Targeted photodynamic therapy may be a potential approach to treat prostate cancer, according to the results of a new preclinical study.
The study, titled “Characterization of an In-111-labeled anti-PSMA antibody-photosensitizer conjugate for targeted photodynamic therapy of PSMA-expressing tumors,” was presented at this year’s Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI).
Targeted photodynamic therapy is a technique that uses an antibody to target prostate cancer cells combined with specialized photosensitizers that tumor cells internalize. When the prostate is illuminated with light with a particular wavelength, tumor cells containing these molecules start dying. This method allows doctors to treat tumors with a minimally invasive procedure, while sparing nearby structures and their functions.
In this study, researchers used an antibody targeting the PSMA protein, labeled with a radioactive tracer (indium-111), that allowed them to monitor which cells were being targeted. The photosensitizers were activated with a near-infrared (NIR) laser. The drug was called 111In-DTPA-D2B-IRDye700DX.
“Coupling the photosensitizer to an imaging agent that targets PSMA on the tumor surface makes it possible to selectively and effectively destroy prostate tumor remnants and micrometastases while surrounding healthy tissues remain unaffected,” Susanne Lütje, an MD and PhD and the study’s leading author, said in a news release.
Researchers investigated the effectiveness and optimal dose of targeted photodynamic therapy in mice with prostate cancer. They found that the photosensitizers accumulated in tumor cells expressing the PSMA protein.The PSMA-positive tumors were clearly visualized with NIR light and other imaging methods.
The team concluded that treating mice with 80 micrograms of the anti-PSMA antibody and, one day later, illuminating the prostate with NIR light for one, five and 15 minutes allows the visualization of prostate tumors in mice. Importantly, this technique induced modest inhibition of tumor growth compared to nontreated tumors, supporting its potential as a new tool to treat this disease.
More studies are warranted to investigate whether targeted photodynamic therapy can also be used in patients with prostate cancer.
“In the future, this novel approach to prostate cancer could significantly improve the effectiveness of treatment, reduce recurrent disease, and ultimately prolong survival and protect quality of life for patients,” Lütje said.
According to the American Cancer Society, about one in seven men will develop prostate cancer in their lifetime. The estimates for prostate cancer in the U.S. include nearly 161,360 new cases and about 26,730 deaths are expected in 2017.