DCIS: More is better!

[Burt Radnolds]

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From SABCS 2020: This is a bit of a throwback trial. Non low risk DCIS (see above), 1600 patients, 2x2 design (kind of), 50/25 vs 42.56/16 (versus preselecting conv vs hypofx for your center), boost (1600/8!) vs no boost.

Boost improved 5yr local recurrence 93 vs 97% (p< 0.001), independent of fractionation. All subgroups benefitted Cosmetic factors crudely worse but not SS.

Takeaways:
More is better!
First randomized data that boost helps in DCIS.
First randomized data that boost helps in hypofractionation.
Cosmesis not dramatically affected.

I realize many might find this quite boring and obvious but hey, at least it's not another de-escalation trial!

 

[drewdog1973]

Interesting, saw that a few days ago.

Not really practice changing, in my opinion. 5 year recurrence rate is 7% with 50 / 25 ? Would you quote 1.5% recurrence risk / year for DCIS treated with RT? Not even for high grade would I quote that. Fractionaters gonna fractionate with boost. Hypo guys gonna hypo sans boost. Don’t see anyone on either side changing what they do based on this.

 

[Palex80]

We included patients in this trial at my institution. I personally view this as practice changing. Evidence for boost in DCIS was scarce before this trial came up and practice recommendations were based on retrospective reviews & analyses.
I will now definetely opt for a boost in all my "high-risk" patients.
Actually, it's quite remarkable that the authors managed to nail their hypothesis so good in the trial, look at the percentages they thought of when they formulated the trial and what came out in the end. Well done!
I do not have any information on how many patients actually received tamoxifen on the trial, we know that this will aid greatly in reducing recurrence rates at 5 years, so we should await for that information. Perhaps the benefit will grow significantly at 10 years, if many patients on the trial had tamoxifen for 5 years, we've seen that pattern in early invasive breast cancer too before.

 

[thecarbonionangle]

4256+ boost seems like slam dunk in DCIS

 

[drewdog1973]

NSABP B17 with 50/25 - the 15 year IBTR was 10% with RT alone, the 15 year IBTR with RT/Tam was 7%.
I'm not sure why the 5 year rate is so high with 50/25 Gy (no boost) in a modern-ish study. Seems oddly high.
Each newer breast study tends to show lower recurrence rates - i.e. PRIME II 10 year IBTR with radiation is about 1%,

 

[Mandelin Rain]

16 + 4 for (most) DCIS <70 over here. If small, wide margin, low grade probably just 16 or 0.

 

[drewdog1973]

16/8 is an odd boost RX. Haven't done that in years.

 

[scarbrtj]

16/8 is an odd boost RX. Haven't done that in years.

It’s not heresy. More Harrisy (Jay) because he likes/liked 45/25 as the whole breast dose usu. But it’s also European/EORTCy as we know. Jay was saying 30 years ago “the whole breast dose may not matter as much as the cavity dose.” Man ahead of his time.

But what is it they say...
IDLE hands are the devil’s workshop? Give rad oncs a positive LC “boost” trial and it’s totally tool time!

 

[BobbyHeenan]

16 + 4 for (most) DCIS <70 over here. If small, wide margin, low grade probably just 16 or 0.

That's my go to as well.

I also offer APBI sometimes for DCIS as well...though obviously not as strong of data as WBRT (now with boost data!).

 

[evilbooyaa]

That's my go to as well.

I also offer APBI sometimes for DCIS as well...though obviously not as strong of data as WBRT (now with boost data!).

Agreed. Good trial to know for non-low risk DCIS (something that wouldn't be eligible for 9804) with boost. I'll probably stick with 2.5Gy x 4 rather than 16/8 in these patients though.

And yes, offer APBI to 'suitable DCIS' patients per most recent APBI guidelines (basically those who meet 9804 criteria)

 

[Palex80]

16/8 is an odd boost RX. Haven't done that in years.

Well, it does come from a randomized trial... Actually it comes from THE randomized boost trial with the longest follow up.

I'll probably stick with 2.5Gy x 4 rather than 16/8 in these patients though.

4 x 2.5 Gy is less dose though.

