18F-FDG PET is an early predictor of pathologic tumor response to preoperative radiochemotherapy in locally advanced rectal cancer.
18F-FDG PET is a useful tool for assessing the effects of chemo- or radiotherapy. The aim of this study was to correlate the change in tumor 18F-FDG standardized uptake value (SUV) during and after preoperative radiochemotherapy, with the pathologic response achieved in locally advanced rectal cancer (LARC) patients.


METHODS
Thirty-three patients with LARC underwent total mesorectal excision after preoperative treatment, including 3 cycles of oxaliplatin, raltitrexed, 5-fluorouracil, and folinic acid during pelvic radiotherapy (45 Gy). Staging procedures included endoscopic ultrasound, MRI, and CT. 18F-FDG PET scans were performed at baseline and 12 d after starting radiochemotherapy (intermediate) in all patients. Seventeen patients also had a presurgical scan. For each scan, mean and maximum SUVs were measured. The percentages of SUV decrease from baseline to intermediate (early change) and to presurgical scan (overall change) were assessed and correlated with pathologic response classified as tumor regression grade (TRG).


RESULTS
Eighteen tumors (55%) showed complete (TRG1) or subtotal regression (TRG2) and were classified as responders, whereas 15 cases (45%; TRG3 or TRG4) were considered nonresponders. The early median decrease of tumor SUV significantly differed between responders (-62%; range, -44% to -100%) and nonresponders (-22%; range, -2% to -48%). A significant correlation was also found between TRGs and early SUV changes (P < 0.0001). Responders were identified correctly by an early decrease of the mean SUV of > or =52%.


CONCLUSIONS
This study shows that early 18F-FDG PET can predict pathologic response to preoperative treatment. These findings support the usefulness of (18)F-FDG PET during the management with radiochemotherapy of LARC patients.
Cascini
Giuseppe Lucio
GL
Nuclear Medicine, IRCCS National Cancer Institute, Fondazione G. Pascale, Naples, Italy.
Avallone
Antonio
A
Delrio
Paolo
P
Guida
Cesare
C
Tatangelo
Fabiana
F
Marone
Pietro
P
Aloj
Luigi
L
De Martinis
Francesco
F
Comella
Pasquale
P
Parisi
Valerio
V
Lastoria
Secondo
S
D000230:Adenocarcinoma / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000494:pharmacology; D003131:Combined Modality Therapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D012372:ROC Curve; D012004:Rectal Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000532:radiotherapy*; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D019788:Fluorodeoxyglucose F18