With respect to the shorter latency period than was observed in the Life Span Study (LSS),1 we agree that this is an area that needs to be explored further. Several possibilities could explain this finding. The patient population in our cohort had about a twofold higher incidence of cancer — independent of exposure to low-dose ionizing radiation2 — than nationally quoted statistics on cancer incidence rates.3 The patients in our cohort were more at risk for cancer (perhaps because of smoking or obesity), and as such the latency time to cancer might have been shortened. To control for this, we used a time-dependant regression analysis, which incorporated a time-lag covariant to allow for cancer “induction” time following exposure. When sensitivity analyses were performed looking at time lags up to five years, there was no appreciable effect on the results. Nonetheless, we agree that important questions about the observed time lag in our study need to be explained further, and we are attempting to define this more extensively in on-going studies.