Question normal

This is a really interesting and valuable study with surprising conclusions. After I have read this paper, here are my questions below:
1. The study included additional 10200 patients later and why? Would it bring in bias for the later data analysis?
2. In Table1, colume"annual rate of distant recurrence". Why the authors calculated the rates for 5 to 10 yrs and for 10 to 20 yrs seperately?
Thanks for your response!