Tumour lysis syndrome and oncologic emergencies: Viva

This is a branching oral built to probe the reasoning that holds the prevention of the tumour lysis at the centre, and to expose the candidate who has memorised the headline without the corners. The questions escalate from the risk assessment to the prophylaxis, the recognition, the management, and the structural emergencies, with the deliberate probes into the pitfalls. [1]

Opening question: the risk and the prophylaxis

The examiner opens with the Burkitt lymphoma and asks how you assess his tumour lysis risk and what prophylaxis you put in place before the first dose. [3]

A strong answer names the Burkitt lymphoma as the very highest-risk tumour, with its rapid doubling time of around twenty-four hours and its large mass, and the high lactate dehydrogenase confirming the high burden. The prophylaxis is the hyperhydration with an isotonic potassium-free fluid at two to three litres per square metre per day to keep the urine output above two millilitres per kilogram per hour, the rasburicase at zero point one five to zero point two milligrams per kilogram, and the four-to-six-hourly biochemistry for the first twenty-four to forty-eight hours. [1]

Model answer. This boy is at the very top of the tumour lysis risk because the Burkitt lymphoma has the highest cell turnover of any childhood tumour. I would start the hyperhydration with an isotonic potassium-free fluid, give the rasburicase at zero point one five to zero point two milligrams per kilogram after checking the glucose-six-phosphate-dehydrogenase status, and monitor the biochemistry every four to six hours, with the renal replacement therapy on standby. [1][4]

Pitfall probe. Why must you check the glucose-six-phosphate-dehydrogenase status before the rasburicase? Because the rasburicase generates hydrogen peroxide, and the deficient child cannot neutralise it, so the rasburicase causes a severe haemolysis and a methaemoglobinaemia. The allopurinol is used where the status is unknown or the deficiency is present. [9]

Probe one: the recognition by the Cairo-Bishop definition

The examiner presses for the exact criteria by which you would recognise the tumour lysis if it declares. [2]

A strong answer reproduces the Cairo-Bishop definition. The laboratory tumour lysis syndrome is two or more of the urate over four hundred and seventy-six micromoles per litre, the potassium over six millimoles per litre, the phosphate over two point one millimoles per litre in the child, and the corrected calcium under one point seven five millimoles per litre, within three days before to seven days after the cytotoxic therapy, each or a twenty-five percent change from the baseline. The clinical form adds the acute kidney injury, the cardiac arrhythmia or sudden death, or the seizure. [2]

Pitfall probe. Why is the phosphate threshold higher in the child than in the adult? Because the children have a higher normal phosphate due to the active bone growth, so the threshold that defines the hyperphosphataemia is set higher, at two point one rather than one point four five millimoles per litre. [1]

Probe two: the management of the declared syndrome

The examiner asks how you would manage the tumour lysis if the potassium reaches seven with the ECG changes. [5]

A strong answer stages the management. The calcium gluconate is given the moment the ECG shows the peaked T waves and the widened QRS, because it stabilises the cardiac membrane within minutes, before the confirmatory biochemistry returns. The insulin with the glucose and the salbutamol shift the potassium into the cell. The refractory hyperkalaemia, the oliguria, and the volume overload are the indications for the renal replacement therapy. [5]

Pitfall probe. Would you correct the asymptomatic hypocalcaemia? No, because the correction in the high-phosphate state drives the calcium-phosphate deposition and worsens the kidney injury, so only the symptomatic hypocalcaemia is corrected. [1]

Branch one: the anterior mediastinal mass

The examiner pivots to the finding of a large anterior mediastinal mass with the facial swelling on the chest film, and asks how this changes the management. [5]

A strong answer names the superior vena cava syndrome and the anaesthetic catastrophe. The child is kept upright, the supplemental oxygen is given, and the sedation is avoided until the airway is secured in a controlled setting, because the loss of the tone can collapse the trachea against the tumour within seconds. The tissue diagnosis is made by the least-invasive route, the peripheral flow cytometry, the effusion cytology, the bone marrow, or the superficial node biopsy under the local anaesthetic. The steroids or the emergency radiotherapy are given first if the obstruction is critical. [5]

Branch two: the progressive leg weakness

The examiner pivots to a progressive leg weakness with the bowel and bladder change, and asks what this is and how you manage it. [7]

A strong answer names the malignant spinal cord compression and the urgency. The intravenous dexamethasone is started early to reduce the cord oedema, the urgent whole-spine magnetic resonance imaging defines the level and the cause, and the definitive management is the emergency decompression, the radiotherapy, or the chemotherapy. The ambulation at the presentation is the strongest predictor of the ambulation at the outcome, and the window is twenty-four to forty-eight hours. [7]

Branch three: the fever in the neutropenic child

The examiner pivots to a fever in the child with a neutrophil count under zero point five times ten to the nine per litre, and asks how this is managed. [10]

A strong answer names the febrile neutropenia as a bacterial emergency. The blood cultures are drawn and an antipseudomonal beta-lactam, such as the cefepime, the ceftazidime, the piperacillin-tazobactam, or the meropenem, is given within one hour, with the aminoglycoside and the glycopeptide added for the unstable child. [10]

Closing question: the single framework

The examiner closes and asks for the single framework that carries the whole topic. [3]

A strong answer states that the paediatric oncologic emergencies share the logic of the anticipation and the speed: the tumour lysis is prevented before the first dose, the hyperkalaemia is treated at the first ECG change, the febrile neutropenia gets the antibiotic within one hour, the hyperleukocytosis is lowered before the transfusion, the mediastinal mass is never sedated before the airway, and the cord compression is imaged and steroided within the day. The candidate who holds these six has the corners that the examination rewards. [1][5]