Table 3.

Interaction between PDGFRb score and RT treatment in Cox regression analysis

Endpoint	PDGFRb score group	Univariable RT vs. non-RT HR (95% CI); p value	Multivariable RT vs. non-RT incl. grade, age group, subtype HR (95% CI); p value
IBTR, 10 years	Low	0.25 (0.11–0.56); p = 0.001	0.29 (0.12–0.67); p = 0.004
	Medium	0.25 (0.13–0.48); p < 0.001	0.31 (0.16–0.59); p < 0.001
	High	0.61 (0.35–1.05); p = 0.073	0.64 (0.36–1.11); p = 0.110
	Interaction PDGFRb score: RT		p = 0.153
Any recurrence, 10 years	Low	0.50 (0.28–0.89); p = 0.018	0.57 (0.32–1.04); p = 0.067
	Medium	0.37 (0.23–0.60); p < 0.001	0.46 (0.28–0.75); p = 0.002
	High	0.70 (0.46–1.06); p = 0.089	0.75 (0.49–1.15); p = 0.192
	Interaction PDGFRb score: RT		p = 0.320
BCSD, 15 years	Low	1.05 (0.51–2.18); p = 0.888	1.12 (0.54–2.32); p = 0.768
	Medium	0.54 (0.29–1.00); p = 0.051	0.70 (0.35–1.26); p = 0.271
	High	0.77 (0.45–1.32); p = 0.338	0.88 (0.51–1.51); p = 0.633
	Interaction PDGFRb score: RT		p = 0.636

p values are based on Wald test; p values < 0.05 in bold text

IBTR ipsilateral breast tumor recurrence, BCSD breast cancer specific death, RT radiotherapy, HR hazard ratio, CI confidence interval