Prostate cancer IMRT - no difference between daily IGRT and weekly KV

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Gfunk6

And to think . . . I hesitated
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http://www.thegreenjournal.com/article/S0167-8140(17)32680-4/fulltext

Interesting Phase 3 study. All patients received dose escalated IMRT to prostate (78 Gy in 39 fractions) with either daily CBCT (7 mm margins) or weekly orthogs (15 mm! margins).

No difference in patient reported toxicity.

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I've seen patients in fu with 15 mm margins who end with up with decent proctitis several years later.... wish they'd post the median f/u in that abstract because my high quality anecdotal experience on that is questioning the data lol
 
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I've seen patients in fu with 15 mm margins who end with up with decent proctitis several years later.... wish they'd post the median f/u in that abstract because my high quality anecdotal experience on that is questioning the data lol

Wait a minute ... it’s self-reported acute toxicity at the end of treatment!?! Why was this study even conducted?

I’d like to see some more objective measures of long-term toxicity a few years later.
 
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Separate, much more provocative RCT reported this week at ASCO GU. OS and 2nd cancer detriment in daily IGRT group. Median FU 4 years
Meeting Library | Meeting Library

Conclusions:Compared to weekly control, daily IGRT in prostate cancer significantly decreases the risks of recurrence and late rectal toxicity but is associated with an increased risk of second cancer. Clinical trial information: NCT00433706
 
This doesn't make a lot of sense. Only 4 years of FU in the French trial and patients are getting secondary malignancies or dying because of daily CBCT???
 
Separate, much more provocative RCT
This is a great example why I never believe single studies anymore. With apologies in advance, it's only provocative if you have little ability to contextualize. I certainly don't make treatment decisions on isolated randomized trials--especially isolated randomized studies which fly in the face of previous years and years and years of good retrospective data and radiobiology theory ("[RTOG 0617 was] counterintuitive in view of previous data suggesting a clear radiation dose–response curve in locally advanced non-small-cell lung cancer"). Science currently suffers from a crisis of reproducibility; we should act/treat accordingly... we're all gamblers in medicine.
 
http://www.thegreenjournal.com/article/S0167-8140(17)32680-4/fulltext

Interesting Phase 3 study. All patients received dose escalated IMRT to prostate (78 Gy in 39 fractions) with either daily CBCT (7 mm margins) or weekly orthogs (15 mm! margins).

No difference in patient reported toxicity.
"Patients eligible for radical RT received it after 3 months of total androgen blockage and were randomly assigned to 78 Gy in 39 fractions guided either by weekly offline orthogonal portal imaging (15 mm margins to PTV) or by daily online CBCT IGRT (7 mm margins to PTV)."

What the hell do they mean here??? A margin on the PTV (this is meaningless in IMRT approaches; i.e., no one marginates the PTV in IMRT)? Block margin on the PTV? A margin from the CTV to the PTV = "margins to PTV"? If they used different PTV margins in the CBCT and non-CBCT groups, this study is pretty useless if it thinks it's "testing" IGRT techniques.

Could they have used 15mm block margins in the weekly orthog group and a CTV-to-PTV 7mm margin in the CBCT group? Perhaps unlikely because that suggests a 3D approach in one group and IMRT in the other; I hope they didn't do that. I tried to explain this many years ago. However, if this is what they did, they compared ~1cm PTV margin in the orthog group with 0.7cm margin in the CBCT group.
 
"Patients eligible for radical RT received it after 3 months of total androgen blockage and were randomly assigned to 78 Gy in 39 fractions guided either by weekly offline orthogonal portal imaging (15 mm margins to PTV) or by daily online CBCT IGRT (7 mm margins to PTV)."

What the hell do they mean here??? A margin on the PTV (this is meaningless in IMRT approaches; i.e., no one marginates the PTV in IMRT)? Block margin on the PTV? A margin from the CTV to the PTV = "margins to PTV"? If they used different PTV margins in the CBCT and non-CBCT groups, this study is pretty useless if it thinks it's "testing" IGRT techniques.

Could they have used 15mm block margins in the weekly orthog group and a CTV-to-PTV 7mm margin in the CBCT group? Perhaps unlikely because that suggests a 3D approach in one group and IMRT in the other; I hope they didn't do that. I tried to explain this many years ago. However, if this is what they did, they compared ~1cm PTV margin in the orthog group with 0.7cm margin in the CBCT group.

It's complicated...

"Clinical target volume (CTV) prostate: the prostate including any suspected extra capsular tumor growth or infiltration into the seminal vesicles (SV) as described by clinical findings, trans-rectal ultrasound and/or pelvic MRI. The CTV-prostate/SV included the basal 1 or 2 cm of the SV in intermediate and high-risk patients, respectively."

...

