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Voxel-based dual-time 18F-FDG parametric imaging for rectal cancer: differentiation of residual tumor from postchemoradiotherapy changes.

Choi H, Yoon HJ, Kim TS, Oh JH, Kim DY, Kim SK - Nucl Med Commun (2013)

Bottom Line: Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01).With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

View Article: PubMed Central - PubMed

Affiliation: aDepartment of Nuclear Medicine bCenter for Colorectal Cancer, National Cancer Center, Goyang, Korea.

ABSTRACT

Introduction: 18F-Fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) has been used for evaluation of the response of rectal cancer to neoadjuvant chemoradiotherapy (CRT), but differentiating residual tumor from post-treatment changes remains a problem. We propose a voxel-based dual-time 18F-FDG PET parametric imaging technique for the evaluation of residual rectal cancer after CRT.

Materials and methods: Eighty-six patients with locally advanced rectal cancer who underwent neoadjuvant CRT between March 2009 and February 2011 were selected retrospectively. Standard 60-min postinjection PET/CT scans followed by 90-min delayed images were coregistered by rigid-body transformation. A dual-time parametric image was generated, which divided delayed standardized uptake value (SUV) by 60-min SUV on a voxel-by-voxel basis. Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).

Results: With respect to the false-positive lesions in the nine post-CRT patients with false-positive standard 18F-FDG scans in case groups who responded to therapy (TRG 3 or 4 tumors), eight were undetectable on dual-time parametric images (P<0.05). The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01). With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

Conclusion: A voxel-based dual-time parametric imaging technique for evaluation of post-CRT rectal cancer holds promise for differentiating residual tumor from treatment-related nonspecific 18F-FDG uptake.

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Related in: MedlinePlus

Two representative cases of post-CRT dual-time parametric images: (a, b) nonresponding case and (c, d) responding case. (a) The post-CRT tumor shows increased SUV in the 18F-FDG PET/CT image (arrow, SUVmax 4.1). (b) The dual-time parametric image shows focal lesion clearly with increased delayed-to-standard SUV ratio (maximum DSR, 2.31). The post-CRT 18F-FDG PET/CT image shows a relatively indistinctive margin and larger extent compared with the dual-time parametric map. The surgical specimen revealed Dworak regression grade 2, regarded as nonresponder. (c) The post-CRT PET/CT scan shows increased 18F-FDG uptake (SUVmax 5.9). (d) The lesion identified on the 18F-FDG PET/CT scan shows a low DSR in the dual-time parametric image (maximum DSR, 1.23). The surgical specimen revealed Dworak regression grade 4, total regression. CRT, chemoradiotherapy; CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose; SUVmax, maximum standardized uptake value; VOI, volume-of-interest.
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Figure 3: Two representative cases of post-CRT dual-time parametric images: (a, b) nonresponding case and (c, d) responding case. (a) The post-CRT tumor shows increased SUV in the 18F-FDG PET/CT image (arrow, SUVmax 4.1). (b) The dual-time parametric image shows focal lesion clearly with increased delayed-to-standard SUV ratio (maximum DSR, 2.31). The post-CRT 18F-FDG PET/CT image shows a relatively indistinctive margin and larger extent compared with the dual-time parametric map. The surgical specimen revealed Dworak regression grade 2, regarded as nonresponder. (c) The post-CRT PET/CT scan shows increased 18F-FDG uptake (SUVmax 5.9). (d) The lesion identified on the 18F-FDG PET/CT scan shows a low DSR in the dual-time parametric image (maximum DSR, 1.23). The surgical specimen revealed Dworak regression grade 4, total regression. CRT, chemoradiotherapy; CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose; SUVmax, maximum standardized uptake value; VOI, volume-of-interest.

Mentions: Representative cases from the responding and nonresponding groups are shown in Fig. 3. As shown in Fig. 3a and b, the post-CRT PET/CT scan shows an ill-defined lesion with mildly increased 18F-FDG uptake; however, the voxel-based dual-time parametric image shows a high DSR in the lesion, which was confirmed as TRG 2, moderate regression. Figure 3c and d shows an example of increased 18F-FDG uptake due to post-CRT inflammation. Intense 18F-FDG uptake at the tumor site was found on the post-CRT PET/CT scan; however, the dual-time parametric map showed no increased DSR in the same lesion. It was confirmed as TRG 4, total regression. More representative cases of each TRG are shown in Supplementary Fig. 1 (Supplemental digital content 1, http://links.lww.com/NMC/A16).


