Routine Neuroimaging in Patients with Stage IV Non-Small Cell Lung Cancer: A Single Center Experience

Round 1

Reviewer 1 Report

Sometimes you stumble upon a paper and wonder why there are so few studies about the subject.
This is a small observational study from Quebec, Canada, reporting about the impact of baseline brain imaging in patients with stage IV NSCLC without neurological symptoms. The study is suffering from its observational nature but offers important baseline information for those planning similar studies in an era with increased opportunities for systemic treatment.

Table 1. Information included in the upper left quadrant is probably misplaced.
Table 1, lowest row. This row does not really fit within the table. Please mention in the results section whether brain imaging was more common among patients receiving systemic treatment.

Line 145. Please report the 3-year cumulative BM% (with 95% CI).
The real cumulative BM% with initial imaging is actually around 35% (32% + ~3%) which is considerably higher than the ~13% observed without initial imaging. Apparently, most asymptomatic BMs remain below radar before death.

Figure 4. I would prefer to see this figure using stratification by systemic treatment. It is rather obvious that imaging will not influence survival in those receiving palliative treatment. The real question is whether we should use brain imaging in patients offered (modern) systemic treatment.

Conclusion. The first part of the conclusion repeats information from the results section. This information may be better suited for the (first paragraph of the) discussion to obtain a concise conclusion.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Formal editing: a) Figures 1, 2 and supplementary figures 1 and 2 are difficult to read for small letters, change format of letters and boxes. b) page 4, row 119 - paragraph of text is inaccurately added to Table 1

Content editing: a) In Table 1 there is important proportion of EGFR mutations, ALK rearrangemet and PD-L1 status characterised as "unknown". As PD-L1status was probably not tested in years before check-point inhibitors advent, the EGFR and ALK not-tested status is mentioned, but it is not clear, what is reason for unknown status. Probably lack of tissue for the test - please ad footnote. b) page 5, line 126: regarding patients with synchronous mets add information about SRS therapy - similarly as for metachronous mets in line 131

Questions: a) Table 1, characteristic "Number of sites of extracranial disease at diagnosis, including lung" - in 20 patients initial CNS imaging found brain mets as only site of M1, is it correct? If yes, it should be discussed, it seems that these patient were staged in M0 basic situation

b) Systemic palliative therapy was administered a little over half of patients. It can be speculated that only these patients with a chance to median survival prolongation of more than 1 year can have benefit from initial CNS imaging. It is suggestion for future analysis - especially in the context of current advances in treatment of NSCLC with imunotherapy

Author Response

Please see the attachment.

Author Response File: Author Response.docx