How might poverty impact childhood cancer?
That's the question pediatric oncologist Dr. Kira Bona, a researcher at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center, set out to answer.
Her findings: Even with the same medical treatment, children with leukemia living in high-poverty areas were more likely to suffer an early relapse compared to their wealthier counterparts. The research, published this week in the journal Pediatric Blood & Cancer, is important, Bona says, because earlier relapses of this particular cancer — the most common pediatric cancer, called acute lymphoblastic leukemia — are harder to treat successfully.
We already know poverty is bad for your overall health. Among children, Bona says, poor kids tend to have worse underlying health, and higher rates of hospitalization, infectious disease and risk of death compared to more affluent children.
When it comes to cancer treatment though, for the 15,000 American children diagnosed with cancer every year, most are enrolled in clinical trials and treated using similar protocols, Bona said. Still, she said: "Historically, in pediatric oncology, we haven't included social determinants of health, like poverty and education, as part of the data we collect in clinical trials; we've had an almost exclusive focus on biology."
But since about 20 percent of kids in the U.S. live in poverty, Bona says, that non-biological data is also critical.
I spoke with Bona more about the latest research. Here, edited, is some of our discussion:
What's the bottom-line finding here?
We looked at 10 years of data; 575 kids ages 1-18 who were treated at major academic medical centers around the U.S, with uniform therapy as part of the same two consecutive clinical trials. We went back and analyzed disease outcome data — overall survival and relapse data — with the question: Does poverty impact these disease outcomes? We used a proxy for poverty, zip codes linked to U.S. census data, to determine high-poverty or low-poverty areas.
We did not see a significant difference in overall survival between high-poverty and low-poverty groups. Additionally, we did not find a significant difference in relapse rates. But we did see a significant difference in the timing of relapse. And the timing of relapse is important, because if you experience an early relapse it's harder for us to ultimately cure you.
In our study, among kids who relapsed, 92 percent of relapses from high poverty areas were early relapse (defined as relapsing less than 36 months after achieving remission) compared to 48 percent in low poverty areas.
[Overall survival for kids with acute lymphoblastic leukemia is around 90 percent. In the new study among children from high-poverty areas, 85 percent survived five years or longer, compared with 92 percent of other children but this difference was not statistically significant after controlling for other risk factors.]
What does this difference in relapse timing mean?
Prior studies have demonstrated that poor children with leukemia have lower overall survival but those studies have been done at a population level....and didn't have data from a uniform care setting.
Our data demonstrate that there is in fact a disease outcome disparity due to poverty even when we treat children with the best available care. The reason that's important is it suggests an opportunity to improve current outcomes if we include poverty and the social determinants of health when we treat and study cancer.
What do you think is going on here? Why are poor children faring worse?
We have two hypotheses:
One is that poor children in the U.S. have worse underlying health. If you present with leukemia and have worse underlying health, you might experience more complications of the chemotherapy we give you, and we know complications of therapy that land you in the hospital or ICU can cause delayed chemotherapy administration or reduced doses of chemotherapy. It's possible that could explain the earlier relapse. it's something we have to study further.
There's also a body of literature that has shown poor families across many diseases have a harder time with adherence to oral medications, and the reasons for that are many, whether it's because you can't afford the co-pay for a prescription, or your mom is working three jobs and can't give you medication at night. If poor children with leukemia had poor adherence to their chemotherapy that could worsen outcomes. (Acute lymphoblastic leukemia therapy lasts for two years — the first month and a half is in the hospital, the rest is outpatient chemotherapy, including a combination of clinic visits and oral chemotherapy administered at home by parents.)
So what's the next step in research?
This is something we are going to be looking at on our next ALL trial, a prospective trial, opening in the fall.
We will be measuring income at the time of diagnosis; and also what's called 'material hardship,' that is food, housing, energy insecurity. In an earlier study we found that one-third of families of children with cancer suffered from material hardship six months after treatment began...
But these are remediable domains of poverty; these are concrete resource needs that can be fixed with interventions.
I just want to emphasize that from my standpoint the take-away of this is that poverty-related outcome disparities exist in pediatric ALL despite highly standardized care, and this suggests a significant opportunity for us as a field to systematically incorporate poverty (and other social determinants of health) into every subsequent trial we run for kids with cancer. If poverty, in addition to biology, is impacting outcomes we have an opportunity to improve outcomes by designing targeted adaptations in care to address it.