medwireNews: A radiotherapy boost to the tumor bed following whole-breast radiotherapy (WBRT) for ductal carcinoma in situ (DCIS) significantly reduces the risk for ipsilateral breast tumor recurrence (IBTR), pooled study data show.
The researchers say that the benefit was “similar to that seen in patients with invasive breast cancer” and suggest “the addition of a radiation boost dose may be considered to provide an incremental benefit in improving local control after whole-breast radiotherapy.”
The retrospective analysis included data for 4131 patients (median age 56.1 years) treated for newly diagnosed pure DCIS (no microinvasion) at 10 academic institutions in the USA, Canada, and France over 30 years. All patients underwent breast-conserving surgery, received WBRT with or without an electron or photon boost (10–16 Gy) boost, and had a minimum of 5 years of follow-up.
During follow-up, there were 253 (6.1%) cases of IBTR, of which 118 (46.6%) were invasive.
Meena Moran (Yale University School of Medicine, New Haven, Connecticut, USA) and colleagues report that the 2661 patients in the boost group had a significant 27% lower risk for IBTR than the 1470 in the no-boost group.
And IBTR-free survival was significantly higher with the RT boost than without it at 5 years (97.1 vs 96.3%), 10 years (94.1 vs 92.5%), and 15 years (91.6 vs 88.0%).
After adjusting for potential confounders including age (<50 vs ≥50 years) and tamoxifen use, which were both associated with reduced IBTR, receipt of an RT boost remained significantly associated with a reduced risk for IBTR, at a hazard ratio (HR) of 0.68.
The researchers also carried out exploratory subset analyses that revealed no significant associations among IBTR, RT boost, and the presence or absence of necrosis, or estrogen receptor status.
Margin status, did, however affect the benefit derived from the RT boost; patients with negative margins who received an RT boost had a significantly reduced risk for IBTR compared with those who did not (HR=0.54), whereas patients with positive margins did not, irrespective of whether positive margins were defined as ink on tumor or as less than 2.0 mm.
However, Moran et al point out that this finding “should be interpreted with caution,” because the small number of patients with positive margins (less than 4% of the cohort) meant the analysis “was substantially underpowered to detect a significant benefit.”
The researchers conclude in JAMA Oncology: “Ultimately, DCIS treatment decisions are complex and need to be tailored to the patient’s age, clinicopathologic features, tumor biology, individualized preferences, and anticipated longevity.
“For patients who have a life expectancy of more than 10 to 15 years and in whom WBRT is part of the treatment plan, the addition of an RT boost to the tumor bed should be considered to provide an added incremental benefit in decreasing IBTR.”
By Laura Cowen
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