Proton Beam Therapy for Prostate Cancer Still Needs Studying

Researchers urge insurance providers to cover proton beam therapy in prostate cancer clinical trials to gain more evidence and reduce racial disparities in care.

The Challenge 

External beam radiation therapy (also called radiotherapy or just radiation treatment) is an integral part of cancer care. Radiation kills cancer cells by directing high-energy particles or rays from outside the body into a tumor. However, radiation therapy also affects nearby noncancerous cells, which can cause side effects.

Proton beam therapy is a potentially superior technology to the traditional photon radiotherapy for tumors with a complex anatomy that are surrounded by sensitive tissues—like the eyes and brain. Unlike photons, proton beams enter and travel through the body without depositing as much radiation along the path to the tumor. This means that proton beam therapy can better target radiation to the cancer and do less damage to nearby healthy tissues.

The upfront cost for establishing and providing proton beam therapy is especially high, so this treatment isn't available in every radiotherapy center in the United States. Coverage of proton radiotherapy varies by health insurance provider, and many do not cover treatments that haven’t been validated in clinical trials.

In 2014, the American Society of Radiation Oncology (ASTRO) created a model policy for health insurance providers about when to cover the costs of proton radiotherapy to treat several types of cancer. Their recommendations apply to cancer types in two groups.

• Group 1 cancer types should be covered by health insurance providers, as research has provided enough evidence to recommend the use of proton beam therapy. Group 1 cancers include certain types of childhood cancer and adult cancers in the eye, brain, central nervous system, head and neck, and liver.
• Group 2 cancer types should be covered by health insurance providers as long as the patient is enrolled in a clinical trial or patient registry that meets Medicare requirements. These cancers need more study to compare their effectiveness with photon-beam radiotherapy. Group 2 cancers include but aren’t limited to: anal, breast, cervical, colorectal, esophageal, kidney, lung, pancreatic, prostate, stomach, testicular, and uterine cancer.

The challenge is that until there is adequate clinical trial evidence about the use of proton beam radiation for these group 2 cancers, health insurers may not cover treatment. What's more is lack of health insurance coverage is a principal barrier for enrollment in clinical trials evaluating proton beam therapy in cancer treatments. The result is a vicious circle--insurance providers need evidence to cover a treatment, but evidence can't be established because enrollment in trials is limited or skewed when the treatments aren't covered by insurance.

Little is known about whether the uses of proton beam therapy followed ASTRO's  recommendations, which were developed based on clinical evidence.

The Research 

A team of American Cancer Society researchers in Surveillance and Health Equity Science led by Leticia Nogueira, PhD, MPH, published two large studies in JAMA Network Open. Other ACS researchers involved in the work include Ahmedin Jemal, DMV, PhD, Robin Yabroff, PhD, and former ACS researcher Helmneh Sineshaw, MD, MPH.

For both studies, Nogueira and her colleagues, reviewed almost 6 million people diagnosed with cancer between 2004 and 2018. They used the National Cancer Database, which is a hospital-based cancer registry jointly sponsored by the American College of Surgeons and the ACS. This database captures information on over 70% of cancer cases in the United States from over 1,500 facilities.

In one study, the team evaluated the use of proton beam therapy for people with cancer based on how they would be classified in the two ASTRO groups as well as by the patient’s age, type of health insurance coverage, and income. In the other study, they looked at racial disparities in the use of proton beam therapy for both group 1 and group 2.

Overall, they found that both the number of facilities offering proton beam therapy and the number of patients treated with proton radiotherapy increased over time. They also found substantial racial disparities in the use of proton beam therapy. Black patients were less likely to be treated with proton beam therapy than White patients, especially for Group 1, for which proton beam therapy is the recommended treatment. Alarmingly, as the number of facilities with this type of radiation increased, the disparities also increased, meaning availability of the treatment did not reduce the gaps in quality health care.

