pT4N0 larynx - post op radiation volume

[drewdog1973]

How about 30 Gy... 0% Gr3 or greater(!) toxicity rate. Regardless, 56/35 to elective areas is tougher on patients IMHO versus 50/25 (or 40/20), either of which can only be rationally achieved by staging (ie "two-scan planning," or more) the dosing.

Though I’m a SIB fan, this is true. Acute toxicity is going to increase with higher absolute dose. this is the problem with 0529 for Anal when you give 45 / 30 to elective / low risk areas that previously were treated to 30.6/17 fx ... but I love SIB in general. Just finding the magic doses... I like 54/33..

---

Members don't see this ad.

 

[Krukenberg]

The 44Gy/22fx for "subclinical neck" is very old stuff, going back to Fletcher's, Ang's days...

In the RTOG 1016 (The Cetuximab thingy), the 44Gy/22fx idea is there:

https://clinicaltrials.gov/ProvidedDocs/34/NCT01302834/Prot_SAP_001.pdf

Anyway, I think 56Gy (lower daily fractional dose) is overkill, just my 2 pennies.

Wait since when does clinicatrials.gov have protocol documents???

 

[evilbooyaa]

How about 30 Gy... 0% Gr3 or greater(!) toxicity rate. Regardless, 56/35 to elective areas is tougher on patients IMHO versus 50/25 (or 40/20), either of which can only be rationally achieved by staging (ie "two-scan planning," or more) the dosing.

Why would you say 56/35 is worse than 50/25 on patients? I'll concede that it'll be worse than 44/22 or 40/20 or 30/15, or 0/0

 

[scarbrtj]

Why would you say 56/35 is worse than 50/25 on patients? I'll concede that it'll be worse than 44/22 or 40/20 or 30/15, or 0/0

My theory, and experience, based on years and years of doing things many different ways. Plausible? YMMV of course. The Y-axis (pardon the chicken scratch) is all the subjective complaints and objective toxicities lumped together...

 

[evilbooyaa]

My theory, and experience, based on years and years of doing things many different ways. Plausible? YMMV of course. The Y-axis (pardon the chicken scratch) is all the subjective complaints and objective toxicities lumped together...

Do we expect 1.6Gy/day to cause the same amplitude of side effects as 2Gy/day? I certainly agree with a longer duration of symptoms. My SIB patients I have not seen anything more than G1 dermatitis in the 56Gy region, can folks say the same for 50/25?

 

[scarbrtj]

Do we expect 1.6Gy/day to cause the same amplitude of side effects as 2Gy/day?

All things being equal and ignoring time, no we do not. Which I tried to subtly suggest on the graph. BED-10's of 56*(1.16)=65 versus 50*(1.2)=60.

 

[evilbooyaa]

All things being equal and ignoring time, no we do not. Which I tried to subtly suggest on the graph. BED-10's of 56*(1.16)=65 versus 50*(1.2)=60.

Hmm, I guess what I was thinking, is that the highest amplitude at 1.6Gy/day would be clinically less than it was at 2.0Gy/day. BED I would consider more in-line with 'cumulative AUC' of skin reaction.

I am thinking of it similar to the acute rectal toxicity curves seen in prostate RT for conventional fx (may look like 1.6Gy/day) vs moderately hypofx (may look like 2.0Gy/day), where the amplitude is higher with increased fraction size, but for a decreased duration of time due to shorter treatment.

 

[scarbrtj]

I am thinking of it similar to the acute rectal toxicity curves seen in prostate RT for conventional fx (may look like 1.6Gy/day) vs moderately hypofx (may look like 2.0Gy/day), where the amplitude is higher with increased fraction size, but for a decreased duration of time due to shorter treatment.

This mindset explains the people still giving 17 times 1.5 in seminoma versus 20 in 10 It's (supposed to be) a rad bio truism that total dose governs acute toxicity to a much larger degree than fraction size does.