Voxel-based dual-time 18F-FDG parametric imaging for rectal cancer: differentiation of residual tumor from postchemoradiotherapy changes.

Choi H, Yoon HJ, Kim TS, Oh JH, Kim DY, Kim SK - Nucl Med Commun (2013)

Two representative cases of post-CRT dual-time parametric images: (a, b) nonresponding case and (c, d) responding case. (a) The post-CRT tumor shows increased SUV in the 18F-FDG PET/CT image (arrow, SUVmax 4.1). (b) The dual-time parametric image shows focal lesion clearly with increased delayed-to-standard SUV ratio (maximum DSR, 2.31). The post-CRT 18F-FDG PET/CT image shows a relatively indistinctive margin and larger extent compared with the dual-time parametric map. The surgical specimen revealed Dworak regression grade 2, regarded as nonresponder. (c) The post-CRT PET/CT scan shows increased 18F-FDG uptake (SUVmax 5.9). (d) The lesion identified on the 18F-FDG PET/CT scan shows a low DSR in the dual-time parametric image (maximum DSR, 1.23). The surgical specimen revealed Dworak regression grade 4, total regression. CRT, chemoradiotherapy; CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose; SUVmax, maximum standardized uptake value; VOI, volume-of-interest.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3815117&req=5

Figure 3: Two representative cases of post-CRT dual-time parametric images: (a, b) nonresponding case and (c, d) responding case. (a) The post-CRT tumor shows increased SUV in the 18F-FDG PET/CT image (arrow, SUVmax 4.1). (b) The dual-time parametric image shows focal lesion clearly with increased delayed-to-standard SUV ratio (maximum DSR, 2.31). The post-CRT 18F-FDG PET/CT image shows a relatively indistinctive margin and larger extent compared with the dual-time parametric map. The surgical specimen revealed Dworak regression grade 2, regarded as nonresponder. (c) The post-CRT PET/CT scan shows increased 18F-FDG uptake (SUVmax 5.9). (d) The lesion identified on the 18F-FDG PET/CT scan shows a low DSR in the dual-time parametric image (maximum DSR, 1.23). The surgical specimen revealed Dworak regression grade 4, total regression. CRT, chemoradiotherapy; CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose; SUVmax, maximum standardized uptake value; VOI, volume-of-interest.
Mentions: Representative cases from the responding and nonresponding groups are shown in Fig. 3. As shown in Fig. 3a and b, the post-CRT PET/CT scan shows an ill-defined lesion with mildly increased 18F-FDG uptake; however, the voxel-based dual-time parametric image shows a high DSR in the lesion, which was confirmed as TRG 2, moderate regression. Figure 3c and d shows an example of increased 18F-FDG uptake due to post-CRT inflammation. Intense 18F-FDG uptake at the tumor site was found on the post-CRT PET/CT scan; however, the dual-time parametric map showed no increased DSR in the same lesion. It was confirmed as TRG 4, total regression. More representative cases of each TRG are shown in Supplementary Fig. 1 (Supplemental digital content 1, http://links.lww.com/NMC/A16).

Bottom Line: Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01).With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

View Article: PubMed Central - PubMed

Affiliation: aDepartment of Nuclear Medicine bCenter for Colorectal Cancer, National Cancer Center, Goyang, Korea.

ABSTRACT

Introduction: 18F-Fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) has been used for evaluation of the response of rectal cancer to neoadjuvant chemoradiotherapy (CRT), but differentiating residual tumor from post-treatment changes remains a problem. We propose a voxel-based dual-time 18F-FDG PET parametric imaging technique for the evaluation of residual rectal cancer after CRT.

Materials and methods: Eighty-six patients with locally advanced rectal cancer who underwent neoadjuvant CRT between March 2009 and February 2011 were selected retrospectively. Standard 60-min postinjection PET/CT scans followed by 90-min delayed images were coregistered by rigid-body transformation. A dual-time parametric image was generated, which divided delayed standardized uptake value (SUV) by 60-min SUV on a voxel-by-voxel basis. Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).

Results: With respect to the false-positive lesions in the nine post-CRT patients with false-positive standard 18F-FDG scans in case groups who responded to therapy (TRG 3 or 4 tumors), eight were undetectable on dual-time parametric images (P<0.05). The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01). With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

Conclusion: A voxel-based dual-time parametric imaging technique for evaluation of post-CRT rectal cancer holds promise for differentiating residual tumor from treatment-related nonspecific 18F-FDG uptake.

Show MeSH
Related in: MedlinePlus