Feasibility to reach LCRT study endpoint based on cohort
characteristics
Based on demographic characteristics of the enrolled
population (Table 1), we expect lung cancer incidence in
the LCRT study to be similar to the 3.1 % incidence over
3.9 years reported by Bach et al. [40] in which mean age
was 60.1 and smoking history of 52 pack-years. The five
incidental lung cancers observed two years after initiation
of the study are consistent with this rate. Taking
into account that some of the 384 study subjects will
have died from causes other than bronchogenic carcinoma
prior to these time points and that some will be lost
to follow up we estimated incidental lung cancers in the
cohort based on 300 subjects. As such we expect to observe
approximately 12 incidental lung cancers by the
2016 follow up (mean time since enrollment approximately
5 years) and 17 by the 2018 follow up point
(mean time since enrollment approximately 7 years),
which will be more than sufficient to reach the proposed
endpoint of a risk ratio of ≥ 5.0.