I see wide variance in radiation dose length and total dose.
How is the best dose determined? How does one know if their radiation oncologist is making the best choice?
For example, for consolidative radiation, in STAMPEDE, the dose was 55 Gy in 20 fractions over 4 weeks, or weekly fractions totaling 66 Gy over 6 weeks.
In contrast, PEACE 1 Arm D, not yet reported, used 74 Gy in 37 fractions.
How is the dosing determined? I would appreciate greater clarity on this.
You can't just compare totals - it doesn't work that way - you have to include fractionation and the characteristics of tissue being irradiated. The STAMPEDE trial of debulking allowed either 55 Gy in 20 daily treatments, or 36 Gy (not 66 Gy) in 6 weekly treatments . The 36 Gy/6 fraction dose is actually bioequivalent to a dose is 15% higher. The PEACE 1 bioequivalent dose is about 10% lower. The best dose is determined by clinical trials.
You are always so so knowledgeable.
May I ask you an estimated number of hours per week you spend reading the clinical trials?
If I were to be required to guess... has to be at least 20 to 30.
And if I were to guess for the average doc, it would be less than 2 or 3 hours.
I scan them everyday- takes about 5 minutes - and pick out the ones that look important and are authored by the top people (usually). Then I read the abstracts of the important ones- that can take up to half an hour. Only one or two a week are worth reading in full, and only one or two a month are practice-changing and worth writing about. I spend much more time responding to patients, here and in my email, or going with patients to see doctors - that can take 2- 3 hours/ day. Knowing where the research lies in the scheme of things and knowing what the unresolved issues are helps a lot.
But you are right that most doctors that have a full patient load stay on top of research only their own field.
Well... Please don't age out on us. Lol
Tall Allan is one of the stalwarts of this forum a saviour for many and a sound voice through the chaos He helped me so much I pray he lives to 100 we are gonna need him
I asked my oncologist about a suggestion from Tall Allan
He mumbled something then said it was a very good idea he was sorry he didn't think of it sooner lolol
There are other who are also quite knowledgeable
"There are other who are also quite knowledgeable"
In my opinion I disagree.
Ta has steadily gotten better and better.
At this point he is way better than most Docs.
He does have one unfair advantage over them.
He is willing and able to invest the time to keep up with the literature. He also, at this point, has the ability to absorb and integrate all this information into a unified understanding.
I do not think that you will able to tell your RO that he is not using the right dose. What you can do is calculate the "Biologically Effective Dose" (BED) to compare different radiation schedules. You will find that different ROs apply different BEDs. Here is a calculator for you:
mdcalc.com/radiation-biolog...
For prostate cancer you have to set the a/b ratio to 1.5.
I had no plans to tell the RO he was wrong, but am hoping for some insight into how the dose was chosen, since the trial data is far from robust, and the trials differ in their schedules. Obviously 4 weeks sounds a lot better than 7 weeks, but hoping my relief at a 4 week stint is not blinding me to the possibility of the longer series being preferable.
Also curious as to know how to choose an RO; that seems not nearly as straight forward or as easy to find stats etc.
A good be place to start is your nearest cancer center of excellence. Reasonable chance someone here could recommend one there.
We are at Mayo. I guess I should just trust the guy. Everything up to now, was completely in my comfort zone for research, etc, but radiation is just such a mystery. (I am a nurse.) Thank you for your reply! I think we are in pretty good hands so I will stop second guessing!
Can only add my experience. Wasn't a candidate for RP. I went to the Google School of PCa and concluded that it was least damaging to take the most radiation you could stand in the least amount of times. RO wanted 42 sessions and we finally agreed on 28. Also had the SpacOar hydro gel shield. Can say I had fewer problems than most others reported.
Thank you for your input; I appreciate it. It makes sense to me. My husband is not a good candidate for SpaceOar, as he has a lesion right there against the rectum, so there is a danger of missing some cancer cells behind there. Or so the RO says. He is very nervous about this, as he has tolerated everything so well so far. Waiting for the proverbial other shoe to drop!
Beth, using the vague "everyone is different" rule, I did 9-weeks of IGRT totalling 81 or 82gy. The first 28 sessions were the entire pelvic area and the remainder was targeting my prostate and pelvic lymph nodes only. I had no issues or side-effects except I now hate the Gatorade I drank before each session 😉. BTW I hated the thought of doing RT but it ended up being a breeze.
The R.O. picks out of a hat............. when he's sober...........
Good Luck, Good Health and Good Humor.
j-o-h-n Tuesday 08/31/2021 6:01 PM DST
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