To be able to completely remove the tumor during resection, photodynamic diagnostics (PDD) can make sense. In this interview with MEDICA.de, Peter Solleder, Executive Director New Applications at KARL STORZ, explains the advantages of this process in combination with a transurethral resection of the bladder tumor (TURBT) and provides an overview of the current research status.
Mr. Solleder, what is meant by photodynamic diagnostics?
Peter Solleder: Photodynamic diagnostics (PDD) is the combined use of light and fluorescent dyes in medical imaging. On the one hand, tumors can be made visible with the help of applicable substances and light to enable better detection while making a more successful therapy possible on the other.
Today, these substances are routinely used to diagnose bladder cancer. To do this, they are instilled into the urinary bladder where they subsequently accumulate in the cancerous tissue. After the bladder has been emptied and flushed with a saline solution, it is irradiated with light in the 400-430 nanometer short wavelength range. The fluorophores subsequently send back light in the red spectral range. That means the malignant tissue lights up red.
For which types of tumors is this method particularly beneficial?
Solleder: PDD in addition to an endoscopic treatment with transurethral resection of the bladder tumor (TURBT) has a significant advantage, especially for tumors that are not visible under white light and could thus be overlooked. This is especially important in the case of the so-called carcinoma in situ since this type of tumor can break into the muscle layer of the bladder. Carcinoma in situ is a very flat lesion that is difficult to spot under white light. Once the bladder muscles are affected, the urinary bladder is normally being removed and the patient receives a neobladder or an artificial bladder, which significantly restricts the quality of life.
Aside from diagnostics, this method can also be used for therapy purposes. What does the treatment entail?
Solleder: At KARL STORZ, we differentiate between "flexible" and "rigid" PDD. Flexible video cystoscopes by KARL STORZ are being used in "flexible PDD". The flexible system is perfectly suited for diagnostics in outpatient settings and is also often used in follow-up care. Using the flexible endoscope, the physician checks if there are any new tumors that require another treatment or if the patient is tumor-free.
PDD is mainly used in urology…
Solleder: That’s correct. There are two approved fluorescent dyes in Europe. These are 5-aminolevulinic acid (5-ALA) and a 5-ALA hexyl ester. The latter is approved for diagnosing and treating bladder cancer. 5-ALA is used to diagnose brain tumors, the very aggressive glioblastoma multiforme. These are essentially the only substances that are officially approved for these two indications.