Originally published as JCO Early Release 10.1200/JCO.2008.20.8579 on January 12 2009

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In Reply

H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, FL

We appreciate an insightful comment by Hanna et al on our recent finding that a tumor response by positron emission tomography (PET) scan was not a reliable prognostic factor for survival after neoadjuvant chemotherapy for resectable non–small-cell lung cancer.¹ We believe the results we describe are representative not only of our experience, but likely of other centers using similar techniques in daily PET/computed tomography practice. We agree with Hanna et al that technical variations in the conduct of PET scans can affect data interpretation, especially on the visual analysis of PET scans; however, it is unlikely that this reason alone accounts for all of our findings.

In most of our 59 patients who had semi-quantitative PET scan responses, the baseline and follow-up PET scans were conducted at one institution, thus minimizing an intrapatient technical variation. In this data set, as Patz² has pointed out, "No matter how the data were analyzed, the investigators could not find changes in FDG uptake that predicted outcome." It is also important to point out that there was no difference in the attenuation correction technique between baseline and subsequent scans, and although there were two patients with serum glucose higher than 200 mg/dL in the data set, both had long-standing diabetes.

Moreover, as a prospective research protocol, technical variations among patients were also minimized. All imaging times were set between 90 and 120 minutes after a [¹⁸F]fluorodeoxyglucose injection. Therefore, any deviation in the standardized uptake value maximum was theoretically less than 1.0, except some unusually hypermetabolic tumors.³ Besides, all patients in our study underwent an overnight fast. We found only two occasions in which our patient glucose level went marginally beyond this. We did not discard these patients, given that we typically complete examinations at glucose levels judged to reflecting reasonable control for the particular patient.

Finally, we agree with Hanna et al that timing of PET examinations is important. Our work should encourage additional research to determine optimal timing. The timing as used in our study allowed for tumor response by computed tomography scan to predict survival. But performing a PET scan every week, as outlined in the study by Nahmias et al,⁴ is burdensome. At this time, it seems that the most widely used PET response criteria, when applied under conditions representative of daily clinical practice, fail to predict survival after neoadjuvant chemotherapy for patients with resectable non–small-cell lung cancer.

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The author(s) indicated no potential conflicts of interest.

REFERENCES

1. Tanvetyanon T, Eikman EA, Sommers E, et al: Computed tomography response, but not positron emission tomography scan response, predicts survival after neoadjuvant chemotherapy for resectable non–small-cell lung cancer. J Clin Oncol 26:4610–4616, 2008.[Abstract/Free Full Text]

2. Patz EF Jr: Does computed tomography or positron emission tomography response after neoadjuvant chemotherapy for resectable non–small-cell lung cancer predict survival? J Clin Oncol 26:4542–4543, 2008.[Free Full Text]

3. Shankar LK, Hoffman JM, Bacharach S, et al: Consensus recommendations for the use of 18F-FDG PET as an indicator of therapeutic response in patients in National Cancer Institute Trials. J Nucl Med 47:1059–1066, 2006.[Free Full Text]

4. Nahmias C, Hanna WT, Wahl LM, et al: Time course of early response to chemotherapy in non–small cell lung cancer patients with 18F-FDG PET/CT. J Nucl Med 48:744–751, 2007.[Abstract/Free Full Text]

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• In Reply
  Tawee Tanvetyanon, Edward A. Eikman, and Gerold Bepler
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