To boost or not to boost?

[Aphtalyfe]

Hey guys I just started residency (PGY2) and am on the breast service... I was wondering how often you guys hypofx vs standardfx and then also how often and how much you boost; 42.4 -> 5_ or 50 -> 6_?

I'm asking because the practice here is typically to selectively boost for hypofx but consistently boost intact breast if using standardfx. That seems odd to me if the study everyone quotes was comparing 42.5/16 vs 50/25 with no boost.

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[ramsesthenice]

We treat almost all of our T1-T2 N0 BCT patients with 42/16 with a 10/2 boost if we can keep the 3D hot spot <110%.

Now, if you look close there are several points in the data is unclear on. First, the boost question. Whelen didn't do a boost. But thats not the only trial. If you look at the STARTB trial almost half of the patients got a 10/5 boost. Unclear if it helped or not. But a lot of people feel more comfortable with a boost extrapolating from conventional data.

Second is nodes. Again, Whelen included node negative only but 25% of the START patients were N1. Some places don't treat regional nodes in patients with 1-3 nodes. We do and our attendings are scared of hypofractionating the SCv. Therefore, we generally restrict hypofractionation to N0 patients. My point is, you see how many assumptions I had to make to get from point A-B? Its not always straight forward.

 

[Aphtalyfe]

So for a 3 field BCT do you guys boost the cavity every time? To 60?

I'm really asking these questions because I figured there was no real standard of practice. I'm just wondering how other institutions treated and how they reasoned.

 

[ramsesthenice]

Most cases yea are something like 50/25 with a boost to 60. Close margins, bad histology, big primary, etc will go a little higher, closer to 66.

There is no universal standard. Most places will be in that range. Beyond that, like I hinted above, then there are questions of when to include nodes, which nodes to include, etc. That is going to be variable as well. Your job is to learn the data and understand why they practice the way they do at your institution. For your boards it is perfectly fine to say at our institution we would do X. Then, when you are an attending you can do what makes sense to you based on the data and practice guidelines.

One of my favorite attendings is a head and neck guy and I have heard him say many times managing the breast is easy, but breast attendings do everything they can to make it hard

 

[Gfunk6]

Although close margins are a common reason for boost, it is fairly clear that increased radiation dose cannot compensate for poor surgery.

In my mind, the best reasons to boost are: premenopausal, grade 3 disease, triple negative receptor status, or extensive LVI

 

[grayharbor]

The Whelan trial did not include a boost. Don't know if actually true but I heard from a breast RadOnc that in his personal practice Dr. Whelan would often boost after hypofrac. Even though there a was non-significant trial difference in cosmetic outcome, we've seen some worse cosmetic outcomes with 42.56/16 + 10/2. Our institution often does 40.05/15 (START-B) + 10/2. No hypofrac for chemo patients or when treating SCV. Interestingly on subgroup analysis for the Whelan trial there were outcomes with hypofrac for G3 disease (10y LRR 4.7% standard fractionation vs 15.6% hypofractionated approach). So maybe some caution here.

There were a recently released SSO-ASTRO margin consensus statement (based on meta-analysis) which recommended no re-excision or dose alteration (for boosts or otherwise) if margin negative -- no tumor on ink. https://www.astro.org/News-and-Medi...ng-surgery-with-whole-breast-irradiation.aspx.

Published in JCO and RedJournal. http://www.ncbi.nlm.nih.gov/pubmed/24521674

 

[thesauce]

We nearly always std frac and always boost unless there's a compelling reason against it

 

[deleted171718]

Just playing devil's advocate/curious: What's the rationale for treating the whole breast at ~265 cGy/fraction, then boosting (a much smaller area) at 2 Gy/fraction?

 

[Gfunk6]

Just playing devil's advocate/curious: What's the rationale for treating the whole breast at ~265 cGy/fraction, then boosting (a much smaller area) at 2 Gy/fraction?

All the long-term breast boost data (EORTC, et. al.) was produced using conventional fractionation.

 

[Cancerdancer]

To that point, I hypofx almost everyone, and boost most pts with 10 Gy in 4 fx's, which means 20 total fractions, nice round number.

 

[Palex80]

When in doubt... do the boost.

We generally boost more than 80% of our patients. When we use hypofx (START B), we generally boost with 4 x 2.66 Gy and sometimes with 5 x 2.66 Gy for patients with a higher risk of recurrence (G3, L1, etc)
The most solid data for boost is for 16 Gy with long term outcome. The French 10Gy-boost-trial-team never published long term results.

 

[mavrik13]

Interestingly on subgroup analysis for the Whelan trial there were outcomes with hypofrac for G3 disease (10y LRR 4.7% standard fractionation vs 15.6% hypofractionated approach). So maybe some caution here.

Not to turn this into a hypofractionation debate, but to the above point, no difference in outcomes were seen with Grade 3 disease in the START A and B trials: http://www.nejm.org/doi/full/10.1056/NEJMc1002798