I too had high BP before cancer, but it was under control and I was slowly being weaned from my meds. Chemo drugs do not help BP, I've been having this issue on and off (some times mostly on) since I started my initial treatment for Kidney Cancer in 2009. I've been seeing a cardiologist since Jan 2011. I do not know what drugs you DH is on but when they started me on carbo, gemzar and avasitain to treat both my cancers, my BP rocketed after about 4 months.
I would recommend that you speak to your DH oncology team about a referral to a cardiologist who can review the meds he is taking - My BP is coming down, as I'm on an different cocktail, but for a few months my cardiologist was unhappy, but decided that 150/90 was the best we could do (the worst was 190/105) and that it was an acceptable short term risk