13.3 Oncologic Emergencies: TLS, Hypercalcemia, Spinal Cord Compression & SVCS

13.3 Oncologic Emergencies: TLS, Hypercalcemia, Spinal Cord Compression & SVCS

Oncologic emergencies are acute, life-threatening metabolic, structural, or vascular complications resulting directly from malignant cell proliferation, tumor mass effects, or rapid cytotoxic lysis. Prompt recognition, risk stratification, and targeted pharmacotherapy interception by board-certified oncology pharmacists prevent permanent neurological deficits, irreversible organ damage, and early cancer mortality.

This section provides an exhaustive review of four core oncologic emergencies encountered across hematology and solid tumor oncology: Tumor Lysis Syndrome (TLS), Hypercalcemia of Malignancy (HCM), Malignant Spinal Cord Compression (MSCC), and Superior Vena Cava Syndrome (SVCS).

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1. Tumor Lysis Syndrome (TLS)

Tumor Lysis Syndrome is a metabolic emergency triggered by massive, rapid lysis of neoplastic cells, releasing massive quantities of intracellular potassium, phosphorus, and nucleic acids (purines) into the systemic circulation. Catabolism of purines generates uric acid, which precipitates with calcium phosphate in the renal tubules, causing acute kidney injury (AKI), life-threatening arrhythmias, and death.

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|                         CAIRO-BISHOP TUMOR LYSIS SYNDROME (TLS) CRITERIA                          |
|                                                                                                   |
|   [LABORATORY TLS (LTLS)]: Defined as >= 2 of the following within 3 to 7 days post-chemo:        |
|   1. Hyperuricemia: Uric Acid >= 8.0 mg/dL (476 mcmol/L) OR 25% increase from baseline            |
|   2. Hyperkalemia: Potassium >= 6.0 mEq/L (6.0 mmol/L) OR 25% increase from baseline              |
|   3. Hyperphosphatemia: Phosphorus >= 4.5 mg/dL (1.45 mmol/L) OR 25% increase from baseline        |
|   4. Hypocalcemia: Corrected Calcium <= 7.0 mg/dL (1.75 mmol/L) OR 25% decrease from baseline     |
|                                                                                                   |
|   [CLINICAL TLS (CTLS)]: Defined as Laboratory TLS PLUS >= 1 of the following clinical toxicities:|
|   1. Renal: Serum Creatinine >= 1.5x upper limit of age-adjusted normal (or oliguria/anuria)      |
|   2. Cardiac: Cardiac Arrhythmia or Sudden Cardiac Death (due to hyperkalemia / hypocalcemia)     |
|   3. Neurologic: Seizures, Neuromuscular Irritability, Tetany (due to severe hypocalcemia)        |
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Neoplasm Risk Stratification for TLS

• High Risk (>5% TLS incidence): Burkitt lymphoma; Lymphoblastic lymphoma; ALL with WBC >= 100,000/mcL; AML with WBC >= 50,000/mcL; Bulky DLBCL with elevated LDH >= 2x ULN; Venetoclax ramp-up in CLL with lymph nodes >= 10 cm or >= 5 cm with ALC >= 25,000/mcL.
• Intermediate Risk (1–5% incidence): ALL with WBC < 100k; AML with WBC 10k–50k; Indolent NHL / CLL treated with targeted therapies with moderate tumor burden; Bulky solid tumors highly sensitive to chemo (small cell lung, germ cell).
• Low Risk (<1% incidence): Most solid tumors, indolent lymphomas with low tumor burden, multiple myeloma.

