st: Using Aalen's linear hazards model

[Anwar Musah <mcxam23@nottingham.ac.uk>]

Dear Statalist,

I have an outcome which is a right censored variable coded as 1 for those who developed cancer and 0 otherwise. The main predictor variable is the individual's exposure level to an environmental contaminant which is categorised using quintiles and labelled as follows: 1 (<=10.8 mg/kg), 2 (10.9 - 14.2 mg/kg), 3 (14.3 - 17.3 mg/kg), 4 (17.4 - 21.4 mg/kg) and 5 (>=21.5 mg/kg).

Initially, I fitted a Cox's proportional-hazards model to estimate the risk of developing cancer according to these exposure categories; however, there is violation of the proportional-hazards assumption due the time-dependent effects the exposure might have on the cancer outcome. My question - is it possible to use the Aalen's model as an alternative to generate cumulative hazard coefficients for each of the last four categories of my exposure variable with the first category being the referent group? 

Thank you,
Anwar
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