Endocrine Abstracts

Introduction: Cinacalcet therapy remains the only alternative to elective parathyroidectomy (EP) for lowering serum calcium (Ca) in patients with primary hyperparathyroidism (PHPT). National Institute of health and Care Excellence (NICE), UK support use of cinacalcet in symptomatic patients with PHPT who decline surgery (or deemed unfit for surgery), if serum Ca levels >2.85 mmol/l. The limitation in wider use of cinacalcet remains cost effectiveness apart from limited data related to its long term efficacy and safety.

Objective: To evaluate long term safety & efficacy of cinacalcet in patients with PHPT.

Methodology: We carried out a retrospective observational study of all patients with a biochemically confirmed diagnosis of PHPT who were initiated on cinacalcet therapy in Cwm Taf healthboard. The clinical records were accessed and with a focus on noting the indication, duration, dose and side effects of cinacalcet. Biochemical results were analysed for Serum Ca, Phosphate, PTH (pre and post cinacalcet therapy) and a note was made of relevant radiological investigations.

Results: We identified a total of 56 patients with PHPT who received cinacalcet therapy from September 2013 to January 2021. Cinacalcet use was observed to be associated with a reduction of mean serum calcium level by 0.4 mmol/l (P<0.001; CI 0.369- 0.484). There was a decrease in mean serum PTH level by 3.6 mmol/l (P<0.001; -1.6914 to - 5.438; n=17). The adverse drug reactions (ADR) encountered in this study were mainly gastrointestinal (GI) symptoms such as nausea, vomiting and abdominal discomfort. 5 of the patients discontinued cinacalcet due to GI side effects. Mild hypocalcaemia was noticed in 2 of the patients.

Discussion: Our retrospective observational study results show a significant as well as sustained reduction in serum Calcium and PTH levels with use of cinacalcet in patients with PHPT. This therapy is generally well tolerated with no long term safety concerns. The threshold for offering cinacalcet therapy should be lowered in patients with PHPT considering significant reduction in serum calcium and PTH levels which may translate into improved intermediate to long term secondary outcomes.