Socioeconomic Status Most Important Factor in NHL Survival

Roxanne Nelson

October 23, 2008

October 23, 2008 — Low socioeconomic status is significantly associated with a higher risk for mortality among elderly patients with non-Hodgkin's lymphoma (NHL), whereas the use of chemotherapy is associated with prolonged survival. Researchers also found that there were no differences in all-cause and lymphoma-specific mortality between black and white patients, after they controlled for confounders that included treatment, patient demographics, socioeconomic status, and tumor factors.

The 3-year survival rate for stage 1 and 2 disease was 55.8% in white patients, 52.6% in black patients, and 44.7% in others. For all tumor stages, 3-year survival was 45.3% in white patients, 37.7% in black patients, and 39.5% in other ethnicities. The researchers observed that increased survival rates were associated with a higher socioeconomic status. Among patients living in the highest socioeconomic quartile, the 3-year observed survival rate was 59.9%, compared with 48.8% for patients in the lowest quartile.

"Our key finding was that if patients with NHL receive standard therapy in a timely manner and comply with therapy, the survival rates should be similar across the different ethnic groups," Xianglin Du, MD, PhD, the study's senior author and associate professor at the University of Texas School of Public Health, in Houston, told Medscape Oncology.

The study was published online October 20 in Cancer.

"Very few studies have looked at disparities among patients with NHL," said Dr. Du. "Disparities have been seen for other tumor types, in terms of survival, access to care, and the type of treatment received."

Previous studies have reported survival disparities between black and white cancer patients, but these differences may disappear when the data are adjusted for confounding factors, he added.

Treatment for NHL has improved during the past few decades. In particular, combination chemotherapy has improved outcomes and increased survival rates. Although several studies have shown that there are ethnic disparities in the treatment received, none have thus far addressed disparities in survival or the underlying factors leading to disparities.

Black Patients Less Likely to Receive Treatment, More Likely to Have Poorer Socioeconomic Status

Dr. Du and colleagues used Surveillance, Epidemiology, and End Results (SEER)–Medicare linked data to identify 13,321 patients, aged 65 years and older, who were diagnosed with NHL from 1992 to 1999. Of these patients, 11,868 were white, 533 were black, and the remaining 920 patients were of other ethnicities. The researchers used a time-to-event Cox regression model to assess the relative risk for all-cause and disease-specific mortality.

They found that 72.2% of black patients lived in the lowest socioeconomic quartile, compared with 21.8% of white patients. Black patients with NHL were also less like to receive chemotherapy (43.2%) than white patients (52.4%). This was true for black patients with both early- and late-stage tumors. Among patients who received chemotherapy, the median survival was 32.5 months, compared with 11.9 months for those who didn't receive it. Black patients were also less likely to receive radiation therapy than white patients (18.2% vs. 24.3%).

Men had significantly higher mortality than women, and unmarried patients had a significantly higher mortality than married ones. The hazard ratio of all-cause and disease-specific mortality increased with age, advanced tumor stage, higher comorbidity scores, and lower socioeconomic status.

Adjustment for Confounders Important

A much larger proportion of black patients lived in the poorest areas, so controlling for socioeconomic factors was important when examining racial disparities in survival, the researchers note.

"If we do not control for factors like socioeconomic status or treatment, then we will find a racial disparity," Dr. Du said. "The data could then be misleading, showing a racial disparity when there may not really be one."

Dr. Du pointed out that, in this study, all the patients were Medicare recipients, so they all had coverage. "So there are other factors involved that we have to look at among patients with poorer socioeconomic status," he said. "They may have to travel a distance to get care or there may be other compliance issues. They may also have out-of-pocket expenses, even with coverage."

"I suspect that, similar to other cancers, barriers to treatment include cost, lack of knowledge about cancer, and/or cultural beliefs," said Carmel Bitondo Dyer, MD, Roy M. and Phyllis Gough Huffington Chair in Gerontology at the University of Texas Medical School, in Houston, in a statement. "Although data on functional status could have provided further insight into the findings, this study suggests that a need for increased access to care and patient education still exists."

Dr. Du is supported in part by a grant from the Agency for Healthcare Research and Quality.

Cancer. Published online October 20, 2008.

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