What total dose do you use for a close and positive breast cancer margin that cannot be re-excised?
What total dose do you use for a positive margin that cannot be re-excised?
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Based on consensus guidelines, there is no such thing as a close margin as HR for recurrence did not change based on margin width. That was the reason for group to conclude that no tumor at inked margin is a negative margin (except for pure DCIS or those who had neoadjuvant chemo).
If we give a boost after whole breast with hypofractionation in any patient with a negative margin, then our dose is 10 Gy in 4 fractions.
As far as a positive margin is concerned, the long term results of EORTC boost vs. no boost trial after central pathology review showed for those patients with invasive breast cancer and positive resection margins, the IBTR rate was decreased from 13% to 4% with the addition of a 16 Gy boost.
In a separate EORTC study for positive margins, the cumulative incidence of IBTR in the group of patients who had incomplete tumor resections was 17.5% versus 10.8% for patients receiving a 10 Gy boost versus those receiving a 26 Gy boost (p = NS).
Based on this, our dose is between 66-70 Gy for a positive margin.
According to the most recent 2018 ASTRO whole breast fractionation guidelines, in the presence of strong risk factor(s) for local recurrence, such as the single risk factor of positive margins or a combination of risk factors such as young age and close margins, a higher radiation boost dose of 1400 to 1600 cGy in 7 to 8 fractions or 1250 cGy in 5 fractions may also be used.
Piggybacking on some of the above comments on positive margins and surgery, I do wish every institution used intraoperative pathology for all breast cancer cases, similar to the Mayo Clinic. An anecdotal case to share is a patient who sought a second opinion at the Mayo Clinic and underwent a third excision of a positive margin, which at the initial treating institution was deemed clinically negative margins, as there was no additional breast parenchyma to resect. With a confident reassurance to the patient, we got it all. Given the intraoperative pathology availability at Mayo, the surgeon was able to make an elliptical incision over the prior tumor site and detected an area of gross residual disease, and cleared it to negative margins. I would love to see intraoperative pathology become a standard when patients go in for a reexcision of a breast cancer, or educating patients to go seek an institution that utilizes this approach.