Incidental thyroid cancer and overdiagnosis: response to Drs Tsybrovskyy, Sobrinho-Simões, and Tallini

Abstract

Drs Tsybrovskyy, Sobrinho-Simões, and Tallini (1) argue that, when we conclude that the incidental detection of tumors larger than 2 cm suggests that overdiagnosis is the most likely cause for the rise in the incidence of thyroid cancer (TC), we are equating carcinomas found incidentally with ‘overdiagnosis’. According to Tsybrovskyy et al., the term ‘overdiagnosis’ can only be attributed to a condition that is both incidental and harmless, which would not be the case in our study since a significant proportion (36%) of incidental thyroid carcinomas (ITC) were larger than 2 cm in size, and only 61.5% of the patients were completely disease free at the 5-year follow-up. We think that Tsybrovskyy et al. have misinterpreted our writing since our conclusion, which was clearly stated in the manuscript, is that because a significant proportion of ITC patients had tumor diameters above 20 mm, overdiagnosis, and not environmental or lifestyle risk factors, is the most likely cause for the rise in the incidence of TC that is occurring worldwide. This is so because the rising incidence of TCs of all sizes and stages at diagnosis has been an argument used by others to consider that overdiagnosis alone is unlikely to account entirely for the increased TC incidence (2).