This is probably a topic that you have not thought much about. If you have ever read The Immortal Life of Henrietta Lacks (and, if you haven't, you should do so), you are aware of the less positive parts of the system. Fortunately things have changed a lot over the decades since her contributions to science, but people still worry about ethics and privacy when considering donating body samples (usually blood, saliva, tissue, cells from a biopsy, etc.).
Generally this is not a conversation that a patient initiates. It comes up when a doctor asks if you might be interested in participating in a study that involves such collections. Most often, this happens prior to surgery, but it can come along any time during cancer treatment.
From Cancer Net comes this interesting interview. Here is the start and a link to read more:
Donating Biospecimens for Cancer Research: An Expert FAQ
What are biospecimens?
Biospecimens are materials from the human body. Sometimes, they are called “samples.” The biospecimens most commonly used in cancer research are blood, urine, saliva, or remaining tissue from biopsies or surgeries.
Why are these samples valuable for cancer research?
These samples contain a lot of information about the body, including genes and proteins. Biospecimens also tell doctors a lot about the biology of a specific type of cancer. This information helps researchers learn:
How cancer grows and spreads
How certain drugs work in different groups of people
New ways to prevent and treat cancer
Research that involves biospecimens is an important step to finding new and better ways to prevent, treat, and cure cancer now and for future generations.
Read more: https://www.cancer.net/blog/2017-10/donating-biospecimens-cancer-research-expert-faq?et_cid=39759756&et_rid=970623634&linkid=biospecimens