Second Ten Year Data Report Demonstrates Efficacy of Isoray’s Cesium-131 Internal Radiation Therapy in the Treatment of Prostate Cancer

Jun 2, 2020

RICHLAND, WASHINGTON – June 2, 2020 – Isoray, Inc. (NYSE American: ISR) today announced that the results of a new ten year study show positive outcomes for low-risk and intermediate-risk prostate cancer patients treated with Isoray’s Cesium-131 (Cesium Blu) internal radiation therapy (brachytherapy).

The observational study from the University of Pittsburgh School of Medicine followed a large group of patients for up to ten years. Using a biochemical endpoint*, the data show the ten year success rates for treatment with Cesium-131 were 95.3% for patients in the low-risk category (200 patients under study), 90.1% for patients in the intermediate-risk category (372 patients under study) and 56.6% for 97 high-risk patients. Patients with higher risk cancers were treated with external beam radiation therapy in addition to their Cesium-131 implant, while lower risk patients underwent only a Cesium-131 implant.

Dr. Ronald Benoit, lead author of the study from the Department of Urology, University of Pittsburgh School of Medicine, addressed the findings, “As our data matures, our findings continue to demonstrate the excellent oncologic outcomes in men undergoing prostate brachytherapy with Cesium-131.”

Speaking to the data on higher risk cancers, Dr. Benoit noted, “We do believe our long-term outcomes in men with high risk disease are somewhat underestimated in this manuscript due to a low number of patients at risk at ten years. As our database matures, we expect our ten-year outcome in this group to improve significantly.”

Commenting together, the authors said, “…the shorter duration of urinary morbidity along with lack of differences in long-term adverse effects support our preference for this isotope.” The authors concluded that the study demonstrates that, “Prostate brachytherapy treated with Cesium-131 achieves excellent long-term biochemical control.” Dr. Ronald Benoit and the co-authors of the study observed that the results of the study mirror those published last fall by the Chicago Prostate Cancer Center. The study, Cesium-131 prostate brachytherapy: A single institutional long-term experience, was posted on the website of the peer-reviewed journal, Brachytherapy.

Isoray CEO Lori Woods said the study represents an important milestone for Isoray. “We now have two mature studies together counting well over one thousand patients treated with Cesium Blu that demonstrate significant success in treating low and intermediate risk localized prostate cancer.“ Woods noted that emerging treatment strategies for localized prostate cancer require years of follow-up, given the long natural history of this cancer.

Cesium-131 has the shortest half-life and highest energy of brachytherapy seeds commonly used in the treatment of prostate cancer. Cesium’s energy is powerful, allowing it to aggressively attack the cancer being treated. Its shorter half-life means the radiation delivers its treatment dose faster, reducing other issues for the patient that can come from prolonged radiation exposure. The rapid resolution of side effects is an important advantage for patients, allowing them to return to their normal lives faster. Unlike external beam radiation, Cesium-131 internal radiation therapy is able to deliver a precise dosage and placement of Cesium-131 seeds, leaving healthy tissues and organs undamaged.

Isoray is a medical technology company and innovator in seed brachytherapy powering expanding treatment options throughout the body. The company is the world’s only producer of Cesium-131 brachytherapy, which expands internal radiation treatment for difficult to treat lung, brain, gynecological, head and neck, pelvic, and colorectal cancers as well as prostate cancer.

*All estimates of biochemical success are based on Kaplan-Meier methodology using the Phoenix definition of biochemical failure (see Kuban, et al. Comparison of biochemical failure definitions for permanent prostate brachytherapy. International Journal of Radiation Oncology Biology Physics 65(5):1487-93, 2006.)

Contact

Media and Public Relations: Sharon Schultz (302) 539-3747

Investor Relations: Mark Levin (501) 255-1910

About Isoray

Isoray, Inc., through its subsidiary, Isoray Medical, Inc. is the sole producer of Cesium-131 brachytherapy seeds, which are expanding brachytherapy options throughout the body. Learn more about this innovative Richland, Washington company and explore the many benefits and uses of Cesium-131 by visiting www.isoray.com. Join us on Facebook/Isoray. Follow us on Twitter @Isoray.

Safe Harbor Statement

Statements in this news release about Isoray’s future expectations, including: efficacy of the biochemical success rate for 10 year results, the advantages of Cesium-131 and its delivery systems, whether additional studies are released that support the conclusions of the study discussed in this news release, the perception by patients of quality of life outcomes compared to other treatment options, whether demand for and use of Cesium-131 will increase or continue as anticipated, continued positive industry data fueling renewed interest in brachytherapy patient results, and all other statements in this release, other than historical facts, are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995 (“PSLRA”). This statement is included for the express purpose of availing Isoray, Inc. of the protections of the safe harbor provisions of the PSLRA. It is important to note that actual results and ultimate corporate actions could differ materially from those in such forward-looking statements based on such factors as the impact of COVID-19 on our financial results, suppliers, employees and scheduling of procedures, whether additional studies are released that support the conclusions of past studies, whether ongoing patient results are favorable and in line with the conclusions of clinical studies and initial patient results, physician acceptance, training and use of our products, our ability to successfully manufacture, market and sell our products, our ability to manufacture our products in sufficient quantities to meet demand within required delivery time periods while meeting our quality control standards, whether we, our distributors and our customers will successfully obtain and maintain all required regulatory approvals and licenses to market, sell and use our products in its various forms, changes in laws and regulations applicable to our products, and other risks detailed from time to time in Isoray’s reports filed with the U.S. Securities Exchange Commission. Unless required to do so by law, we undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

Investor Relations:

Mark Levin

Global IR Group
(501) 255-1910

Media and Public Relations:

Sharon Schultz
Schultz Public Relations
(302) 539-3747
schultzpr@mchsi.com