Objectives: To assess diagnostic accuracy
of FDG PET/CT and the added value of
dual time point PET/CT (DTP) in detection
of local recurrence (LR) in patients with
rectal cancer (RC). Methods: Patients (n =
50, 41 males and 9 female, mean age 52 ±
11 years). All patients underwent resection
± chemotherapy and/or radiotherapy. 37
patients were suspicious for LR on contrast
enhanced CT (ce CT). All patients
underwent whole body FDG PET/CT scan.
In 18 patients 2 hours delayed pelvic
PET/CT images were done. SUVmax cut
off of 3.0 was set to differentiate benign
from malignant lesions based on ROC
analysis. Suspicious pelvic lesions were
correlated with biopsies in 28 patients
(56%) and with clinical and/or imaging
follow-up (FDG PET/CT, CT or MRI) in
22 patients (44%). Sensitivity, specificity,
positive and negative predictive values, and
accuracy in detection of LR using ce CT
data and following PET/CT were
calculated. Results: Nine patients had LR
(18%). SUV max was higher in all patients
with LR. Sensitivity specificity, PPV,
NPV, and accuracy for detecting recurrent
lesions were significantly higher for
PET/CT and PET/CT with tumor markers
versus ce CT (p<0.05). Delayed pelvic
PET/CT revealed increase in delayed SUV
max (ΔSUV max >0) in 4/18 patients with
confirmed LR (true positive) and revealed
increase in delayed SUV max (ΔSUV max
>0) 4/18 with no evidences of LR (false
positive) while 10/18 showed decrease in
SUV max (ΔSUV max ≤0) in delayed
images with confirmed no LR (true
negative). The combined early SUVmax
and delayed increase in SUVmax revealed
improvement in overall accuracy compared
to either parameter alone. Conclusions:
PET/CT has an excellent sensitivity and a
higher overall accuracy for detection of
local rectal cancer recurrence when
compared to ce CT. Delayed PET/CT when
performed is capable of improving the
specificity, PPV and accuracy of the
PET/CT study.