Table 3.

Cox regression analyses of cumulative incidence of severe radiation-induced lymphopenia (absolute lymphocyte count < 0.3 × 10⁹cells/L) during treatment stratified by the number of risk factors.

Number of Risk Factors	HR	95% CI	P Value
1 vs. 0	2.155	0.659–7.042	0.204
2 vs. 0	5.682	1.767–18.182	0.004
3 vs. 0	9.346	2.625–33.333	0.0006
2 vs. 1	2.632	1.686–4.098	<0.0001
3 vs. 1	4.329	2.232–8.333	<0.0001
3 vs. 2	1.642	0.984–3.012	0.110
0–1 vs. 2–3	3.111	2.046–4.729	<0.0001

Note: Risk factors were age ≥ 56 years, Lung V5 ≥ 51%, and XRCC1 rs25487 AA genotype.