Eye Therapy

Proton Therapy

Ocular melanoma treatment at CNL

Since 1994 more than 1,600 patients have been treated for ocular—or “uveal”—melanoma at Crocker Nuclear Laboratory (CNL).

The cornerstone of the treatment program is the laboratory’s particle accelerator, a 200-ton cyclotron that generates a proton beam: a high-energy stream of subatomic particles that can be focused with extraordinary precision to destroy small tumors while causing far less damage to surrounding tissue than conventional radiation therapy.

Established in conjunction with the radiation oncology department at University of California San Francisco, the proton therapy program at CNL is one of the oldest in the nation and the only one to exclusively treat tumors of the eye. With its long history of research, clinical practice and technical expertise, the UCSF/CNL uveal melanoma program offers patients one of the most experienced teams in the country.

Proton therapy

Because a proton beam can be manipulated to deliver almost all of its radiation to a precise shape and depth within a patient’s body, it causes very little damage to nearby healthy tissue. This differs from standard radiation therapy that uses either x-ray or gamma-ray beams. These treatments deliver radiation all along the beam’s path, damaging healthy as well as cancerous tissue as the beam enters and leaves the body.

The special characteristics of a proton beam make it exceptionally useful for treating small tumors located within or near sensitive structures and organs—such as the eye, spinal cord and other parts of the nervous system. With minimal radiation exposure to surrounding tissue, proton therapy can be applied at higher, more effective doses than standard radiation therapy.

Proton therapy has been an FDA-approved treatment for certain cancers since 1988.

Why isn’t proton therapy more widely available?

In 2013 there were about a dozen proton therapy centers in the United States and only about twice that many worldwide, while another 17 were under construction or in development in the U.S.

Cost and size of these facilities are two of the major factors limiting their widespread distribution. Until recently, it took a piece of ground as large as a basketball court plus as much as $150 to $200 million to build a particle accelerator and the necessary infrastructure to establish a treatment center.

Another challenge is finding medical and technical personnel with the expertise required to conduct treatment. The learning curve is steep and long, both for the doctors who direct proton therapy treatment and for the technicians responsible for the high-energy physics technology on which treatment is based.

Eye therapy professionalsThe UCSF and CNL proton therapy treatment team. Left to right: Dolores Andy Sevier;  Rajinder P. Singh; Kavita K. Mishra; Inder K. Daftari; Genevieve Baliantz; Dan Shadoan.

CNL and UCSF provide an experienced staff and a superior proton beam

As a treatment team with an exclusive focus on ocular tumors for two decades, UCSF and CNL have been in the forefront of exploring the science of uveal melanomas and advancing radiation treatment for the condition. We have successfully treated a high volume of uveal melanoma cases and understand the complexities in planning and treatment.

The design of our cyclotron at CNL provides extra benefits to our patients. The low-energy, adjustable beam produced by the equipment penetrates only about an inch or two (3 cm) into the body, making it perfect for treating cancers of the eye. Most other particle accelerators in use today produce higher-energy beams that utilize additional technology to adjust the beam to appropriate levels. Our beam does not require such adjustments, resulting in a more stable beam with less energy spread.