16 July 2021
Written by Anna Cheng
A cancer diagnosis can be difficult for anyone to navigate, but did you know that cancer does not affect all races equally? There has been a lot of research into how and why cancer affects people differently depending on their ethnicity.
This disparity goes beyond how you live your life, where you were born or the type of area you live in, although these do play a role in how likely you are to develop cancer. These factors also play a role in what treatment is available and how well people do on treatment. Research shows that, compared to their Caucasian, Hispanic, and Asian counterparts, Black individuals of African ancestry show a significant risk of cancerous malignancy.
So, what does all this mean? Let’s break it down. We'll talk about the role of our environment (we call this non-genetic); then we will talk about the things we can't control (our DNA and the genes we're born with). Next, we’ll investigate what is causing the gap in when people are diagnosed and the treatment they receive. Finally, we’ll explore what can be done to level the medical playing field and how to finally bridge the statistical gap once and for all.
Non-genetic risk factors refer to the things we can't control - they're part of our social, cultural or financial life. However, these things can and often do affect our chance of developing cancer and our likelihood of surviving cancer once diagnosed.
Lifestyle factors include diet, exercise, tobacco and alcohol use, rest, and even stress levels. These are the so-called ‘preventable’ risk factors. We say ‘so-called’ because, while one does have a say in how they eat, sleep, drink, and so on, these factors are also intrinsically tied to socioeconomic status, which is much harder to control. Unfortunately, whole ingredients, healthy, home-cooked meals, low stress levels, and a good night’s rest are luxuries not everyone can afford.
It’s well-documented that those who live under or near the poverty line are much more susceptible to the effects of poor nutrition. Essentially, poverty creates a downward spiral: if you can’t afford to eat well, do not have the time or energy to exercise, or experience high stress levels, you’re much more likely to have poor overall health and chronic medical conditions.
Likewise, access to health care is also tied to socioeconomic status. In countries with private healthcare systems, such as the United States, access can be exceedingly difficult. Those living in poverty have less money to access to medical treatment for serious or chronic conditions and, when they do access care, they are less likely to be taken seriously by healthcare professionals. This causes a disproportionately higher death rate in these communities.
Authors of a 2016 research review revealed that Black patients are 66% less likely than white patients to receive timely and appropriate treatment for lung cancer. This may partly reflect the fact that Black Americans are more likely than white Americans to be uninsured or lack private health insurance due to long-standing economic inequalities.
Access to health care may also be influenced by location (rural vs. urban living), mobility and transportation, as well as the availability of medical practitioners. The latter is much more common in countries with public or universal healthcare. Medically underserved populations living in poverty are made all the more vulnerable by their lack of access to timely and affordable healthcare.
Unfortunately, racism has a home within the walls of the nation’s medical facilities. An abundant volume of research attests that people of colour are provided with subpar care when compared to their white counterparts. Despite its promise to “do no harm,” the medical field is rife with discriminatory practices from long-held biases. What makes this discrimination so insidious is that it takes place at both an individual and systemic level. Because of this, and fearing they won’t be treated fairly, people of colour are often hesitant to seek the care they need.
There are instances of individual practitioners providing inferior care to their patients of colour, disbelieving their symptoms, and assuming they have a higher degree of pain tolerance. The most egregious examples include outright intolerance and degradation towards patients seeking care. The medical education provided to these professionals is also skewed by racial bias and lack of diversity. It seems that many professionals are simply not equipped to assess, diagnose, and treat people of different races equally.
Although the aforementioned comorbidities play a part in the disparate cancer rates, this racial disparity goes beyond lifestyle factors, access to healthcare, and even racism. Epidemiological studies indicate that genetic determinants also play a role in the cancer susceptibility and survival rates of people with African ancestry. In layman’s terms, people of African heritage are at a higher risk of developing cancer and have a lower survival rate.
Through no fault of their own, Black individuals are simply more genetically susceptible to conditions correlated with cancer. There is a clear indication that Black populations are more vulnerable, even among groups with similar lifestyle factors and socioeconomic conditions. Ultimately, Black populations are simply more susceptible to cancer than their counterparts due to genetic determinants.
This correlation becomes clear when Black populations are compared directly to other racial groups with comparable lifestyles and socioeconomic status. For example, when examining a phenomenon called the ‘Hispanic paradox', despite similar non-genetic factors, Hispanic individuals have some of the lowest rates of cancer susceptibility among all groups. When it comes to mortality rates measured by racial grouping, Hispanics were the second-lowest, with a rate of 110.8 per 100,000. Asian/Pacific Islanders were the lowest out of all the categories, with a rate of 97.2 per 100,000.
So just what makes certain racial groups more likely to get more severe types of cancer and have less chance of survival?
To understand why cancer affects races differently, we first have to understand the meaning of genetic polymorphism. In simplest terms, polymorphism refers to a genetic variant of alleles. It’s the diversification of DNA, where two or more trait variations are found on a single gene.
For the average citizen, talk of polymorphism may as well be Greek; it’s a highly complicated biological process, and even scientists don’t fully understand the extent of its medical significance and implications yet.
