Thanks for the link, gwendolyn.
I would still caution about being too vague about where you were for the missing time. Vague answers will not get you hired if the HR people think you are hiding something (or worse, lying) and, as the link points out, they can't really ask direct questions so their imagination will fill in the blanks. If you decide to go the "I was dealing with a medical issue which is now resolved." route (Which is a pretty good way to handle this, imho if you aren't going to be upfront. Its not a lie. Above all else, honesty is most important.), I would add that it wasn't an addiction problem or mental health. HR will automatically go to drug/alcohol abuse as the cause first (because it usually is), depression second if you don't tell them otherwise and being vague says to them that it is still an issue (recovering addicts are encouraged to be honest). Wouldn't it be a kick in the a s s to lose a job because they thought you were hooked on crack when the reality was you were hooked on chemo?
Cancer is rarely the first thought about resume breaks unless it is pretty obvious (bald, wearing a head scarf etc.). Of course, it gets easier the longer you are a survivor. A resume break that ended 5 years ago (and its cause) is far less of a concern than one that has not yet finished.
And even though the link/law promises lots of protections, there are many ways around those for potential employers. While they may not legally be able to ask certain questions, you have to be able to prove they did......if they do.....and you don't get hired.....and your cancer was the reason.....and it wasn't "We found someone we think is a better fit.".....and you can prove they are lying......and......and.....
And.....as if that isn't enough....if you aren't going to be upfront about your cancer, I would clear any mentions of cancer from social media. Facebook, twitter, LinkedIn, no mention of What Next anywhere, no blog about your journey, nothing that can give you away, etc. Almost everyone checks SM out to see if you are a guy who likes to trash the boss on line and if they see cancer there and you were mysterious about that time off.............. At that point, it won't be the cancer that keeps you from being hired, it will be the subterfuge.