PET/CT using [11C] choline may be useful to restage in patients with prostate cancer who had increasing prostate specific antigen (PSA) after radical prostatectomy and no disease evidence on conventional imaging, according to a study published in the September issue of the Journal of Urology.
The value of [11C] choline PET/CT in patients with prostate cancer in whom biochemical failure developed after radical prostatectomy but who showed no disease evidence on conventional imaging was assessed by Maria Picchio, MD, an associate researcher in the department of nuclear medicine at the Institute H. San Raffaele in Milan, Italy, and colleagues.
The researchers considered 2,124 patients treated with radical prostatectomy and who underwent [11C] choline PET/CT to restage disease between December 2004 and January 2007 for the study.
Of the 2,124 patients considered, 109 met the criteria. Study inclusion criteria were: 1) previous radical prostatectomy and pelvic lymph node dissection; 2) increasing PSA beyond 0.2 ng/ml after radical prostatectomy; 3) no lymph node disease at radical prostatectomy; 4) no evidence of metastatic disease on conventional imaging; 5) no androgen deprivation therapy; and 6) no adjuvant or salvage radiotherapy.
The percent of positive [11C] choline PET/CT scans increased with increasing PSA. “[11C] choline PET/CT imaging was positive in three of 65, four of 26 and five of 18 patients with PSA between 0.2 and 1, between 1 and 2, and greater than 2 ng/ml, respectively,” wrote Picchio and colleagues.
PET/CT was positive in 11 percent of the patients and negative in 89 percent, according to Picchio and colleagues. Of the 12 patients with positive scans, eight had increased [11C] choline uptake in the pelvic lymph nodes. A median of two lymph nodes had increased [11C] choline uptake and mean maximal diameter was 8.7 mm. Four patients had increased [11C] choline uptake in the prostatectomy bed.
“The resolution of [11C] choline PET/CT, which is about 6 mm, limits the ability to detect small lymph node metastasis and micrometastasis. This contributes to the low positive detection rate of [11C] choline PET/CT and accounts for the two patients with false-negative findings in the prostatectomy bed compared to anastomotic biopsy findings,” wrote Picchio and colleagues.
PET/CT detected increased [11C] choline uptake, suggesting recurrent disease in 11 percent of patients with prostate cancer, increasing PSA after radical prostatectomy and no evidence of disease on conventional imaging. This modality may be useful to restage disease but it cannot be used to guide therapy, concluded Picchio and colleagues.