Table 5 SAS computing code for counter-matched WECARE data (wecare.dat) as illustrated in Table 4

   infile 'wecare.dat';

   input id setno cc rrt m_rrt n_rrt true_rt rad_dose atm chemo;

   logw = log(n_rrt/m_rrt);

   rad_atm_int = rad_dose^*atm;

run;

* Radiation treatment yes/no, use true RT value;

proc phreg data = wecare;

   model setno^*cc(0) = true_rt/offset = logw;

   strata setno;

run;

* Radiation-AT mutation interaction model;

proc phreg data = wecare;

   model setno^*cc(0) = rad_dose atm rad_atm_int/offset = logw;

   strata setno;

run;