I doubt it's actually the drug. ..but here are my thoughts.
BC diagnosis impacts on our sleep pattern..and especially if your sleep is particularly affected by hot flushes etc. Now...can you recall being woken in the past mid dream by someone. ..you vividly recall the dream happened. So if your sleep is disturbed by treatment or stress of diagnosis. ..then being aware of your dreams is more likely.
Women can have some PTSD type symptoms from treatment also which can include dreams.
It might be an unreported side effect. I know although I sleep better now I certainly used to sleep much lighter after bc treatment and any noise woukd wake me.