Disparities in Guideline-Concordant Initial Systemic Treatment in Women with HER2-Negative Metastatic Breast Cancer: A SEER-Medicare Analysis

Figures & data

Table 1 Description of Medicare FFS Beneficiaries with Metastatic HER2-Negative Breast Cancer by Receipt of Guideline-Concordant Initial Systemic Treatment SEER-Medicare 2010–2013 Cases

Variables	Total Cohort		Guideline-Concordant Treatment		Non-Guideline-Concordant Treatment		p-value
	N = 1089	%	N = 787 (72.3%)	%	N = 302 (27.7%)	%
Age at Diagnosis							<0.0001
66–69	203	18.6%	169	83.3%	34	16.7%
70–74	266	24.4%	202	75.9%	64	24.1%
75–79	225	20.7%	168	74.7%	57	25.3%
80+	395	36.3%	248	62.8%	147	37.2%
Race/Ethnicity							0.8381
Whites	927	85.1%	671	72.4%	256	27.6%
Others	162	14.9%	116	71.6%	46	28.4%
Marital Status							0.0010
Married/Partnered	318	29.2%	252	79.3%	66	20.7%
Single/Divorced/Widowed	771	70.8%	535	69.4%	236	30.6%
Location of Residence							0.0336
Metro	922	84.7%	655	71.0%	267	29.0%
Non-metro	167	15.3%	132	79.0%	35	21.0%
SEER Region							0.2950
North East	284	26.1%	199	70.1%	85	29.9%
South	266	24.4%	198	74.4%	68	25.6%
North Central	158	14.5%	107	67.7%	51	32.3%
West	381	35.0%	283	74.3%	98	25.7%
Census Tract Household Income							0.5412
LE $45,000	237	21.8%	177	74.7%	60	25.3%
$45,001–$60,000	369	33.9%	268	72.6%	101	27.4%
GT $60,000	483	44.5%	342	70.8%	141	29.2%
Census Tract Education							0.9947
0–22.0	300	27.6%	217	72.3%	83	27.7%
22.1–30.3	278	25.5%	201	72.3%	77	27.7%
30.4–37.7	247	22.7%	177	71.7%	70	28.3%
GT 37.7	264	24.2%	192	72.7%	72	27.3%
Hormone Receptor Status							<0.0001
Positive	901	82.7%	697	77.4%	204	22.6%
Negative	188	17.3%	90	47.9%	98	52.1%
Grade of Tumor							0.0038
Well/Moderately differentiated	493	45.3%	375	76.1%	118	23.9%
Poorly/Very poorly differentiated	361	33.1%	238	65.9%	123	34.1%
Unknown	235	21.6%	174	74.0%	61	26.0%
Number of Metastatic Sites*							0.9633
0–1	785	72.1%	567	72.2%	218	27.8%
2–4	304	27.9%	220	72.4%	84	27.6%
Performance Status							0.0212
Good	804	73.8%	596	74.1%	208	25.9%
Poor	285	26.2%	191	67.0%	94	33.0%
Comorbidity							0.0206
0	429	39.4%	325	75.8%	104	24.2%
1	241	22.1%	179	74.3%	62	25.7%
2+	419	38.5%	283	67.5%	136	32.5%
Oncology Visits							<0.0001
0–8	368	33.8%	215	58.4%	153	41.6%
9–25	323	29.7%	226	70.0%	97	30.0%
GT 25	398	36.5%	346	86.9%	52	13.7%
Hospitals Offering Oncology Services							0.6072
0–1	361	33.2%	270	74.8%	91	25.2%
2–3	228	20.9%	160	70.2%	68	29.8%
4–6	263	24.2%	188	71.5%	75	28.5%
GT 6	237	21.7%	169	71.3%	68	28.7%

Note: *Number of metastatic sites refers to metastasis to brain, liver, lung, or bone.

Abbreviations: FFS, fee for service; LE, less than or equal to; GT, greater than.

Figure 1 Patient flow diagram.

Table 2 Adjusted Odds Ratios and 95% Confidence Intervals from Logistic Regression on Guideline-Concordant Initial Systemic Treatment Among Medicare FFS Beneficiaries with Metastatic HER2-Negative Breast Cancer SEER-Medicare 2010–2013 Cases

Variables	Guideline-Concordant Care
	AOR	95% CI	p-value
Age at Diagnosis
66–69	Reference
70–74	0.581	[0.352, 0.960]	0.0339
75–79	0.593	[0.355, 0.990]	0.0456
80+	0.410	[0.259, 0.651]	0.0002
Race/Ethnicity
White	Reference
Others	1.395	[0.989, 2.169]	0.1388
Location of Residence
Metro	Reference
Non-metro	1.537	[0.945, 2.500]	0.0834
Census Tract Household Income
LE $45,000	Reference
$45,001–$60,000	0.679	[0.426, 1.081]	0.1027
GT $60,000	0.487	[0.265, 0.894]	0.0203
Census Tract Education
0–22.0	Reference
22.1–30.3	1.162	[0.735, 1.836]	0.5214
30.4–37.7	1.570	[0.891, 2.767]	0.1190
GT 37.7	2.058	[1.111, 3.810]	0.0217
Marital Status
Married/Partnered	1.528	[1.079, 2.164]	0.0171
Single/Divorced/Widowed	Reference
Hormone Receptor Status
Positive	Reference
Negative	0.250	[0.171, 0.366]	<0.0001
Grade of Tumor
Well/Moderately differentiated	Reference
Poorly/Very poorly differentiated	0.724	[0.510, 1.026]	0.0697
Unknown	0.886	[0.598, 1.312]	0.5447
Oncology Visits
0–8	Reference
9–25	1.592	[1.136, 2.233]	0.0070
GT 25	4.868	[3.292, 7.197]	<0.0001

Abbreviations: GT, greater than; LE, less than equal to; AOR, adjusted odds ratio; CI, confidence interval.

Table 3 Nonlinear Decomposition of Guideline-Concordant Initial Systemic Treatment Among Medicare FFS Beneficiaries with Metastatic HER2-Negative Breast Cancer with Positive and Negative Hormone Receptor Status SEER-Medicare 2010–2013 Cases

	Guideline-Concordant Treatment
% of HR-positive cases with guideline-concordant care	77.4%
% of HR-negative cases with guideline-concordant care	47.9%
Difference	29.5
Total “Explained” (%)	2.22
Variables	% of “Explained” Difference	% Contribution to the “Explained” Portion
Predisposing factors (Age at breast cancer diagnosis*, Race/Ethnicity)	0.24%	3.19%
Enabling factors (Marital status, Census tract median household income** and education*)	−2.64%	−35.11%
Need-related factors (Grade of tumor*, Comorbidity, Performance status, Number of sites of cancer metastasis)	5.03%	66.89%
Healthcare use (Medical oncology office visits***)	4.19%	55.72%
External healthcare environmental factors (Location of residence, SEER region, Hospitals offering oncology services)	0.70%	9.31%
Total Difference Explained	7.52%	100%
Total Difference Unexplained	92.48%

Notes: *p<0.1; **p<0.05; ***p<0.001. We used the p-value of <0.1 due to relatively smaller sample size of HR-negative cases compared to HR-positive cases.