The question (How sample size was determined?) automatically arose, when we loaded article to the site of journal. But we are not defined in advance the required size of the compared groups. How acceptable answer to this question (for to pass this filter)?
The essence of the study is that we compared (by Kaplan-Meier curves) groups of patients with new and standard treatment. The study ended when the study period ended. (Survival curves statistically significant divergent!)