Onco-cardiology (or cardio-oncology) is the study of the cardiac effects of cancer treatment but also used to refer to patients who are cancer survivors with a cardiac condition or people living with both conditions.
Though not a new term, I don't remember coming across it before.
Here is some introductory reading:
Some recent freely available articles (with links to PubMed):
The American College of Cardiology and American Society for Clinical Oncology have pages about onco-cardiology.
Some Canadian guidelines on the evaluation of cardiovascular complications of cancer therapy are here.
A (freely available) 2013 European Heart Journal article about cancer drugs and the heart is here.