I am reading Dirk Moore's Applied Survival Analysis 11.2.
"...However, patients actually enter over an accrual period of length a, and then, after accrual to the trial has ended, they are followed for an additional time f...."
Is this asserting all trials are left truncated? Since you will not start treatment until the end of accrual period, there is possibility of patient dying during that accrual period. Hence we can only follow people not dying during accrual period.
If the treatment starts right at beginning of accrual period, I would say this is right censored. However, I am not sure what is accrual period for here. Is it only used for accumulating enough patient to start trial? Or one can start trial right at the beginning of accrual period?