Emerging Technologies in Prostate Cancer Radiation Therapy: Improving the Therapeutic Window

Matthew C. Biagioli, MD, MS; Sarah E. Hoffe, MD

Disclosures

Cancer Control. 2010;17(4):223-32. 

In This Article

High-dose-rate IPB

HDR IPB was first introduced in 1986 at Kiel University in Germany. As opposed to LDR IPB, whereby radioactive seeds are permanently implanted into the prostate, HDR IPB involves the temporary transperineal placement of catheters into the prostate where aradioactive iridium-192 source is moved in and out of each of the catheters over the course of 5 to 10 minutes. HDR IPB has several potential advantages over LDR IPB. HDR IPB does not have the any radiation safety issues associated with LDR IPB. Additionally, alterations in the position of the iridium source can overcome suboptimal intraoperative catheter placement. Also, it allows for potential increased dose to the periprostatic tissue and seminal vesicles with gross disease or at risk for microscopic spread. In addition, it permits dose escalation to areas of the prostate harboring tumor as well as easier reduction of dose to urethra and rectum.

As with LDR IPB, HDR IPB has been used alone as monotherapy for low-risk prostate patients and in combination with EBRT for intermediate- and high-risk patients. Because HDR IPB as monotherapy without supplemental EBRT did not emerge as a therapeutic option until the mid-1990s, long-term data are limited. However, like LDR IPB, when used as monotherapy for low-risk patients, results have been favorable thus far. Demanes et al[72] evaluated 298 patients treated with HDR IPB as monotherapy and found 5-year bFS and CSS rates of 94% and 100%, respectively. Similarly, 3-year results from the University of Utah of 209 low-risk patients showed a bFS and CSS of 99% and 100%.[73] Additionally, Mark et al[74] published 8-year results among 278 patients demonstrating a bFS rate of 88.5%. These promising findings warrant further investigation.

For patients with intermediate- and high-risk disease, HDR IPB is typically combined with supplemental EBRT and has been performed not only longer, but also on a greater scale than HDR IPB monotherapy. A retrospective analysis of three of the initial prospective studies performed at the Seattle Prostate Institute, William Beaumont Hospital, and Kiel University has been published involving 188 intermediate-risk patients and 359 high-risk patients.[75] The 5-year bFS and CSS rates for intermediate-risk patients were 88% and 99%, respectively. Likewise, for high-risk patients, bFS and CSS rates were 69% and 95%. Additionally, the California Endocurietherapy group found the 8-year bFS rates for 146 intermediate- and high-risk patients to be 87% and 69%, respectively.[76] Bachand et al[77] recently published their results on 153 patients treated in Quebec, of which 88% were either intermediate- or high-risk. Of the entire group, the 5-year bFS rate was 96%. Additionally, 94 of these patients consented to re-biopsy at 24 months after treatment with a negative biopsy rate of 92%. Unfortunately, patients were not stratified by risk group, so it is unclear if these data are biased by a disproportionate representation of intermediate-risk patients. Long-term results analyzing only high-risk patients have been published. Researchers at Kiel University found an 8-year bFS rate of 73% and a dFS rate of 82.6%.[78] Similarly, Swanson et al[79] evaluated 1,697 patients from three institutions and found a 10-year bFS and dFS rates of 67% and 80%. These data likely represent the best clinical result of any modality for high-risk patients; however, randomized studies are needed.

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