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|                               TLS PHARMACOTHERAPY & MANAGEMENT                                    |
|                                                                                                   |
|   1. INTRAVENOUS HYDRATION (FOUNDATION OF ALL TLS PROTOCOLS):                                     |
|      - Rate: **2.5 to 3.0 L/m2/day (or 150 to 200 mL/hr)** of Isotonic Saline (0.9% NaCl) or D5W   |
|        with 0.45% NaCl.                                                                           |
|      - Urine Output Target: Maintain **>= 100 mL/m2/hour (or > 2 mL/kg/hour)**.                    |
|      - Diuretics: Furosemide 20-40 mg IV ONLY after intravascular volume is fully repleted.        |
|                                                                                                   |
|   2. THE URINARY ALKALINIZATION CONTROVERSY (PHARMACY PRACTICE MANDATE):                          |
|      - Adding Sodium Bicarbonate to IV fluids to alkalinize urine is **NO LONGER RECOMMENDED!**    |
|      - *Clinical Rationale:* Uric acid is more soluble at alkaline pH (>7.0), BUT **Calcium        |
|        Phosphate is significantly LESS soluble at alkaline pH**! Alkalinizing the urine           |
|        precipitates calcium phosphate crystals into the renal tubules, worsening renal failure,   |
|        and exacerbates hypocalcemia-induced tetany/arrhythmias. Rasburicase eliminates the need!  |
|                                                                                                   |
|   3. URIC ACID-LOWERING PHARMACOTHERAPY:                                                          |
|      - **Allopurinol (Xanthine Oxidase Inhibitor):**                                              |
|        * Indication: Prophylaxis in **Intermediate- and Low-Risk TLS**.                           |
|        * Dose: 300 mg PO daily (up to 800 mg/day; reduce dose in renal impairment).               |
|        * Mechanism: Blocks xanthine/hypoxanthine conversion to uric acid. Prevents NEW uric acid  |
|          formation, but does NOT degrade pre-existing uric acid. Takes 24-72 hours to act.        |
|        * Accumulation of xanthine can cause **xanthine nephropathy / crystallization**.           |
|      - **Rasburicase (Elitek - Recombinant Urate Oxidase):**                                      |
|        * Indication: Treatment of established TLS or Prophylaxis in **High-Risk TLS**.            |
|        * Mechanism: Enzymatically catabolizes insoluble uric acid directly into **Allantoin**     |
|          (a highly water-soluble, non-toxic metabolite excreted freely in urine).                 |
|        * Dosing: FDA-approved dose is 0.15-0.2 mg/kg IV daily for up to 5 days.                   |
|        * Evidence-Based Practice: **Single fixed-dose 3 mg or 6 mg IV** is equally effective and  |
|          vastly more cost-effective (rapidly drops uric acid to < 2 mg/dL within 4 hours).        |
|        * BLACK BOX WARNING 1: **Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency**.             |
|          Rasburicase produces **Hydrogen Peroxide (H2O2)** as a metabolic byproduct. In G6PD      |
|          deficiency, lack of NADPH-dependent glutathione causes massive oxidative **Hemolytic     |
|          Anemia** and **Methemoglobinemia**! SCREEN high-risk ancestries (African, Mediterranean).|
|        * BLACK BOX WARNING 2: **Ex Vivo Blood Sample Handling Artifact**.                          |
|          Rasburicase continues enzymatically destroying uric acid at room temperature in blood    |
|          tubes. Blood MUST be drawn in **pre-chilled heparin tubes**, placed immediately into     |
|          an **ICE-WATER BATH**, and assayed within 4 hours, otherwise false low results occur!    |
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Management of Acute Electrolyte Disturbances in TLS

• Hyperkalemia (K+ >= 6.0 mEq/L or rapid rise):
  • Cardiac stabilization: Calcium Gluconate 1–2 g IV over 5–10 min if ECG changes (peaked T-waves, widened QRS, loss of P-waves).
  • Cellular shifting: Regular Insulin 10 units IV push PLUS 25–50 g Dextrose (D50W 50 mL); Nebulized Albuterol 10–20 mg; IV Sodium Bicarbonate (50 mEq) if acidemic.
  • Potassium elimination: Sodium Zirconium Cyclosilicate (Lokelma 10 g PO TID) or Patiromer (8.4 g PO daily); Loop diuretics; Urgent Hemodialysis.
• Hyperphosphatemia (Phos >= 4.5 mg/dL):
  • Administer non-calcium phosphate binders (e.g., Sevelamer carbonate 800–1600 mg PO TID with meals).
  • Restrict dietary phosphorus. Avoid IV calcium administration unless life-threatening tetany is present (maintains Calcium x Phosphate product <55 mg2/dL2 to avoid soft-tissue/renal mineralization).
• Hypocalcemia (Corrected Ca <= 7.0 mg/dL):
  • TREAT ONLY IF SYMPTOMATIC (tetany, carpopedal spasm, seizures, prolonged QTc) with short-acting IV Calcium Gluconate (50–100 mg/kg).
  • Asymptomatic hypocalcemia should NOT be treated with IV calcium, because infusing calcium in the presence of severe hyperphosphatemia triggers massive calcium phosphate crystal precipitation in the kidneys and myocardium!

