Positron Emission Tomography after Three-Dimensional Conformal Radiation
William Levin, MD
University of Pennsylvania Cancer Center
Last Modified: November 6, 2001
Presenter: K.E. Rosenzweig
Presenter's Affiliation: Memorial Sloan-Kettering Cancer Center, New York
Type of Session: Scientific
Frequently, clinicians have difficulty interpreting CT scans and MRI's
on patients with cancer, particularly after surgery or radiation
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
Fluorodeoxyglucose (FDG)is the radioactive tracer used in this
Standard uptake values (SUV) measure the intensity of tracer identified
the PET study. It is generally accepted that a higher SUV is more likey
represent malignancy as opposed to scaring or inflammation.
MethodsIn this study, PET was used to evaluate response after treatment of
(non-small cell lung cancer) with three-dimensional conformal radiation
This was a review of 50 patients, the majority of which had stage III
Median radiation dose was 70 Gy.
Median age was 68.
The majority of patients also received chemotherapy.
Median time to first post-treatment PET scan was 4 months.
Local failure was determined by clinical assessment, pathology and
SUV's were calculated for the primary tumor in all patients.
ResultsMedian follw-up was 9 months.
Patients with a post-treatment SUV of less than or equal to 3.5 and
than 3.5 had subsequent local failure rates of 17% and 77%,
This was a highly significant difference.
Patients who had a subsequent local failure had an increse in the SUV.
In fact, all patients with SUV >3.5 failed.
Patients with SUV <3.5 had longer survival than those >3.5.
Author's ConclusionsA decrease in post-treatment SUV to <=3.5 on PET scan after 3D-CRT is
highly predictive for subsequent local control.
This suggests that PET scans can be used to assess treatment response
Clinical/Scientific ImplicationsThe ability of PET to distinguish between cancer and non-malignant
continues to be evaluated.
Further studies should be done to compare pretreatment PET scans with
post-treatment scans in patients with lung cancer.
Additionally, administration of the PET scan and interpretation of
must be done by a dedicated, experienced team.
The role of PET scans in the diagnosis, treatment planning, and
of patients with lung cancer will continue to evolve as more studies on
important technology are reported.
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