Girard et al. (A-6) conducted a study to identify prognostic factors of improved
ID: 3239530 • Letter: G
Question
Girard et al. (A-6) conducted a study to identify prognostic factors of improved survival after resection of isolated pulmonary metastases (PM) from colorectal cancer. Among the data collected were the survival (in months), status (dead=1 or dead=0, if alive) and dichotomized number of resected PM (ResectedPM=1 or ResectedPM =’>1’) for 77 patients who underwent complete resection at the first thoracic operation.
What are the study questions?
What is the outcome of interest (dependent variable)?
What are the predictors of outcome (independent variables)?
What statistical model was used?
What statistical hypotheses were tested to address the study questions?
Were the null hypotheses rejected at the level 0.05?
What conclusions should be made based on the statistical analysis results?
In addition to summary questions 1-7 answer the following questions:
What is the median survival (with corresponding confidence interval) in the group with ResectedPM=1 and in the group ResectedPM =’>1’?
What is the estimated hazard ratio (with corresponding confidence interval) associated with the difference in survival between patients with ResectedPM=1 vs. ResectedPM =’>1’? What is the meaning?
Stratum 1: ResectedPM-1 Product-Limit Survival Estimates Survival Standard Number Number MONTHS Survival Failure Error Failed Left 0 0 0 46 1.0000 0.000 0.9783 002 17 0.0215 1 45 2.000 3000 0.9560 0.0440 0.0304 5.000 10.000 3 42 0.9116 0.0884 0.0422 14000 0.8893 0.1107 0.0467 51 401 61 15.000 7 38 15.000 0.8449 0.1551 0.0539 16000 0.8226 0.1774 0.0569 37 91 36 17.000 10 35 0.7782 0.2218 0.0619 17.000 0.7559 0.2441 0.0640 18.000 0.7337 0.2663 0.0659 19.000 19,000 12 32 12 24000 12 301 24.000 13 26.000 0.6848 0.3152 0.0700 26.000 16 26 0.6359 0.3641 0.0730 27.000 0.6114 0.3886 0.0742 241 29.000 0.5859 0.4141 0.0753 33.000 18 35.000 0.5593 04407 0.0765 19 21 37.000 39.000 19 20 40,000 191 191 0.5299 0.4701 0.0779 20 17 42.000 R 43.000 43.000 0.4675 0.5325 0.0803 45.000 14Explanation / Answer
1) The study is conducted to identify prognostic factors of improved survival after resection of isolated pulmonary metastases (PM) from colorectal cancer.(given in the question)
2) From the PHREG table, we can clearly see that the dependent variable under study is Months.
3)The independent variables in the study are status (dead=1 or dead=0, if alive) and dichotomized number of resected PM (ResectedPM=1 or ResectedPM =’>1’) .
Change of value of these independent variables will lead to change in the value of the dependent variable ( Months ).
4) From the last table i.e. Testing Global null hyposthesis table , it is clear that we have used Chi-square test for our study.
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