Hi

At the current point, I am wondering about which survival analysis to use for my data. My data is consisting of one control group and three exposure groups. One of the exposure groups is known to have a difference in toxicity over time (in my case, taken into account by making a gradient over distance). Therefore it is necessary to divide the groups into three stages, making 12 survival curves (with eight individuals per stage) per experiment. The data is only right-censored, but the amount of censoring in the different groups is wearing much. That being, the control and one of exposure group has almost no censoring (three of the six stages in the two groups has only censored data, the rest of the stages only one or two deaths) The survival curves between two of the exposure groups are crossing.

Also, many of the survival curves inside the different exposure groups (two of the exposure groups and the control) are crossings, as they do not have a difference in toxicity over time.

What would be a soothing survival analysis for such an experiment? Moreover, how problematic is the crossing of the curves if it's expected?