What is it?
A raised level of corrected* calcium in the blood.
*TOTAL plasma calcium is the combination of free, ionised calcium and protein-bound calcium. If the albumin level is low, protein bound calcium is low. This may mask a high concentration of free, ionised calcium. Calcium is therefore 'corrected' for albumin level.
Why is it important?
1. It may cause symptoms. These do not always relate to the level of serum calcium.
Common symptoms are:
- Polyuria, polydipsia
- Tiredness and lethargy
- Muscle weakness
2. It may cause pain, or make existing pain worse.
3. It may cause dehydration, coma and cardiac arrest.
How common is it?
- 10-20% of all cancer patients
- 20-40% of patients with cancer of the bronchuse, breast or myeloma will have hypercalcaemia
What sort of cancer produces hypercalcaemia?
- Myeloma is the most likely tumour to produce hypercalcaemia (a third of patients admitted to hospital).
- Carcinoma of lung and breast account for over half the cases seen.
- Carcinoma of stomach and large bowel rarely produce hypercalcaemia.
Hypercalcaemia of malignancy is caused by the secretion of a PTH-like substance by the tumour. Contrary to popular belief, it can occur in the absence of bone metastases. Conversely, patients can have widespread bone metastases and remain normocalcaemic.
What is the significance of hypercalcaemia?
It usually indicates disseminated disease (74%). 95% of patients with breast cancer and hypercalcaemia have disseminated disease. 61% of patients with lung cancer and hypercalcaemia have disseminated disease.
There are only four cases in the world literature of a cure in the presence of malignant hypercalcaemia; Hypercalcaemia usually means a very poor prognosis - 4/5 of patients die within a year.
Treatment is aimed at improving wellbeing and symptoms for symptomatic patients for weeks or even months. The treatment of choice is an intravenous bisphosphonate infusion (Pamidronate). Zoledronic acid is even more potent. Before treatment, the following need to be considered:
- Is the patient symptomatic or is the seum corrected calcium >3mmol/l?
- Is this the first episode? If so, an oncology opinion is warranted. A change in anti-tumour therapy may be indicated.
- Is the patient's quality of life good (in their opinion)? - Is the patient willing to undergo IV therapy/blood tests?
- Will the treatment work? (What response was there to previous treatment?)
Treatment is usually simple and well tolerated. Sometimes transient flu-like symptoms occur which respond to oral Paracetemol. A typical dosing schedule for Pamidronate is given below.
|Corrected Serum Calcium mmol/l||Pamidronate dose (mg)|
The dose is made up in 500mls of N saline and given over two hours. With appropriate supervision and training it can be given in day case units, community hospitals or in the home if nursing support is available.
It takes up to 3 days to start working and 5-7 days to exert its maximum effect. Patients who are very symptomatic, clinically dehydrated or with a calcium > 3.5 will need admitting for rehydration for 3 days while it takes effect. The dose can be repeated after a week if the initial response is inadequate. Zoledronic acid 4mg is as effective as pamidronate 90mg, can be given I/V over 5-10 minutes and response can last up to five weeks. This makes it advantageous in a primary care setting, but choice of bisphosphonate may depend on local guidelines and protocols.
How long does treatment last?
A single infusion will usually maintain normocalcaemia for three weeks. Hypercalcaemia tends to recur. Consider monitoring the serum calcium weekly and ensure the patient and family know the symptoms to watch for. Pamidronate infusions can be repeated every three -four weeks according to the serum calcium. There is no evidence that oral bisphosphonates prevent further episodes of hypercalcaemia and they are poorly tolerated.
- Hypercalcaemia of malignancy usually indicates disseminated disease and a poor prognosis.
- Anticipate hypercalcaemia in patients with myeloma, carinoma of the lung and carcinoma of the breast.
- Always check a serum calcium for patients with unexplained vomiting, thirst, polyuria or confusion.
- Treatment with intravenous bisphosphonates is simple, effective and can give useful palliation.
- Once hypercalcaemia has occurred, it may recur. Patients should be aware of symptoms and have serum corrected calcium monitored.
© Dr. Eileen Palmer, Dr John Howarth Palliative Care for the Primary Health Care Team (2004) Quay Books ISBN 1856422291