Residency · Residency · Internal Medicine
Oncologic Emergencies for the Internist
Overview
Oncologic emergencies are life-threatening complications of cancer or its treatment that require rapid recognition and management. Internists frequently encounter these conditions on the wards, in the emergency department, and in the ICU. Early involvement of oncology and relevant subspecialties is essential. The five major oncologic emergencies are tumor lysis syndrome, hypercalcemia of malignancy, superior vena cava syndrome, malignant spinal cord compression, and febrile neutropenia.
Tumor Lysis Syndrome (TLS)
Pathophysiology
Tumor lysis syndrome results from the massive release of intracellular contents during rapid tumor cell death, whether spontaneous or treatment-induced. This produces hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia (secondary to phosphate binding calcium). These metabolic derangements can cause acute kidney injury (through uric acid crystal nephropathy and calcium-phosphate deposition), cardiac arrhythmias, seizures, and death.
High-Risk Malignancies
The highest-risk malignancies are Burkitt lymphoma and acute lymphoblastic leukemia. Acute myeloid leukemia with high white blood cell counts also carries substantial risk, as does any bulky, rapidly proliferative tumor with high tumor burden. Risk is further elevated by LDH elevation, renal impairment, and volume depletion.
Cairo-Bishop Diagnostic Criteria
| Lab Parameter | Threshold (or 25% change from baseline) |
|---|---|
| Uric acid | ≥ 8 mg/dL |
| Potassium | ≥ 6 mEq/L |
| Phosphorus | ≥ 4.5 mg/dL |
| Calcium | ≤ 7 mg/dL |
| Laboratory TLS | 2 or more of above within 3 days pre- or 7 days post-treatment |
| Clinical TLS | Lab TLS + renal failure, arrhythmia, seizure, or death |
Laboratory TLS requires 2 or more of the following within 3 days before or 7 days after cytotoxic therapy: uric acid at or above 8 mg/dL or 25% increase, potassium at or above 6 mEq/L or 25% increase, phosphorus at or above 4.5 mg/dL or 25% increase, or calcium at or below 7 mg/dL or 25% decrease. Clinical TLS adds renal failure, arrhythmia, seizure, or death to the laboratory criteria.
Prevention
Aggressive IV hydration at 3 L/m2/day should begin 24 to 48 hours before chemotherapy. Allopurinol at 300 to 800 mg/day PO is started 1 to 2 days before treatment and prevents new uric acid formation but does not reduce existing uric acid. Rasburicase at 0.2 mg/kg IV as a single dose is a recombinant urate oxidase that rapidly converts uric acid to allantoin and is used for high-risk patients or established TLS. It is contraindicated in G6PD deficiency due to methemoglobinemia risk, and samples must be processed on ice since it keeps degrading uric acid in the test tube at room temperature. Urine alkalinization is no longer recommended because it can worsen calcium-phosphate precipitation. Labs (uric acid, potassium, phosphorus, calcium, creatinine, LDH) should be monitored every 6 to 8 hours during high-risk periods.
Treatment
Hyperkalemia is treated with the standard protocol (calcium, insulin/dextrose, albuterol, potassium binders, dialysis). Hyperphosphatemia is managed with phosphate binders, IV hydration, and dialysis if severe. Hyperuricemia is treated with rasburicase if not already given. Hypocalcemia should only be treated if symptomatic, as correcting calcium in the setting of high phosphorus can worsen calcium-phosphate deposition. AKI or renal failure may require dialysis for refractory electrolyte abnormalities or volume overload.
<image>Tumor lysis syndrome pathophysiology showing intracellular contents release, resulting metabolic derangements, and end-organ complications with prevention and treatment strategies</image>
Hypercalcemia of Malignancy
Mechanisms
Humoral hypercalcemia from PTHrP accounts for 80% of cases and is associated with squamous cell carcinomas (lung, head/neck), renal cell, and bladder cancer. Local osteolytic hypercalcemia from bone metastases occurs with breast cancer and multiple myeloma through cytokine-mediated osteoclast activation. Vitamin D-mediated hypercalcemia occurs in lymphoma via extrarenal 1-alpha-hydroxylase activity. Ectopic PTH secretion is very rare.
Clinical Features
Manifestations include altered mental status, dehydration, polyuria, constipation, nausea, and bone pain. Severe cases produce coma and cardiac arrhythmias (shortened QT, Osborn waves). Hypercalcemia of malignancy is often a sign of advanced disease with poor prognosis.
