NEW YORK (Reuters Health) - A radiotherapy (RT) boost to the tumor bed after whole-breast RT for ductal carcinoma in situ (DCIS) appears to reduce ipsilateral breast tumor recurrence (IBTR), according to a retrospective analysis.
As Dr. Meena S. Moran told Reuters Health by email, "Many radiation oncologists routinely deliver a boost after whole-breast RT for DCIS, anticipating a similar benefit to our experience with invasive cancers. But we haven't had consistent data to demonstrate this benefit in DCIS."
In a March 30 online paper in JAMA Oncology, Dr. Moran of Yale University School of Medicine, New Haven, Connecticut and colleagues note, "Despite its excellent prognosis relative to invasive breast cancer, DCIS remains a heterogeneous disease for which optimal treatment management is commonly debated."
They go on to say that "enrolling patients in DCIS trials remains a challenge." To gain further information, they pooled data on more than 4,100 patients with at least five years of follow-up treated at 10 academic institutions between 1980 and 2010.
All had newly diagnosed pure DCIS without microinvasion. They were treated with breast-conserving surgery and whole breast RT with or without boost.
Overall, 2,661 patients received the boost (median dose, 14 Gy) and 1,470 did not. There was no difference between boost or no-boost distribution according to age or disease grades. However, patients with positive margins and unknown estrogen receptor status were among those more likely to have received a boost.
With median follow-up of nine years, the boost was significantly associated with lower IBTR (hazard ratio, 0.73). At five years, IBTR-free survival was 97.1% with a boost versus 96.3% with no boost. The pattern was similar at 10 years (94.1% versus 92.5%) and 15 years (91.6% versus 88.0%).
On multivariable analysis, independent of age and tamoxifen use, boost was significantly associated with reduced IBTR (HR, 0.68).
The researchers say the findings are in line with "what has been demonstrated across all age groups and grades for invasive breast cancers."
Summing up, Dr. Moran concluded, "Our study has demonstrated that the use of a radiation boost provides an albeit small but significant long-term benefit in reducing breast tumor recurrence for DCIS patients and supports the consideration of a DCIS boost in patients undergoing WBRT who have life expectancies of 10 or more years."