Table 2.

Left‐sided and right‐sided breast cancer, numbers of women and percentages irradiated

	Number of women		Percentage irradiated			p‐value
	Left	Right	Left	Right	Difference
Women diagnosed before 1990 (Mean follow‐up 8.9 years)
Age at cancer diagnosis (years)
<60	164,208	154,272	53.02	52.91	0.11	0.54
60+	147,154	135,599	44.81	44.85	−0.04	0.81
All ages	311,362	289,871	49.14	49.14	0.00	0.98
Women diagnosed 1990+ (Mean follow‐up 5.8 years)
Age at cancer diagnosis (years)
<60	375,479	359,179	56.95	57.11	−0.16	0.16
60+	309,444	288,913	50.66	51.01	−0.35	0.007
All ages	684,923	648,092	54.10	54.39	−0.29	0.001
All women	996,285	937,963	52.55	52.77	−0.22	0.003

For a more detailed tabulation see Supporting Information Table S5.