Time to Recurrence as a Prognostic Factor in Parathyroid Carcinoma

BACKGROUND: Parathyroid carcinoma (PC) is a rare and challenging disease without clearly understood prognostic factors. Adequate management can improve outcomes. Characteristics of patients treated for PC over time and factors affecting prognosis were analyzed. METHODS: Retrospective cohort study including surgically treated patients for PC between 2000 and 2021. If malignancy was suspected, free-margin resection was performed. Demographic, clinical, laboratory, surgical, pathological, and follow-up characteristics were assessed. RESULTS: Seventeen patients were included. Mean tumor size was 32.5 mm, with 64.7% staged as pT1/pT2. None had lymph node involvement at admission, and 2 had distant metastases. Parathyroidectomy with ipsilateral thyroidectomy was performed in 82.2%. Mean postoperative calcium levels were different between patients who developed recurrence vs those who did not (P = .03). Six patients (40%) had no recurrence during follow-up, 2 (13.3%) only regional, 3 (20%) only distant, and 4 (26.6%) both regional and distant. At 5 and 10 years, 79% and 56% of patients were alive, respectively. Median disease-free survival was 70 months. Neither Tumor, Nodule, Metastasis system nor largest tumor dimension (P = .29 and P = .74, respectively) were predictive of death. En bloc resection was not superior to other surgical modalities (P = .97). Time between initial treatment and development of recurrence negatively impacted overall survival rate at 36 months (P = .01). CONCLUSION: Patients with PC can survive for decades and have indolent disease course. Free margins seem to be the most important factor in initial surgery. Recurrence was common (60%), but patients with disease recurrence within 36 months of initial surgery had a lower survival rate.