Hello@beccabecca the chemotherapy generations refer to the changes over time as a result of research and the benefits found with combinations of chemotherapy agents. Treatment is based on individual pathology and a range of other considerations. If you have any questions about your regime and why it is chosen for you it is a very worthwhile discussion to have with your oncologist. The following article talks about the generations of chemotherapy and advances in knowledge over time https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-015-0439-8