What intracavitary brachytherapy regimen would you use after EBRT for a 4cm vaginal leiomyosarcoma the mid vagina with positive margins?

In general. I agree with @Dr. First Last's opinion. Vaginal sarcomas are rare, comprising less than 5% of all malignant vaginal cancer. Therefore, experience is limited and published reports sparse. It is stated that in this patient the tumor WAS 4 cm (in diameter?, largest dimension?) I assume it h...

I would try to deliver dose equivalent to at least 66 Gy or so. I would use 5 Gy x 4 fractions prescribed to visible thickness using multichannel applicator and MRI based planning.