High index of clinical suspicion with optimal surgical techniques and adjuvant radiotherapy is critical to reduce locoregional disease progression in parathyroid carcinoma.

Aims: We have analyzed the risk factors and the impact of external beam radiotherapy (EBRT) in reducing the locoregional recurrence of parathyroid carcinoma (PTC).

Methods: Various parameters such as clinical presentation, intraoperative findings, surgical methods, and usage of parafibromin were analyzed. Selected endpoints were locoregional progression-free survival and overall survival.

Results: Three patients had local recurrence. Two of them received EBRT after the first recurrence but continued to have local recurrence. One patient was lost to follow-up. Six patients with EBRT remain asymptomatic with a locoregional progression-free survival and overall survival of 42 months. The presence of a palpable nodule in the neck, serum calcium >14 mg/dL, and intraoperative substrap adhesion (OR=9.3, 95% confidence interval, 1.76-56.1; P<0.05) should raise suspicion. Four of 5 patients showed a predominantly negative staining with parafibromin.

Conclusions: PTC should be suspected in the preoperative and intraoperative period. EBRT may reduce local recurrence by 65%. Parafibromin staining with no more than 0 to 1+ intensity in 80% to 100% of cells can predict carcinoma with specificity up to 100%.