I have 159 tumor patients, of which I know several parameters: age, sex, stage, ... and x.
X is a continuous covariate corresponding to the percentage of tumor cells currently dividing (biological mitosis) in the tumor specimen. Thus, X potentially ranges from 0 to 1.
I used restricted cubic splines to test for non-lineary effects of X, and found that effect was linear. Thus, x was not further modulated.
I want to investigate if increasing X correlates to an increased risk of recurrence. Therefore, my time-to-event is recurrence-free survival in months and the event of interest is recurrence.
I have no missing values.
In total, I have 29 / 159 recurrences (18%) during a follow-up of 10-yrs. In the multivariate analysis,
I found that One-percentage point increase of X yielded a hazard ratio of 1.25 (95% CI: 1.02 - 1.52, p=0.03).
How do I know whether I have enough power to conclude that increasing X correlates to an increased risk of recurrence? I mean, 29 cases is not that much.