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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

Receiver-operating characteristic curves of delayed-to-standard SUV ratio (DSR), volume-of-interest-based dual-phase index (DI) and pre/post-CRT response index (RI). (a) DSR had a significantly higher AUC compared with RI for all cases (P<0.01). (b) Excluding the cases with undetectable 18F-FDG uptake in post-CRT scans, DSR and DI showed significantly higher AUCs compared with RI (P<0.001 for DSR vs. RI; P<0.05 for DI vs. RI). AUC, area under the curve; CRT, chemoradiotherapy; 18F-FDG, 18F-fluorodeoxyglucose.
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Figure 4: Receiver-operating characteristic curves of delayed-to-standard SUV ratio (DSR), volume-of-interest-based dual-phase index (DI) and pre/post-CRT response index (RI). (a) DSR had a significantly higher AUC compared with RI for all cases (P<0.01). (b) Excluding the cases with undetectable 18F-FDG uptake in post-CRT scans, DSR and DI showed significantly higher AUCs compared with RI (P<0.001 for DSR vs. RI; P<0.05 for DI vs. RI). AUC, area under the curve; CRT, chemoradiotherapy; 18F-FDG, 18F-fluorodeoxyglucose.

Mentions: The results of the ROC analysis of the RI, DI, and maximum DSR in relation to pathological response grade are shown in Fig. 4. DI values were obtained from the VOI-based maximum SUV ratio between standard and delayed scans, whereas maximum DSRs are the SUV ratios on a voxel-based parametric image. ROC analysis identified maximum DSR as the best indicator of response to CRT. Area under the curve (AUC) was significantly higher in maximum DSR compared with the pre/post-CRT RI. The analysis also suggested that DSR is a better indicator of CRT response compared with the VOI-based dual-phase index, although not to a statistically significant extent (AUC: 0.923 for DSR, 0.889 for DI, 0.758 for RI; P<0.01 for DSR vs. RI, P=0.44 for DSR vs. DI) (Fig. 4a).


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)

Receiver-operating characteristic curves of delayed-to-standard SUV ratio (DSR), volume-of-interest-based dual-phase index (DI) and pre/post-CRT response index (RI). (a) DSR had a significantly higher AUC compared with RI for all cases (P<0.01). (b) Excluding the cases with undetectable 18F-FDG uptake in post-CRT scans, DSR and DI showed significantly higher AUCs compared with RI (P<0.001 for DSR vs. RI; P<0.05 for DI vs. RI). AUC, area under the curve; CRT, chemoradiotherapy; 18F-FDG, 18F-fluorodeoxyglucose.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Receiver-operating characteristic curves of delayed-to-standard SUV ratio (DSR), volume-of-interest-based dual-phase index (DI) and pre/post-CRT response index (RI). (a) DSR had a significantly higher AUC compared with RI for all cases (P<0.01). (b) Excluding the cases with undetectable 18F-FDG uptake in post-CRT scans, DSR and DI showed significantly higher AUCs compared with RI (P<0.001 for DSR vs. RI; P<0.05 for DI vs. RI). AUC, area under the curve; CRT, chemoradiotherapy; 18F-FDG, 18F-fluorodeoxyglucose.
Mentions: The results of the ROC analysis of the RI, DI, and maximum DSR in relation to pathological response grade are shown in Fig. 4. DI values were obtained from the VOI-based maximum SUV ratio between standard and delayed scans, whereas maximum DSRs are the SUV ratios on a voxel-based parametric image. ROC analysis identified maximum DSR as the best indicator of response to CRT. Area under the curve (AUC) was significantly higher in maximum DSR compared with the pre/post-CRT RI. The analysis also suggested that DSR is a better indicator of CRT response compared with the VOI-based dual-phase index, although not to a statistically significant extent (AUC: 0.923 for DSR, 0.889 for DI, 0.758 for RI; P<0.01 for DSR vs. RI, P=0.44 for DSR vs. DI) (Fig. 4a).

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