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2. Hypercalcemia of Malignancy (HCM)

Hypercalcemia of Malignancy occurs in up to 30% of cancer patients and is associated with poor long-term prognosis (median survival <3–6 months). It is classified into four distinct pathophysiologic mechanisms:

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|                         PATHOPHYSIOLOGIC SUBTYPES OF HYPERCALCEMIA                                |
|                                                                                                   |
|   1. HUMORAL HYPERCALCEMIA OF MALIGNANCY (HHM; ~80% of Cases):                                    |
|      - Mechanism: Systemic tumor secretion of **Parathyroid Hormone-Related Protein (PTHrP)**.    |
|      - Cancers: Squamous cell carcinomas (Lung, Head/Neck, Esophagus), Renal, Bladder, Ovarian.   |
|      - Lab Pattern: **High Calcium, High PTHrP, Suppressed Intact PTH (<5 pg/mL), Low 1,25-(OH)2D|
|                                                                                                   |
|   2. LOCAL OSTEOLYTIC HYPERCALCEMIA (LOH; ~20% of Cases):                                         |
|      - Mechanism: Direct tumor bone metastasis inducing local cytokine release (RANKL, IL-1, TNF) |
|        that drives massive osteoclastic bone resorption.                                          |
|      - Cancers: Breast Cancer, Multiple Myeloma, Non-Small Cell Lung Cancer.                      |
|      - Lab Pattern: **High Calcium, Normal/Low PTHrP, Suppressed PTH, Bone Mets on Imaging**.    |
|                                                                                                   |
|   3. 1,25-DIHYDROXYVITAMIN D3 (CALCITRIOL) PRODUCTION (~1% of Cases):                             |
|      - Mechanism: Ectopic tumor expression of **1-alpha-hydroxylase** enzyme.                     |
|      - Cancers: Hodgkin Lymphoma, Non-Hodgkin Lymphoma.                                           |
|      - Lab Pattern: **High Calcium, Suppressed PTH, Normal PTHrP, HIGH 1,25-(OH)2-Vitamin D3**.   |
|                                                                                                   |
|   4. ECTOPIC PTH SECRETION (<1% of Cases):                                                        |
|      - Rare neuroendocrine tumors secreting authentic intact PTH (High Calcium, High intact PTH). |
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Diagnostic Calcium Formula & Severity Strata

Because approximately 40–50% of circulating serum calcium is bound to albumin, serum total calcium must be corrected for hypoalbuminemia (or ionized calcium measured directly):

$\text{Corrected Calcium (mg/dL)} = \text{Measured Total Calcium (mg/dL)} + [0.8 \times (4.0 - \text{Serum Albumin [g/dL]})]$

• Mild HCM: Corrected Calcium < 12.0 mg/dL (often asymptomatic; polyuria, polydipsia, constipation).
• Moderate HCM: Corrected Calcium 12.0 to 13.9 mg/dL (fatigue, weakness, nausea, dehydration).
• Severe HCM (Crisis): Corrected Calcium >= 14.0 mg/dL OR acute symptoms (altered mental status, lethargy, confusion, coma, shortened QTc interval, cardiac arrhythmias, acute renal failure).

