Problem 2: The remission times of 42 patients with acute leukemia were reported from a clinical trial undertaken to assess the ability of a drug called 6-mercaptopurine (6-MP) to maintain remission. Each patient was randomized to receive either 6-MP or placebo. The study was terminated after one year. Patients have different follow-up times because they were enrolled sequentially at different times.

(Times in weeks, Group1 = Treatment, Group2 = Placebo; Status: 0 = censored)

Data acute_leukemia;

input group $ wktime status @@;

datalines;

T 6 1 T 6 1 T 6 1 T 7 1 T 10 1 T 13 1 T 16 1 T 22 1 T 23 1 T 6 0 T 9 0 T 10 0 T 11 0 T 17 0

T 19 0 T 20 0 T 32 0 T 32 0 T 32 0 T 34 0 T 35 0

P 1 1 P 1 1 P 2 1 P 2 1 P 3 1 P 4 1 P 4 1 P 5 1 P 5 1 P 8 1 P 8 1 P 8 1 P 8 1 P 11 1 P 11 1

P 12 1 P 12 1 P 15 1 P 17 1 P 22 1 P 23 1

;

Proc Freq; run;

Questions:

1. What percent of patients had acute leukemia in the treatment vs. placebo group?
2. What is the K-M survivor curve in the treatment, placebo, and all, respectively? Show 95% confident intervals (CI) for the survival curves using Hall-Wellner simultaneous CI.
3. What does each estimated survivor curve mean?
4. What is the difference in median survival time between treatment and placebo group?
5. Show number of patients at risk on the plot.
6. What is the command to suppress the K-M table under Proc Lifetest?

Problem 3: The remission times of 42 patients with acute leukemia were reported from a clinical trial undertaken to assess the ability of a drug called 6-mercaptopurine (6-MP) to maintain remission. Each patient was randomized to receive either 6-MP or placebo. The study was terminated after one year. Patients have different follow-up times because they were enrolled sequentially at different times.

Data acute_leukemia;

input group $ wktime status @@;

datalines;

T 6 1 T 6 1 T 6 1 T 7 1 T 10 1 T 13 1 T 16 1 T 22 1 T 23 1 T 6 0 T 9 0 T 10 0 T 11 0 T 17 0

T 19 0 T 20 0 T 32 0 T 32 0 T 32 0 T 34 0 T 35 0

P 1 1 P 1 1 P 2 1 P 2 1 P 3 1 P 4 1 P 4 1 P 5 1 P 5 1 P 8 1 P 8 1 P 8 1 P 8 1 P 11 1 P 11 1

P 12 1 P 12 1 P 15 1 P 17 1 P 22 1 P 23 1

;

Proc Freq; run;

(Times in weeks, Group1 = Treatment, Group2 = Placebo; Status: 0 = censored)

Questions:

1. What is the SAS command to specify the life table method in Proc Lifetest?
2. What are estimated survivor curves in the treatment, placebo and all patients using the life table method?
3. What is the difference in median survival time between treatment and placebo group?