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PET Response is the Most Powerful Predictor of Survival after Radical Radiotherapy/Chemoradiotherapy for Unresectable Non-Small Cell Lung Cancer
William Levin, MD
University of Pennsylvania Cancer Center
Last Modified: November 6, 2001
Presenter: M.P. MacManus
Presenter's Affiliation: Peter MacCallum Cancer Institute, East Melbourne, Australia
Type of Session: Scientific
Frequently, clinicians have difficulty interpreting CT scans and MRI's
done on patients with cancer, particularly after surgery or radiation therapy. Positron emission tomography (PET) is an imaging technique that measures glucose metabolism in cells. There is evidence that tumor cells have increased uptake and metabolism of these sugar molecules, as compared to non-malignant cells. Fluorodeoxyglucose (FDG)is the radioactive tracer used in this technique. Standard uptake values (SUV) measure the intensity of tracer identified on the PET study. It is generally accepted that higher SUV are more likey to represent malignancy as opposed to scaring or inflamation.
MethodsThis was a prospective study evaluating PET as a prognosticator in patients with non-small cell lung cancer who received chemotherapy or chemoirradiation.
88 patients were evaluated, most had stage III disease.
Most got chemoirradiation.
Most had good performance status.
The majority had squamous cell histology.
PET responses were assessed by comparing initial and post-treatment scans.
Scans were graded as either complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD).
ResultsThe majority of patients received 60 in 2 Gy fractions.
Median time to follow-up PET scan was 69 days after completion of treatment.
Survival was 91% and 78% at 1 and 2 years respectively for patients who achieved a CR on PET and 48% and 36% respectively for the 48 remaining patients (p=0.00002).
Survival was strongly correlated with PET response, but not with CT scan response.
On multivariate analysis, when there was correction for stage, ECOG status and weight loss, PET response remained a powerful predictor of survival (p=0.0005).
PET-response to radical RT was a more powerful predictor of survival in NSCLC than any of the recognized prognostic factors. CT response was not strongly correlated with survival.
Clinical/Scientific ImplicationsPET appears to be useful in the follow-up of lung cancer patients after completion of radiation therapy.
One must remember that the accuracy of PET is highly dependent on the people administering the study and those interpreting the results.
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