Hypercalcemia of malignancy

- Common (10 - 30% of patients with Ca will have it)
- Most common malignancies re breast, lung and multiple myeloma
- Poor prognosis, particularly if high PTH-rP
- 3 Types:

1. Humoral, PTH-rP mediated, most frequent cause.
2. Local bone destruction, with cytokines produced by tumor (breast, lung, MM) that induce differentiation os fibroblasts in osteoclasts.
3. Overproduction of Vitamin D, most frequent cause in lymphomas and Hodgkins + granulomatous disorders.

- Non specific symptoms: lethargy, confusion, anorexia, nausea, abdominal pain, constipation, polyuria & polydipsia. Usually patients are dehydrated and hypovolemic.

- Laboratory diagnosis is made with ionized calcium; if total serum calcium is used, it shold be corrected for the albumin level. Other electrolytes should be measured. Hypochloremia is suggestive of hypercalcemia of malignancy. Intact PTH is usually low and PTH-rP may be measured for understanding mechanism of hypercalcemia and to predict response to biphosphonates.

- Treatment
Hydration (aggressive) with NS
Diuretics only when euvolemia has been reached
Biphosphonates (Pamidronate 60 - 90mg IV infusion in 2-4h, Zoledronic acid 4mg if in 15min)
Glucocorticoids (most useful when Vitamin D is involved (Hodgkin's, NHL)
Calcitonin (IM or SC, intranasal doesn't work for hypercalcemia)(usually short lived effect)

- Prevention of recurrence:
Therapy of underlying malignancy; adequate hydration; interminttent biphosphonates (particularly if bony mets); stop meds that raise Ca++; stop oral sources of phosphate