Integrated positron emission tomography and computed tomography (PET/CT) with radiolabeled choline as an imaging agent may improve early detection of recurrent prostate cancer following radical prostatectomy, according to a study.
The study, led by Paolo Castellucci, MD, of the University of Bologna in Italy, included 190 men who had undergone radical prostatectomy and had biochemical relapse. It found that whole body PET/CT imaging with 11C-choline was significantly more accurate that conventional techniques in detecting cancer.
Overall, PET/CT detected cancer in 74 patients (38.9%). Men with positive and negative findings differed significantly with respect to median and mean PSA values at the time of the PET/CT studies. The values were 1.5 and 2.4 ng/mL, respectively, in 116 patients with negative findings compared with 4.2 and 6.7 ng/mL in the 74 patients with positive findings, the authors reported in The Journal of Nuclear Medicine (2009;50:1394-1400).
The researchers also examined PET/CT findings relative to PSA kinetics (PSA velocity and PSA doubling time). Of 106 patients for whom PSA kinetics could be calculated, 41 had positive findings and 65 had negative findings. Median and mean values of PSA velocity were 3.4 and 9.0 ng/mL/year in the PET/CT-positive patients compared with 1.0 and 3.2 ng/mL/year in PET/CT-negative patients.
Median and mean values of PSA doubling time were 3.9 and 6.2 months, respectively, in the PET/CT-positive patients compared with 6.2 and 10.1 months in PET/CT-negative patients. The differences between the groups were significant.
Dr. Castellucci’s team observed a linear relationship between PSA, PSA velocity, and PSA doubling time values and PET/CT detection rate.
In 35 patients, PET/CT detected lesions located only within bone. Eighteen of these patients had single lesions and 17 had multiple lesions. Twenty patients had lymph node lesions (11 single and nine multiple). Another 10 patients had lesions in both bone and lymph nodes. Moreover, five patients experienced local relapse, three had parenteral recurrence, and one had lung metastasis.
Of the 190 men who underwent PET/CT, 84 also underwent CT or MRI scans. PET/CT detected single or multiple sites of relapse in 29 of the 84 patients, whereas CT or MRI detected single lesions in only 15 of the 84 patients.
“Our study found that for some patients, PET/CT with choline can improve the detection of cancer soon after PSA levels are measured,” Dr. Castellucci said. “This enables physicians to tailor treatment to individual patients in the early stages of recurrence, thus increasing their chances of recovery.
However, despite the better sensitivity compared with conventional imaging, the detection rate of 11C-choline PET/CT in patients with low PSA values is still poor (for example, it is about 20% in patients with PSA levels below 1ng/mL). “PSA kinetics could be useful in selecting patients in order to reduce the number of negative or inconclusive PET scan findings,” Dr. Castelluci said.
He and his colleagues suggest that only patients with a high probability of having a positive scan based on PSA levels and kinetics should undergo choline PET/CT scans.