invasive procedures?

Splenectomies and radical inguinal orchiectomies.

(Totally kidding)

Brachytherapy is all, but believe me, it's enough. Gyn (intracavitary and interstitial), prostate, and breast do a fairly high volume of procedures (possibly reflective of my own institutional bias). There are also brachy procedures for head and neck, lung, CNS, sarcomas; I'm sure I'm leaving some out. The techniques vary by anatomic site, certainly enough to satisfy most in the field with a procedural bent.

I've intentionally left out things like IORT, intravascular brachy, and ocular plaques since, in my limited experience, you are basically riding shotgun with the surgical or interventional team.

I don't know if you would count radioisotope injection, but that's a pretty anti-climactic procedure.