Livre d'Or

It is sufficiently common for marriages to break up during or after cancer treatment, that Maggies Wallace offers couples counselling.

From gossip, I gather it's usually after, because either the well spouse waits until the sick spouse is better, so they don't feel too evil for leaving someone while they are very ill. Or the sick spouse starts getting well and thinking about the future and deciding they don't want the other person in it any more.