Overview
1.Shown below are the 30 survival times (months) of 30 melanoma patients, 11 of which were treated with the
immunotherapy BCG and 19 treated with the immunotherapy c. parvum. The "+" indicates censoring. BCG: 3.9 5.4 7.9 10.5 16.6+ 16.9+ 17.1+ 19.5 23.8+ 33.7+ 33.7+ c parvum: 6.9 7.7 7.8+ 8.0 8.2+ 8.2+ 8.3 10.8+ 11.0+ 12.2+ 12.5+ 14.8+ 16.0+ 18.1+ 21.4+ 23.0+ 24.4 24.8+ 26.9+ a. Estimate the survival curves for each treatment using the Kaplan-Meier method by hand. b. Plot the curves on the same graph. 2. As one example of survival data, we looked at the remission duration times on 42 patients with acute leukemia, half of which received 6-MP and the other half a placebo. The dataset LEUKEMIA.DAT on Canvas has with the following format: Variable Columns Group (1 = 6-MP, 2 = Placebo) 1 Remission time (in weeks) 3-4 Censoring status (1=censored, 2=not censored) 6 a. Estimate the Kaplan-Meier remission duration curves using SAS. b. Test to determine if the groups are significantly different and interpret your results. 3. A study examines the effect of stopping smoking on survival in advanced lung cancer patients. Of 137 patients, 122 died by the end of the study period. Survival time is taken from date of diagnosis to death or last contact. The following variables are included in the analysis: Variable Coding _ 1. Smoking status 0: continues smoking after Dx 1: stopped >1 yr prior to Dx 2. Performance status 0 : ≥ 80 1 : ≤ 70 3 & 4. Weight loss prior to therapy (3 categories) (2 dummy variables created: WTL1 and WTL2) None WTL1=0 and WTL2=0 ≤ 10% WTL1=1 and WTL2=0 > 10% WTL1=0 and WTL2=1 5 & 6. Histology (3 categories) (2 dummy variables created: HIST1 and HIST2) Squamous Cell HIST1=0 and HIST2=0 Adenocarcinoma HIST1=1 and HIST2=0 Larqe cell HIST1=0 and HIST2=1
The table below summarizes the results of fitting several proportional hazard models. Regression coefficients & log likelihoods are shown. Model Variables 1 * 2 3 4 5 Smoking(SMK) -0.552 -0.162 -0.032 Perf. Status (PS) 0.561 0.588 0.513 WTL1 0.056 0.058 0.063 WTL2 0.083 0.094 0.110 HIST1 0.061 0.066 0.132 HIST2 0.811 0.766 0.435 SMKxPS interaction -0.006 SMKxWTL1 '' 0.012 SMKxWTL2 '' 0.003 SMKxHIST1 '' -0.002 SMKxHIST2 '' -0.105 Log likelihood -486.54 -483.20 -476.12 -475.84 -472.73 * No variables in model a. Compare the unadjusted survival curves for smoking status. If significant, describe the relationship (direction, magnitude). b. Determine whether the interaction terms of smoking status with performance status, weight loss and histology taken together affect survival. c. Assuming no interactions, compare the survival curves for smoking status adjusted for performance status, weight loss and histology. If significant, describe the relationship. d. What are your conclusions?