Hypercalcemia of Malignancy: A common and life-threatening metabolic complication of cancer
About 2% to 25% of cancer patients will be affected with a condition called hypercalcemia of malignancy (HCM). HCM occurs when there are very high calcium levels circulating in the blood. It is a life-threatening complication and usually carries a poor outcome. However, when recognized and treated early, HCM can be successfully managed.
Common signs include gastrointestinal disturbance (constipation, nausea, and vomiting) and fatigue. When severe, it is life-threatening: seizures, coma or cardiac arrest can occur. Hence, once identified, the condition is regarded as a medical emergency.
Certain cancers such as those of the breast, lung, multiple myeloma, head and neck, renal, ovarian, and lymphomas are more commonly associated with HCM. These cancers secrete a protein similar to parathyroid hormone released by the parathyroid gland that controls calcium levels in the blood. The protein secreted by those cancers cause an increase in the calcium levels in the blood. In addition, when there is spread of cancer to the bones, such as in breast cancer and multiple myeloma, the cancer cells in the bone marrow also start releasing excessive calcium into the blood. These disturbances cause the high blood calcium levels associated with HCM.
Monitoring of calcium in the blood is essential to distinguish severity. HCM is mild, moderate, or severe depending on how fast the calcium is rising. Initially patients may not exhibit signs of severity. Your doctors will also test parathyroid gland function to explain or corelate the abnormal calcium levels. Similarly, vitamin D also regulates calcium in the blood, and will be evaluated by a simple blood test.
Once diagnosed, HCM symptoms do reduce with normalization of calcium levels. Rapid hydration with intravenous (I.V.) normal saline is the first line of treatment as HCM causes severe dehydration. Other treatment options include drugs that lower calcium levels. The latest Endocrine Society Clinical Practice Guideline strongly recommends the use of I.V. bisphosphonates or the human monoclonal antibody denosumab for adults with HCM. In severe HCM, a combination of calcitonin and I.V. bisphosphonate or denosumab is recommended. Corticosteroids are highly effective in blood cancers (lymphomas). Other promising new treatments for patients with HCM are also being researched.
It is heartening to note that the incidence of HCM and the associated life-threatening complications is declining because of potent and highly effective therapeutic agents used for cancer treatment. Successful treatment of the underlying cancer itself can control HCM and prevent recurrence.