Association between Metformin Use and Cancer Stage at Diagnosis among Elderly Medicare Beneficiaries with Preexisting Type 2 Diabetes Mellitus and Incident Prostate Cancer

Table 1

Characteristics of the study cohort elderly Medicare beneficiaries with diabetes and incident prostate cancer by metformin use SEER-Medicare linked database, 2007–2010.

All	Overall		Metformin users		Non-metformin-user		Sig.
	N	%	N	%	N	%
	2,652	100	948	35.7	1,704	64.3
Predisposing characteristics
Age at diagnosis, in years
66–74	1,579	59.5	609	64.2	970	56.9
75+	1,073	40.5	339	35.8	734	43.1
Race/ethnicity
Whites	1,914	72.2	680	71.7	1,234	72.4
African American	323	12.2	108	11.4	215	12.6
Hispanic/Latino	150	5.7	70	7.4	80	4.7
Others	265	10.0	90	9.5	175	10.3
Marital status
Unmarried	222	8.4	73	7.7	149	8.7
Married	1,550	58.4	581	61.3	969	56.9
Divorced/separated	393	14.8	136	14.3	257	15.1
Others	487	18.4	158	16.7	329	19.3
Enabling characteristics
Quartile of median census of 2000 income
7–34,522	664	25.0	265	28.0	399	23.4
34,523–46,224	664	25.0	243	25.6	421	24.7
46,229–62,764	664	25.0	229	24.2	435	25.5
62,767–200,008	660	24.9	211	22.3	449	26.3
Quartile of median census of 2000 education
0–8.52	666	25.1	222	23.4	444	26.1
8.53–15.16	655	24.7	229	24.2	426	25.0
15.17–26.09	664	25.0	248	26.2	416	24.4
26.1–100	667	25.2	249	26.3	418	24.5
PSA screening
Yes	2,415	91.1	872	92.0	1,543	90.6
No	237	8.9	76	8.0	161	9.4
Visit to a PCP
Yes	1,858	70.1	672	70.9	1,186	69.6
No	794	29.9	276	29.1	518	30.4
Statin use
Yes	1,576	59.4	656	69.2	920	54.0
No	1,076	40.6	292	30.8	784	46.0
Insulin
Yes	102	3.8	62	6.5	40	2.3
No	2,550	96.2	886	93.5	1,664	97.7
External environment characteristics
SEER-regions
Northeast	487	18.4	146	15.4	341	20.0
South	570	21.5	223	23.5	347	20.4
North-central	351	13.2	112	11.8	239	14.0
West	1,244	46.9	467	49.3	777	45.6
Need characteristics
DCSI quartile
0 to 0	846	31.9	305	32.2	541	31.7
1 to 1	476	17.9	195	20.6	281	16.5
2 to 3	811	30.6	297	31.3	514	30.2
4 to 13	519	19.6	151	15.9	368	21.6

Notes: based on the data of 2,652 elderly men aged 66 years and older diagnosed with prostate cancer between 2008 and 2009 using a surveillance, epidemiology, and end-results- (SEER-) Medicare linked Part D data. Significant group differences by metformin use are based on chi-square tests. % represented in the column is row percentages.
DCSI: diabetes complication severity index; PCP: primary care physician; PSA: prostate specific antigen; Sig.: level of significance. ; ; .