Retrospective Study
Copyright ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Dec 6, 2022; 10(34): 12532-12542
Published online Dec 6, 2022. doi: 10.12998/wjcc.v10.i34.12532
Significance of incidental focal fluorine-18 fluorodeoxyglucose uptake in colon/rectum, thyroid, and prostate: With a brief literature review
Haejun Lee, Kyung-Hoon Hwang
Haejun Lee, Kyung-Hoon Hwang, Department of Nuclear Medicine, Gachon University College of Medicine, Gil Medical Center, Incheon 21565, South Korea
Author contributions: Lee H and Hwang KH contributed to this work, designed the research study, performed the research, analyzed the data, and wrote the manuscript; Lee H contributed analytic tools; All authors have read and approved the final manuscript.
Institutional review board statement: The study was reviewed and approved by the Institutional Review Board at our institution.
Informed consent statement: The requirement for informed consent was waived by the Institutional Review Board at our institution.
Conflict-of-interest statement: The authors declare that they have no conflicting interests.
Data sharing statement: The data that support the findings of this study are available from the corresponding author, [Hwang KH], upon reasonable request.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Kyung-Hoon Hwang, MD, PhD, Professor, Nuclear Medicine, Gachon University College of Medicine, Gil Medical Center, Namdong-daero 774beon-gil, Namdong-gu, Incheon 21565, South Korea. forrest88@hanmail.net
Received: June 17, 2022
Peer-review started: June 17, 2022
First decision: July 29, 2022
Revised: August 10, 2022
Accepted: November 8, 2022
Article in press: November 8, 2022
Published online: December 6, 2022
Processing time: 168 Days and 7.2 Hours
ARTICLE HIGHLIGHTS
Research background

Regions of unexpected hypermetabolism were not rare findings on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT). There are studies on the incidentally identified FDG uptake and some suggested a high possibility of malignancy.

Research motivation

A confirmation of high malignancy rate in incidentally observed focal FDG uptake may assist physicians to conduct further investigations more reliably and confidently.

Research objectives

To investigate the malignancy rate, useful PET parameters and their cutoffs in discrimination between malignant and benign lesions for the assessment of clinical implications of the incidentally identified focal F-18 FDG uptake.

Research methods

The final reports of 16510 F-18 FDG PET/CT scans performed at our hospital between January 2016 and March 2022 were retrospectively reviewed to identify incidentally observed FDG uptake in the colon/rectum, thyroid, and prostate. Eighty-eight regions of colon/rectum, 48 regions of thyroid, and 39 regions of prostate were eligible for this study. For the total of 175 regions, the classification as malignant, premalignant, or benign was performed according to the final histopathological reports. PET parameters such as maximum and peak standardized uptake values (SUVmax and SUVpeak), MTV, mean SUV of metabolic tumor volume (mSUVmtv), and TLG were measured or calculated for the regions and compared among the malignant, premalignant, and benign lesions. ROC curves were plotted to determine the cutoff values for the parameters.

Research results

For the incidental focal colorectal hypermetabolic regions, 62.5% (55/88) had malignant or premalignant lesions. Both SUVmax and SUVpeak differentiated malignant/premalignant from benign lesions. No PET parameters involved in this study could differentiate malignant from premalignant lesions. SUVmax showed higher AUC than SUVpeak and had a cutoff of 7.6. For thyroid, 60.4% (29/48) of the cases were malignant. A high rate (89.7%, 26/29) of well-differentiated thyroid cancers were identified on FDG PET. BRAF mutation test results were available for 20 of 26 well-differentiated thyroid cancers and all 20 were confirmed to have the mutation. SUVmax alone differentiated malignant from benign lesions and a cutoff was 6.9. For prostate, 56.4% (22/39) were malignant. Only SUVmax differentiated malignant from benign lesions and a cutoff was 3.8. Overall, of the 175 focal hypermetabolic regions with final histopathological reports, 60.6% (106/175) were proven to be malignant or premalignant (in colon and rectum) lesions.

Research conclusions

Approximately up to 60% of malignancy rate was shown for the incidentally observed focal hypermetabolic uptake in the colon/rectum, thyroid, or prostate. Overall, SUVmax was superior to several other PET parameters in distinguishing between malignant/premalignant and benign lesions. Hence, these findings may lead physicians to conduct further investigations more reliably and confidently.

Research perspectives

A high rate of malignancy in the unexpectedly identified focal FDG uptake may assist the decision-making process for the nuclear medicine physicians, radiologists, and clinical physicians.