PET/CT early restaging best suited for prostate cancer with fast-rising PSA

After prostatectomy, prostate cancer patients with a short prostate-specific antigen (PSA) doubling time should undergo [11C]choline PET/CT for early restaging to optimize potentially needed salvage therapy, according to a study published in the January issue of Journal of Urology.

Authors Giampiero Giovacchini, MD, of the University of Milano-Bicocca in Italy, and colleagues explained that salvage therapy can be effective in treating prostate cancer recurrence following prostatectomy, but primarily for patients with low PSA values. [11C]choline PET/CT has been shown to be useful in restaging, but the threshold for referring patients with low PSA for imaging is not defined.

“While there is generally good agreement that patients with a PSA greater than 1.5 ng/ml should be referred for PET/CT, the use of this technique is less established for lower PSA values when the positive detection rate of [11C]cholinePET/CT definitely decreases,” wrote the authors.

The use of PET/CT for early restaging in those with low PSA would mean higher costs, so the authors devised a study to look at factors associated with a positive [11C]choline PET/CT scan to improve patient selection and better plan salvage therapy.

Giovacchini and colleagues conducted a retrospective study of 75 patients with prostate cancer and increasing PSA less than 1.5 ng/ml. All patients had undergone radical prostatectomy and had not yet received anti-androgen deprivation therapy or salvage radiotherapy. They underwent [11C]choline PET/CT for restaging and the authors looked at an assortment of variables that could be associated with a positive scan, including age, pathological stage and Gleason score.

PET/CT was positive in 21 percent of patients. On univariate analysis, a PSA doubling time of less than six months was the only factor significantly associated with an increased risk of a positive scan, reported the authors. The positive detection rate of [11C]choline PET/CT in these patients rose to 50 percent.

“These results support the use of [11C]choline PET/CT for the early restaging of carefully selected hormone sensitive [prostate cancer] cases with biochemical failure after radical prostatectomy,” wrote the authors.