11C-acetate PET in the early evaluation of prostate cancer recurrence
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The first aim of the study was to investigate the diagnostic potential of 11C-acetate PET in the early detection of prostate cancer recurrence. A second aim was the evaluation of early and late PET in this context.
The study population comprised 32 prostate cancer patients with early evidence of relapse after initial radiotherapy (group A) or radical surgery (group B). The median PSA of group A (n=17) patients was 6 ng/ml (range 2.6–30.2) while that of group B (n=15) was 0.4 ng/ml (range 0.08–4.8). Pelvic-abdominal-thoracic PET was started 2 min after injection of 11C-acetate and evaluated after fusion with CT.
Group A: Taking a SUVmax≥2 as the cut-off, PET showed local recurrences in 14/17 patients and two equivocal results. Distant disease was observed in six patients and an equivocal result was obtained in one. Endorectal MRI was positive in 12/12 patients. Biopsy confirmed local recurrence in six of six (100%) patients. PET was positive in five of the six patients with biopsy-proven recurrences, the result in the remaining patient being equivocal. Group B: Among the 15 patients, visual interpretation was positive for local recurrences in five patients and equivocal in four. One obturator lymph node was positive. Endorectal MRI was positive in 11/15 patients and equivocal in two. Positional correlation of positive/equivocal results on PET and endorectal MRI was observed in seven of nine patients. PSA decreased significantly after salvage radiotherapy in 8/14 patients, providing strong evidence for local recurrence. PET of the eight patients responding to RT was positive in three and equivocal in two.
11C-acetate PET was found to be valuable in the early evaluation of prostate cancer relapse. Optimising scanning time and use of modern PET-CT equipment might allow further improvement.