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|                         STEPWISE PHARMACOTHERAPY OF SEVERE HCM                                    |
|                                                                                                   |
|   [STEP 1: AGGRESSIVE INTRAVENOUS ISOTONIC HYDRATION] (Immediate First Action)                    |
|   - Fluid: **0.9% Sodium Chloride (Normal Saline)** at **200 to 500 mL/hour** initially to correct|
|     volume contraction, then **150 to 250 mL/hour** (target urine output 100-150 mL/hr).         |
|   - Mechanism: Re-expands extracellular volume, enhances GFR, and promotes proximal tubular       |
|     sodium-calcium co-excretion (lowers calcium by 1.5-2.0 mg/dL within 24-48 hours).             |
|   - Loop Diuretics (Furosemide 20-40 mg IV): Indicated ONLY AFTER full volume resuscitation is    |
|     complete, specifically to manage fluid overload in oliguric or heart failure patients.        |
|                                                                                                   |
|   [STEP 2: SALMON CALCITONIN (Miacalcin)] (Rapid-Acting Bridging Agent)                           |
|   - Dose: **4 to 8 units/kg SC or IM every 12 hours** (for 24 to 48 hours).                      |
|   - Mechanism: Directly inhibits osteoclastic bone resorption and promotes renal calcium excretion.|
|   - Onset: Rapid (**2 to 4 hours**); lowers serum calcium by 1 to 2 mg/dL.                        |
|   - Limitation: **Tachyphylaxis (receptor downregulation)** develops within **48 hours**, making  |
|     calcitonin ineffective for maintenance. Functions strictly as a rapid bridge to bisphosphonates|
|                                                                                                   |
|   [STEP 3: INTRAVENOUS BISPHOSPHONATES] (First-Line Definitive Therapy)                           |
|   - **Zoledronic Acid (Zometa):** **4 mg IV infused over >= 15 minutes** (Preferred over Pamidro)|
|     * Superior response rate (88% vs 70%) and longer duration of normocalcemia (32 vs 18 days).   |
|     * Onset: **2 to 4 days**; Peak nadir effect at **Day 4 to 7**.                                |
|     * Mechanism: High-affinity binding to hydroxyapatite; inhibits farnesyl pyrophosphate synthase|
|       in osteoclasts, inducing osteoclast apoptosis.                                              |
|     * Renal Safety: In acute life-threatening HCM, full 4 mg dose is administered even if renal   |
|       impairment is present, provided benefits outweigh risks (infuse over >=15-30 min).          |
|   - **Pamidronate:** 60 to 90 mg IV infused over 2 to 4 hours.                                    |
|                                                                                                   |
|   [STEP 4: RANK LIGAND INHIBITOR: DENOSUMAB (Xgeva)]                                              |
|   - Indication: **Bisphosphonate-Refractory HCM** (calcium not responsive within 7-30 days of IV  |
|     bisphosphonates) OR **Severe Renal Impairment (CrCl < 30 mL/min or Hemodialysis)**.           |
|   - Dose: **120 mg SC** on Days 1, 8, 15 of Month 1, then 120 mg SC every 4 weeks.                |
|   - Mechanism: Fully human IgG2 monoclonal antibody binding RANKL; does NOT undergo renal clearance!|
|   - Safety Warning: High risk of **severe hypocalcemia** in renal disease; monitor calcium weekly! |
|                                                                                                   |
|   [STEP 5: CORTICOSTEROIDS] (For Calcitriol-Mediated Lymphoma HCM)                                |
|   - Dose: **Prednisone 40 to 60 mg PO daily** (or IV Methylprednisolone).                         |
|   - Mechanism: Inhibits 1-alpha-hydroxylase and reduces gastrointestinal calcium absorption.      |
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3. Malignant Spinal Cord Compression (MSCC)

Malignant Spinal Cord Compression represents a true oncologic neuro-emergency occurring in 5–10% of advanced cancer patients (most common in prostate, breast, lung cancers, multiple myeloma, and renal cell carcinoma). Direct tumor metastasis to the epidural space compresses the thecal sac and spinal cord, causing venous congestion, vasogenic cord edema, ischemia, and irreversible paraplegia within 24–48 hours if left untreated.

Clinical Presentation & Diagnostic Urgency

• Symptoms: Progressive, unremitting localized back pain (90% of patients; exacerbated by lying flat, coughing, or Valsalva; worse at night), followed by motor weakness (gait instability, spasticity, hyperreflexia), sensory deficit with a distinct dermatomal sensory level, and finally autonomic dysfunction (urinary retention/overflow incontinence, fecal incontinence). The ability to ambulate at presentation is the single most important predictor of long-term functional recovery.
• Diagnostic Gold Standard: Emergency whole-spine MRI with contrast (imaging the entire cervical, thoracic, and lumbosacral spine, because up to 30% of patients harbor multiple non-contiguous epidural metastases).

