What radiation sensitizer do you recommend for early stage poorly differentiated squamous cell carcinoma of the anus, in a patient with stage IV chronic kidney disease?

I have used carboplatin (AUC 2 weekly) + 5-fluorouracil in this setting with good tolerance. I acknowledge that the substitution of carboplatin for cisplatin is largely an extrapolation from the approach to squamous cell carcinomas of other primary sites. However, I feel very comfortable with this s...