Program Code
The program is written in JavaScript.
Input
Follow-up Time: Enter the number of years between the last patient accrual to the time of the final analysis.
Accrual Time: Enter the number of years of patient accrual.
Sample Size: Enter n, the planned sample size.
*Hazard rate: Enter l, the exponential event rate.
*Survival probability and time(default): Enter a time, t (in years), and the probability of patients alive at that time, S(t). The program will calculate l as
l=-ln(S(t))/t
*Median Survival: Enter the median survival, MS. The program will calculate l as
l=-(ln(0.5))/MS
Percentage of patients cured: A number between 0 and 1.
*Does not include cured individuals
Calculation of the Expected Number of Events
Probability of event at analysis time is
P(event|Analysis time t)=1 - e(-l*follow) *(1-e(-l*accrual) )/l*accrual).
At times before accrual has completed
P(event|t) =(l-1 e(-l t) + t - l-1)/accrual.
At other times
P(event|t) = 1 - e(-l (t-accrual)) *(1-e(-l*accrual) )/(l*accrual).
The survival density f(t) is assumed to be exponential with rate l and cure rate p, i.e.,
f(t)=(1-p)(l) e(-lt)
Output
There are three options for calculations. The default option is a table of results in new page. The second and third options provide expected events for a given time, or time at which the expected proportion of events have occurred.