The 2024 Assisi think tank on breast cancer: Focus on the use of a tumour bed boost after breast conserving therapy.

Summary

Expert consensus synthesizing literature concludes that tumor bed boost after whole-breast irradiation halves 10-year local recurrence but worsens cosmesis and fibrosis without survival benefit. A pragmatic 3% absolute 10-year risk-reduction threshold is proposed to guide omission vs. use with shared decision-making.

Key Findings

• Boost halves 10-year local recurrence after whole-breast irradiation.
• No overall survival improvement with boost despite lower local recurrence.
• Cosmetic outcomes worsen and fibrosis increases with boost.
• Recommends omitting boost if absolute 10-year reduction is <3%; shared decision-making if >3%.
• Calls for better boost volume precision and subgroup identification for safe omission.

Clinical Implications

Adopt a shared decision-making framework using a 3% 10-year local recurrence risk-reduction threshold to decide on boost; prioritize cosmesis in low-risk cases and refine boost volume for necessary cases.

Limitations

• Consensus review without new primary data; subject to publication and selection bias.
• Heterogeneity in source studies may limit generalizability; lacks patient-level meta-analysis.

Future Directions

Prospective identification of low-risk subgroups for safe boost omission and trials testing precise boost volume delineation to mitigate cosmetic toxicity.