Take home message
  • To improve disparities in cancer care and outcomes, health equity research priorities must shift towards achieving justice by funding minoritized scholars and community-based interventions investigating complex social and political determinants of health
  • Disparities in radiation oncology care are influenced by the logistical, social, financial, and time obstacles posed by daily travel to radiation oncology clinics for multi-week treatment courses, which disproportionately affect rural and American Indian/Alaska Native patients
  • Clinical education and training through volunteer-led free online lecture courses make immediate contributions to the global equity of radiation oncology care and outcomes
  • Medical physicists in low-resource countries need training and resources to safely implement advanced radiation techniques and benefit from direct mentorship

Dr. Gita Suneja opened the radiation oncology session by discussing current and future priorities in cancer equity research. Although the last several decades have seen decreased cancer mortality, disparities in radiation oncology care and outcomes have widened.1–5 Disparities in access to radiation therapy are heavily influenced by upstream factors, including structural inequities and conditions in institutional and living environments that predispose to inequities.2–5 Health system factors include the geographic distribution of treatment machines, radiation oncology expertise, and referral patterns by other oncology specialists, who are the primary gatekeepers for evaluation and consultation with a radiation oncologist.6 Social determinants of health may exert an outsized influence on utilization of radiation therapy compared to other cancer treatments, because standard courses often involve multiple weeks of sequential weekday visits, which creates financial, time, and geographic barriers for patients.

Clinical trials recruit the most privileged, advantaged, educated and well-resourced patients, so the strongest available evidence on treatment efficacy, toxicity, and outcomes is often limited to these patients, and results may not be generalizable to patients who are at risk for or who experience disparities. Specific populations that experience disparities include racial, ethnic, ancestral, and sexual or gender minorities, patients with low socioeconomic status, disabilities or who are under- or uninsured, rural or geriatric patients, immigrants, refugees, and asylees, and adolescents and young adults.

Dr. Suneja addressed the theoretical basis for health disparities research by emphasizing that social determinants of health, i.e., the conditions into which we are born and live and which influence both the incidence and outcomes of cancer, are closely related to political determinants of health, reflecting historical distributions of power and wealth in society.7 Although traditional frameworks distinguish between equality (providing uniform support across groups) and equity (providing the support needed for equal outcomes by addressing specific needs of different groups), a more modern health equity construct is justice, which addresses removal of the underlying determinants of disparate outcomes. Although contemporary health disparities research has focused on health equity, the focus needs to shift to health justice to identify upstream systemic causes of disparate outcomes and potential solutions.

To improve the quality and impact of health equity research, she proposed two solutions: funding the right people and asking the right questions. Black scientists are less likely to receive National Institutes of Health (NIH) funding than White researchers8 and furthermore are more likely to propose projects related to equity and public health, a topic choice that is less likely to receive national scientific funding.9 Improving funding opportunities for minoritized researchers and health equity topics is needed to support progress in health equity research. In addition, an emphasis on community-based research, both funding investigators from communities of interest and collaborating with community partners, should be prioritized. Second, data collection instruments, including cancer registry data, need to be enhanced to harness their full potential to address significant health equity questions. Social determinants of cancer outcomes are often poorly defined, difficult to interpret or unavailable in clinical datasets. Qualitative or mixed-methods research provides an alternative avenue to elucidate the influence of social factors and identify opportunities for interventions, for example in ongoing work in Malawi on cancer stigma.10 In the US, one of the most pervasive social determinants is racism, and scholars such as Dr. Rhea Boyd provide guidance on how to address racism in the biomedical literature from the perspective of an investigator, reviewer, and journal editor.11 Finally, examples of upstream intervention to address social determinants and social needs were provided, including the ongoing SISTER trial of social support for Black women with endometrial cancer (NCT04930159).

Dr. Solmaz Amiri discussed two studies of geographic disparities in access to radiation oncology facilities in the United States, with a focus on American Indian/Alaska Native (AI/AN) patients.

In the first study, geospatial analysis of census block groups in the contiguous US grouped by majority race and ethnicity revealed differences in driving distance to the nearest facility.12 The median driving distance to the closest radiation facility was 4 – 7 miles for census block groups with majority White, Black, Asian, Hispanic, or multi-racial populations, but for people living in majority-AI/AN census block groups, the median driving distance was 72 miles. Driving distance to the closest facility was similar across block groups of lower and higher socioeconomic status (7 versus 6 miles) nationwide and by majority race and ethnicity, except for block groups with majority White (14 versus 7 miles) and AI/AN (81 versus 44 miles) populations. Rural block groups were associated with longer driving distances nationally across all racial and ethnic groups, with the largest distances seen for AI/AN-majority block groups in the most rural areas, with a median driving distance of 103 and 93 miles associated with living in small towns and rural areas respectively, which was 2 – 3 times farther than the driving distance from other racial and ethnic majority block groups with the same degree of rurality. Mixed effects modeling estimated that driving distance was 39 – 41 miles longer from AI/AN block groups than from areas with other racial and ethnic majorities after adjusting for socioeconomic status and rurality.

