PET in rectal cancer
Blood glucose level normalization and accurate timing improves the accuracy of PET-based treatment response predictions in rectal cancer

https://doi.org/10.1016/j.radonc.2010.01.021Get rights and content

Abstract

Purpose

To quantify the influence of fluctuating blood glucose level (BGLs) and the timing of PET acquisition on PET-based predictions of the pathological treatment response in rectal cancer.

Material and methods

Thirty patients, diagnosed with locally advanced-rectal-cancer (LARC), were included in this prospective study. Sequential FDG–PET–CT investigations were performed at four time points during and after pre-operative radiochemotherapy (RCT). All PET-data were normalized for the BGL measured shortly before FDG injection. The metabolic treatment response of the tumor was correlated with the pathological treatment response.

Results

During RCT, strong intra-patient BGL-fluctuations were observed, ranging from −38.7 to 95.6%. BGL-normalization of the SUVs revealed differences ranging from −54.7 to 34.7% (p < 0.001). Also, a SUVmax time-dependency of 1.30 ± 0.66 every 10 min (range: 0.39–2.58) was found during the first 60 min of acquisition. When correlating the percent reduction of SUVmax after 2 weeks of RCT with the pathological treatment response, a significant increase (p = 0.027) in the area under the curve of ROC-curve analysis was found when normalizing the PET-data for the measured BGLs, indicating an increase of the predictive strength.

Conclusions

This study strongly underlines the necessity of BGL-normalization of PET-data and a precise time-management between FDG injection and the start of PET acquisition when using sequential FDG–PET–CT imaging for the prediction of pathological treatment response.

Section snippets

Patient characteristics

Thirty patients diagnosed with non-metastasized locally advanced-rectal-cancer (LARC) were included in this study from which the clinical TN staging was evaluated on a pre-treatment magnetic resonance (MR) scan (Table 1). All patients were referred to pre-operative treatment with radiotherapy (28 fractions of 1.8 Gy daily) and concomitant chemotherapy (capecitabine 825 mg/m2 BID), followed by a total mesorectal excision (TME). According to the Dutch law, the medical ethics committee approved the

Intra-patient BGL-fluctuations

For the included patients, large intra-patient BGL-fluctuations were observed, ranging from −38.7 to 95.6% (average: 5.2 ± 20.9%) when compared to the pre-treatment-measured BGL (Table 1). BGL-normalization of the sequential PET-data resulted in an average increase of SUVmax of 9.7 ± 14.1% (range: −54.7 to 34.7%) when comparing the maximum SUVs before and after BGL-normalization (p < 0.001) (Table 2). Large individual differences were noticed in the magnitude of the intra-patient BGL-fluctuations,

Discussion

Over the last years, sequential FDG–PET–CT imaging has been shown to be of promise for the prediction of pathological treatment response in an increasing number of malignancies [1], [2], [3], [5], [6], [7], [8], [9], [10], [11], [12], [13], [15], [16]. However, a diversity of factors are known to influence the results of PET-imaging, for instance the used equipment and protocol, uptake time of the FDG and the patients BGL at the time of PET-imaging [5], [19], [20]. When performing sequential

Conflict of interest notification

We are not aware of any actual or potential conflicts of interest.

Acknowledgements

The authors would like to thank Siemens MI for technical and financial support. We acknowledge financial support from the Netherlands Organization for Health Research and Development (ZonMw; clinical fellowship awarded to G.L.).

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