Letter regarding "The prognostic value of p16 and p53 expression for survival after vulvar cancer: A systematic review and meta-analysis".

Dear Editor,

We read the paper by (Sand et al., 2019) with interest. The authors performed a meta-analysis with 18 studies met the inclusion criteria, providing data for 785 patients to examine the prognostic value of p16 and p53 expression status on survival after vulvar squamous cell carcinoma (VSCC). They concluded that p53 and especially p16 expression status are of prognostic importance in women diagnosed with VSCC. After carefully reading, we wish to put forth the following suggestion.

Repeatedly including the same study population will affect the total sample size and the number of participants in each group; thus, duplicated studies using the same study population should not be included in a meta-analysis. However, we found that data from several studies may have by error been included twice due to reporting of different aspects of the study in separate publications, which significantly affect the reliability of the results. For instance, the studies in the references 272 and 283 included for the characteristics of included trial comparisons, were conducted by the same group of authors, the participants are from the same country, have the same number of participants. Hence, we suspect that these are two duplicate studies. Therefore, we suspected that this article might include more of the same studies and the same patients. The authors should formulate strict inclusion and exclusion criteria, eliminate duplicate documents that employ the same study population, and select the ones with the best quality or the largest sample size for analysis.

Sources of funding

None.

Disclosures

None.

Author contribution

M. J. designed the letter, H. D. wrote the letter, S. S. reviewed the letter.

Declaration of Competing Interest

The authors declared that there was no conflict of interest.