GYN Collaborative Procedure Question


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I'm a coding student and have a question about coding when two physicians collaborate in a surgical session.
Scenario: Patient with cervical cancer to receive brachytherapy via a Syed template. A GYN surgeon and the radiation oncologist are in attendence in the OR suite. An EUA is performed first by the surgeon, then the rad onc. Then the radiation oncologist personally inserts needles as described by CPT 55290 with surgeon present. After recovery, the patient proceeds to radiation oncology department for high dose rate brachytherapy 77784.
When I look up CPT 55290, I see that co-surgery or team surgery modifiers are not allowed.
My question: What specific coding guidance determines which physician reports 55290? Thanks!