Change in glucose metabolism measured by 18F-FDG PET/CT as a predictor of histopathologic response to neoadjuvant treatment in rectal cancer.
OBJECTIVE
In order to analyze the changes of glucose metabolism by maximum standardized uptake value (SUVmax) of 18F-FDG PET/CT in patients with rectal cancer submitted to neoadjuvant radiochemotherapy (nRCT) and to correlate SUV changes with tumor regression grade (TRG).


METHODS
Three sequential 18F-FDG PET/CT studies were performed in 31 patients with rectal cancer at the following time point: before starting the treatment (PET/CT1), during the treatment (PET/CT2), and after completion of neoadjuvant treatment (PET/CT3). The SUVmax values of the rectal lesion in the PET/CT1 (SUV1), PET/CT2 (SUV2), and PET/CT3 (SUV3) were obtained; deltaSUV1 [(SUV1 - SUV2)/SUV1] and deltaSUV2 [(SUV1 - SUV3)/SUV1] were also calculated. Metabolic parameters were compared to TRG.


RESULTS
Significant differences in pathologic responder and non-responder patients were found only for SUV2 (6.4 ± 2.9 in responder and 10.7 ± 4.8 in non-responder patients, respectively; P = 0.006) and SUV3 (3.6 ± 1.4 in responder and 6.6 ± 2.1 in non-responder patients, respectively; P = 0.0009). The best predictor for TRG response was SUV3 (threshold of 4.4) with sensitivity, specificity, accuracy, negative predictive value, and positive predictive value of 77.3%, 88.9%, 80.7%, 61.5%, and 94.4%, respectively.


CONCLUSIONS
18F-FDG PET/CT is a reliable and accurate technique to assess the response to nRCT in rectal cancer. In our population, the absolute value of SUVmax after treatment was the best predictor of pathological response.
Guerra
Luca
L
Department of Nuclear Medicine, PET Unit-Molecular Bioimaging Centre, San Gerardo Hospital-University of Milan-Bicocca, Monza, Italy.
Niespolo
Rita
R
Di Pisa
Giuseppe
G
Ippolito
Davide
D
De Ponti
Elena
E
Terrevazzi
Sara
S
Bovo
Giorgio
G
Sironi
Sandro
S
Gardani
Gianstefano
G
Messa
Cristina
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001786:Blood Glucose / Q000378:metabolism*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000379:methods*; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D001786:Blood Glucose; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18