Partial Breast RT mainstream?

[1r1d1um]

Hi, New to the forum. I visited a center recently that did a lot of APBI for early stage breast cancer patients. I also spoke with a radonc who is fairly well known who made it seem like apbi was akin to malpractice! I'm confused as to why there is such polarized opinions. it makes sense to me, and despite what little i know about the data, it seems like there's nothing really showing those who get partial radiation to the breast fare any worse in any major outcome. so what's the deal? just curious and would love the peanut gallery to weigh in. Thanks,

1r

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[Gfunk6]

From my perspective, APBI is pretty mainstream and I see it in the community quite frequently. One potential problem is that (like many areas in our field) the technology is rapidly outpacing evidence-based medicine. For instance, APBI randomized trials were done primarily with three technologies:

1. Catheter-based balloon systems (Mammosite)
2. kV energy photons (Intrabeam)
3. Electrons w/ lead shielding (mainly used in Europe)

All three of these technologies are easiest to use in the academic setting. For #1, HDR is required so you need an afterloader, Iridium sources, have to meet federal regulations for radioactive isotopes, etc. #2 and #3 are intraoperative approaches and generally only academic places have the volume and expertise to use them, not to mention the capital costs.

In the community, electronic brachytherapy (Zoft) is more commonly used, but this has not really been validated in randomized trials like the above technologies. Of course, one could argue that the physical principles are the same and therefore the efficacy must also be (like was done for IMRT and protons).

ASTRO has published guidelines for who is a good ABPI candidate (i.e. > 50 yrs old, no pure DCIS, no node positive disease, no positive margins, etc).

 

[medgator]

From my perspective, APBI is pretty mainstream and I see it in the community quite frequently. One potential problem is that (like many areas in our field) the technology is rapidly outpacing evidence-based medicine. For instance, APBI randomized trials were done primarily with three technologies:

1. Catheter-based balloon systems (Mammosite)
2. kV energy photons (Intrabeam)
3. Electrons w/ lead shielding (mainly used in Europe)

All three of these technologies are easiest to use in the academic setting. For #1, HDR is required so you need an afterloader, Iridium sources, have to meet federal regulations for radioactive isotopes, etc. #2 and #3 are intraoperative approaches and generally only academic places have the volume and expertise to use them, not to mention the capital costs.

In the community, electronic brachytherapy (Zoft) is more commonly used, but this has not really been validated in randomized trials like the above technologies. Of course, one could argue that the physical principles are the same and therefore the efficacy must also be (like was done for IMRT and protons).

ASTRO has published guidelines for who is a good ABPI candidate (i.e. > 50 yrs old, no pure DCIS, no node positive disease, no positive margins, etc).

And #4, APBI given via 3DCRT. If I recall correctly, there is the least amount of long-term follow-up using 3DCRT external beam approaches for APBI. It is one of the options that is allowed on the current NSABP B-39 trial however, and I know that people do it in the community setting.

 

[seper]

In NSABP B-39, 70% of APBI is actually done via 3-D CRT. It is easy to plan and to use. Safety of this approach, however, is questioned by some.

From my perspective, APBI is pretty mainstream and I see it in the community quite frequently. One potential problem is that (like many areas in our field) the technology is rapidly outpacing evidence-based medicine. For instance, APBI randomized trials were done primarily with three technologies:

1. Catheter-based balloon systems (Mammosite)
2. kV energy photons (Intrabeam)
3. Electrons w/ lead shielding (mainly used in Europe)

All three of these technologies are easiest to use in the academic setting. For #1, HDR is required so you need an afterloader, Iridium sources, have to meet federal regulations for radioactive isotopes, etc. #2 and #3 are intraoperative approaches and generally only academic places have the volume and expertise to use them, not to mention the capital costs.

In the community, electronic brachytherapy (Zoft) is more commonly used, but this has not really been validated in randomized trials like the above technologies. Of course, one could argue that the physical principles are the same and therefore the efficacy must also be (like was done for IMRT and protons).

ASTRO has published guidelines for who is a good ABPI candidate (i.e. > 50 yrs old, no pure DCIS, no node positive disease, no positive margins, etc).

 

[deleted4401]

People use Xoft? I heard it was too expensive to use in the community, b/c not much experience using with Gyn, which is the other higher volume HDR cases. We use HDR for PBI.

The data is really strong for well selected patients, I'm not sure why it wouldn't be mainstream.

