18F-FDG PET early after radiotherapy in lymphoma patients.
OBJECTIVE
The aim of this study was to evaluate the rate of postactinic inflammatory alterations that could lead to false-positive results in FDG-PET images, in a group of lymphoma patients studied with positron emission tomography (PET) early after the end of radiation therapy.


METHODS
Sixteen (16) consecutive patients were referred to our center for malignant lymphoma; 14 of 16 patients had a mediastinal bulky mass at diagnosis. Each patient underwent chemotherapy and then radiotherapy (RT): for clinical reasons, shortly after RT (range, 25-56 days; mean, 38.7 days) a FDG PET scan was required to evaluate the effect of therapy. We intravenously injected 370 MBq of 18F-FDG, and after 60-90 minutes we recorded images.


RESULTS
Despite a relatively short time after RT, there was no pathological tracer uptake in 13 of 16 patients. In 3 cases, a mild increase in FDG uptake was observed, but no findings which would lead to a false-positive diagnosis. In 2 of 3 cases, postactinic pneumopathy was diagnosed (PET scan performed 51 and 52 days after RT); while in 1 patient, soft-tissue inflammation was present (PET scan performed 42 days after RT).


CONCLUSIONS
Our data indicates that the rate of postactinic PET inflammatory alterations in lymphoma patients is not very high and appear to be not strictly linked to the elapsed time since the end of RT treatment.
Castellucci
Paolo
P
U.O. Medicina Nucleare, PET Unit, Policlinico S. Orsola-Malpighi, Bologna, Italy.
Zinzani
Pierluigi
P
Nanni
Cristina
C
Farsad
Mohsen
M
Moretti
Andrea
A
Alinari
Lapo
L
Battista
Giuseppe
G
Pettinato
Cinzia
C
Marengo
Mario
M
Boschi
Stefano
S
Canini
Romeo
R
Baccarani
Michele
M
Monetti
Nino
N
Fanti
Stefano
S
D000328:Adult; D005189:False Positive Reactions; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology*; D006689:Hodgkin Disease / Q000532:radiotherapy; D006801:Humans; D007249:Inflammation; D008223:Lymphoma / Q000188:drug therapy* / Q000532:radiotherapy*; D008228:Lymphoma, Non-Hodgkin / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000494:pharmacology*; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18