Patients with AML Who Achieve Long Term Complete Remission Do Not Have a Normal Life Expectancy When Compared to the General Population. Analysis of 3,012 Patients Enrolled on 9 Consecutive ECOG-ACRIN Trials

Introduction

Several studies reported that AML patients who remain in long-term remission after allogeneic transplant (allo-HCT) or autologous transplant (auto-HCT) have a shorter life expectancy, compared to the general population. However, little is known about the life expectancy of adult long-term survivors of AML who were treated with chemotherapy without HCT and, there have been no comparisons with survival among the general population. The current study reports on the life expectancy of AML patients who survived 3 years in complete remission (CR) after treatment without HCT, and compared this to the gender- and age-matched normal population. At 3 years in CR, the incidence of recurrence is exceedingly low (3%; Watts JM, Leuk Res 2014) minimizing the impact of relapse on the long-term survival.

Methods

Between 1984 and 2008, 3,012 patients, aged 15 years and older, with untreated AML entered 9 consecutive, phase II and III, ECOG-ACRIN trials (E3483, PC486, E3489, E1490, E3993, E4995, E3997, E3999, E1900). Patients in CR and relapse-free at 3 years are included in the analysis . Minimal cytogenetic information was available in the early protocols (E1490, E3483, PC486). A Kaplan-Meier plot was generated for the three groups, allo, auto and no HCT, censoring for patients alive at last contact. Univariate and multivariate cox proportional hazard regression models were generated, considering death as an event.

For comparison of long-term outcomes, patients were grouped together by age and matched to a normative population mortality rate. Subjects were also grouped by gender and treatment allowing for separate analysis of these groups with the no HCT group as the main group of interest. The normative population comparator of expected deaths was derived using mortality rates from United State CDC life table data. The median year was derived by calculating the person-years for each calendar year that patients were followed. To calculate the expected deaths for each age group, person-years was calculated by tabulating the years lived in each age group for all subjects. Each year of follow-up for AML patient was counted as one person year, and the tabulated bin corresponded with their age at the time. Person-years was then multiplied by the matching mortality rate. Chi-square statistics were derived using expected and observed deaths and then summed for each gender and treatment.

The final comparison was of mortality rates since diagnosis in the 3-year alive and relapse-free AML patient population vs the normative population. To produce plots of mortality from diagnosis, person-years was tabulated for every year since diagnosis by treatment. The person-years were tabulated into 2-year bins. The US life tables from the CDC were used to generate a population mortality rate from diagnosis.

Results

A total of 503 adult AML patients in 3 year CR with a mean age of 42.9 years (15-79) were identified; 78 underwent allo, 110 auto and 315 did not undergo transplantation. The patients in the groups differed in age (p<.001) and cytogenetics (p=.01). The multivariate model showed equivalent hazards of death to the 3 groups.

Observed deaths and person-years were given by age group, gender, and treatment group and each were matched to a mortality rate from the United State CDC life table data that matched the median year of each treatment group. A chi square test for each group compared the derived expected to observed deaths. In every treatment group, patients had a shorter survival compared to their age- and gender- matched general population (p-value of 0.004 for the auto-HCT and <0.001 for both allo-HSCT and no transplant groups). Table 1, selected only for the no HCT group, demonstrates the mortality rates by age and gender.

Figure 1 indicates that AML patients who have survived relapse-free for at least 3 years continue to have higher mortality rates compared to the normative population for up to 14 years. This finding is not altered even if the very small number of patients who die from late relapse (>3 years from diagnosis) are removed from the analysis (data not shown)

Conclusions

Patients with AML who remain in CR at 3 years, do not have a normal life expectancy, even if they do not undergo HCT. The shorter life expectancy observed following an HCT may, at least in part, be related to the prior intensive therapy or other predisposing factors (e.g. CHIP) of the leukemia, rather than the transplant procedure itself.

Figure 1

View largeDownload slide

Figure 1

View largeDownload slide

Close modal