Background
Systematic review and meta-analysis examining the benefit of a radiation boost to the tumor bed after whole-breast irradiation (WBI) in patients with DCIS. Included studies of patients with DCIS treated with BCS + WBI with or without a tumor bed boost. Conducted under ASTRO auspices; published in JAMA Oncology 2017.
Interventions and follow up
Arm A: BCS + WBI + tumor bed boost
Arm B: BCS + WBI alone (no boost)
Primary endpoint: Ipsilateral breast tumor recurrence (IBTR)
mFollow up: Variable across included studie
Arm B: BCS + WBI alone (no boost)
Primary endpoint: Ipsilateral breast tumor recurrence (IBTR)
mFollow up: Variable across included studie
Results
Overall IBTR reduction with boost: Boost significantly reduced IBTR (OR 0.59, 95% CI 0.45–0.77)
Invasive recurrence reduction: Significant reduction in invasive IBTR with boost
Subgroups with greater benefit: Younger age, high nuclear grade, positive/close margins, comedo necrosis
Invasive recurrence reduction: Significant reduction in invasive IBTR with boost
Subgroups with greater benefit: Younger age, high nuclear grade, positive/close margins, comedo necrosis
Adverse events
Main adverse events: Higher-dose boost is associated with increased fibrosis and cosmetic compromise (inferred from WBI boost data in invasive cancer; specific DCIS toxicity data limited in the studies reviewed).
Conclusions
A tumor bed boost after WBI for DCIS reduces IBTR, particularly in higher-risk patients (younger age, high nuclear grade, close/positive margins). The absolute benefit is modest in low-risk DCIS, suggesting boost should be individualized based on patient and pathological risk factors rather than routinely applied.
Key Limitations
Key Limitations: Meta-analysis of heterogeneous, largely retrospective studies — not RCT-level evidence. High-risk DCIS features are likely to be over-represented in the boost arms due to indication bias. Optimal boost dose and technique are not defined. No randomized DCIS-specific boost trial exists (unlike invasive cancer, where EORTC 22881 established the boost benefit). Long-term cosmetic outcomes are incompletely reported.
Clinical Context
In invasive cancer, the EORTC 22881 RCT showed that boost after WBI reduces IBTR with greatest benefit in younger patients. By extension, ASTRO recommends considering a boost in DCIS patients with high-risk features (young age, high grade, close margins). For low-risk DCIS (grade 1-2, older, wide margins), the incremental benefit of boost after WBI is less certain.
References