95 / 1816
•
Valid estimates of the causal effect of radiotherapy on
recurrence rates can only be made in terms of any recurrence.
•
Valid estimates of the effect of radiotherapy on local
recurrence rates
cannot be made
– although many papers
claiming to do so have been published
•
Valid estimates of the effect of radiotherapy on distant
recurrence rates can be made
– but only if information on distant
recurrences occurring after any earlier local recurrence are
available, and these will be affected by the treatment given for the
local recurrence as well as the initial radiotherapy
31
Validity of Estimates of Effect of Treatment on
Recurrence Rates