Halving Time of BCR-ABL1 in Chronic Myeloid Leukemia: Is It Better Than Day-90 Value—A Multicenter Study From South India

The 90-day BCR-ABL1 (breakpoint cluster region-Abelson 1) level has been one of the accepted milestones for predicting the molecular response in patients with chronic myeloid leukemia (CML). The rate of decline in BCR-ABL1 has been considered a better predictor of the response but has not been uniformly accepted. A paucity of evidence is available to predict the accuracy of the rate of decline in the Indian context. Therefore, we tested the accuracy of the rate of decline of BCR-ABL1 in predicting the molecular response compared with the single 90-day values in a retrospective cohort study of selected cancer centers in south India. Patients with chronic-phase CML diagnosed from January 2013 to December 2018, the serial BCR-ABL1 levels were estimated at 0, 45, and 90 days, 6 months, and 1 year. Data on patient demographics, risk stratification assessed using the Sokal and EUTOS (European Treatment and Outcome Study) scores were extracted using a mobile-based data capture tool from the medical records of the enrolled patients. The halving time, determined by log reduction, was compared with the 90-day BCR-ABL1 values using the receiver operating characteristic curve for the major and complete molecular response at 6 months and 1 year as standards. Accuracy was determined from the area under the curve. The cutoff for the halving time was chosen to balance the sensitivity and specificity. The rate of decline had more predictive accuracy compared with the 90-day BCR-ABL1 values (area under the curve for rate of decline, 0.83; 90-day, 0.80). A halving time of < 20 days identified 95% of the patients who had achieved major molecular response at 12 months compared with 80% using the single 90-day BCR-ABL1 response. The halving time of BCR-ABL1 appears promising as a predictor of the outcomes for patients with CML. We found that the rate of decline of BCR-ABL1 (breakpoint cluster region-Abelson 1) is a better predictor of the molecular response in patients with chronic myeloid leukemia than the single 90-day value. The present retrospective cohort study of 90 patients is the first study in the Indian context comparing the rate of decline of BCR-ABLl against the single 90-day value.