However, here’s one particularly noteworthy example. The TP53 P72R polymorphism is the primary P/P allele found preferentially in African-Americans with colon cancer and Asians with gastric cancer. It’s believed that the TP53 P/P-related cancer susceptibility is caused by a faster accumulation of mutations, and subsequently, a wider pool of cells thought to be cancer-initiating. Effectively, individuals with this polymorphism have genetically evolved to be more prone to developing cancer.
There are hundreds upon hundreds of these polymorphisms currently under examination by scientists. While there is no simple answer to the question,“what makes some races more prone to incidences of cancer?”, research indicates that it may come down to genome sequencing.
With this in mind, there are several genetic mutations thought of as ‘cancer drivers’ found particularly in populations with African ancestry. These mutations make certain groups genetically prone to obesity, chronic inflammation, and suppressed immune responses.
There is already a strong association between obesity and cancer, which has been observed over the past 20+ years. Both incidences and mortality due to cancer are increased several-fold by obesity. While Black and Hispanic populations have a higher prevalence of obesity than Caucasians and Asians, it’s the Black populations that experience the most cancerous comorbidities.
Black populations, according to research, already have other biological components that make them predisposed to obesity and other metabolic disorders. When these genetics are paired with diet and other lifestyle factors, it results in Black populations that are particularly susceptible to obesity-related cancers. We know that the genetic component is important, thanks to the aforementioned Hispanic paradox: however, even with similar rates of obesity to Black populations, Hispanic populations seem relatively unaffected by obesity-related cancers.
This same risk associated with obesity-related cancers is also linked to conditions of chronic inflammation. The serum levels of inflammatory proteins are higher in Black populations than in other races, even after adjusting for BMI. This inflammatory protein polymorphism is thought to account for the discrepancy in racial cancer statistics. Unfortunately, many health conditions can trigger chronic inflammation, making an individual more susceptible to cancer.
Immune response is a subject in which much is still unknown. Scientists are currently investigating the immune responses of different races, and here is what we know so far:
Susceptibility to certain conditions, such as cancer, is determined by genetic variations in the immune system. The genes of the immune system shift due to evolutionary pressure, including that of environmental conditions and population migration. Those with African ancestry show “inherent differences” in their immune system; ostensibly, this is because of selective evolutionary pressure responding to certain African regional diseases.
Even after adjustments for demographic and year of diagnosis, individuals with African heritage were found to present more advanced stages of cancer than their Caucasian counterparts while also undergoing definitive therapeutic treatments less often. African Americans were also found to have greater estimated cancer-specific mortality rates than Caucasians for all cancers combined.
Despite efforts to close this statistical gap, there hasn’t been much change over the past 25 years. According to a 2014 study published in the American Cancer Society Journal, race-based disparities (even after data-point adjustments) have persisted. The study suggests that better and more frequent screening and improved, affordable access to healthcare are not enough to close the gap on their own. While screening and accessible healthcare are crucial components of the puzzle, they must be accompanied by detailed and comprehensive research into tumour biologies that disproportionately affect African descendants. To improve the survival rates of Black cancer patients, there must be more robust and specific research done on the subject.
To facilitate this research, more willing participants are needed. Lack of participation has often been cited as a reason for the lack of data in this area. Unfortunately, people of African heritage simply aren’t enrolling in clinical trials at the same rate as their Caucasian counterparts.
A 2013 article in the Journal of Palliative Medicine cited possible “psychosocial and economic factors” to explain the absence of POC patients enrolled in clinical trials. After analysing the data, the researchers found that Caucasian participants overwhelmed the number of POC participants, but when demographic and socioeconomic factors were accounted for, race was no longer the most prominent predictor of enrolment. Instead, health insurance coverage and locations of recruitment sites had the most marked effect on clinical trial enrolments.
It’s clear that adverse cancer outcomes for Black populations are intrinsically tied to socioeconomic status, especially locations of residence and the ability to obtain sufficient medical insurance. Subsequently, it’s challenging to break the cycle: poverty leads to poor healthcare leads to poor health leads to poverty. Around and around it goes, making it tricky for medical practitioners, scientists, and data analysts to find a handhold on which to stake their research.
So what is the answer? In short, there is no single, simple answer. But we believe that bridging the statistical gap starts when we break down the barriers preventing access to healthcare. Race-adapted cancer screening programs and clinical trials to reduce disparities in the cancer burden may be an integral part of the equation.
Race-adapted cancer screening programs can help improve early detection rates while also informing patients about how race-specific genetics can affect health outcomes. Wide-ranging recruitment sites for clinical trial enrolment can offer unprecedented opportunities to medically underserved communities - especially those in impoverished and geographically isolated areas. But perhaps most importantly, there must be communication between medical professionals and the most vulnerable communities. Not only is this integral to data-gathering and needs assessment; it’s also critical to engage the trust and participation of the communities that require the most support.
Ultimately, the statistical gap between rates of cancer incidence and mortality between races is a long way from being closed. However, with what we know now, there is reason to believe that better genetic research is on the horizon. Now more than ever, we are aware of the role race plays in susceptibility to cancer, and, though we might not be able to solve the problem, being aware of it is an excellent first step.
If you are a member of a Black or other genetically susceptible population, unfortunately it means it's essential to advocate for yourself in medical situations. Non-white must currently be their own best advocates, but pressure has to increase on the healthcare industry to change it's ingrained racism and bias when caring for patients.