DCIS Patients Derive IBTR Benefit From Tumour Bed Radiation Boost During Treatment

The addition of a radiation boost improves ipsilateral breast tumour recurrence rates in patients with ductal carcinoma in situ

medwireNews: A study of women with ductal carcinoma in situ (DCIS) indicates that adding a radiation boost to the tumour bed after breast-conserving surgery and whole-breast radiotherapy (WBRT) reduces the likelihood of long-term ipsilateral breast tumour recurrence (IBTR).

Reporting in JAMA Oncology, the investigators describe a “small but statistically significant benefit” across all age ranges that is “in magnitude similar to that experienced with invasive cancer boost”.

The researchers examined data for 4131 patients, aged 24–88 years, from the USA, Canada and France who received a new diagnosis of DCIS with no microinvasion between 1980 and 2010 and had been followed up for at least 5 years.

This included 1470 patients who underwent surgery plus conventionally fractionated (45.0–50.4 Gy in 25–28 Gy fractions) or hypofractionated (39.0–44.0 Gy in 13–16 Gy fractions) WBRT and 2661 patients whose treatment also included a 10–16 Gy electron or photo boost.

Use of boost was not associated with age or tumour grade but patients were more likely to receive an RT boost if they had positive tumour margins, a positive oestrogen receptor status or comedo necrosis, explain Meena Moran, from Yale University School of Medicine in New Haven, Connecticut, USA, and co-authors.

In all, 6.1% of patients experienced IBTR, almost half (46.6%) of which cases were invasive. And compared with no RT boost, receipt of boost was associated with a significantly lower rate of IBTR, with a hazard ratio of 0.73.

Indeed, IBTR-free survival rates were significantly better with RT boost at 5 years (97.1 vs 96.3%), 10 years (94.1 vs 92.5%) and 15 years (91.6 vs 88.0%).

Initial multivariable analysis showed that RT boost continued to be independently associated with reduced risk of IBTR after adjusting for confounding factors, such as tumour grade, size and presence of comedo necrosis, margin status, age and receipt of tamoxifen.

However, further analysis suggested that the interaction between age and margin status and the effect of boost on outcome was no longer significant after adjustment.

Acknowledging the limitations of the retrospective study design, Meena Moran et al observe: “Given the small numbers of patients with positive margins in the present study, the effect of the RT boost for DCIS specifically for positive margins remains inconclusive.”

The authors conclude: “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.”

Reference

Moran MS, Zhao Y, Ma S, et al. Association of radiotherapy boost for ductal carcinoma in situ with local control after whole-breast radiotherapy.JAMA Oncol; Advance online publication 30 March 2017. doi:10.1001/jamaoncol.2016.6948

medwireNews is an independent medical news service provided by Springer Healthcare. © 2017 Springer Healthcare part of the Springer Nature group