Real-World Differences in Characteristics and Survival of Relapsed AML Patients with and without Transplant

Background: Some AML patients, particularly those relapsing rapidly, may not get a chance to receive a potentially curative stem cell transplant (SCT) due to early death, among other reasons. This study compares the differences in characteristics and survival of relapsed AML patients with and without SCT, as observed in a real-world setting.

Methods: Relapsed AML patients aged 66-75 years were identified from the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database by medical claims associated with ICD-9 code 205.02 (2009-2014). Patients were followed from relapse to the earliest of death, SCT, or end of follow-up. Baseline characteristics were compared between relapsed AML patients with and without SCT. The SCT rates were estimated after adjusting for the competing risk of death. The Fine and Gray method was used to identify predictors of receiving SCT and were reported in terms of sub-distribution hazard ratios (SHR) and 95% confidence intervals (CI). Kaplan-Meier estimates (reported in terms of median and 6-, 12-, and 24-months survival rates, tested with a log Rank test statistic) and a Cox proportional hazards model adjusting for age, sex, race, Census region, marital status, urban location, Charlson comorbidity index (CCI), and diagnosis year (reported in terms of hazard ratios (HR) and 95% CI) was used to assess the difference in survival between patients with and without SCT.

Results: Of the 474 relapsed AML patients (median age, 70 years, median follow up, 4.4 months, male, 55%) included in the study, 8% received SCT, 80% died without having SCT and 12% were administratively censored. Patients were less likely to receive SCT if they were 71-75 years old (SHR 0.28, 95% CI (0.19 to 0.41; P <.001) and had higher comorbidity with CCI >3 (SHR 0.16, 95% CI (0.06 to 0.44; P <.001). The median overall survival was 16.1 months for patients with SCT vs. 4.1 months for those without SCT (log rank P <.001; adjusted HR 0.52, 95% CI (047 - 0.57; P <.001)). The 6-, 12-, and 24-month overall survival for all relapsed AML patients was 42%, 26%, and 12%, respectively. For patients with SCT, the 6-, 12-, and 24-month overall survival was 84%, 59%, and 43%, respectively. For patients without SCT, the 6-, 12-, and 24-month overall survival was 39%, 23%, and 12%, respectively.

Conclusions: Relapsed AML patients who received SCT experienced significantly longer survival compared to those who did not receive SCT in this elderly study population. However, only 8% of all relapsed AML patients received SCT. Therapies that bridge more patients to SCT are expected to improve overall survival in this high unmet need population.