Real Word Autologous Transplant Utilization and Outcomes By Race and Ethnicity

Introduction:

Autologous stem cell transplant (ASCT) is considered standard of care in medically-fit patients with multiple myeloma (MM), with a progression free survival (PFS) benefit across all cytogenetic risk groups but particularly notable in the high-risk population (PFS of 55.5 month versus 17.1 months in the DETERMINATION trial).

At our academic medical center, the stem cell transplantation and cellular therapy team serves a diverse population, with 22.4% of our outpatient cancer patients identifying as Hispanic. Hispanic patients are more likely to be diagnosed with MM at a younger age and have kidney dysfunction; but unfortunately face socioeconomic or geographic barriers preventing access to equitable care including transplant. We conducted a single-center retrospective study to evaluate ASCT utilization and outcomes with a special focus on any differences amongst Hispanic versus non-Hispanic patients.

Methods:

We retrospectively reviewed 344 electronic medical records of patients with newly diagnosed MM between 2016-2022 who received treatment at our institution. Variables reviewed include age, demographics, zip code, cytogenetic risk, transplant status, reasons for not undergoing transplant, time to next therapy, and survival. Multiple logistic regression was conducted to evaluate predictors between transplant (TP) and non-transplant (non-TP) status. Survival analyses for PFS were based on Kaplan-Meier (KM) and Cox proportional hazards methods.

Results:

A total of 334 patients were included in this analysis, including 212 TP and 112 non-TP. Compared to non-TP patients, the TP patients were younger (median 63 vs 67 yr, p<0.001) and there was a trend towards high-risk cytogenetic abnormalities (HRCA, 42% vs 36%, p=0.25). There was no statistically significant difference in the proportion of Hispanic patients in each group (26% vs 25%, p=0.71). In logistic regression analysis, age predicted likelihood of TP (p<0.001), whereas race and ethnicity did not (p=0.71 and 0.63, respectively). Median time from diagnosis to transplant was 6.31 months, and did not significantly differ by ethnicity (p=0.9) or race (p=0.06).

Across both TP and non-TP patients, Hispanic patients were diagnosed at a younger age compared to non-Hispanics (median: 60 vs 65 yr, p<0.001) and were more likely to live farther from our hospital (mean log(distance [miles]) 3.3 vs 2.86 in TP, p=0.034; 3.39 vs 2.78 in non-TP, p=0.0148). However, there was no significant difference in HRCA (33% vs. 42%, p=0.15) or plasma cell burden on diagnostic bone marrow biopsy (50% vs 60%, p=0.19) between Hispanics and non-Hispanics.

At a median follow-up of 51.8 months, PFS was 77.2 mos in TP population (73.5 mos in Hispanics, 77.2 mos in non-Hispanics, p=0.8). Significant risk factors for PFS on multivariate Cox models included Hispanic (HR 0.18; 95%CI, 0.04–0.91; p=0.038), HRCA (HR 2.24; 95%CI, 1.38–3.64; p=0.001), and interaction between Hispanic and log(distance) (HR 1.71; 1.09–2.68; p= 0.019).

In non-TP, at a median follow-up of 38.8 mos, PFS was 42.4 mos (47.8 mos in Hispanics, 42.4 mos in non-Hispanics, p=0.9). Significant risk factor for PFS on multivariate Cox models was only HRCA (HR 2.04; 95% CI, 1.07–3.88; p=0.03). Reasons for not undergoing ASCT were grouped into clusters (from most to least common): age, medical conditions and treatments, compliance and patient preferences, caregiver and social support, insurance and finances, mortality, procedural issues, and other. No significant differences in cluster frequency were noted amongst ethnicities (p=0.29) and races (p=0.97).

Conclusion:

We demonstrate that our MM patient population mirrors that of historically published data, with Hispanic patients being younger at diagnosis. We demonstrate equitable transplant utilization and time to transplant between Hispanics and non-Hispanics at our institution. In fact, we found longer PFS in transplanted patients who were Hispanic than non-Hispanic, highlighting that it is especially important that this population continues to have equal access to therapy. However, in our TP, Hispanic ethnicity together with distance from the treatment center has a negative impact on PFS. For patients who live further from our academic institution, there is a greater risk of progression for Hispanic patients compared to non-Hispanics, suggesting that this is an area where care delivery can be optimized for our Hispanic patients.