Efficacy of preoperative combined 18-fluorodeoxyglucose positron emission tomography and computed tomography for assessing primary rectal cancer response to neoadjuvant therapy.
OBJECTIVE
Efficacy of F-18 fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) for determining neoadjuvant therapy response in rectal cancer is not well established. We sought to evaluate serial FDG-PET/CT for assessing tumor down-staging, percentage residual tumor, and complete response or microscopic disease with rectal cancer neoadjuvant therapy.


METHODS
Patients with rectal cancer undergoing neoadjuvant therapy, definitive surgical resection, and FDG-PET/CT before and 4-6 weeks after neoadjuvant treatment were included. Tumors were evaluated pretreatment and on final pathology for size and stage. FDG-PET/CT parameters assessed were visual response score (VRS), standardized uptake value (SUV), PET-derived tumor volume (PETvol), CT-derived tumor volume (CTvol), and total lesion glycolysis (delta TLG).


RESULTS
Twenty-one rectal cancer patients over 3 years underwent neoadjuvant treatment, serial FDG-PET/CT, and resection. Complete response or microscopic disease (n = 7, 33%) was associated with higher Delta CTvol (AUC = 0.82, p = 0.004) and Delta SUV (AUC = 0.79, p = 0.01). Tumor down-staging (n = 14, 67%) was associated with greater Delta PETvol (AUC = 0.82, p < 0.001) and Delta SUV (AUC = 0.82, p < 0.001). Pathologic lymph node disease (n = 7, 33%) correlated with Delta CTvol (AUC = 0.75, p = 0.03) and Delta PETvol (AUC = 0.70, p = 0.08).


CONCLUSIONS
FDG-PET/CT parameters were best for assessing tumor down-staging and percentage of residual tumor after neoadjuvant treatment of rectal cancer and can potentially assist in treatment planning.
Melton
Genevieve B
GB
Department of Surgery, The Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287, USA.
Lavely
William C
WC
Jacene
Heather A
HA
Schulick
Richard D
RD
Choti
Michael A
MA
Wahl
Richard L
RL
Gearhart
Susan L
SL
D000230:Adenocarcinoma / Q000175:diagnosis* / Q000601:surgery* / Q000628:therapy; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D049268:Positron-Emission Tomography; D011300:Preoperative Care; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000601:surgery* / Q000628:therapy; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18