Fifty-three patients with medullary thyroid cancer (MTC) were the subjects of a study by Dottorini et al. (A-2), who evaluated the impact of different clinical and pathological factors and the type of treatment on their survival. Thirty-two of the patients were females, and the mean age of all patients was 46.11 years with a standard deviation of 14.04 (range 18–35 years). The following table shows the status of each patient at various periods of time following surgery. Calculate the survival function using the Kaplan–meier procedure and plot the survival curve.

Subject Timea (Years) Statusb Subject Timea (Years) Statusb 1 0 doc 28 6 alive 2 1 mtc 29 6 alive 3 1 mtc 30 6 alive 4 1 mtc 31 6 alive 5 1 mtc 32 7 mtc 6 1 mtc 33 8 alive 7 1 mtc 34 8 alive 8 1 mtc 35 8 alive 9 1 alive 36 8 alive 10 2 mtc 37 8 alive 11 2 mtc 38 9 alive 12 2 mtc 39 10 alive 13 2 alive 40 11 mtc 14 2 alive 41 11 doc 15 3 mtc 42 12 mtc 16 3 mtc 43 12 doc 17 3 alive 44 13 mtc 18 4 mtc 45 14 alive 19 4 alive 46 15 alive 20 4 alive 47 16 mtc 21 4 alive 48 16 alive 22 5 alive 49 16 alive 23 5 alive 50 16 alive 24 5 alive 51 17 doc 25 5 alive 52 18 mtc 26 6 alive 53 19 alive 27 6 alive a Time is number of years after surgery.
b doc ¼ dead of other causes; mtc ¼ dead of medullary thyroid cancer.
source: Data provided courtesy of Dr. Massimo E. Dottorini.