Where domain to map Cycle number in a oncology trial

I don't think there is any…

I don't think there is any set way to do this - I don't recall seeing it in any of the various Cancer TAs.

For myself, as a Cycle will normally start with a visit I would encapsulate the Cycle into VISIT and VISITNUM

If there is only a single visit per cycle - I would probably use something like
VISIT = Cycle x
VISITNUM = x

However, if the protocol calls for multiple visits per cycle, e.g. days 1, 15, 28 in each Cycle I would probably use something like
VISIT                            VISITNUM
Cycle x, Day 1             x01
Cycle x, Day 15           x15
Cycle x, Day 28           x28

That way Cycle number is embedded into VISITNUM in a consistent way, and can be later extracted into an ADaM variable if required.

Thank you.

Thank you.