ASTRO Guidelines are fairly restrictive. All these series are coming out for DCIS and for groups doing PBI in the "cautionary" group who have excellent results (Beaumont and other institutions) - control rates in the upper 90s. ACS guidelines are a little more reasonable. I think offering it for DCIS is fine, as long as margins good, and Grade 1-2.

3D CRT PBI is something we won't do ... I thought someone (Wazer maybe?) presented results showing pretty poor cosmetic outcome. For some reason, the fractionation is different too, isn't it 38.5 Gy instead of 34 Gy?

Curious how its use would change if it was reimbursed less than external beam (I think nearly the same for one week of Mammosite as it is for a 6 week course of EBRT).

-S

 

[Cancerdancer]

Lost in the discussion are interstitial catheters. Per the ASTRO 2009 consensus paper
"interstitial brachytherapy is the technique with the longest follow-up reported, whereas follow-up data for other APBI techniques remain limited."
And the 3 techniques on B-39 are 3D-CRT, MammoSite, and multicatheters. Just thought it deserved a mention.

 

[G'ville Nole]

Lost in the discussion are interstitial catheters. Per the ASTRO 2009 consensus paper
"interstitial brachytherapy is the technique with the longest follow-up reported, whereas follow-up data for other APBI techniques remain limited."
And the 3 techniques on B-39 are 3D-CRT, MammoSite, and multicatheters. Just thought it deserved a mention.

This. In the one phase III trial with mature follow-up (Csaba Polgar), over 2/3 of pts in the PBI arm got multi-cath. Bob Kuske brought his multi cath procedure to UW when he was on staff there, and as a result, most of APBI I did as a resident was done using this technique. The good is that it is highly adaptable to a wide range of lumpectomy cavities, and offers a superior DHI to balloon catheter APBI. The bad is that it has a much steeper learning curve, and is a tough sell outside of academic centers since 1) surgeons either lose out on cath placement or get paid the same for a more difficult and time consuming procedure, and 2) patients view pictures of a single catheter in the breast (Mammosite et al.) vs. the "shishkaboob" they get with multi-cath, and the latter seems less desirable.

On a related note, I'm thinking of patenting the term "shishkaboob".

 

[Gfunk6]

On a related note, I'm thinking of patenting the term "shishkaboob".

We actually use shishkaboob (I mean SAVI) at our practice. I'm curious as why it is considered interstitial when it still inserted in a cavity?

Also, as a side note, it is quite interesting how skewed some of our opinions are (mine anyway) based on where you trained. At UCSF, we use Intrabeam exclusively for APBI so I was only dimly aware of multi-catheter techniques. Once you are out in the "real" world you realize that there's a whole new slew of techniques (and products) out there.

 

[Cancerdancer]

We actually use shishkaboob (I mean SAVI) at our practice. I'm curious as why it is considered interstitial when it still inserted in a cavity?

Multicatheter interstitial brachy, as traditionally practiced, is much more shishkaboob than SAVI, and is not intracavity. A google image search for multicatheter interstitial brachytherapy shows some nice images--focus on the ones with bruised, deformed, skewered breasts, not those of the SAVI device with the surrounding halo

 

[Gfunk6]

Multicatheter interstitial brachy, as traditionally practiced, is much more shishkaboob than SAVI, and is not intracavity. A google image search for multicatheter interstitial brachytherapy shows some nice images--focus on the ones with bruised, deformed, skewered breasts, not those of the SAVI device with the surrounding halo

Ouch.

 

[G'ville Nole]

See, it's catching on!

GFunk, I wouldn't consider SAVI interstitial, although it does share some dose deposition characteristics w/ multi-cath. Namely, the tissue that invaginates between the struts will see some of the same hot spots that you will find in multi-cath, but not in balloon cath treatments. However, like the balloon cath, the only way your dose gets out to the PT_eval is from dwell times within the cavity. With a proper multi-cath implant, one essentially "flanks" the entire PTV_eval (which can now be pretty much any shape), allowing a more even dose distribution. As I said above, you will get a higher V300 and V200 with those plans, but those volumes remain minimal, and you can typically get a superior DHI. Whether that is clinically relevant or only interesting to physicists is a valid question. Anecdotally, we saw a higher than expected number of calcifications following multi-cath that were biopsied and almost universally shown to be fat necrosis, so that may come with the territory when you've got these little areas of 300% dose in the breast tissue.

For the record, I'm an equal opportunity proponent of multi-cath, SAVI and Mammosite in appropriately selected patients, although the predominance of my current practice is with the Mammosite. I remain a bit leery of external beam, and certainly wouldn't offer it off-study.

