Table 3.

The Birmingham classification system for margins and chemotherapy-induced necrosis and corresponding local recurrence-free survival rates

Birmingham classification	5-year LRFS	95% CI	HR	95% CI	p value
1a: Necrosis ≥ 90% and margins > 2 mm	98.6%	90.5%–99.8%	1
1b: Necrosis ≥ 90% and margins ≤ 2 mm	91.7%	83.3%–95.9%	5.9	0.7–47	0.09
2a: Necrosis < 90% and margins > 2 mm	84.0%	72.5%–90.9%	11.0	1.4–84	0.02
2b: Necrosis < 90% and margins ≤ 2 mm	76.1%	72.5%–90.9%	19.6	2.6–144	0.003

LRFS = local recurrence-free survival; CI = confidence interval; HR = hazard ratio.