This interesting example is from a clinical trial conducted by the Veterans Administration Cooperative Urological Research Group. This data on recurrence of bladder cancer has been used by many to demonstrate methodology for recurrent events modelling. In this study, all patients had superficial bladder tumors when they entered the trial. These tumors were removed transurethrally and patients were randomly assigned to one of three treatments: placebo, thiotepa or pyridoxine (vitamin B6). Many patients had multiple recurrences of tumors during the study and new tumors were removed at each visit. For each patient, their recurrence time, if any, was measured from the beginning of treatment.
bladder is the data set that appears most commonly in the literature. It uses only the 85 subjects with nonzero follow-up who were assigned to either thiotepa or placebo and only the first four recurrences for any patient. The status variable is 1 for recurrence and 0 for everything else (including death for any reason). The data set is laid out in the competing risks format of the paper by Wei, Lin, and Weissfeld (WLW).
bladder1 is the full data set from the study. It contains all three treatment arms and all recurrences for 118 subjects; the maximum observed number of recurrences is 9.
bladder2 uses the same subset of subjects as bladder, but formated in the (start, stop] or Anderson-Gill (AG) style. Note that in transforming from the WLW to the AG style data set there is a quite common programming mistake that leads to extra follow-up time for 12 subjects: all those with follow-up beyond their fourth recurrence. Over this extended time these subjects are by definition not at risk for another event in the WLW data set.
bladder
| id: | Patient id |
| rx: | Treatment 1=placebo 2=thiotepa |
| number: | Initial number of tumours (8=8 or more) |
| size: | size (cm) of largest initial tumour |
| stop: | recurrence or censoring time |
| enum: | which recurrence (up to 4) |
bladder1
| id: | Patient id |
| treatment: | Placebo, pyridoxine (vitamin B6), or thiotepa |
| number: | Initial number of tumours (8=8 or more) |
| size: | Size (cm) of largest initial tumour |
| recur: | Number of recurrences |
| start,stop: | The start and end time of each time interval |
| status: | End of interval code, 0=censored, 1=recurrence, |
| 2=death from bladder disease, 3=death other/unknown cause | |
| rtumor: | Number of tumors found at the time of a recurrence |
| rsize: | Size of largest tumor at a recurrence |
| enum: | Event number (observation number within patient) |
bladder2
| id: | Patient id |
| rx: | Treatment 1=placebo 2=thiotepa |
| number: | Initial number of tumours (8=8 or more) |
| size: | size (cm) of largest initial tumour |
| start: | start of interval (0 or previous recurrence time) |
| stop: | recurrence or censoring time |
| enum: | which recurrence (up to 4) |
Byar, DP (1980), "The Veterans Administration Study of Chemoprophylaxis for Recurrent Stage I Bladder Tumors: Comparisons of Placebo, Pyridoxine, and Topical Thiotepa," in Bladder Tumors and Other Topics in Urological Oncology, eds. M Pavone-Macaluso, PH Smith, and F Edsmyn, New York: Plenum, pp. 363-370.
Andrews DF, Hertzberg AM (1985), DATA: A Collection of Problems from Many Fields for the Student and Research Worker, New York: Springer-Verlag.
LJ Wei, DY Lin, L Weissfeld (1989), Regression analysis of multivariate incomplete failure time data by modeling marginal distributions. Journal of the American Statistical Association, 84.