 

[medgator]

Just curious as to why not offer 3D-CRT off protocol? The data on the technique currently published is comparable to what was published with MammoSite when it began being used off-protocol. Cosmesis at institutions doing fair amounts of 3D-CRT has been good with two small series reporting poor cosmesis.

Of all the APBI techniques, 3DCRT has the least amount of long-term data. I agree with others in that I would not offer it off protocol.

 

[medgator]

3D CRT PBI is something we won't do ... I thought someone (Wazer maybe?) presented results showing pretty poor cosmetic outcome. For some reason, the fractionation is different too, isn't it 38.5 Gy instead of 34 Gy?

Correct. There's a reason for that and I can't remember why at the moment

 

[G'ville Nole]

Just curious as to why not offer 3D-CRT off protocol? The data on the technique currently published is comparable to what was published with MammoSite when it began being used off-protocol. Cosmesis at institutions doing fair amounts of 3D-CRT has been good with two small series reporting poor cosmesis.

Everyone (myself included) is a slave to their own biases, but as a rule conflicting data about an investigational technique will make me less likely to use that technique. A couple other peripheral observations feed my own bias:

1) I've generated and evaluated a fair number of 3D-CRT APBI plans pursuant to my research in residency. When conforming to the specs outlined in B-39, the integral dose to the breast is significantly higher than comparable brachy techniques. This is due to higher prescription dose delivered over a larger PTV out of necessity (correcting for respiratory motion and set-up variation is a non-issue w/ brachy). Entry and exit doses also result in a larger tissue area receiving 80-100% of rx. When I see these dose characteristics on a plan eval, and then hear negative things about cosmesis, they're difficult to dismiss.

2) Historically, we have a nice dose-response data set for late tissue effects in several of the trials run in the UK (Royal Marsden-->START A-->START B). In the initial RMH trial, the high dose arm was whole breast RT, 42.9 Gy/13 fx (3.3 Gy/fx). That arm was modified downward to 3.2 Gy x13 for the START A trial on the basis of a significant increase in late effects. If one uses an a/b of 3 for late effects, that was a BED of 90.1 Gy that was scrapped. Carrying the BED calculation further, we get 89.7 Gy for APBI, 86 Gy for the reduced START A dose, 83.3 Gy for standard 50/25, and 80.4 Gy for NCI-Canada. Of those 5 regimens, only the bottom two have good mature data on cosmesis, and the APBI dose is pretty close to one that has data supporting inferior cosmesis. A rational counter to this would be to point out that the other regimens are whole- rather than partial-breast, but as I alluded to above, a plan that passes RTOG muster is honestly not too far removed from whole breast.

My final reason for concern is ill-suited for posting on a public board, since the plural of "anecdotes" is not "data", and I have no wish to undermine the good researchers who are trying to illuminate this issue further.

 

[Houston500]

In the community, electronic brachytherapy (Zoft) is more commonly used, but this has not really been validated in randomized trials like the above technologies. Of course, one could argue that the physical principles are the same and therefore the efficacy must also be (like was done for IMRT and protons).

I don't know where you got the information that Zoft is commonly used in the community for APBI. Medicare and most major insurance carriers still consider Zoft and e-brachy as experimental, so it's still very hard to collect payment for this. Zoft was recently sold to another company and shortly there after, it's intra-op applicator was found to be defective (coincidence??). 3D conformal RT and HDR brachy are the most common methods used in my experience.

 

[Gfunk6]

Perhaps it's regional bias on my part? Quite a few practices signed on to Zoft when they first started out, before issues with tungsten leakage into lumpectomy cavities were well-known.

One of the biggest advantages of e-brachy is that you don't have to apply for a Radioactive Material (RAM) License to use it. It's a huge pain in the ass to meet all the federal regulations to use HDR brachy not to mention the capital costs (like a shielded room for afterloader). In fact, they make your life difficult adding a user to an existing license. Also e-brachy is quite a bit easier to use for surgeons as they don't have to shield their OR or evacuate personnel every time the machine is on.

3DCRT, while easy to do with existing hardware/software systems has numerous drawbacks as described by previous posters.

Nowadays, people who use Zoft have a "Zoft van" parked nearby for emergency situations.

I don't know where you got the information that Zoft is commonly used in the community for APBI. Medicare and most major insurance carriers still consider Zoft and e-brachy as experimental, so it's still very hard to collect payment for this. Zoft was recently sold to another company and shortly there after, it's intra-op applicator was found to be defective (coincidence??). 3D conformal RT and HDR brachy are the most common methods used in my experience.