. 2003 Dec;38(6 Pt 1):1385–1402. doi: 10.1111/j.1475-6773.2003.00184.x

Table 3.

Instrumental Variable and OLS Estimates of the Effectiveness of Breast Conserving Surgery Plus Irradiation on Survival Relative to Mastectomy

					After Diagnosis, Effect of BCSI on Patient Survival:

Row	Analysis Method	Instruments Specified	Number of Groups perInstrument	Instrument F-Statistic	1 year	2 years	3 years	4 years
1	Unadjusted OLS	None	na	na	0.01	0.02	0.04^**	0.06^**
2	Adjusted OLS^a	None	na	na	−0.001	−0.003	−0.0001	0.007
3	Instrumental Variable Estimates^a	BCSI Rate	2	8.57^***	−0.32	−0.68	−0.57	−0.51
4			4	5.19^***	−0.37^**	0.54^**	−0.45	−0.65^*
5			8	3.43^***	−0.33^**	−0.50^**	−0.46^*	−0.52^*
6			12	3.00^***	−0.23^**	0.41^**	−0.33	−0.11
7			Radiation Distance	2	21.79^***	−0.21^*	−0.12	−0.33	−0.23
8			4	7.52^***	−0.14	−0.22	−0.39	−0.38
9			8	3.30^***	−0.14	−0.19	−0.35	−0.28
10			12	2.94^***	−0.05	−0.14	−0.33	−0.40^*
11		BCSI Rate and Radiation Distance	2	13.08^***	−0.24^**	−0.25	−0.38^*	−0.30
12			4	4.99^***	−0.24^**	−0.32^*	−0.39^*	−0.45^*
13			8	2.76^***	−0.24^**	−0.31^**	−0.34^*	−0.27
14			12	2.74^***	−0.12^*	−0.23^**	−0.30^**	−0.15

^***

Statistically significant at .99 confidence.

^**

Statistically significant at .95 confidence.

Statistically significant at .90 confidence.

Models also specified binary variables for age groups (<50, 50–64, 65–69, 70–74, 75–79, 80–84, 85+), tumor sizes (<2 cm, 2–5 cm, 5+cm), positive lymph node involvement, tumor grade groups (1, 2, 3, 4, 9–unknown), tumor location groups (nipple, central portion, upper-inner quad, lower-inner quad, upper-outer quad, lower-outer quad, axillary tail, overlapping lesion, not stated), Charlson comorbidity index (0, 1, 2, 3+), residence zip code poverty percentage (#7, 7–10, 10–13, 13– 20, >20), distance from residence to nearest hospital (#2.83, 2.83–9, 9–15,>15), payer (Medicaid, Medicare, Blue Cross/Blue Shield, other private, other government, self-pay), and year of diagnosis (1989, 1990, 1991, 1992, 1993, 1994).