TOPIC DISCUSSION: Hypercalcemia of Malignancy

Few tips on Hypercalcemia of Malignancy.
1.Occurs in 20-30% of patients with cancer
2. Usually the cancer is evident 90% of the time before the calcium problem arises.
3. Highest risk is Renal Cell Cancer, followed by Non small cell lung, Myeloma and then leukemia and breast cancer
4. 3 main mechanisms:- replacement of normal bone structure by metastatic cells and destruction via IL-6, IL-1 and TNF-alph stimulating osteoclastic activity; pthRp production by the tumor leading to binding to pth receptors in kidney and bone and causing similar effects as pth would; 1,25 0h vitamin D production mainly by lymphomas leading to increased intestinal absorption.
5. pth production (ectopic) is rare but can be seen. Primary hyperparathyroidism can occur in cancer patients as well.
6. Vitamin D(25-0H) can be elevated if there is excessive Vitamin D intake.
7. IV fluids, furosemide, calcitonin are few initial drugs to be used. Dialysis might be needed in some serious cases.
8. Pamidronate is safe in patients with CKD and hypercalcemia. It does cause Collapsing glomerulopathy. Zolendronate is to be used with caution in CKD as it can cause ATN.
9. Based on ASO guidelines, patients with moderate CrCl 30-60ml/min require no dose adjustment for pamidronate but require it for zolendronate.  For severe disease <30cc.min, zolendronate is contraindicated and pamidronate infusion time is increased to 4-6 hours and dose decreased.

Ref:
http://www.ncbi.nlm.nih.gov/pubmed/8706358
http://www.ncbi.nlm.nih.gov/pubmed/15673803
Cancer and the Kidney, Eric Cohen, 2nd Edition.