Decedent-level analysis of the driving distance between radiation therapy facilities and the residential location for cancer patients at the time of death in Washington state also showed stark associations between ethnicity, rurality, and access to radiation therapy.13 Non-Hispanic AI/AN patients lived at a greater driving distance from radiation facilities compared to any other racial or ethnic group (median 9 versus 5 – 7 miles). Mixed effects modeling estimated that non-Hispanic AI/AN patients would have had to travel 16% farther than non-Hispanic Whites, which increased to 39% farther in non-metro counties.

Geographic radiation therapy disparities have been further investigated by LaVigne et al who examined the national county-level density of radiation oncologists versus the incidence and mortality rates for prostate and breast cancer.14 Geographic areas with heightened incidence and mortality rates were predominantly non-metropolitan, and these areas were also associated with lower physician density, suggesting unmet need for radiation therapy services. Radiation therapy is commonly recommended as definitive, adjuvant, or palliative treatment for approximately 50% of all cancer patients.15 Treatment traditionally involves up to nine weeks of daily visits to a radiation facility such as a cancer center, which may pose financial, time, transportation, and social obstacles for patients as well as costs to integrated healthcare systems. Given the capital and infrastructure investments needed to build and safely maintain radiation facilities, creating new centers in rural areas with low population density may not be feasible. Thus, programs that provide patient navigation, transportation, and housing resources during treatment may alleviate geographic barriers.

Dr. Benjamin Li shared the background, purpose, and efforts of the non-profit Rayos Contra Cancer (RCC), which he founded to make a tangible immediate impact in global cancer equity by providing radiation therapy educational lectures to practicing clinicians.

Although high-income countries generally have adequate population-level density of radiation therapy machines, most low and middle-income countries (LMICs) have inadequate facilities on a per-capita basis. In addition to hardware, software, and physical clinic infrastructure, the provision of radiotherapy services depends on adequate integration with the local healthcare system and human resources. Human resource challenges include inadequate or no formal training in many countries, where physicians and staff often learn on the job, limited training from equipment vendors, and limited support from local governments for ongoing training and quality assurance. However, local clinicians highly value opportunities for additional clinical training. For example, a survey of 132 radiotherapy staff in Latin America found that 76% would pay out of pocket for additional clinical training, while an additional 22% would attend if training were free, resulting in 98% that would participate in training opportunities.16

To meet this need, RCC leveraged the skill of US volunteer clinicians to develop a scalable model of free online educational courses, which over the first four years has reached over 3500 local clinic staff from over 600 clinics in at least 75 countries. Courses typically involve 17 weeks of weekly live video lectures, and cover clinical topics such as brachytherapy, intensity-modulated radiotherapy, stereotactic body radiotherapy, contouring, and hypofractionation, for physicians, medical physicists, and radiation therapy technologists. Specific content for each course is based on input from local leaders in the region. The most recent courses include more than 500 participants, potentially influencing the care of a large number of patients treated per year worldwide. Initial participant feedback has been highly positive, as for some staff this is the first didactic clinical training that they have received, and RCC plans to implement additional measures of impact on patients and practice. RCC routinely collects data on participant demographics, as well as surveys and multiple-choice exams before and after courses, and is working on developing optimal metrics to evaluate educational program performance and clinical improvements, as well as tailor educational courses for the local context.17

Dr. Afua Yorke discussed RCC’s program evaluation process and the medical physics educational partnership between the University of Washington and Ghana.

Ghana has a history of high-quality medical physics training and was recognized as a Regional Designated Centre for Academic Training of Medical Physicists in Africa by the International Atomic Energy Agency.18,19 However, there are gaps in the infrastructure and technology needed to safely and accurately deliver contemporary advanced radiotherapy techniques. Direct mentorship provides an opportunity to fill this gap, because it enables US clinicians to learn about the specific limitations that are barriers to improving cancer care in LMICs and work with local clinicians to address them. Dr. Yorke shared her experience hosting a visiting medical physics scientist from Ghana at the University of Washington and mentoring her on advanced clinical techniques. This mentorship and training support her as a catalyst of change in her home institution in Ghana to implement advanced techniques and safely deliver hypo-fractionated radiation therapy and increase patient throughput.


Radiation oncology is an essential component of cancer care. Disparities in radiation therapy access and outcomes are associated with geographic barriers in high-income countries and limitations in clinical education and technological infrastructure in low-income countries. Systemic interventions within cancer centers and national programs are needed to overcome disparities. Radiation oncologists, medical physicists, and other members of the radiation oncology treatment team have opportunities to directly address disparities by contributing to research, clinical education, and capacity-building in low-resource settings.

Conflict of Interest


Funding information

SA and LMH received funding from the Kuni Foundation that supported this work.

Ethical statements

All human subjects research discussed was performed in accordance with the Declaration of Helsinki and previously approved by an ethics committee as detailed in the respective publications.



Author contributions

  1. All authors: conception and design,

  2. All authors: data collection and assembly

  3. All authors: data analysis, manuscript writing

All authors have approved the manuscript