BERKELEY, CA (UroToday.com) - In the treatment of prostate cancer, technological advancements in radiotherapy provided safe dosage escalation.
However, in intermediate/high-risk prostate cancers, a high, local recurrence rate of 10 to 30% was reported. We are in need of both safe dosage escalation techniques for these refractory cancers and safe re-irradiation techniques for relapsed prostate cancers.
Because the rectum is adjacent to the prostate, the radio tolerance limit of the rectum becomes smaller than normal after curative, external-beam radiotherapy.
Recent studies on re-irradiation reported approximately 1/3 of the 5-year, biological, disease-free survival of the initial curative dose treatment, with an approximately 4% incidence of grade III gastrointestinal or higher, and 14% incidence of genitourinary toxicity.
An increase, possible (fear) or actual (event), of rectal toxicity in dosage escalation attempts has been the biggest hurdle.
To deliver higher dosages safely while preserving the rectum, we created a general solution with minimally invasive, interventional procedures using a hyaluronate gel injection (HGI) into the perirectal space. This minimally invasive, interventional technique modifies the geometry by direct intervention. It not only adds a small distance, but it decreases the rectal volume (prevents gas inflation) and provides a wider distance. We applied this procedure in this case and observed for over 3 1/2 years. As described in the abstract, the enhancement ratio was approximately 3, which means we may deliver a safe dosage that is 3 times the size of the tolerated rectal risk, which has never been tried.
Related ongoing studies of us are dosimetric, and clinical comparisons of the therapeutic ratio (rectal dose to prescribed dose) between the HGI group and the non-HGI group are almost finished.
Kazushi Kishi, MD, PhD., Et Al., as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Kazushi Kishi, MD, PhD., Dept of Radiation Oncology, Wakayama Medical University, Kimiidera 811-1, Wakayama City, 641-8510 Japan