Endocrine Abstracts

Introduction: Cinacalcet is a positive allosteric modulator of the calcium sensing receptor successfully used to decrease serum calcium in primary hyperparathyroidism (pHPT) patients in the short-term, but long-term data are scarce. In this single-centre retrospective analysis, we investigated the efficacy and safety of cinacalcet in pHPT patients who received more than 5 years of treatment.

Methods: Statistical analysis was performed using free online software (www.socscistatistics.com) and Excel database statistics functions; a non-paired t-test was used in the analysis of pre-treatment biochemistry in low vs high dose cinacalcet therapy, and a paired t-test was used for the analysis of pre- vs post-treatment biochemistry. A P-value of <0.05 was considered statistically significant.

Results: 21 patients (81% females) were treated for a mean of 7.3 years (SD 1.74). Patients were commenced on cinacalcet due to increased surgical and/or anaesthetic risk (8), persistent/recurrent disease (4) and patient unwilling to undergo surgery (3). 6 patients received cinacalcet since adenomas were not localized preoperatively. Initial dose was 30 mg/day in 76% of cases, with the remainder starting at 60 mg/day. Baseline calcium levels did not differ between the two different starting dose groups (11.35 mg/dl vs 11.84 mg/dl: P 0.06). 47% remained on same dose and 42% increased dose during follow up. Serum calcium level decreased significantly at 3 months (11.47 mg/dl vs 10.7 mg/dl; P<0.05), with 66% reaching serum calcium <10.5 mg/dl. Compared to basal levels, at last appointment calcium decreased significantly (11.47 mg/dl vs 9.7 mg/dl; P<0.05), phosphorus increased significantly (2.57 mg/dl vs 3.2 mg/dl; P<0.05). There was a non-significant decrease in PTH (217 pg/ml vs 191 pg/ml; P= 0.1). 3 patient developed adverse events (myalgia, headache and no-specified), all of which could be managed without a definitive withdraw of treatment (temporal stop 2, decrease dose 1). 6 patients died during follow up, 5 of them were initially classified as “increased surgical and/or anaesthetic risk”. One death could be related to HPP: pancreatitis, with calcium levels of 12.5 mg/dl probably due to temporal suspension of the treatment of unknown reason, with previous excellent calcium control. The rest of exitus were due to age related diseases. 2 patient developed hip fracture during treatment with cinacalcet.

Conclusion: Cinacalcet seems effective in lowering serum calcium and PHPT patients in the long-term. The high mortality of our study seems to be related to the fact that cinacalcet is mainly used in patients who are poor surgical candidate.