Proper adoption of SOUND trial for Radonc practice?

[communitydoc13]

Sentinel Lymph Node Biopsy vs No Axillary Procedure in Small Node-Negative Breast Cancer

This randomized clinical trial assesses whether the omission of sentinel node biopsy is noninferior to sentinel lymph node biopsy in female patients with small breast cancer and negative results on preoperative ultrasonography of axillary lymph nodes.

jamanetwork.com

There is a real push at my center to minimize SLN bx in low risk patients based on the above SOUND trial. During discussion, there was a reference to MAYO guidelines, which apparently adopt negative exam and U/S as adequate for all patients >50 yo with T1, ER+, Ki-67<20% non-lobular breast cancers. The MAYO guidelines are based on adjuvant systemic therapy considerations only.

A couple questions:

1. Is this really a proper application of the trial? The paper references as a primary endpoint distant outcomes at roughly 5 years in patients that are overwhelmingly low risk, ER+ patients who receive endocrine therapy and XRT (I'm assuming universally WBRT). This seems like a specious endpoint to me. There were 13.7% positive nodes in the SLN bx group. This functionally becomes a 200 person trial (actually quite worse than this as we anticipate no difference in outcomes for all those patients who are truly node negative) regarding looking at outcomes based on therapeutic decision making in overwhelmingly low risk cancers. We know that SLN bx is not therapeutic, and we expect the benefits of RNI or chemotherapy to have a delayed impact on distant outcomes in ER+ patients.

The sound trial does not answer whether differences in therapy matter for those patients that are node positive!

2. Are we willing to go here as radoncs regarding APBI? For these patients, are we willing to accept the 14% risk of occult node positivity and just offer APBI per existing guidelines? Or, are we going to advocate for WBRT or even high tangents in patients who forego a SLN bx?

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[brushbeamscanning]

Yea, not sure if it's sound.

 

[Reaganite]

In CALGB 9343, regional recurrence risk in undissected axilla, no RT arm was about 3%.

"There were no axillary recurrences among the 244 women who underwent initial axillary dissection. Among those who did not undergo axillary dissection, there were no axillary recurrences in the TamRT group; there were six of 200 in the Tam group."

Granted, these were all women over 70. But just seems like in general what we find pathologically in the axilla and nodes in general in breast isn't translating into equivalent regional recurrence risks.

 

[OTN]

In CALGB 9343, regional recurrence risk in undissected axilla, no RT arm was about 3%.

"There were no axillary recurrences among the 244 women who underwent initial axillary dissection. Among those who did not undergo axillary dissection, there were no axillary recurrences in the TamRT group; there were six of 200 in the Tam group."

Granted, these were all women over 70. But just seems like in general what we find pathologically in the axilla and nodes in general in breast isn't translating into equivalent regional recurrence risks.

That RT was different than APBI though

 

[radoncftw]

Sentinel Lymph Node Biopsy vs No Axillary Procedure in Small Node-Negative Breast Cancer

This randomized clinical trial assesses whether the omission of sentinel node biopsy is noninferior to sentinel lymph node biopsy in female patients with small breast cancer and negative results on preoperative ultrasonography of axillary lymph nodes.

jamanetwork.com

There is a real push at my center to minimize SLN bx in low risk patients based on the above SOUND trial. During discussion, there was a reference to MAYO guidelines, which apparently adopt negative exam and U/S as adequate for all patients >50 yo with T1, ER+, Ki-67<20% non-lobular breast cancers. The MAYO guidelines are based on adjuvant systemic therapy considerations only.

A couple questions:

1. Is this really a proper application of the trial? The paper references as a primary endpoint distant outcomes at roughly 5 years in patients that are overwhelmingly low risk, ER+ patients who receive endocrine therapy and XRT (I'm assuming universally WBRT). This seems like a specious endpoint to me. There were 13.7% positive nodes in the SLN bx group. This functionally becomes a 200 person trial (actually quite worse than this as we anticipate no difference in outcomes for all those patients who are truly node negative) regarding looking at outcomes based on therapeutic decision making in overwhelmingly low risk cancers. We know that SLN bx is not therapeutic, and we expect the benefits of RNI or chemotherapy to have a delayed impact on distant outcomes in ER+ patients.

The sound trial does not answer whether differences in therapy matter for those patients that are node positive!

2. Are we willing to go here as radoncs regarding APBI? For these patients, are we willing to accept the 14% risk of occult node positivity and just offer APBI per existing guidelines? Or, are we going to advocate for WBRT or even high tangents in patients who forego a SLN bx?

I do high tangents and treat lvl 1/2 in any patient who doesn't get a SLN bx.
I agree, one of the surgeons I work with omits SLN bx in a lot of patients.

 

[Reaganite]

That RT was different than APBI though

2/3s of the NO RT group in 9394 had NO axillary intervention with ultimate axillary recurrence risk of 3%. #1 complaint by far from my breast patients these days is axillary pain/arm stiffness, especially as hypofx has reduced skin reactions. My breast OTVs feel more like postop visits. Surgeons in our tumor boards have made it pretty clear they'd rather salvage the 3% than put everyone through SLNB, especially if no difference in survival. My surgeons are pretty adamant about following SOUND, so happy to see this question raised.

 

[metallica81788]

2/3s of the NO RT group in 9394 had NO axillary intervention with ultimate axillary recurrence risk of 3%. #1 complaint by far from my breast patients these days is axillary pain/arm stiffness, especially as hypofx has reduced skin reactions. My breast OTVs feel more like postop visits. Surgeons in our tumor boards have made it pretty clear they'd rather salvage the 3% than put everyone through SLNB, especially if no difference in survival. Just throw this out because my surgeon's are pretty adamant about following SOUND. So interested in everyone's opinions here.

Call me jealous - my surgeons will remove between 4-30 axillary nodes on any breast patient almost regardless of severity or age