How would you manage a patient with a h/o HSIL & VAIN3 and recent colposcopic vaginal biopsies "highly concerning for exophytic pattern squamous cell carcinoma" refusing vaginectomy?

She has extensive colposcopic lesions at upper/mid vagina, but no palpable/visible lesions on standard pelvic exam. Pelvic MRI with 20cc US gel in vagina showed no mass or adenopathy. Expert path review of her vagina biopsies stated, "suspect the lesion may represent an exophytic pattern squamous cell carcinoma arising in HSIL/VAIN3 and we recommend clinical management as such." So seems like T1N0 vaginal SCC. Patient desires organ preservation and is sexually active; declines vaginectomy from gynonc. If HDR vaginal cylinder is a good option, how would you dose/fractionate?