https://orcid.org/0000-0002-6467-0316
Dear Sir,
We read the two articles by Li et al. published in your journal in April 2018 (Study A) [Citation1] and June 2019 (Study B) [Citation2], with interest. Microwave ablation (MWA) has been shown to be an effective alternative to surgery in patients with primary thyroid microcarcinoma (PTMC) who cannot tolerate surgery [Citation3]. Both studies were retrospective cohort studies of patients treated at the same hospital. Both studies compared the effectiveness and safety of MWA with surgery for PTMC, and demonstrated that patients treated with MWA had a lower incidence of complications than patients treated surgically, and that MWA had a good therapeutic effect.
However, we have some questions regarding the methodology of the two studies. First, Study A included 46 patients who were treated with MWA and a ‘select’ 46 of 482 patients who had undergone surgery. The authors did not provide a justification for including only 46 of the 482 patients who had undergone surgery, and did not describe the method that they used to select the 46 patients. If the intention was to balance the two groups with respect to potential confounders, the specific method, such as a logit model for propensity score matching analysis [Citation4], should have been described in detail, otherwise, all patients undergoing surgery who met the inclusion criteria should have been included in the analysis in order to minimize selection bias.
Second, both studies had exactly the same inclusion and exclusion criteria. The enrollment period for Study A was from February 2014 to August 2017, while the enrollment period for Study B was from January 2013 to September 2018. Why were patients treated between January 2013 and January 2014 were excluded from Study A?
Third, the authors reported that no lymph node metastases or recurrences were observed among the patients in Study A. However, they reported that in Study B, ten patients developed lymph node metastases (at 180–1696 d of follow-up) and three patients experienced a carcinoma recurrence (at 1078–1348 d of follow-up). Some of the lymph node metastases and carcinoma recurrences experienced by patients in Study B, fell within the period covered by Study A.
We request that the authors explain the reasons for these inconsistencies between the two studies and suggest that they carefully check the data from the two studies in order to confirm the accuracy of the results.
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References
- Li J, Liu Y, Liu J, et al. Ultrasound-guided percutaneous microwave ablation versus surgery for papillary thyroid microcarcinoma. Int J Hyperthermia. 2018;34(5):653–659.
- Li J, Liu Y, Liu J, et al. A comparative study of short-term efficacy and safety for thyroid micropapillary carcinoma patients after microwave ablation or surgery. Int J Hyperthermia. 2019;36(1):640–646.
- Yue W, Wang S, Yu S, et al. Ultrasound-guided percutaneous microwave ablation of solitary T1N0M0 papillary thyroid microcarcinoma: initial experience. Int J Hyperthermia. 2014;30(2):150–157.
- Choi Y, Jung SL, Bae JS, et al. Comparison of efficacy and complications between radiofrequency ablation and repeat surgery in the treatment of locally recurrent thyroid cancers: a single-center propensity score matching study. Int J Hyperthermia. 2019;36(1):359–367.