A C18 HPLC column is preferred for accurate doxorubicin analysis, but your existing C15 column can be tested with possible compromises in separation and sensitivity.

As Abdelhak Maghchiche have mentioned above, C18 is a better choice for you. As far as I know, C15 is not commonly used so check first its history use (what analysis has been done, when was it purchased, how it was stored when not used) and its performance according to its manufacturer (something like an inspection report delivered with the column). If ok, you just need to optimize your separation condition. However if you have concern about its current performance, I suggest you to invest in a new C18 column. Note that depending on the base matrix of your column (pure silica, hybrid silica), the separation might slightly differ as well. Best of luck.

Yes, if you optimised your mobile phase according to the C18 column, then definitely. But C18 will be a better choice.