How do you boost patients with IVA cervical cancer who present with a large fistula that worsens during chemoradiation?

After a diversion, would any other factors impact your recommendation (residual disease/response to chemoradiation, performance status)? Although brachytherapy with interstitial implant would be standard, what if unable to get adequate coverage due to residual disease? If EBRT boost (palliative) is recommended, which technique? Dose and fractionation is preferred?