Endocrine Abstracts

Malignancy-related hypercalcaemia occurs in over 20% of cancer patients. Most cases are due to enhanced production of parathyroid hormone-related peptide (PTHrP) by tumours and carry a poor prognosis of survival of weeks to months. A 74 year old man with a history of prostate cancer treated with radical radiotherapy in 2013 and androgen blockade until 2015 underwent CT and PET/CT scans in 2017, which showed liver and spleen abnormalities, suggestive of metastases, but unlikely to be related to prostate cancer due to radiological appearance. The patient declined further investigation, prioritising his good quality of life. In 2020 he presented with lethargy and tests showed adjusted calcium 3.1 mmol/l (2.2-2.6) and low PTH 1.0 pmol/l (1.6-6.9). He had multiple hospital attendances with recurring symptoms and hypercalcaemia, despite treatment with IV fluids and pamidronate. Further imaging and liver biopsy confirmed pancreatic neuroendocrine tumour. The patient’s performance status deteriorated from 0 to 3 over months, no further oncological treatment was deemed possible and palliative care team were involved in anticipation of further decline. No bony metastases were seen and myeloma screen was negative, so PTHrP-mediated hypercalcaemia was suspected, although testing for this is not routinely available and costly. Hypercalcaemia continued to recur despite monthly zolendronic acid, so a trial of cinacalcet was started, successfully stabilising calcium. However, once the dose was titrated up to 30 mg twice daily, calcium fell to 1.8 mmol/l and cinacalcet was stopped. Calcium has since slowly risen to 2.61 mmol/l over several months. Over a year after his first presentation with hypercalcaemia, the patient continues to have a reasonable quality of life. Although no studies have yet been performed to evaluate the use of cinacalcet in PTHrP-mediated hypercalcaemia of malignancy, a growing number of case reports suggest it may be effective in stabilising calcium, thereby controlling symptoms and potentially improving prognosis.