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|                         MSCC INTERVENTION ALGORITHM (Patchell Paradigm)                           |
|                                                                                                   |
|   HIGH CLINICAL SUSPICION OF MALIGNANT SPINAL CORD COMPRESSION                                    |
|                               |                                                                   |
|   * IMMEDIATE EMERGENCY PHARMACOTHERAPY:                                                          |
|     - **Dexamethasone 10 to 24 mg IV push loading dose** (IMMEDIATELY prior to MRI!).             |
|     - Followed by **Dexamethasone 4 to 10 mg IV every 6 hours** with PPI gastroprotection.        |
|     - *Clinical Rationale:* Rapidly suppresses vasogenic spinal cord edema, reduces epidural mass |
|       pressure, preserves spinal cord microvascular blood flow, and provides profound analgesia.  |
|                               |                                                                   |
|                               v                                                                   |
|   [EMERGENCY WHOLE-SPINE CONTRAST-ENHANCED MRI CONFIRMS THECAL SAC COMPRESSION]                   |
|                               |                                                                   |
|         +---------------------+---------------------+                                             |
|         |                                           |                                             |
|         v                                           v                                             |
|   [SURGICAL DECOMPRESSION CANDIDATE]          [RADIATION THERAPY CANDIDATE]                       |
|   - Single-area of spinal cord compression    - Highly radiosensitive histology (e.g., Lymphoma,  |
|   - Spinal instability / bony retropulsion      Multiple Myeloma, Small Cell Lung Cancer, Seminoma)|
|   - Prior radiation to the compressed field   - Multiple non-contiguous sites of compression      |
|   - Unknown primary histology (needs biopsy)  - Medically inoperable or paraplegic > 48 hours     |
|   - Life expectancy >= 3 months               - Poor functional status / life expectancy < 3 mos  |
|         |                                           |                                             |
|         v (Landmark Patchell Trial: Lancet 2005)    v                                             |
|   **URGENT SURGICAL RESECTION & STABILIZATION** **URGENT EXTERNAL BEAM RADIOTHERAPY (EBRT)**     |
|   followed by postoperative EBRT:             - 30 Gy in 10 fractions or 20 Gy in 5 fractions     |
|   (84% regained ambulation vs 57% with RT alone)                                                 |
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4. Superior Vena Cava Syndrome (SVCS)

Superior Vena Cava Syndrome results from external compression, direct tumor invasion, or intravascular thrombosis of the superior vena cava, impairing venous return from the head, neck, and upper extremities to the right atrium.

Etiology & Pathophysiology

• Malignant Causes (~90%): Non-Small Cell Lung Cancer (~50%), Small Cell Lung Cancer (~25%), Non-Hodgkin Lymphomas (DLBCL, Primary Mediastinal B-cell Lymphoma, T-cell ALL; ~10–15%), Thymoma, Germ Cell Tumors.
• Non-Malignant / Iatrogenic (~10%): Intraluminal thrombosis associated with indwelling Central Venous Catheters (CVCs), Port-a-caths, or pacemaker leads.
• Clinical Presentation: Dyspnea (most common), facial plethora/edema, periorbital swelling, distended jugular and collateral chest wall veins, arm edema, hoarseness, cough. Pemberton's Sign: Facial flushing, stridor, and jugular venous engorgement provoked by elevating both arms above the head for 60 seconds.

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|                         SUPERIOR VENA CAVA SYNDROME MANAGEMENT                                    |
|                                                                                                   |
|   1. IMMEDIATE SUPPORTIVE MEASURES:                                                               |
|      - Elevate Head of Bed to 45° to decrease hydrostatic venous pressure.                       |
|      - Supplemental Oxygen; avoid IV lines in the upper extremities.                              |
|      - Furosemide (20 to 40 mg IV) for acute symptom relief / orthopnea.                          |
|      - Dexamethasone (4 to 8 mg IV/PO every 6 hours) to reduce peritumoral edema, particularly in |
|        steroid-responsive malignancies (Lymphoma, Thymoma) or impending airway compromise.        |
|                                                                                                   |
|   2. HISTOLOGY-DIRECTED DEFINITIVE THERAPY:                                                       |
|      - *Clinical Practice Pearl:* Unless acute stridor / airway compromise or cerebral edema is   |
|        present, **obtain tissue biopsy for definitive histopathologic diagnosis BEFORE starting   |
|        radiation or chemotherapy!**                                                               |
|      - **Chemo-Sensitive Malignancies (SCLC, DLBCL, Germ Cell):** Urgent Systemic Chemotherapy    |
|        (produces rapid symptom resolution in >80% within 3 to 7 days).                            |
|      - **Chemo-Refractory / Non-Small Cell Lung Cancer:** Urgent **Endovascular SVC Stenting**    |
|        (immediate relief in >90% within 24-48 hours) +/- External Beam Radiation Therapy.         |
|      - **Catheter-Associated Thrombosis:** Systemic Anticoagulation (Therapeutic LMWH / DOAC)    |
|        +/- Catheter removal or catheter-directed thrombolysis (Alteplase).                        |
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