Three-fourths of men with prostate cancer may be eligible for focal ablation

Sep 01, 2009

Due to PSA screening practices in the U.S., three-fourths of American men with prostate cancer may be eligible for focal ablation.

Study co-author Mathias H. Winkler, MD, consultant urologist at Charing Cross Hospital, London, suggested that PSA screening practices in the U.S. raise the percentage of American men who may meet criteria for focal ablation.

"Looking at some of the contemporary series of studies coming from the U.S., I would suspect that something like 70% to 80% of men might be eligible [for focal ablation]," said Dr. Winkler, who conducted the study with Paul Abel, ChM and colleagues.

"In the U.S., you have a high PSA screening penetrance, with perhaps 80% to 90% of asymptomatic men being screened for prostate cancer in some regions. The tumors you find are smaller and are found much earlier. Here, the screening penetrance is around 6%. Cancers are detected incidentally or when symptoms are present. As a result, the tumors are more advanced. We thought we would look at a cohort of unscreened radical prostatectomy patients to determine what proportion of these patients might be eligible for hemi-ablation or focal ablation," he said.

The study, which was presented at the AUA annual meeting, was a comprehensive pathologic review of 100 cases of whole-mount radical prostatectomy samples acquired between 2001 and 2003. The 100 samples held 270 tumor foci. The majority (78%) of the samples demonstrated multifocality, but there were no significant differences between unifocal and multifocal tumors in the samples with respect to total tumor volume, proportion of Gleason scores, or proportion of locally advanced disease.

Eligibility criteria for unifocal cancer included organ-confined disease with a Gleason score ≤7. For multifocal cancer (pT2, Gleason ≤7), the criteria were one large index lesion and clinically insignificant disease in the remaining lesions (ie, total secondary tumor volume <0.5 cc with Gleason <7). The lesion with the largest volume was defined as the index lesion.

The median total volume of unifocal tumors was 3.45 cc; the proportion of tumors that were Gleason ≥7 was 30.7% and the proportion of unifocal samples with locally advanced disease was 31.8%. The median volume of multifocal tumors was 2.24 cc; the proportion with Gleason ≥7 tumors was 31.8%, and the proportion of samples with locally advanced disease was 21.79%.

Some 86.4% (147) of the 170 secondary foci that were identified had a volume of <0.5 cc, and 99.4% of these foci were Gleason ≤6. Given these findings, slightly over half (51%) of the men in this series met the criteria for focal ablation.

The authors noted that the histologic features associated with poor prognosis were arguably associated with the index lesion, the lesion that would be the target of focal ablation.

"In our series, with the exception of two patients, the secondary foci were very small and not very aggressive. This seems to strengthen the argument that the index lesion is going to be the troublemaker," Dr. Winkler noted.

He said large, prospective studies are needed to evaluate outcomes and clarify the eligibility criteria for the procedure, as focal ablation appears to have significant advantages over current procedures.

"It is much better tolerated. Early results from hemi-ablation suggest that most patients remain potent and very few leak urine. If these results are reproducible, then it is possible that focal ablation might produce even better results," Dr. Winkler said.

One of the co-authors of this study discloses affiliations with Focus Surgery, UKHIFU, and US HIFU.