A first Kaplan–Meier curve: the 1963 leukemia trial of 6-MP

In 1963 Freireich and colleagues published an early randomized, placebo-controlled trial of a chemotherapy drug: 42 patients under 20 with acute leukemia in remission got either 6-mercaptopurine (6-MP) or a placebo, and were followed until they relapsed or the trial was stopped, which happened early, once 6-MP was clearly ahead. These are the weeks each patient stayed in remission. A + means the patient was still in remission when the trial was stopped.

6-MP: 6, 6, 6, 6+, 7, 9+, 10, 10+, 11+, 13, 16, 17+, 19+, 20+, 22, 23, 25+, 32+, 32+, 34+, 35+
Placebo: 1, 1, 2, 2, 3, 4, 4, 5, 5, 8, 8, 8, 8, 11, 11, 12, 12, 15, 17, 22, 23

Draw the Kaplan–Meier curve of each arm, with tick marks for the + patients and the numbers at risk under the plot. Give the median remission time in each arm and compare the arms with a log-rank test. Then show me what happens to the 6-MP median if I count every + as a relapse, or if I leave those patients out. Explain each step as you would to a medical student.