City of Hope researchers find longer overall survival rates among nonsmall cell lung cancer patients (NSCLC) who are immigrants. Could this be another instance of the healthy immigrant paradox?
Immigrants may face barriers to receiving healthcare in the U.S. But in a surprising finding, a City of Hope National Medical Center research team found that nonsmall cell lung cancer (NSCLC) patients born outside the U.S. have better overall survival rates those born inside the country.
Using data from the California Cancer Registry on more than 68,000 NSCL patients. Brittney Chau and her colleagues found that Asian borns outside the U.S. had the highest median overall survival (15 months) followed by foreign-born whites (14 months), Asians born inside the U.S. (13 months), and Blacks born outside the U.S. (13 months).
The median overall survival for whites born in the U.S. was 11 months, or three months shorter than whites born outside the country. Similarly, the median overall survival rate among Blacks born in the U.S. was three months shorter than Blacks born outside the country (13 months vs. 10 months).
The findings, reported in March in Cancer Medicine, also identified differences in overall survival when people are grouped by race and ethnicity. After statistical adjustments were made for age, gender, year of diagnosis, and tumor histology, Blacks born in the U.S. had a 6% higher risk of death when compared with whites born in the U.S. and other groups had better overall survival rates than whites, except for Hispanics, for which the rate was the same.
"Race continues to play a major factor in survival outcomes for NSCLC in California and remains an important disparity that ought to be addressed," wrote Chau and her colleagues.
NSCLC is the most common type of lung cancer, accounting for more than 80% of all lung cancer diagnoses.
A retrospective study like this one can't really answer questions about the reasons for differences. Researchers can only posit possible explanations — or do further statistical analyses that tease out associations that provide hints. In this study, Chau and her colleagues did a multivariate analysis that found that the US-born NSCLC patients tend to be older, more often women, more likely to have private insurance than NSCLC patients and more likely to have a higher socioeconomic status than those born outside the country. Of course, private insurance and socioeconomic status would seem to be factors leading to longer overall survival rates not shorter ones
But ,any studies have found a healthy immigrant effect — it is sometimes referred to as a paradox — that shows immigrants tend to be healthier than their counterparts. Explanations vary but some point to healthier diets and greater physical activity among immigrants. But researchers have found that the health differences tend to fade as people age and even reverse.
Chau and her co-author mention prior findings that are consistent with theirs, including a 2013 study of one of Hispanics with NSCLC that showed a lower rate of disease-specific mortality among those who were born outside the U.S. The authors of that study discussed dense social networks as a possible explanation — that people born outside the country may benefit from social support that results in better care in myriad ways.
The City of Hope researchers also found that foreign-born NSCLC patients were less likely to have been treated with surgery and radiation than those born in the country. People born outside the country tend to treatment for NSCLC when it is at a more advanced stage, but the researchers said their analysis accounted for that, so it doesn't seem like that is the full story. They float the possibility that the fatalistic attitudes and mistrust of the healthcare system could be factors in people avoiding treatment.