I am trying to compare two different treatment arms and looking at CTCAE toxicity data. There are two treatments and I have the toxicity over a 6 month period. I have 3 data points in that time period (1 month, 3 month and 6 month) which I compiled into if the patient experienced any Grade 1,2,3 or 4 toxicity during that time period. So if a patient had grade 1 toxicity at month 1 but then grade 2 at month 3 and then grade 0 at month 6, I would only include them in the grade 2 toxicity over that time period to avoid over counting the toxicities. Then the patients are split depending on which treatment modality they received. My question is how can I compare the two arms? Would a two-sided z-test work? I am looking to compare grade 1 toxicity between the two, grade 2 between them and so on but I am worried that since I only count them once, some of the lower toxicity comparisons may not be correct. Would it be better to count the patients for any toxicity that they had over that time period?

Thanks