Narrowing of the Racial Disparities Gap in Survival of Patients with Mycosis Fungoides: A Longitudinal Analysis of the SEER Database (1988 to 2011)

Introduction: Mycosis Fungoides (MF) is the most common subtype of cutaneous T-cell lymphomas. Prior Studies have identified Black race as a risk factor for earlier age at diagnosis, more advanced stages at time of diagnosis and poor prognosis in patients with MF. Data examining differences in racial disparities outcomes over time are limited.

Objective: This retrospective analysis aims to examine if the racial disparities in survival outcomes of MF patients have improved over time.

Subjects and Methods: Using the United States Surveillance, Epidemiology and End Results (SEER) 1988-2011 public use database, we examined survival patterns for patients with MF (with the code of 9700) between 1988 and 2011. Cases were divided into three cohorts based on the year of diagnosis; "1988 - 1995", "1996 - 2003", and "2004 - 2011". Univariable and multivariable analysis were conducted to assess for factors significantly associated with the overall survival. The nonparametric estimates of the survival distribution function, Kaplan and Meier survival curves, and Cox proportional hazards model were used to investigate the factors affecting the survival time.

Results: From 1988 to 2011, a total of 2896 cases of MF were identified with a median follow-up of 60 months. The difference in the survival time between the years of diagnosis 1988-1995 and 2004-2011 is significant (p-value=0.05). The parameter estimate of the Cox proportional hazards model for the "1988-1995" and the "2004-2011" period as a reference is also significant (p-value = 0.024) and the hazard ratio (HR) is 1.407, which means that patients diagnosed in 1988-1995 were 1.4 times likely to die from the disease compared to the patients diagnosed in 2004-2011 (i.e. patients in 1988-1995 were more likely to not survive than in 2004-2011) (Table 1 and 2). There is no significant difference in the survival of the patients between "1996-2003" and "2004-2011" (p-value 0.998), Cox model estimate is not significant (p-value = 0.178), and the HR is 0.94 (Table 1 and 2). For the time period 1988-1995, the survival of Black patients was inferior to White (p= 0.0339), Asians (p=0.001), and other races (p=0.0011); Figure 2 and Table 3. For the time period 1996-2003, there was no difference in survival across races (p-value=0.7599); Figure 3 and Table 3. For the time period of 2004-2011, survival of Black patients was similar to White (p-value=1) but again inferior to Asian (p-value=0.05) and other races (p-value=0.09); Figure 4 and Table 3. Across the entire time period of 1998-2011, the survival of Black patients was inferior to White (Chi-square=6.59 and p-value=0.0084); Figure 5. The survival gap between Black and White patients seems to be obliterated in subsequent; "1996 - 2003" and "2004 - 2011" vs 1988-1995 (Figures 3 and 4) due to improvements in survival of Black patients over time (Figure 6) while the survival of White patients remained rather steady over time (Figure 7).

Conclusions: Our study demonstrated that Black race was significantly correlated with poorer survival in patients with MF. The etiology of this poorer prognosis can be related to access to medical care, socioeconomic disparities, or possibly difference in disease biology and immune response. Despite the persistent pattern of lower survival across all time periods, the gap in survival between White and Black races seems to be narrowing overtime.

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