ASTRO’s group 1 cancers: Key Findings between 2010 and 2018

• Most people who received proton beam therapy for a group 1 cancer were between 40 and 64 years old, and most had private health care insurance.
• Use of proton beam therapy significantly increased (from 0.4% to 2.2%) for all types of cancer and for every type of insurance coverage. The greatest increase was after 2010. In 2018, more than 30% of people treated with proton beam therapy had a group 1 type of cancer, even though these cancers are rare.
• Use increased most rapidly for head and neck cancers.
• By 2018, nearly 15% of children diagnosed with group 1 tumors were treated with proton beam therapy.
• Racial disparities for treatment of these cancers were higher for this group than for those in group 2—even though cancers in group 1 are the types for which proton beam therapy has been proven to be medically necessary. In fact, racial disparities were highest for the two most common types of childhood cancer. This is especially concerning because children benefit the most from proton radiotherapy because it reduces the risks of late effects of radiotherapy, compared to traditional photon-beam radiotherapy.
• In 2018, the last year with available data to study, disparities in the receipt of proton beam therapy for Black patients were highest.

ASTRO’s group 2 cancers: Key findings between 2010 and 2018

• Most people who received proton beam therapy for a group 2 cancer were between 65 and 74 years old, and most had health care coverage with Medicare.
• Use of proton beam therapy increased (from 0.03% to 0.1%) for all types except for prostate cancer. The greatest increase was after 2014, though, clearly, few people with a “group 2” cancer were treated with proton beam therapy.
• Use increased most rapidly for breast cancer, and in 2018, proton beam therapy was used most often in group 2 for breast cancer.
• Use decreased for prostate cancer from its high in 2011 at 1.4% to its low in 2014 at 0.8%. Then use of proton beam therapy increased in 2018 to 1.3%. Even with the significant decrease, in 2018, prostate cancer was the second-most-frequent group 2 type to be treated with proton beam therapy.
• Racial disparities for treatment of these cancers were highest for Black people with breast or prostate cancer—the types that ere most frequently treated with proton beam therapy during the years studied. In fact, Black women with breast cancer were half as likely to receive proton beam therapy as White women were. This is worrisome because Black women are more frequently diagnosed with breast cancer at younger ages, when late effects are a concern.
• Disparities in the receipt of proton beam therapy for Black patients seems to have decreased in more recent years, mainly because more Black patients are receiving this treatment for prostate and breast cancer.

Why It Matters 

Findings from these large, comprehensive studies suggest that adoption of ASTRO policies by private and public health insurance providers could help people with cancers in both group 1 and group 2 access quality and affordable cancer care.

Adoption of these policies by Medicare especially could lead to a requirement that people with one of ASTRO’s group 2 cancers be enrolled in a clinical trial. Trial results could help resolve the lack of evidence about whether proton beam therapy is a medical necessity for cancers in group.

Continued monitoring of how insurance policies affect proton beam therapy use and enrollment in clinical trials that generate medical evidence for its role in treating group 2 cancers is vital. The study authors said, “To our knowledge, no study has shown a clear clinical benefit for PBT [proton beam therapy] in prostate cancer, and PBT for primary treatment of prostate cancer is recommended by the ASTRO only within the context of a prospective clinical trial or registry.” There is also no consensus on the use of proton beam therapy for treating breast or lung cancers.

The studies’ findings also suggest that decreasing racial disparities in treatment will require identifying and modifying the social determinants of health and structural racism that bar access to care, not just increasing regional availability of technology.

Matching health insurance coverage type and income narrowed racial disparities in proton beam therapy but didn’t eliminate them. That suggests other factors may contribute to racial disparities like health care professionals’ referral patterns and their implicit bias, as well as patient experiences of discrimination.

Study authors said, “Increased diversity and training among health care professionals could improve sensitivity to cultural contexts. Disparities could be diminished by policies and incentives aimed at developing a more diverse and culturally competent oncology workforce.” Future research should investigate the contribution of these factors to racial disparity in receipt of proton beam therapy.