I want to calculate the Standarized incidence ratio of second primary malignancies.

I have a database with patients that were diagnosed with lung cancer as first cancer and these were followed up to find if they developed a second primary malignancy. The patients were diagnosed with lung cancer between 1990 and 2013 and the follow up started in 1990 and finished in 2014.

For calculating the amount of expected cases one needs the amount of person years for every age category and also the age specific incidence rate . I only have the age specific incidence rates between 1999 and 2014.

How could I calculate the SIR? Should I exclude all the patients that were diagnosed with lung cancer before 1999 and:

- Calculate the person years from date of first diagnosis ( 1999) until outcome or end of follow up , count the observed cases from 1999 onwards?

Does anyone with experience in this topic have a suggestion?

Thanks in advance!

I want to calculate the Standarized incidence ratio of second primary malignancies.

I have a database with patients that were diagnosed with lung cancer as first cancer and these were followed up to find if they developed a second primary malignancy. The patients were diagnosed with lung cancer between 1990 and 2013 and the follow up started in 1990 and finished in 2014.

For calculating the amount of expected cases one needs the amount of person years for every age category and also the age specific incidence rate . I only have the age specific incidence rates between 1999 and 2014.

How could I calculate the SIR? Should I exclude all the patients that were diagnosed with lung cancer before 1999 and:

- Calculate the person years from date of first diagnosis ( 1999) until outcome or end of follow up , count the observed cases from 1999 onwards?

Does anyone with experience in this topic have a suggestion?

Thanks in advance!