“Does chemo and radiation treatments shorten your lifespan?”

I would say that chemotherapy and radiation treatments are two types of medical treatment that come with risk. They are typically used to treat very severe diseases. In medicine we measure treatments and diseases, and we do a "risk: benefit analysis." If the risk outweighs the benefit, then the treatment is worth it. As these two treatments are used to treat very serious and often fatal diseases, such as cancer, you could say that these treatments actually extend the lifespan of patients with these diseases. So the answer is not simple. These treatments do come with a risk, and then can shorten the lifespan of a person who does not have the diseases for which they are meant to be used. However, for people who have the diseases that they are meant to be used for, they can extend these patients' lifespans.