Management
Treatment proceeds stepwise: IV normal saline resuscitation at 200-300 mL/h, calcitonin 4 IU/kg subcutaneously or IM every 12 hours (rapid but temporary effect), zoledronic acid 4 mg IV (onset 2-4 days, first-line), denosumab for bisphosphonate-refractory cases, glucocorticoids for lymphoma or vitamin D-mediated disease, and treatment of the underlying malignancy as definitive therapy.
Superior Vena Cava Syndrome (SVCS)
Etiology
Malignancy accounts for 90% of cases, with lung cancer being most common (especially SCLC and NSCLC), followed by lymphoma, mediastinal germ cell tumors, and thymic malignancies. Non-malignant causes (10%) include thrombosis from indwelling central venous catheters, pacemaker leads, and fibrosing mediastinitis. The mechanism involves external compression, direct invasion, or thrombosis of the SVC.
Clinical Features
Patients present with facial and neck swelling and plethora (worse when supine or bending forward), upper extremity edema, dyspnea (the most common symptom), and dilated collateral chest wall veins. Headache, dizziness, and altered mental status from cerebral edema are late and ominous findings. The Pemberton sign (bilateral arm elevation causing facial plethora and JVD) may be present.
Diagnosis
CT with contrast (CT venography) defines the site and extent of obstruction and identifies the underlying mass. Tissue biopsy for histologic diagnosis should be obtained before treatment whenever possible, as most SVCS is not immediately life-threatening.
Management
Initial measures include head-of-bed elevation and supplemental oxygen. Dexamethasone 4 mg IV every 6 hours is appropriate for steroid-responsive tumors like lymphoma or thymoma, with less clear benefit for other malignancies. Endovascular stenting provides rapid symptom relief and is first-line for severe symptoms or when tissue diagnosis is not obtainable, serving as a bridge to definitive therapy. Definitive therapy depends on the underlying malignancy: SCLC responds highly to chemotherapy plus radiation, NSCLC is treated with chemotherapy, radiation, or targeted therapy, and lymphoma responds to chemotherapy with or without radiation. Anticoagulation is indicated if thrombosis contributes to the obstruction. Diuretics may provide modest symptomatic relief but volume depletion should be avoided.
<image>Superior vena cava syndrome showing CT imaging of SVC obstruction with clinical features including facial swelling, dilated collateral veins, and management approach with stenting and tumor-directed therapy</image>
Malignant Spinal Cord Compression (MSCC)
Epidemiology
Malignant spinal cord compression occurs in 5 to 10% of all cancer patients. The most common primary tumors are lung, breast, prostate, kidney, and myeloma. The thoracic spine is most commonly affected (60-70%), followed by the lumbar and cervical spine. Compression typically results from vertebral body metastasis with epidural extension.
Clinical Features
Back pain is the first symptom in over 90% of cases and may precede neurologic symptoms by weeks. The pain worsens with recumbency (unlike degenerative disease) and with Valsalva, with point tenderness over the involved vertebra. Progressive bilateral weakness develops with lower extremity predominance. Sensory changes with a sensory level on exam may be present. Autonomic dysfunction including urinary retention and bowel incontinence are late findings suggesting severe and potentially irreversible compression.
Diagnosis
MRI of the entire spine with contrast is the gold standard. The entire spine must be imaged because 10 to 30% of patients have multiple levels of compression. CT myelography is an alternative if MRI is contraindicated.
Management
Dexamethasone should be started immediately when clinical suspicion is high, without waiting for MRI. A standard dose is 10 mg IV bolus followed by 4 mg IV every 6 hours, with high-dose protocols (96 mg IV bolus) used for severe deficits. Radiation therapy is the mainstay for most patients using external beam radiation. Surgery (decompressive laminectomy with stabilization) is considered for single-level compression, good performance status and prognosis, spinal instability, radioresistant tumors (renal cell, melanoma), and based on the Patchell trial which showed surgery plus radiation is superior to radiation alone for survival and ambulation in selected patients. Pre-treatment neurologic status is the strongest predictor of outcome: ambulatory patients before treatment are most likely to remain ambulatory, while paraplegia at presentation rarely improves.
