Isoray - Innovative Brachytherapy

Patient-Centered Brachytherapy Solutions

With high energy and a short half-life, Cesium-131 effectively treats many types of cancers from the inside out.

Brachytherapy with Cesium-131: Proven Personalized Precise.

Cancer care teams work hard to provide the highest-quality patient-centered care possible. Isoray shares your mission, providing brachytherapy products designed to help treat prostate and other cancers. 1

We believe that radiation should spare healthy tissues and be delivered from the inside out. We also believe in a targeted personalized approach to treating each patient’s cancer.

Our groundbreaking brachytherapy isotope, Cesium-131, combines high energy with a short half-life. This allows radiation to leave the body quickly after delivering its therapeutic dose. Patients can get back to their daily activities while receiving highly targeted therapy.2

Patients Treated

Day Half Life

Years of Data

ICD-10-PCS Codes

Our History

Formed in 1998 by a team of nuclear experts, Isoray is the only manufacturer and distributor of Cesium-131, a brachytherapy seed used in the treatment of prostate, brain, head, neck, lung, and other cancers. Over the years, the company has grown from a few dedicated innovators to a company of over 70 people working to improve cancer treatment for patients worldwide.

Your Brachytherapy Partner in the Fight Against Cancer

Cesium-131 is a preferred treatment for prostate cancer among physicians looking for broad coverage and potentially fewer urinary tract symptoms.2 Research is also mounting for its effectiveness in treating brain tumors, head and neck cancers, and other aggressive and recurrent tumors.

Isoray with Cesium-131 can treat Prostate, Head and Neck, Lung, Brain and Gynecological cancers



Isoray was founded in Richland, Washington


Received FDA clearance for Cesium-131


Isoray becomes a publicly traded company


Received FDA clearance for the Cesium-131 strand, preloaded needles, and seeds in Mick cartridges


Received FDA clearance for Sirius MRI Marker with Cesium-131

Our friend call center staff are always ready to help!

To find out how Cesium-131 can enhance your oncology practice...

Our Commitment to Quality

As the only manufacturer and distributor of Cesium-131 brachytherapy seeds, Isoray provides products and solutions that align with personalized cancer treatments. We maintain rigorous quality standards, operating a quality management system that complies with ISO 13485.

Dedicated to Eradicating Cancer

In addition to providing effective, precise prostate cancer treatment, leading cancer institutions have approached us to discuss combination therapies using Cesium-131 to treat complex cancers. Notable clinical trials include:

  • The first brachytherapy PD-1 inhibitor combination study in recurrent head and neck cancer combining Cesium-131 with Keytruda (pembrolizumab).5
  • A study that combines Cesium-131 with Opdivo (nivolumab) to treat metastatic melanoma.

The Research Backing Cesium-131 for Prostate and Other Cancers

Over the past 15 years, researchers have published notable favorable outcomes for patients treated with Cesium-131. A few highlights include:

  • \Ten-year biochemical freedom from disease of 95.3% for low-risk cancers and 90.1% for intermediate-risk cancers.2
  • \Return to pre-treatment urinary and bowel scores within 3 to 6 months.1
  • \5.5-year maintenance of baseline quality of life measures, suggesting durable long-term tolerability.1
  • \Cesium-131 brachytherapy combined with surgery demonstrated acceptable safety and compelling outcomes in patients with recurrent head and neck cancers.3
  • \Multiple studies have shown the safety and effectiveness of Cesium-131 a treatment for a variety of brain cancers.4


We are always looking for talented people to join our team.


  1. Glaser SM, Chen KS, Benoit RM, Smith RP, Beriwal S. Long-Term Quality of Life in Prostate Cancer Patients Treated With Cesium-131. Int J Radiat Oncol Biol Phys. 2017;98(5):1053-1058. doi:10.1016/j.ijrobp.2017.03.046
  2. Benoit RM, Horne ZD, Houser CJ, Smith RP, Beriwal S. Cesium-131 prostate brachytherapy: A single institutional long-term experience. Brachytherapy. 2020 May-Jun;19(3):298-304. doi: 10.1016/j.brachy.2020.02.006. Epub 2020 Apr 2. PMID: 32249178
  3. Luginbuhl A, Calder A, Kutler D, et al. Multi-Institutional Study Validates Safety of Intraoperative Cesium-131 Brachytherapy for Treatment of Recurrent Head and Neck Cancer. Front Oncol. 2021;11:786216. Published 2021 Nov 26. doi:10.3389/fonc.2021.786216
  4. Palmisciano P, Haider AS, Balasubramanian K, D’Amico RS, Wernicke AG. The role of cesium-131 brachytherapy in brain tumors: a scoping review of the literature and ongoing clinical trials. J Neurooncol. 2022;159(1):117-133. doi:10.1007/s11060-022-04050-3
  5. Trial Combining Pembrolizumab and Cesium 131 Brachytherapy with Salvage Surgery in HNSCC. Identifier: NCT04340258

Recent News