HemOncRx

HYPERCALCEMIA OF MALIGNANCY (HCM)

HCM occurs in 20-30% of cancer patients and is a poor prognostic indicator.

High burden cancer: lung (metastatic NSCLC > SCLC), breast, multiple myeloma, head and neck, renal cell, and non-Hodgkin lymphoma.

Pathophysiology: Cancer-associated hypercalcemia results from increased bone resorption with calcium release into the extracellular fluid; in addition, renal clearance is decreased.

  • Some tumors release PTH–related protein , results in osteoclastic bone resorption and renal Ca reabsorption (humoral hypercalcemia, 80%).
  • Some tumors (breast cancer, MM) cause direct bone destruction, resulting in osteolytic hypercalcemia (20%).
  • 1,25-dihydroxyvitamin D (calcitriol)-mediated hypercalcemia – Lymphomas produce excessive calcitriol → increased gut calcium absorption.
  • Immobile patients are also at an elevated risk of hypercalcemia because of increased resorption of calcium.
  • Medications (hormonal therapy, thiazide diuretics, vitamin D analogs, lithium) may precipitate or exacerbate hypercalcemia.

Diagnosis: Ionized calcium is a more accurate reflection of calcium status in critically ill patients.

Symptoms of hypercalcemia: Lethargy, confusion, anorexia, nausea, constipation, polyuria, and polydipsia

Management

  • Mild hypercalcemia (corrected calcium <12 mg/dL): Hydration with normal saline followed by observation
  • Moderate hypercalcemia (corrected calcium 12–14 mg/dL): Basic treatment of clinical symptoms with aggressive hydration.
  • Severe hypercalcemia (corrected calcium >14 mg/dL; symptomatic): admission, hydration ± loop diuretics, bisphosphonates or denosumab, calcitonin, steroids, dialysis
    • Hydration with normal saline about 3–6 L in 24 hours
    • Loop diuretics may be administered after volume status has been corrected
      • Thiazide diuretics are contraindicated in hypercalcemia because of the increase in renal tubular calcium absorption.
    • Bisphosphonates bind to hydroxyapatite in calcified bone, prevents dissolution by phosphatases and inhibits both normal and abnormal bone resorption. The onset of action is 3–4 days.
    • Calcitonin (intramuscular formulation) inhibits the effects of PTH and has a rapid-onset (though short-lived) hypocalcemic effect. May cause tachyphylaxis
    • Steroids may be used to lower calcium in patients with steroid-responsive tumors (lymphoma and myeloma).
    • Phosphate: hypophosphatemic and hypercalcemic..
    • Dialysis may be needed in patients with hypercalcemia and renal failure.

IV Hydration (Cornerstone of Treatment)

  • Initial therapy for all patients with symptomatic hypercalcemia
  • Dose: 0.9% Normal Saline (NS) at 200-500 mL/hr until euvolemic (reduce to 100-150 mL/hr once stable).
  • Goal: Increase renal calcium excretion by promoting natriuresis.
  • Caution in CHF/CKD: Use slower rates or consider loop diuretics once volume replete.

Bisphosphonates (First-Line Anti-Resorptive Therapy)

  • MOA: Inhibits osteoclastic bone resorption.
  • Onset: 24-72 hours; Max effect at 4-7 days.
  • Dosing:
    • Zoledronic acid (preferred, most potent): 4 mg IV over 15 min, repeat in 7 days if needed.
    • Pamidronate: 60-90 mg IV over 2-4 hrs (alternative in renal impairment).
    • Ibandronate (less common): 4 mg IV over 15 min.
  • Clinical Pearls: Monitor for hypocalcemia, osteonecrosis of the jaw (ONJ), and nephrotoxicity. Renal dosing; avoid if CrCl <30 mL/min.

Calcitonin (Rapid, Short-Term Calcium Lowering) 4 units/kg IM or SC q12h (up to 8 units/kg for refractory cases).

  • MOA: Inhibits osteoclasts and increases renal calcium excretion.
  • Onset: 2-4 hours (faster than bisphosphonates).
  • Duration: Use only for 48 hrs due to tachyphylaxis.
  • Clinical Pearls: Best for severe symptomatic hypercalcemia while waiting for bisphosphonates to work. May cause flushing, nausea, hypersensitivity (especially in salmon allergy).

Denosumab (Alternative to Bisphosphonates) 120 mg SC on days 1, 8, and 15 in the first month, then every 4 weeks.

  • MOA: RANKL inhibitor, prevents osteoclast maturation.
  • Indication: Refractory hypercalcemia or renal failure (CrCl <30 mL/min).
  • Clinical Pearls: Use in bisphosphonate-refractory hypercalcemia. Can cause hypocalcemia, ONJ, musculoskeletal pain.

Glucocorticoids (For PTHrP-secreting or calcitriol-mediated hypercalcemia)

  • MOA: Reduces calcium absorption & inhibits 1α-hydroxylase (calcitriol production).
  • Indications: Steroid-sensitive tumors (lymphoma, multiple myeloma), vitamin D-mediated hypercalcemia.
  • Dosing: Prednisone 40-60 mg PO daily OR Dexamethasone 4-8 mg IV/PO daily.
  • Clinical Pearls: Not effective in osteolytic hypercalcemia. Long-term use → hyperglycemia, immunosuppression, muscle wasting.

Loop Diuretics (Only After Hydration): Furosemide 20-40 mg IV q6-12h (adjust based on response).

  • Use only after adequate hydration to enhance calcium excretion.
  • Avoid thiazides (they worsen hypercalcemia!).

Dialysis (For Severe/Refractory Cases)

  • Consider HD with low-calcium dialysate if: Ca >18 mg/dL, AKI or severe CKD, life-threatening cardiac arrhythmias, mental status changes.