Results of cryopreserved parathyroid autografts: a retrospective multicenter study

The functionality of cryopreserved parathyroid autotransplantation (CPAT) has been evaluated in few studies, mostly conducted by experienced single-institution centers that have reported different success rates ranging from 17% to 83%. In France, CPAT are rare and their functionality has never been evaluated. Moreover, French tissue banks are facing an accumulation of ungrafted samples. The aim of our work was to evaluate the implantation rate of cryopreserved parathyroid samples and the functionality of CPAT in a multicenter study.

Data from 9 French tissue banks were analyzed. CPAT functionality was defined as fully functional (normal parathyroid hormone [PTH] and calcium levels without treatment), partially functional (normal PTH levels but need for treatment to maintain normocalcemia), and nonfunctional (low PTH levels and need for treatment). For dialyzed patients, CPAT was considered nonfunctional if the PTH level in the nongrafted arm was less than 20 pg/mL, partially functional if the PTH level was between 20 and 50 pg/mL, and fully functional if the PTH level was between 50 and 300 pg/mL.

The 9 centers had cryopreserved 1376 samples of parathyroid tissue and only 22 (1.6%) had been autografted in 20 patients (65% renal hyperparathyroidism, 20% multiple endocrine neoplasia type 1, 15% "other") by 12 different surgical teams. The median duration of storage was 11.1 months (range, 0.4-28.5). Only 2 autografts (10%) were fully functional, 2 (10%) were partially functional, and 17 (80%) were nonfunctional at 26 months median follow-up.

The reimplantation rate is low, and the functionality of CPAT is less than those published by experienced centers. Logistical and technical problems occurring in less experienced centers are probably the main reasons for nonfunctioning implants. Considering the results of this study, we suggest that cryopreservation of parathyroid glands should be abandoned when not performed in very large experimented centers, that CPAT should be used only for patients with hyperplasic parathyroid tissue, and that tissue samples should be systematically destroyed when patients do not have hypoparathyroidism or after 1 year of storage.