Hypercalcaemia associated with malignancy

Hypercalcaemia is seen in around 20-30% of patients with cancer (1).

It may develop by a combination of increased osteoclastic bone resorption and increased absorption of calcium by the kidney.

• these effects are mediated by parathyroid hormone related protein (PTHrP) which is secreted in excessive amounts by a tumor
• in myeloma, production of PTHrP has been described although osteoclastic activation occurs due to bone-resorbing cytokines such as interleukin-1 (2)

PTH levels are suppressed and calcitriol levels are normal (3).

The precise intervention required is dependent upon the level of the hypercalcaemia. In all cases, rehydration is necessary using 3-4 litres of 0.9% saline intravenously over 24 hours and subsequently 2-3 litres/day till a satiafactroy urine output (2 L/day) is established (2).

Frusemide should be given only in the presence or expectation of cardiac failure.

Pamidronate can be added to the hydration fluid. It takes 24-48 hours to take effect with full effect at 4-7 days. In the presence of renal impairment i.e. serum creatinine greater than 400, the pamidronate should be administered in daily divided doses.

Treatment may be repeated at 30 days.

Reference:

• (1) Joshi D, Center JR, Eisman JA. Investigation of incidental hypercalcaemia. BMJ. 2009;339:b4613
• (2) Ralston SH et al. Medical management of hypercalcemia. Calcif Tissue Int. 2004;74(1):1-11
• (3) Carroll MF, Schade DS. A practical approach to hypercalcemia. Am Fam Physician. 2003;67(9):1959-66