Table 3. Predictors of underascertainment of radiation therapy by registries in the SEER-Medicare Cohort^*.

		OR	95% CI	P
Age
	66-69	1
	70-74	1.06	0.99-1.14	0.11
	75-79	1.14	1.05-1.23	0.001
	80+	1.10	1.02-1.20	0.02
Race
	White	1
	Black	0.95	0.85-1.07	0.40
	Other	0.89	0.78-1.01	0.06
County of residence
	Urban	1
	Rural	1.34	1.21-1.48	<0.001
Year of Diagnosis
	2001	1
	2002	1.13	1.02-1.25	0.02
	2003	0.93	0.84-1.03	0.14
	2004	0.99	0.89-1.09	0.77
	2005	0.94	0.85-1.04	0.24
	2006	0.98	0.88-1.08	0.65
	2007	1.13	1.02-1.26	0.02
Registry*
	SEER-9	1
	SEER-Other	1.70	1.60-1.80	<0.001
Surgery
	Biopsy only	1
	BCS	1.11	0.95-1.30	0.19
	Mastectomy	1.23	1.04-1.45	0.02
Interval from diagnosis to start of radiation therapy (days)
	Continuous	1.006	1.006-1.007	<0.001

Abbreviations: SEER, Surveillance, Epidemiology and End Results; OR, odds ratio; CI, confidence interval; BCS, breast-conserving surgery

^*This table presents a multivariate logistic regression model conducted in patients who received radiation therapy (RT) according to their Medicare claims (n=36,047). The modeled outcome is underascertainment of RT, defined as the number of cases where Medicare claims indicated that the patient received RT but registry data indicated that the patient did not receive RT, divided by the total number of cases where Medicare claims indicated that the patient received RT. In this model, an OR > 1 indicates a higher of odds of underascertainment.

^†The original SEER 9 registries include Atlanta, Connecticut, Detroit, Hawaii, Iowa, New Mexico, San Francisco-Oakland, Seattle-Puget Sound, and Utah. The SEER-other registries include those added in 1992 and later (San Jose, Los Angeles, Rural Georgia, Greater California, Kentucky, Louisiana, and New Jersey).