Survival of patients with chronic myelocytic leukemia: comparisons of estimates from clinical trial settings and population-based cancer registries

Abstract

Introduction: The survival of patients with chronic myelocytic leukemia (CML) has improved during the past decades. However, there have been discrepancies between results reported from clinical trials and population-based studies. We aimed to elucidate the extent of these discrepancies.

Methods: We examined the 5-year survival rate of patients in clinical trials of CML treatment and compared these results with the survival of patients in the general population using the Surveillance, Epidemiology, and End Results (SEER) database, correcting for differences in the age structure of the patient populations.

Results: Twenty-nine trials were identified for data extraction. The survival rate calculated from SEER data was lower than the survival rate in clinical trials in the corresponding period, with differences of 2.1%-50.7%. Age-adapted survival was similar for four trials, but differences up to 35.8% were seen in most. Limitations of the study include the lack of information on chemotherapy in the SEER database and possible heterogeneity of cases.

Discussion: The survival rate in clinical trials of CML treatment is higher than the survival rate of all patients with CML. We speculate that the difference may be a result of access to better medications, selection of healthier patients for trials, and the time necessary for adoption of new treatments. This finding underscores the need for population-based studies to give a more realistic idea of survival for patients with a given malignancy in the general population.

Figure 1.

Diagram of clinical trials identified, excluded, and included in this study. Abbreviation: CML, chronic myelocytic leukemia.

Figure 2.

The 5-year survival rate of patients participating in clinical trials (squares) and age-adapted survival for patients in the Surveillance, Epidemiology, and End Results database diagnosed in the same time period as patients in the related clinical trial (triangles) are shown. In trials in which there was a difference in survival between arms of the trial, the higher survival rate is given as a thicker, red square; the lower survival rate is shown as a lighter, orange square. Reference numbers for the relevant trial are given next to the red squares.

Figure 3.

The 5-year survival rate of patients participating in clinical trials (squares) and the age-adapted survival rate for patients in the Surveillance, Epidemiology, and End Results database for the 5 years prior to and including the year of publication of the relevant trial (blue triangles) and the 5 years following publication of the relevant trial (green triangles) are shown. If survival differed in different arms of the clinical trial, the arm with the best survival was used. Reference numbers for the relevant trials are included next to squares representing trials.