Title: Role of breast cancer screening in the overdiagnosis of thyroid cancer: results from a
cross-sectional nationwide survey
Version: 1 Date: 04 Jan 2023
Reviewer:  Per-henrik Zahl
Reviewer's report:
Second review on Submission ID f502967b-f891-4575-9b17-1b2d888d02a4
“Role of breast cancer screening in the overdiagnosis of thyroid cancer: Results from a
nationwide survey”
First, I apologize for writing this in my first review: “This message is dulled in complex statistics
and many numbers. I would have liked to see in Table 1 the first 4 lines high-lighted. The
associations here are the core of the manuscript. For example, splitting the table in Table 1a and
Table 1b would have made it easier to read, I think.” It meant Table 2 and not Table 1. The
authors have defined what is dependent variable (line 137) and independent variable (line 145).
I did not see this.
Background
Sentence 2, lines 64-65. Not necessary, delete it.
Lines 65-67: Thyroid cancer is three times more common in women than in men and is strongly
associated with female hormones, …
Lines 68-69: I suggest rephrasing the sentence: Women often undergo thyroid ultrasonography
when being screened for breast cancer,…..
Line 74: “second for breast cancer (57.9 cases per 100.000 people)” Per women or per people?
If its is per individual, then it is only half the rate in Europe and USA. Do you men the second
most frequent cancer in South-Korean women?
Line 82: delete it.
Lines 83-90. I suggest that the authors state/rephrase that there is overdiagnosis of thyroid cancer
because incidence is increasing and mortality is unchanged. When mortality is unchanged and
incidence is increased 10-20 times, this is by definition overdiagnosis.  This is not surprising
because autopsy studies show that 1 of 3 healthy young Finish individuals have tumours
cells if you look carefully (Ref: Harach HR, Franssila KO, Wasenius VM. Occult papillary
carcinoma of the thyroid: a “normal” finding in Finland -- a systematic autopsy study. Cancer
1985;56:531-538)
Line 100: factors that affect initiate screening for thyroid cancer.
Statistical analysis
Lines 167-169. I still do not understand why you do subgroup analysis to determine the effect of
age, educational level, participants’ concern about their risks and family history. Only age and
family history are significant in the initial analysis. One sentence to justify subgroup analysis
of educational level and participants’ concern about their risks would be good. Unless it looks
like random testing.
Lines 170-176: This subgroup analysis I do understand. Doctors/hospitals may have different
incentives for doing screening.
Results
The authors have reduced number of covariates from 12 to 9. Now only age and family history
is significant.
Lines 196-212: These analyses seem not justified to me. It would be sufficient to state that
subgroup analyses were done, and did not yield new or more information about OR for thyroid
cancer.
Discussion
I find this far too long. It is 5-6 pages. It can be deleted 50 percent.
Line 299: it is reduction in cancer -specific mortality. No RCT of screening have proved to
reduce total mortality.
Line 337: If there are other studies, the authors should list them. If not write it is the only study
as far as you know.
Line 342: First, many relevant items were not analyzed in this study. Please be specific about
items or delete this sentence.
Line 344. What is a system failure?
Conclusion
I suggest that you delete line 364-369.
Reference 7: add i5745 after BMJ 2016;355
Table 1, fourth line: after mammography it should be ultrasonography.