Racial and Socioeconomic Disparities in Patients with Waldenström’s Macroglobulinemia. a SEER Database Analysis

Background:

Waldenström’s Macroglobulinemia (WM) is defined as a lymphoplasmacytic lymphoma associated with a monoclonal IgM protein. Patients with WM frequently have a smoldering course and do not always require immediate treatment. The median survival of WM varies between 4-8 years, and it mostly depends on the age at diagnosis. The impact of other factors, such as race/ethnicity and socioeconomic status (SES), on WM outcomes is less clear. Therefore, we designed a study to assess the impact of race/ethnicity and socioeconomic status on WM treatment and survival.

Methods:

This is a retrospective cohort study using the Surveillance, Epidemiology, and End Results (SEER) database. We included patients diagnosed with WM between 2006-2020. We collected demographic variables such as age, race/ethnicity, and socioeconomic status (SES) based on the Yost index. The Yost index uses data from the US Census to calculate SES. Then, SES was divided into 5 quintiles, with a Yost of 5 corresponding to the highest SES and a Yost of 1 to the lowest. We collected treatment-related variables, such as chemotherapy and radiation use, and we collected survival status, survival (in months), and cause of death. We used logistic regression analysis to assess factors associated with chemotherapy use. Additionally, we used Cox regression models to analyze the factors associated with cancer-specific survival (CSS) and overall survival (OS).

Results

We found 8,530 patients with a diagnosis of WM. There were 3,384 females and 5,146 males. There were 7,199 non-Hispanic White (NHW) patients, 379 non-Hispanic Black (NHB) patients, 542 Hispanics, and 348 in other racial groups. There were 62 patients with unknown race/ethnicity. In terms of SES, we found that 3,151 of the patients were in the highest quintile (Yost index of 5). There were 1967 whose Yost index was 4, 1415 with a Yost index of 3, 1052 with a Yost index of 2, 749 with a Yost index of 1 (the lowest SES), and 196 with an unknown Yost index.

The median OS for the whole population was 115 months. Further survival analysis showed that patients in the highest SES quintile and second-highest SES were linked to significantly improved overall survival when compared to patients in the lowest SES quintile (aHR=0.65, 95% CI 0.57 – 0.74) and (aHR=0.79, 95% CI 0.69 – 0.90), respectively. In an analysis looking only into CSS, we found that only patients in the highest SES quintile had improved CSS as compared to patients in the lowest SES (HR=0.69, 95% CI 0.57 – 0.83). No significant association between race/ethnicity and OS or CSS was found in our cohort.

In regard to factors associated with chemotherapy use, we found that compared to NHW; NHB, and Hispanics had higher odds of receiving chemotherapy (OR=1.25, 95%CI 1.01 – 1.53) and (OR=1.69, 95%CI 1.42 – 2.01) respectively. Patients aged ≥65 years had lower odds of receiving chemotherapy compared to younger patients (OR=0.71, 95%CI 0.65 – 0.79). , Patients with the highest and second-highest SES quintile had lower odds of receiving chemotherapy compared to patients in the lowest quintile (OR=0.68, 95%CI 0.58 – 0.80) and (OR=0.76, 95%CI 0.64 – 0.90), respectively.

Conclusions

We found that Hispanics and NHB patients with WM, as well as patients living in the lowest SES, are more likely to be treated with chemotherapy. We also note that these patients had significant associations with worse CSS and OS. It is unclear whether biological differences in the course of the disease or other factors might explain these findings. Unfortunately, our study was limited by a lack of detailed information about the treatment provided, dosage, and compliance. Future studies should consider integrating SES and look at how this interacts with WM outcomes.