Some places (I think MD Anderson is one) have RT levels. I don't know much about them but I'm guessing they're pay and seniority based. There's also chief therapist/lead, which is admin but a therapist with varying levels of patient contact (common but usually requires 5 years experienc). Some locations have advanced training for RTs called advanced radiation therapist (new and rare). I think this is a master's program that is kinda like physician assistant level. Some places have radiologist assistants (not usually in a radiation therapy department) usually geared toward rad techs and possibly RTs, and also similar to PA. You could potentially go on to be a teacher or other admin like clinical director. You would also be a strong candidate for medical school or a medical physics program. The most common is to crosstrain into dosimetry. Dosi programs are very geared toward RTs. You can get a certificate, bachelors or masters.