Viable prostate cancer was detected on histologic examination of the surgical specimen from about half of patients who underwent radical cystoprostatectomy for nonprostate cancer-related disease after having received definitive radiation therapy for localized prostate cancer.
At the AUA annual meeting here, researchers from Fox Chase Cancer Center, Philadelphia, and the University of Kansas Medical Center, Kansas City, both reported that viable prostate cancer was detected on histologic examination of the surgical specimen from about half of patients who underwent RCP for nonprostate cancer-related disease after having received definitive radiation therapy for localized prostate cancer.
The Fox Chase study included 23 patients who underwent RCP for reasons unrelated to prostate cancer at a median of 71 months following RT. Of the 23 patients, four were treated with brachytherapy and 19 received external beam radiotherapy. Median radiation dose was 7,200 Gy, and none of the patients included in the study had received any adjuvant hormone therapy.
"Most striking to us was that there was no significant difference in mean PSA in patients with and without histologic evidence of recurrent/residual disease (1.6 vs. 0.74 ng/mL)," said David Kaplan, MD, a urologic oncology resident at Fox Chase working with Robert Uzzo, MD, and colleagues. "These data suggest that prostate cancer disease surveillance after radiotherapy using PSA does not capture all patients with recurrent or persistent disease, and underlines a need to review and revise the criteria for following prostate cancer after RT."
He added that the presence of active prostate cancer in patients treated with radiation therapy has been examined in previous studies that included men undergoing transrectal ultrasound-guided prostate biopsy. In those reports, a positive biopsy was found in about 15% to 30% of men who demonstrated biochemical freedom from disease.
"Although the interval between radiation therapy and histologic evaluation in those studies was shorter than in our series, we believe they may likely underestimate the true incidence of active disease given the sampling error inherent with transrectal biopsies. To our knowledge, ours is the first study investigating this question based on examination of whole prostate specimens," Dr. Kaplan told Urology Times.
He acknowledged there are limitations inherent in the study as it is a retrospective chart review and several patients had radiation therapy performed at outside institutions. In addition, the study may be underpowered because of its small sample size.
"Nevertheless, our series provides a unique look at the occurrence of histologic prostate cancer after radiation therapy in patients who meet the current definition of biochemical success," he said.
Residual PCa found
Researchers at the University of Kansas also conducted a retrospective study in which they reviewed records to identify patients with a history of prostate cancer and incidental prostate cancer found at RCP, then correlated the findings with a history of pelvic radiotherapy. Between 1997 and 2007, 253 men underwent radical cystectomy or RCP for bladder cancer. Eight of those patients had a history of prostate cancer treated primarily with radiotherapy and no clinical or biochemical evidence of recurrence.
Pathologic examination of the RCP specimen showed four of the eight men harbored significant viable prostatic adenocarcinoma. Two of the four men had been treated for prostate cancer with brachytherapy and two had undergone external beam radiation therapy. The four patients had an average Gleason sum score of 6.25 and an average tumor volume of 10.8%; three had T2c disease and one had T2a prostate cancer.
"Our study includes just a small number of patients, but its results are very consistent with the findings from the larger population included in the Fox Chase Cancer Center study," said Sara Hoestje, MD, a urology resident working with Jeffrey Holzbeierlein, MD, and colleagues. "Although the lifetime significance of the residual disease found at the time of RCP cannot be ascertained, we believe the findings raise a question about the ability of radiotherapy to completely eradicate prostate cancer."
The Kansas researchers also reported that a significant percentage of patients who underwent RCP for bladder cancer were diagnosed with unsuspected incidental findings of prostate cancer based on the results of RCP histology. Of the 253 men included in the review, 211 had no history of prostate cancer nor received prior RT for prostate cancer or other malignancies. Within that subgroup, 59 men (28%) had incidental findings of prostate cancer in the RCP specimen. Their average Gleason score was 6.3 and average tumor volume was 5.5%.
"Previous studies of men who underwent RCP for bladder cancer reported that prostate cancer was incidentally found on final pathology in between 4% and 60% of men, with an overall average of 29%," Dr. Hoestje noted.