The rising disparities in breast cancer diagnoses and survival rates is a critical issue that lies at the intersection of health, race, age and gender.

A new study from the American Cancer Society shows that women younger than 50 and Asian-American Pacific Islander women of all ages are seeing an increase in breast cancer rates.
Another study from Mass General Brigham shows that Black women continue to face higher mortality rates despite having lower incidence overall.

Dr. Erica Warner, a Mass General Cancer Center epidemiologist and investigator, joined GBH’s All Things Considered host Arun Rath to discuss the factors contributing to these disparities and what can be done to address them. What follows is a lightly edited transcript.

Arun Rath: Let’s talk about age first. This just is universally troubling, obviously — the rise in cancer rates for women under 50. This also comes with a U.S. task force recommendation that regular mammograms should start at the age of 40 rather than 50. Do you have a sense at all of what is behind this rise?

Erica Warner: Yeah, it’s not totally clear. Honestly, I should point out that this is not just a phenomenon that we’re seeing in breast cancer. In fact, we’re seeing rises in incidences of cancer in young individuals across multiple cancer sites — I think, most notably, colorectal cancer has received a fair amount of attention recently.

A lot of us are working to try and understand what it is. You know, there are hypotheses around changes in our chemical exposures to differences in lifestyle. For example, breast cancer is a hormonally driven disease, so changes in reproductive patterns in women can drive changes in incidence of cancer.

There has been a trend towards later age at first birth and fewer births, which could contribute to some of the differences. But we might expect that to occur in both younger and older women, so that sort of differential increase in younger women, I think, couldn’t be completely explained by that.

Rath: How do you proceed from an epidemiologist standpoint in trying to understand something like this when there are so many factors to take in?

Warner: We start with things that are plausibly biologically connected to risk of cancer and things that we might hypothesize would be [that] people might be exposed to [risks] at younger ages.

In general, if you developed cancer younger, that means the exposures that increased your risk for cancer happened earlier in life. So that’s been a hot area of research — trying to understand childhood and early life and early adulthood exposures and how they relate to risk of cancer, and specifically, risk of breast cancer.

Rath: There’s also an increase in breast cancer among Asian American/Pacific Islander women of all ages. Is there any sense of why this particular population is at higher risk?

Warner: Yeah, I think it’s, again, another area in which we’re not totally clear, but there are some ideas. One is demographic changes. Asian/Pacific Islander and also Hispanic/Latino individuals have been among the youngest on average in the United States in terms of the distribution of age in that population.

That has been, in part, due to a sort of continuous immigration of younger individuals into the United States. We have seen, over time, more aging, so a shift in the demographics of those populations — still younger, on average, than the Black and white populations in the United States, but older than we’d seen in the past.

You know, age is one of the strongest predictors of cancer risk, so that might contribute in some ways. Again, it doesn’t explain this specific impact on younger Asian American and Pacific Islander women.

And then, I think there are some shifts that come with acculturation to the United States. Unfortunately, our Western diet — our higher prevalence of overweight and obesity — tends to become more common in populations that have immigrated to the United States over time. The more time they’ve been in the United States, the longer and more generations there are, so it may be a combination of some acculturation factors, changes in lifestyle and behavioral factors that have become more like the rest of the United States, aging.

You also cannot rule out that there may be other exposures that disproportionately affect Asian/Pacific Islander individuals in the United States in terms of their environment — both their physical and social environments.

Rath: This finding from the Mass General study that Black women have a 38% higher mortality rate from breast cancer than white women, despite a slightly lower overall incidence — is that as simple as disparities in care? What are the factors that are leading to that?

Warner: Yeah, we think there are several things going. In my study — the Mass General study you mentioned — we looked across different types of breast cancer. So often, we talk about breast cancer [as though] it’s one thing, but there actually are multiple subtypes that are different in terms of how they’re treated and how deadly they are.

There had been a thought that the higher mortality observed among Black women was really being driven by the fact that Black women are more likely to get a more deadly form of breast cancer called triple-negative breast cancer. I had done some previous work that showed that this was not the case.

In this study, we pulled together data on over 200,000 women who had been diagnosed with breast cancer and found that the disparities were pretty similar across all of the different subtypes that we examined, including in the triple-negative tumors. Why that’s the case is for sure multifactorial from differences in care.

Interestingly, when we look at mammography, which is often our first thought and first-line approach to breast cancer — early detection and reducing mortality — we’ll see that, for the most part, mammography rates are pretty similar in Black and white women and, in fact, in some cases appear higher in Black women than in white women. [The findings] suggest that we have this opportunity for early detection and lower mortality that’s not being fully realized.

There’s been some evidence that Black women have longer delays in care, so that transition from having a mammogram that shows a potential abnormality to being diagnosed with cancer and getting into treatment tends to be longer for Black women than white women.

Some of that has to do with, you know, the social determinants of health and barriers that Black women might experience to being able to get timely follow-up care. Some of that speaks to our complicated healthcare system that may be challenging to navigate and creates additional barriers, and some may be about healthcare systems needing to do better in identifying where these gaps exist and implementing focus programs to address them.

Rath: Well, it sounds like there could be cause for optimism for the possibility of turning the tide on this.

Warner: I’m always optimistic. You know, I think one thing that we should point out is that breast cancer mortality has been declining for 30 years now. There are disparities, and they have been persistent, but overall, we are moving in the right direction in terms of our ability to find breast cancer early, treat it, and have patients live long and high-quality lives after. The fact that we are able to do that overall tells me that we have the ability to do that for Black women.