Febrile Neutropenia
Definition
Febrile neutropenia is defined by a single temperature at or above 38.3 degrees Celsius (101 degrees Fahrenheit) or sustained temperature at or above 38.0 degrees Celsius (100.4 degrees Fahrenheit) for 1 hour, combined with an absolute neutrophil count below 500 cells/mcL or expected to decline below 500 within 48 hours. This is a medical emergency because infectious mortality rises rapidly without prompt empiric antibiotics.
Risk Stratification — MASCC Score
High-risk patients have a MASCC score below 21, anticipated prolonged neutropenia exceeding 7 days, hemodynamic instability, significant comorbidities, or were inpatient at fever onset. Low-risk patients have a MASCC score of 21 or greater, anticipated short neutropenia under 7 days, no comorbidities, and solid tumors.
Empiric Antibiotic Therapy
| Agent | Dose | Notes |
|---|---|---|
| Cefepime | 2 g IV q8h | Most commonly used first-line |
| Piperacillin-tazobactam | 4.5 g IV q6h | Alternative first-line |
| Meropenem | 1 g IV q8h | High-risk or prior resistant organisms |
| + Vancomycin | 15-20 mg/kg IV q8-12h | Add if line infection, MRSA, hemodynamic instability |
| + Antifungal (micafungin/voriconazole) | Standard dosing | Add if fever persists 4-7 days on antibiotics |
Blood cultures (at least 2 sets, including from a central line if present) must be obtained before antibiotics, but antibiotics should be administered within 1 hour of presentation. Empiric monotherapy with an anti-pseudomonal beta-lactam is standard: cefepime 2 g IV every 8 hours (most commonly used), piperacillin-tazobactam 4.5 g IV every 6 hours, or meropenem 1 g IV every 8 hours (reserved for high-risk patients or prior resistant organisms). Vancomycin is added if there is suspected line infection, skin/soft tissue infection, hemodynamic instability, or known MRSA colonization, but the need should be reassessed at 48-72 hours and vancomycin discontinued if not indicated. Empiric antifungal coverage (micafungin, caspofungin, or voriconazole) is added if fever persists after 4 to 7 days despite broad-spectrum antibiotics. G-CSF (filgrastim) is not routinely recommended for treatment but may be considered with high-risk features, expected prolonged neutropenia, or clinical deterioration.
Outpatient Management of Low-Risk Febrile Neutropenia
Selected low-risk patients (MASCC score 21 or higher with reliable follow-up and no hemodynamic compromise) can be treated as outpatients with oral ciprofloxacin plus amoxicillin-clavulanate. Daily reassessment is required with admission if clinical worsening occurs. This approach has growing acceptance but requires careful patient selection and close monitoring.
<image>Febrile neutropenia management algorithm showing risk stratification with MASCC score, empiric antibiotic selection, indications for vancomycin and antifungal addition, and criteria for outpatient management</image>
Clinical Pearls
TLS can occur spontaneously without chemotherapy in high-burden hematologic malignancies, so high-risk patients should be monitored proactively. Rasburicase blood samples must be placed on ice immediately because the enzyme continues to degrade uric acid in the test tube, giving falsely low results at room temperature. SVCS is rarely a true emergency, and time should be taken to obtain tissue diagnosis before starting treatment unless cerebral edema or airway compromise is present. In spinal cord compression, pre-treatment neurologic status is the strongest predictor of outcome — ambulatory patients who receive prompt treatment usually retain ambulation, while paraplegic patients rarely regain function. Febrile neutropenia requires empiric antibiotics within 1 hour because every hour of delay increases mortality. Rectal examination and rectal temperature measurement are contraindicated in neutropenic patients due to the risk of bacteremia from mucosal disruption.
References
- Cairo MS, Bishop M. Tumour Lysis Syndrome: New Therapeutic Strategies and Classification. Br J Haematol. 2004;127:3-11.
- Howard SC, et al. Tumor Lysis Syndrome. N Engl J Med. 2011;364:1844-1854.
- Taplitz RA, et al. Outpatient Management of Febrile Neutropenia in Cancer (ASCO/IDSA). J Clin Oncol. 2018;36:1443-1453.
- Patchell RA, et al. Direct Decompressive Surgical Resection in the Treatment of Spinal Cord Compression. Lancet. 2005;366:643-648.
- Freifeld AG, et al. Clinical Practice Guideline for the Use of Antimicrobial Agents in Neutropenic Patients (IDSA). Clin Infect Dis. 2011;52:e56-e93.
