4. Discussion

This study shows that MWA is a successful treatment modality and provides a rapid improvement in Ca and PTH values ​​in a short period of 24 h. Both PTH and Ca levels returned to normal range in 28 of 32 patients (87.5%) and remained normal for 6 months. A similar success rate was observed in the literature 5,10. In the study of Fan et al. 10, PTH and Ca decreased to normal levels in 19 of 22 patients (86.3%) and remained within the normal range for 12 months after MWA. In the study of Liu C et al.5 all the fifteen patients had good response to initial therapy. However, 2 patients relapsed (5 months and 32 months after the initial therapy) and they underwent second MWA sessions. The authors argued that MWA can reduce nodule size, decrease serum PTH, and Ca levels in a single session in most patients, and the second session can be applied when necessary. In our study the procedure was not repeated in unsuccessfully treated lesions.
In the study by Liu et al. 9, comparing surgery and MWA, the success ratio of MWA and surgery were found to be similar in the sixth month of treatment (82.1%, 89.3%, respectively). While PTH levels in the surgery group decreased much faster than the MWA group in the first 3 months of treatment, no significant difference was detected between the two groups in the sixth month after treatment. There was no significant difference in mean serum Ca and P levels between the MWA group and the surgery group during the 6 months after treatment. Although the authors drew attention to literature data showing the cure rates of over 95% in centers specializing in parathyroid surgery, they declared similar clinical efficacy with MWA and surgery in PHPT.
Although the efficacy of MWA in secondary hyperparathyroidism has been found to be related to baseline PTH level in a study15, a reason that can be directly associated with treatment success in PHPT has not been clearly revealed. In our study, there was no difference in PTH values between the groups in terms of treatment success.
Patient with the largest lesion diameter (4.8 cm diameter) did not respond to MWA in the study of Liu et al. 9. Fan et al. 10 observed that treatment efficacy was not significantly associated with lesion size, PTH and Ca levels, as in our study. We argue that the main reason for not responding to treatment may be related to the procedure technique. Probably some parathyroid tissues could not be completely removed by this technique depending on the experience of radiologist applying the process.
This treatment procedure was well tolerated as we did not observe major complications or need for hospitalization during MWA or follow-up period. Complication rate in the present study was low. According to Society of Interventional Radiology Clinical Practice Guidelines17, no major complications were observed except than the minor one of a case of cellulitis requiring drainage and antibiotics. Therefore, the MWA procedure was observed as safe.
The limitations of the study are the small sample size and the short follow-up period. Longer follow-up is required to determine the long-term effectiveness of the treatment and whether there will be a recurrence.
In conclusion, MW ablation is a safe and effective treatment method in the treatment of PHPT, and it can reduce Ca and PTH levels and nodule size. Although surgery is still the gold standard, it is an alternative for patients for whom surgeries are risky or who refuse surgery.