"In patients receiving standard treatment (arm A), the planning target volume (PTV2) receiving 0–70 Gy included the CTV-prostate/SV with an additional 15 mm margin in all directions. In arm B the corresponding PTV2 (0–70 Gy) included the CTV-prostate/SV with an additional 7 mm margin in all directions."

...

"The PTV 1 (70–78 Gy) was equal to the CTV-prostate with an additional 3 mm margin in both study arms. "



So, it's the CTV-PTV-margin.
 
This doesn't make a lot of sense. Only 4 years of FU in the French trial and patients are getting secondary malignancies or dying because of daily CBCT???

Well median 4 years. Many patients had more than that. At the oral presentation they showed the cumulative hazard curves for 2nd cancers and they track each other for 4.5 years and then separate.
 
I hate to be cynical, but we've got one trial suggesting that if you do an invasive procedure and inject a very expensive hydrogel to buy yourself 7 mm then it helps toxicity...and I've got this study showing that those 7mm don't matter....

Hard to tease this all out. I still haven't found the margins used in the SpaceOar trial either.

For now I'm sticking with daily image guidance. I feel that it helps me keep tighter margins so that I don't feel a big need to do an invasive procedure because rectal toxicity with tight margin IGRT is relatively low.
 
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what margins you guys using with fiducials in. There was that astro slide a couple years ago maybe from the msk guys at refresher and the majority were like 5-6mm and some were 4mm all around.
 
what margins you guys using with fiducials in. There was that astro slide a couple years ago maybe from the msk guys at refresher and the majority were like 5-6mm and some were 4mm all around.

I do 7mm everywhere and 4 mm posteriorly. That's what we did in training as well and many of those patients didn't even have fiducials - CBCT daily.
 
15mm to PTV is basically saying the CTV to PTV expansion is 15mm (or 7mm).

Patient reported outcomes aren't really that useful IMO, especially in acute toxicities. Some people have it bad and are like "meh, whatever", others have it OK but are panicking because they have 2 BMs a day.

The issue with big margins is late rectal toxicity. Nobody realistically expects a huge difference in acute toxicity hopefully. Wonder how they did the dose constraints.

Unfortunately, both sets of treatments were done using 3D-CRT.

"CT-based, 3-D conformal treatment planning was mandatory, as were multi- leaf collimators (MLC). Using a four-field box technique with necessary supplemental field segments, 15 megavolt (MV) photon beams from 0 to 70 Gy were applied. For the 70–78 Gy boost, a 5 field (1 anterior, 2 oblique anterior and 2 lateral) technique was applied. Isocenter was placed in the fiducial gold marker located closest to the base of the prostate. The target volume doses should be within 95–107% of the prescribed dose. However, the rectal dose constraint was defined as 60 Gy to no more than half of the circumference in both study arms. If necessary, posterior blocking with MLC was accepted."
 
This is a great example why I never believe single studies anymore. With apologies in advance, it's only provocative if you have little ability to contextualize. I certainly don't make treatment decisions on isolated randomized trials--especially isolated randomized studies which fly in the face of previous years and years and years of good retrospective data and radiobiology theory ("[RTOG 0617 was] counterintuitive in view of previous data suggesting a clear radiation dose–response curve in locally advanced non-small-cell lung cancer"). Science currently suffers from a crisis of reproducibility; we should act/treat accordingly... we're all gamblers in medicine.
I completely agree with this. I practice in a medium sized hospital based group with seven attendings with weekly chart rounds. Drives me nuts when folks use such and such single institution data to justify whatever they are trying to do.
 
I completely agree with this. I practice in a medium sized hospital based group with seven attendings with weekly chart rounds. Drives me nuts when folks use such and such single institution data to justify whatever they are trying to do.

Definitely agree with you on single institution but the French trial that was presented at asco gu was multicenter RCT. The results for daily CBCT compared to weekly are mostly consistent with what we’d expect: lower rectal toxicity, better BCRFS, no difference in overall RFS. The surprising part was SS more 2nd cancers in Daily IGRT arm and lower OS
 
I'm curious to see if IGRT in the French trial was megavoltage cone-beam CT. If so, results might turn out to be believable.

Separate, much more provocative RCT reported this week at ASCO GU. OS and 2nd cancer detriment in daily IGRT group. Median FU 4 years
Meeting Library | Meeting Library

Conclusions:Compared to weekly control, daily IGRT in prostate cancer significantly decreases the risks of recurrence and late rectal toxicity but is associated with an increased risk of second cancer. Clinical trial information: NCT00433706
 
I'm curious to see if IGRT in the French trial was megavoltage cone-beam CT. If so, results might turn out to be believable.

Me too. Eager to see the publication. If it’s a real difference in 2nd cancers then I fear what we’ve been doing to patients with VMAT.
 
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