In Reply.—In his letter, Dr Spratt refers to the "Will Rogers Phenomenon" of stage drift and lead time bias to explain the increased survival noted in various subgroups of a population after a new, more sensitive diagnostic test is introduced. A more sensitive diagnostic test would allow patients with silent metastases to "migrate" from lower to higher tumor stages. The migration would improve survival in lower stages, because fewer patients with metastases would be assigned to them. Migration would also improve survival in the higher stages because the metastases in the newly added patients would be occult rather than grossly apparent. However, the survival of the entire cohort would not improve.1 In essence, there is a "reshuffling of the deck," but in the absence of any effective therapy, no survival benefit is achieved.
We fully agree with Dr Spratt's point with a minor reservation. Accurate staging of disease at