Parathyroid carcinoma. The experience of treatment of 15 patients and a review

Background. Parathyroid cancer (PC) is extremely rare, usually diagnosed after surgery, there are no clinical recommendations for the treatment of metastatic PC.

The study objective is to present the results of a clinical examination and treatment of patients with PC.

Materials and methods. Retrospective analysis of 15 PC patients treated from 2001 to 2019. The results of laboratory tests, the surgical approach, the results of treatment, the rate of metastasis and relapse within 19 months (3 months – 11.6 years) after surgery are presented.

Results. Tumor size is 35 mm (20–45 mm). Lymph node metastases – 1 (6.7 %), distant metastases – 2 (13 %). The median initial parathyroid hormone (PTH) is 735 pg/mL, calcium 3.22 mmol/L. Severe hyperparathyroidism with osteitis fibrosa cystica – in 6 (40 %). The surgical approach was parathyroidectomy in 10 (67 %), en bloc resection in 5 (33 %). Normalization of PTH and calcium after surgery – 13 (87 %). In two patients with distant metastases, the PTH and calcium remained high. A patient with Th6 vertebral metastasis was successfully operated on, with normalization of PTH and calcium, and 1.5 years was without relapse. A patient with lung and liver metastases received sorafenib after surgery, with decrease in calcium level. She died of progression 12 months after operation. Among patients with normalization of postoperative PTH, one had local relapse after 4 years. The patient was re-operated and 1 year after the second operation without relapse. The remaining patients are without relapse/progression.

Conclusion. At the time of diagnosis, lymph node metastases are in 6.7 %, distant metastases – 13 %. Normalization of PTH and calcium after surgery suggests a good prognosis, but does not exclude the recurrence in the future, which requires long-term follow-up. Repeated surgery for local recurrence or solitary distant metastases can provide stable remission. Sorafenib in metastatic PC has managed to control hypercalcemia in the short term, however, antitumor efficacy requires further study.