FDG-PET/MRI for Nonoperative Management of Rectal Cancer: A Prospective Pilot Study
, Malak Itani 1, Lauren E. Henke 2, Radhika K. Smith 3, Paul E. Wise 3, Matthew G. Mutch 3, Sean C. Glasgow 3, Matthew L. Silviera 3, Katrina S. Pedersen 4, Steven R. Hunt 3, Hyun Kim 2 and Tyler J. Fraum 1
Round 1
Reviewer 1 Report
The authors present a pilot study for assessing the added value of PET/MRI in the non-operative management of the patients with stage I-III rectal cancers following TNT. The article is highly relevant in the current clinical practices of rectal cancers where NOM is gaining popularity. As stated by the authors in the limitations, one of the main criticisms of this study is the small sample size. However, it does present some interesting results which would be interesting concepts to study in further studies with larger studies.
The study is well designed and well presented. I have only a few minor comments:
Page 2, Line 51 - Please change the abbreviation of cCR to clinical complete response.
Page 3, Line 113 – Please specify type of high resolution ( for example – spatial)
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
Thanks for the opportunity to review this manuscript. This is the first report of PET MRI following TNT for rectal cancer, and the effort of the Authors to conduct a pilot study is appreciable. The manuscript is well written and presented, the idea is original and innovative, and the study design and methods of the study are well explained. Nevertheless, the main limitation of the study is obviously related to the very small number of patients included and very few evidences can be infer from their study even if some important considerations can be done.
Methods
· In case of incomplete response at MRI or PET MRI, were the patients re-discussed in a multidisciplinary context, evaluating also the endoscopic response?
Results
· In results section and in Table 2 it would more useful if the Authors specified the endoscopic clinical response at follow up1 instead of Endoscopy +/- biopsy (cCR, near complete response, or incomplete response) according to some of the definition proposed in the present literature, for example by Habr Gama (Habr-Gama A (2010) Complete clinical response after neoadjuvant chemoradiation therapy for distal rectal cancer: characterization of clinical and endoscopic findings for standardization. Dis Colon Rectum 53 (12):1692-1698. doi:10.1007/DCR.0b013e3181f42b89). This also applied for the rest of the manuscript.
· At page 9, line 259 there is typo, (“among the 77 subjects that …”).
· It is interesting the fact that even if max SUV is decreased importantly in all the patients, this does not correlate with residual disease considering that most of the patients had a TME and residual tumor. Please discuss this comment.
Discussion
· You mentioned the local regrowth in patients followed with NOM, and most recently the OPRA trial reported a rate of local regrowth of 33% in patients in a Watch and wait program. Please discuss, in your opinion, if PET MRI may have a potential role in detecting early local regrowth.
· Please discuss the present literature of other studies comparing MRI and PET-MRI in restaging following neoadjuvant treatment, even considering radiomic features as ADC or TA for example Capelli G, et al (2022) 18F-FDG-PET/MRI texture analysis in rectal cancer after neoadjuvant chemoradiotherapy. Nucl Med Commun 43 (7):815-822. doi:10.1097/mnm.0000000000001570
Author Response
Please see the attachment.
Author Response File: Author Response.docx
