Hypercalcemia (cancer-related)

When you have cancer, one of the side effects may be hypercalcemia, indicated by too much calcium in the blood. Whether mild or severe, the condition and its symptoms may be treated with medication and infusion of fluids.

Cancer is one of the two main causes of hypercalcemia, the other being hyperparathyroidism, which is when the parathyroid glands in your neck secrete too much hormone.

About one in five cancer patients experience hypercalcemia at some point during their treatment, according to StatPearls, and this rate has been decreasing through the years.

There are three main causes of cancer-related hypercalcemia:

• Extreme levels of parathyroid hormone-related protein (PTHrP) are responsible for about 80 percent of cases, according to StatPearls. This condition is sometimes referred to as humoral hypercalcemia of malignancy. PTHrP causes bone to break down, releasing calcium into the bloodstream.
• Cancers that have spread to bone, or metastasized, account for about 20 percent of cases, according to StatPearls. These secondary tumors stimulate osteoclasts, specialized cells that resorb bone. This type is associated with multiple myeloma and metastatic breast cancer.
• Increased production of 1,25-dihydroxyvitamin D triggers hypercalcemia in most Hodgkin lymphoma cases and roughly a third of non-Hodgkin lymphoma cases. These cases and the production of parathyroid hormone by tumors together probably amount to fewer than 1 percent of cancer-related hypercalcemia cases, according to Therapeutics and Clinical Risk Management.

Calcium and your body

Your body uses the mineral calcium for many things. It’s important for strong teeth and bones, and the proper functioning of your muscles, cardiovascular system, nerves and brain. It aids in secretion of hormones and enzymes. Normally, when you’re healthy, your body regulates calcium levels.

Hypercalcemia tends to develop late in cancer progression. If you develop this condition, you may not be aware of any symptoms at first, as they tend to progress gradually. Some are:

• Nausea, vomiting, decline in appetite
• Abdominal discomfort, constipation
• Frequent need to urinate, increased thirst
• Fatigue, weakness, muscle pain
• Headaches
• Confusion, difficulty concentrating, depression

More severe symptoms include:

• Poor kidney function or failure
• Cardiac arrhythmia, heart attack
• Seizures
• Loss of consciousness, coma

Cancers associated with hypercalcemia

Certain cancers are more associated with hypercalcemia than others.

• Multiple myeloma has the highest risk of occurrence (7.5 percent to 10.2 percent annually in the United States), according to Cancer Medicine.
• Lung and breast cancers also have high rates. Other cancers associated with hypercalcemia include renal, ovarian and squamous cell cancers of the head and neck.
• Colorectal and prostate cancer patients seldom develop hypercalcemia. Prostate cancer has the lowest occurrence rate (1.4 percent to 2.1 percent annually).

The annual occurrence rate of hypercalcemia for all cancers is 2 percent to 2.8 percent, according to a 2016 analysis of U.S. cases from 2009 to 2013.

Diagnosis and treatment

Tests to measure the amount of calcium in your blood are able to tell whether you have hypercalcemia. Other blood tests check to see whether it’s hampering kidney function.

Hypercalcemia patients often have low fluid levels, which contribute to poor kidney function, so treatment may start with intravenous (IV) fluids to restore volume and help flush out excess calcium through urine. For both initial and long-term treatment, you may be given bisphosphonates, which reduce resorption of bone by osteoclasts. Because these drugs may adversely affect your kidneys, which may already be impaired by hypercalcemia, your care team will have to weigh whether use is worth the risk, determine the appropriate dosage, and ensure you’re fully hydrated before administering these drugs.

To quickly lower blood calcium levels, calcitonin may be given, sometimes with steroids to extend its effectiveness. Calcitonin is a thyroid hormone that hampers osteoclasts and promotes excretion of calcium. It may be combined with bisphosphonates to drop calcium levels even faster.

The monoclonal antibody denosumab, which affects osteoclasts and lowers bone resorption, may be given if hypercalcemia persists despite treatment with bisphosphonates.

Simultaneous treatment of your cancer may help keep calcium levels under control.

Your doctor will likely review all of the medicines or supplements you take, and advise you to stop those that may worsen hypercalcemia, such as:

• Thiazide diuretics
• Lithium
• Calcium supplements
• Antacids high in calcium
• Vitamin D

Even if you don’t have cancer, taking too many calcium supplements or antacid tablets over an extended period can cause hypercalcemia and poor kidney function.