For a Blue Light Cystoscopy (BLC™) with Cysview® urologists use a cystoscope equipped with both white and blue light. Before the procedure Cysview is instilled into the bladder. Cysview is absorbed by the cancer cells and makes them fluoresce bright pink in blue light so they stand out against the blue of the healthy tissue.
During the procedure, when the urologist switches from white light to blue light, the fluorescence improves the detection of non-muscle invasive bladder cancer (NMIBC) lesions. Studies have found that there is a significant increase in the detection of NMIBC versus white light alone.1
Mechanism of Action Pathway2
Here’s what happens on the cellular level.
- After instillation in the bladder, Cysview penetrates the cellular membrane of cancer cells.
- In the cancer cells, enzymes in the heme biosynthetic pathway metabolize Cysview, leading to accumulation of protoporphyrin IX (PpIX). The immediate precursor to heme PpIX is a photoactive porphyrin (PAP) with fluorescence excitation between 360-450 nm (blue light) and emission peak at 635 nm (red or pink light).
- PAPs selectively amass in rapidly proliferating cells (e.g., tumor cells). After one hour, sufficient PAPs have accumulated to achieve the desired effect.
- With levels PpIX in neoplastic cells up to 10 times greater in tumors than in normal tissue, the high fluorescence intensity creates an excellent contrast between normal and malignant urothelial cells under blue light illumination (Blue Light Cystoscopy).
- The PAPs emit pink light that makes fluorescing tumors easier to detect and more completely seen.
How Cysview (HAL) is metabolized in cancer cells
1 Cysview® [prescribing Information]. Photocure Inc. Princeton, NJ; 2018.
2 WachoskaM, MuchowiczA et al. AminolevulinicAcid (ALA) as a Prodrug in Photodynamic Therapy of Cancer. Molecules. 2011;16:4140-4164.