Papers presented at academic conferences can be found in a variety of places. Sometimes they are collected and published in book form or in academic journals - often in supplements. These proceedings may be found through a search of a library catalog (see some options listed on this page) or through many of the databases that you use to locate regular journal literature such as Scopus or Medline.
In some databases, you can limit your search to these types of publications. So, you could run a search on a general subject area, like cancer, and limit the publication type to retrieve only conference proceedings. These documents are referred to in different ways, including congresses, meeting papers, and conference proceedings. You can also use keywords such as "proceedings" or "abstracts" to search along with your other search terms.
Remember that often the terms you search with in databases will need to relate to the conference as a whole, rather than to specific abstracts or topics that interest you.
More often than not, conference proceedings will be more difficult to locate than this. Another strategy is to identify the organizations that hold these conferences and check their Web sites for information on them. Many do make their proceedings and other information from conferences available For example, the American Society of Clinical Oncology site provides access to past meeting abstracts. You can find many organizations of this type using the directories listed here.
These are good places to look for records of conference proceedings. Contact a librarian if you need help locating the full-text.