosphatemia (Phosphate High)
• Hypocalcemia (Calcium Low)
• Acute kidney injury (Urea 570)
• Nausea and vomiting 3, 4

This presentation represents a life-threatening oncologic emergency with significant risk for cardiac arrhythmias, seizures, and death 3, 5.

Why Allopurinol Prevents This Presentation

Allopurinol works by inhibiting xanthine oxidase, the enzyme responsible for converting hypoxanthine to xanthine and xanthine to uric acid. 6 This prevents the massive hyperuricemia that occurs when tumor cells lyse and release intracellular contents, thereby preventing:

• Uric acid crystallization in renal tubules
• Acute kidney injury from uric acid nephropathy
• The cascade of metabolic derangements (hyperkalemia, hyperphosphatemia, hypocalcemia) that follow renal failure 1, 6, 7

Prophylactic Dosing Strategy

• Start allopurinol 48 hours before chemotherapy when possible 2
• Initial dose: 100 mg daily, increase weekly by 100 mg until serum uric acid <6 mg/dL 6
• For high-risk patients (bulky lymphoma): 600-800 mg daily for 2-3 days before chemotherapy 6, 7
• Maximum dose: 800 mg daily 6

Why the Other Options Are Incorrect

Thiazide Diuretics (Option A)

• Thiazides are contraindicated - they can actually worsen hyperuricemia and precipitate TLS
• They reduce uric acid excretion and would exacerbate the problem 6

Furosemide (Option C)

• Loop diuretics are used for treatment, not prevention of TLS 1
• They help maintain urine output (≥100 mL/hour) once TLS develops, but do not prevent the initial cellular lysis and metabolic derangements 1, 2
• They are adjunctive therapy to hydration, not primary prevention 1

Critical Prevention Algorithm for High-Risk Patients

Risk Stratification

High-risk patients include those with:

• Bulky lymphomas (like B-cell lymphoma)
• Elevated LDH
• Pre-existing renal impairment
• Hyperuricemia
• Large tumor burden 2, 4, 7

Prevention Protocol

1. Start aggressive IV hydration 48 hours before chemotherapy - target urine output ≥100 mL/hour 1, 2
2. Administer allopurinol 600-800 mg daily for 2-3 days before chemotherapy 6, 7
3. Monitor electrolytes every 12 hours for first 3 days 2
4. Maintain adequate urine output with loop diuretics if needed (but only after hydration established) 1

Important Caveat: Rasburicase vs Allopurinol

While the question asks what "can prevent" this presentation and allopurinol is the correct answer among the choices given, it's crucial to note that rasburicase is superior to allopurinol in high-risk patients 1, 2, 4:

• Rasburicase immediately converts existing uric acid to allantoin, providing rapid reduction of pre-existing hyperuricemia 2
• Allopurinol only prevents new uric acid formation but doesn't address existing hyperuricemia 6
• In randomized trials, rasburicase achieved significantly lower uric acid levels (p<0.001) 1
• However, allopurinol remains effective for prevention when started 48 hours before chemotherapy 6, 7

When Allopurinol Alone Is Insufficient

If this patient had received prophylaxis and still developed TLS, rasburicase would be required for treatment 1. The combination of hydration plus rasburicase is the standard for treating established clinical TLS 1, 2.

Common Pitfalls to Avoid

• Never use thiazide diuretics in cancer patients at risk for TLS - they worsen hyperuricemia 6
• Don't rely on loop diuretics alone for prevention - they are adjunctive to hydration, not primary prophylaxis 1
• Don't start chemotherapy without adequate prophylaxis in high-risk patients - TLS carries 33% mortality when it occurs 7
• Don't administer allopurinol concurrently with rasburicase - this causes xanthine accumulation and removes rasburicase substrate 8, 2