BERKELEY, CA (UroToday.com) - Superficial bladder cancer is often treated by combining transurethral resection of the tumor with the instillation of antitumor agents or bacillus Calmette-Guérin (BCG), and BCG instillation is promising treatment preventing the recurrence or progression of carcinoma in situ (CIS) and high-grade superficial bladder tumor. When the CIS or high-grade superficial tumor is BCG-resistant, however, there has been no effective therapy that can preserve the bladder. Most patients with BCG-resistant bladder cancer need radical cystectomy because for these patients the risk of disease progression is very high. Since cystectomy decreases the patient’s quality of life, photodynamic therapy (PDT) is an attractive alternative treatment for high-risk superficial bladder cancer.
Over the past 30 years there have been many studies conducted in efforts to establish effective PDT for bladder cancer, but progress in this field has been limited by heterogeneous irradiation (i.e., excessive irradiation and incomplete irradiation). Excessive irradiation may lead to irritative symptoms and, at worst, bladder contracture. Incomplete irradiation, of course, leads to disease recurrence.
Dr. Morimoto’s research group has therefore developed a homogeneous irradiation fiber probe (HIFiP) for bladder wall photodynamic therapy. It provides a wide-area homogenous irradiation, and the fluence distribution of the light from it nearly coincides with the 3D configuration of the rat bladder cavity. In their study, the homogenously irradiated area in the bladder of a rat treated by PDT with the HIFiP was almost twice the size of that in the bladder of one treated by PDT with a control probe, and the intravesical tumor volume after PDT in rats treated with the HIFiP was less than half in those treated with a control probe. Several devices such as a bulb diffuser attached to the end of the fiber, a balloon that inflates the bladder, and specially structured catheters have been used in efforts to obtain homogeneous irradiation, but they have not been sufficiently effective. The HIFiP does not need special devices and thus can simplify the delivery of homogeneous irradiation to the bladder wall. Because the mucosal surface of the human bladder is much larger than of the rat bladder, clinical application of the HIFiP will require the use of a high-power laser. The simplicity of the HIFiP can minimize the transmission loss in an irradiation system comprised of a high-power laser and HIFiP.
PDT using the HIFiP may be a minimally invasive treatment for bladder cancer. It is important to minimize adverse events such as irritative symptoms and bladder contracture. HIFiP PDT using photosensitizers that selectively accumulate in bladder cancers may become an effective treatment for high-risk bladder cancer. The development of PDT that can affect normal bladder mucosa minimally and enhance the antitumor effect should lead to the clinical use of PDT in patients with bladder cancer.
Keiichi Ito, MD, PhD 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.
Department of Urology
National Defense Medical College