Can cancer patients donate blood. Do so?

There isn't a simple 'yes' or 'no' answer to whether cancer patients can donate blood. Many people who have been treated for cancer are eligible to donate blood, provided they fall within certain guidelines and eligibility guidelines do vary among organizations... Cancer survivors may sometimes be able to donate blood if they are more than a year out from therapy. Yet there are situations, such as with leukemias and lymphomas and more, where donating isn't considered safe for those who would receive the blood. When can people who have had cancer donate blood, when can they not, and what are the reasons behind this? It's important to note that individual blood donation organizations, as well as different countries, have different requirements.