Changes in burden of ALL as determined by MFC of BMAs collected before and after each cycle of pembrolizumab. To better discriminate changes at the lower range of detection, blast percentage is plotted with a base-8 logarithmic scale. This graph depicts outcomes for the 11 patients who had disease detectable by MFC during study treatment. The course for the 1 patient who experienced a complete MRD response is depicted as a hashed line.