Hello Werner,

PlosONE or Oncotarget may be a good choice, but both of them feature good and also some rather bad publications.

There is the "Directory of Open Access Journals (DOAJ)" at https://doaj.org/

This will list a lot of journals for cancer res./oncology - how good they are can be determined by impact factor (should they have one) or researching about the reputation that specific journal online.

You may also be interested in a list of OA Journal's to be careful about: https://scholarlyoa.com/publishers/

Hope that helps

thank you very much for the informations.