Tim From what you describe, it seems like you've gotten clear feedback that telling people that you left your last job due to cancer is hurting your job prospects. 

Is there a reason that you say this?  Is there something else you could say that wouldn't feel like a lie but that wouldn't be a red flag to a prospective employer or hiring manager? 

A key question that I  ask my clients to consider is: Is the cancer currently a concern for you as an employee and if so, how does this impact your performance?  This can help you formulate whether to disclose this information, when to say it and what to say and not say.

Just as importantly, it sounds like you're not sure about what you want to do, where your strengths lie or what direction to go in.  That could also be hurting your ability to get a job.  Good hiring managers sniff this out and it's never a point in your favor.  It also gets in your way of finding career satisfaction.

There are excellent resume writing resources on the web and you can find out about them through social media -- twitter and linked in, for sure.  I'd suggest that you invest the money in working with someone who can help you figure out what you want and are capable of doing  --  a career coach or some resume writers do this as well. I suggest that you invest the time/resources here.  I also suggest that you find someone who understands the issues around illness disclosure, gaps in resume due to illness and how illness can continue to impact your work life.

My best to you in your search. 
Rosalind