What recourse do I have: my boss told mutual friends and a former employer that I have cancer and am dying, which is untrue?

I told my boss and provided her with a letter from my doctor stating that I would be receiving chemotherapy for a period of time and it might affect my job performance. My doctor did not provide any details (diagnosis, prognosis, detail possible side effects) because I asked him to be vague unless I developed specific problems with my job performance. Fortunately, it did not affect my job. I found out from a very good friend and former co-worker that my current boss told my former boss that I was taking chemotherapy because I was dying from cancer. This is false information. Do I have any recourse? Is this considered defamation?