What is the radiobiological basis for two fractions only per week in HDR brachytherapy in cervical c

[Radoncologist]

---

Members don't see this ad.

Can u guys please explain the radiobiological basis behind two fractions only per week in ca cervix HDR brachytherapy

 

[BobbyHeenan]

Can u guys please explain the radiobiological basis behind two fractions only per week in ca cervix HDR brachytherapy

I don't know if I can give a great alpha/beta radiobiological basis....but 3 fractions a week of 4-6 Gy/fraction HDR is a lot of dose to the vagina - vaginal mucositis will become problematic and I'd bet your rate of vaginal necrosis would be higher in doing three per week. Remember the dose at the edge of the ovoid is upwards of 130-150% hot depending upon ovoid size.

I prefer 2 per week spaced out at least by 48 hour minimum or one per week if geometry/schedule allows it (ie start at ~30 Gy or so if a smaller tumor and can get good geometry).

 

[Radoncologist]

Thank you

 

[seper]

I do it to keep weekly dose as low as possible to decrease mucositis and other acute effects.
IMHO, it does not affect necrosis which is a delayed reaction, dependent mostly on dose per fraction.
I also prefer fractions to be 72 hours apart, not 48.

 

[nkmiami]

I cant think of a good answer. In one patient, I wanted to do 3 per week because of overall treatment time issues, and my physicist got very unhappy.

 

[Neuronix]

HDR from a practical standpoint is much simpler for all parties involved. Also, the planning can be customized with much more precision than LDR (i.e. dwell positions vs. stranded seeds). Those improvements in dose deposition are probably more important than dose rate.

Besides, radiation biology has come up with all kinds of ideas and nuances that turned out not to be true in practice.