Table 1.

Characteristics in invasive breast cancer patients treated with HF-WBI vs. CF-WBI

	CF-WBI (n=433,152)	HF-WBI (n=81,864)	%HF-WBI	AOR (95% CI)a	Chi-square*
Age at diagnosis					4175.14
<40	16,045	921	5.43	1.0 (ref)
40–44	31,208	2,574	7.62	0.74 (0.67–0.82)
45–49	54,150	5,930	9.87	0.94 (0.86–1.04)
50–54	64,826	10,606	14.06	1.43 (1.31–1.57)
55–59	71,909	13,944	16.24	1.66 (1.51–1.82)
60–64	74,557	17,714	19.20	1.93 (1.76–2.12)
65–69	68,444	19,681	22.33	2.25 (2.04–2.47)
70–74	23,398	4,053	14.76	2.53 (2.28–3.69)
75–79	16,611	3,065	15.58	3.32 (2.98–3.69)
80+	12,004	3,376	21.95	5.96 (5.35–6.65)
Race/ethnicity					355.84
White	346,741	65,473	15.88	1.0 (ref)
Black	46,907	6,838	12.72	0.85 (0.82–0.88)
Hispanic	19,738	4,098	17.19	1.05 (1.01–1.10)
Asian	13,041	4,017	23.55	1.48 (1.41–1.55)
Other/unknown	6,725	1,438	17.62	1.08 (1.00–1.17)
Insurance status					40.70
Not Insured	7,556	1,033	12.03	1.04 (0.96–1.13)
Private Insurance	278,025	48,487	14.85	1.0 (ref)
Medicaid	24,711	3,945	13.77	0.91 (0.87–0.95)
Medicare	112,990	26,681	19.10	0.93 (0.90–0.96)
Other Government	4,407	820	15.69	0.88 (0.80–0.96)
Insurance Status Unknown	5,463	898	14.12	1.03 (0.94–1.13)
Charlson/Deyo comorbidity index					48.79
0	377,767	70,130	15.70	1.0 (ref)
1	46,102	9,441	17.00	0.92 (0.89–0.95)
2	7,372	1,698	18.72	0.88 (0.82–0.94)
≥3	1,911	595	23.74	0.86 (0.76–0.96)
N stage in invasive cancer					5902.16
pN0	335,194	75,205	18.32	1.0 (ref)
pN1	91,714	5,372	5.53	0.26 (0.25–0.26)
T stage in invasive cancer					285.38
No Tumor	3,033	498	14.10	0.53 (0.47–0.59)
≤2.0 cm	329,214	67,925	17.10	1.0 (ref)
2.1–5.0 cm	99,573	13,242	11.74	0.80 (0.78–0.82)
Laterality			4		54.71
Right	213,775	41,715	16.33	1.0 (ref)
Left	219,081	40,122	15.48	0.93 (0.91–0.95)
Histology in invasive cancer
Ductal	355,692	65,660	15.58
Lobular	31,315	7,277	18.86
Ductal & lobular	21,755	4,403	16.83
Others	24,390	4,524	15.65
Grade					324.77
1	105,244	26,505	20.12	1.0 (ref)
2	178,282	35,781	16.72	0.86 (0.84–0.88)
3	125,906	15,729	11.11	0.75 (0.73–0.78)
Chemotherapy					1999.11
No	236,904	63,183	21.05	1.0 (ref)
Yes	186,779	17,173	8.42	0.54 (0.53–0.56)
Estrogen receptor					25.48
Negative	78,284	9,584	10.91	1.0 (ref)
Positive	348,102	71,874	17.11	1.09 (1.06–1.13)
Surgical margin					48.82
Negative	413,598	79,254	16.08	1.0 (ref)
Positive	16,512	2,241	11.95	0.81 (0.77–0.86)
Facility locationb					3142.51
New England	33,612	5,919	14.97	1.0 (ref)
Middle Atlantic	66,798	15,097	18.43	1.03 (0.98–1.07)
South Atlantic	88,220	15,263	14.75	1.16 (1.11–1.21)
East North Central	80,690	15,251	15.90	1.31 (1.25–1.36)
East South Central	22,798	3,700	13.96	1.15 (1.09–1.22)
West North Central	32,231	5,884	15.44	1.21 (1.15–1.28)
West South Central	23,911	2,798	10.48	0.63 (0.59–0.67)
Mountain	16,335	5,540	25.33	2.99 (2.84–3.16)
Pacific	52,512	11,491	17.95	1.45 (1.39–1.52)
Facility volume, number of breast cancers per year					1452.74
<120	92,402	11,705	11.24	1.0 (ref)
120–207	109,787	17,031	13.43	1.26 (1.23–1.30)
208–342	117,859	21,541	15.45	1.36 (1.31–1.40)
343+	110,329	28,549	20.56	1.84 (1.78–1.90)
Facility type					1204.00
Community Cancer Program	242,626	36,930	13.21	1.0 (ref)
Integrated Network Cancer Program	60,892	12,192	16.68	1.30 (1.26–1.34)
Academic/Research Program	113,589	31,821	21.88	1.54 (1.50–1.58)
Median household income of residential zip code					272.95
<$38,000	59,921	9,117	13.21	1.0 (ref)
$38,000-$47,999	90,593	14,684	13.95	1.05 (1.02–1.09)
$48,000-$62,999	116,182	21,156	15.40	1.14 (1.10–1.18)
≥$63,000	164,431	36,739	18.26	1.29 (1.24–1.33)
Distance to facility					99.23
< 5.0 miles	139,232	24,646	15.04	1.0 (ref)
5.0–9.9 miles	110,744	19,972	15.28	0.92 (0.89–0.94)
10.0–19.9 miles	97,973	19,175	16.37	0.95 (0.92–0.97)
20.0–49.9 miles	63,105	12,743	16.80	0.98 (0.95–1.01)
>=50.0 miles	20,432	5,202	20.29	1.14 (1.09–1.20)
Urban/Rural					330.98
Large metropolis (pop. ≥1 million)	225,462	47,891	17.52	1.0 (ref)
Metropolis (pop. <1 million)	139,480	22,226	13.74	0.83 (0.81–0.85)
Urban (pop. ≥20000)	23,886	3,774	13.64	0.92 (0.88–0.97)
Urban (pop. 2500–19999)	27,159	4,624	14.55	1.04 (0.99–1.09)
Rural	5,839	1,149	16.44	1.20 (1.10–1.30)

^aCalculated from multivariable logistic regression, adjusting for year of diagnosis and all other variables with adjusted odds ratios in the table. Variables without adjusted odds ratios were not included in the final logistic regression model.

^bFacility location: New England (CT, MA, ME, NH, RI, VT), Middle Atlantic (NJ, NY, PA), South Atlantic (DC, DE, FL, GA, MD, NC, SC, VA, WV), East North Central (IL, IN, MI, OH, WI), East South Central (AL, KY, MS, TN), West North Central (IA, KS, MN, MO, ND, NE, SD), West South Central (AR, LA, OK, TX), Mountain (AZ, CO, ID, MT, NM, NV, UT, WY), Pacific (AK, CA, HI, OR, WA).)

^*All p-values <0.001

Abbreviations: HF-WBI, hypofractionated whole breast irradiation; CF-WBI, conventional fractionated whole breast irradiation; pop., population; AOR, adjusted odds ratio; CI, confidence interval