We often boost with 5 x 2.66 Gy. 🙂

 

[evilbooyaa]

Well, it does come from a randomized trial... Actually it comes from THE randomized boost trial with the longest follow up.


4 x 2.5 Gy is less dose though.

We often boost with 5 x 2.66 Gy. 🙂

While I suppose you are correct, I wouldn't do 2Gy x 8 boosts before this trial in the absensce of un-resected positive margins. Let's say my extra 2.56 for whole breast (42.56/16) vs your 40.05/15 equals out on boost?

 

[Palex80]

While I suppose you are correct, I wouldn't do 2Gy x 8 boosts before this trial in the absensce of un-resected positive margins. Let's say my extra 2.56 for whole breast (42.56/16) vs your 40.05/15 equals out on boost?

True, true!

Positive margins call for even MORE dose!
Behold: The "Breast-Grill"-trial: 26 Gy of BOOST!
Impact of the boost dose of 10 Gy versus 26 Gy in patients with early stage breast cancer after a microscopically incomplete lumpectomy: 10-year results of the randomised EORTC boost trial - PubMed

 

[scarbrtj]

DCIS is why I became a rad onc. My mom got DCIS and through her treatment process I met her rad onc and thought he was the smartest coolest guy ever. I went with her to many of the treatments. I knew nothing medically back then. However I do clearly remember her getting 33 treatments.

She hasn’t seen her rad onc in about 15 years and maybe rightly so (she’s about 25y out from dx), but if she did I bet he’d be shocked. She doesn’t really have a left breast anymore as much as a fieldstone. It’s a source of constant minor irritation to her. I haven’t actually seen it because I’m afraid to probably. But on palpating it feels unnatural. She resigns herself to the problems because she knows she had “breast cancer” and the radiation was necessary. I don’t disagree with her ever.

I don’t know if her travails should or shouldn’t color my thinking. Probably shouldn’t. But it does. At SABCS they’re talking about PRIME in invasive; ~10% LC improvement with RT but maybe consider skipping RT altogether. I don’t buy that. But I have to give the logic some credence. Will I ever boost DCIS? Maybe. Would I ever use 16/8 with hypofx? Not in a million years. I bet few of you would either. So let’s all just retreat back to our own logical melanges and biases and give 5 times two or 4 times 2.5 or whatever. Because “it makes sense.” But if we aren’t doing “it” rather similar to what was done in the trial... what purpose was the trial? Proof of concept? Maybe. The therapeutic window in invasive breast cancer is annoyingly narrow; it’s probably insanely narrow in pre-invasive disease.

 

[Palex80]

DCIS is why I became a rad onc. My mom got DCIS and through her treatment process I met her rad onc and thought he was the smartest coolest guy ever. I went with her to many of the treatments. I knew nothing medically back then. However I do clearly remember her getting 33 treatments.

She hasn’t seen her rad onc in about 15 years and maybe rightly so (she’s about 25y out from dx), but if she did I bet he’d be shocked. She doesn’t really have a left breast anymore as much as a fieldstone. It’s a source of constant minor irritation to her. I haven’t actually seen it because I’m afraid to probably. But on palpating it feels unnatural. She resigns herself to the problems because she knows she had “breast cancer” and the radiation was necessary. I don’t disagree with her ever.

I don’t know if her travails should or shouldn’t color my thinking. Probably shouldn’t. But it does. At SABCS they’re talking about PRIME in invasive; ~10% LC improvement with RT but maybe consider skipping RT altogether. I don’t buy that. But I have to give the logic some credence. Will I ever boost DCIS? Maybe. Would I ever use 16/8 with hypofx? Not in a million years. I bet few of you would either. So let’s all just retreat back to our own logical melanges and biases and give 5 times two or 4 times 2.5 or whatever. Because “it makes sense.” But if we aren’t doing “it” rather similar to what was done in the trial... what purpose was the trial? Proof of concept? Maybe. The therapeutic window in invasive breast cancer is annoyingly narrow; it’s probably insanely narrow in pre-invasive disease.

Thank you for sharing this, Scarbtj. I appreciate it a lot. Rarely we get the chance to hear about the real stories behind these avatars. Take care!