Table 1.

Participant characteristics: NSABP P-1

PlaceboTamoxifenTotal
N = 6,707 (50.1%)N = 6,681 (49.9%)(N = 13,388)
CharacteristicaN (%)N (%)N (%)
Age, y (B, L, C, E)
 <655797 (86.4)5783 (86.6)11,580 (86.5)
 ≥65910 (13.6)898 (13.4)1,808 (13.5)
Race (B, L, C, E)
 White6,352 (94.7)6,337 (94.8)12,689 (94.8)
 Black133 (2)143 (2.1)276 (2.1)
 Hispanic94 (1.4)73 (1.1)167 (1.2)
 Other/unknown128 (1.9)128 (2)256 (1.9)
Leisure-time physical activity (B, L, C, E)
 Moderate–heavy3,058 (45.6)3,067 (45.9)6,125 (45.7)
 Inactive–light3,626 (54.1)3,586 (53.7)7,212 (53.9)
 Unknown23 (0.3)28 (0.4)51 (0.4)
Baseline BMI (Bb, Eb)
 Healthy (BMI < 25)2,603 (38.8)2,635 (39.4)5,238 (39.1)
 Overweight (BMI ≥25 to <30)2,233 (33.3)2,157 (32.3)4,390 (32.8)
 Obese (BMI ≥ 30)1,871 (27.9)1,889 (28.3)3,760 (28.1)
Alcohol consumption (B, L, C, E)
 None1,421 (21.2)1,366 (20.5)2,787 (20.8)
 1 drink/day4,383 (65.3)4,439 (66.4)8,822 (65.9)
 >1 drink/day877 (13.1)847 (12.7)1,724 (12.9)
 Unknown26 (0.4)29 (0.4)55 (0.4)
Smoking status (B, L, C, E)
 Never smoked3,707 (55.3)3,612 (54.1)7,319 (54.7)
 Current smoker827 (12.3)847 (12.7)1,674 (12.5)
 Former smoker2,150 (32.1)2,195 (32.8)4,345 (32.5)
 Unknown23 (0.3)27 (0.4)50 (0.4)
Smoking duration (B, L, C, E)
 Never smokedc3,715 (55.4)3,620 (54.2)7,335 (54.8)
 <15 smoking years839 (12.5)825 (12.3)1,664 (12.4)
 ≥15 to <35 smoking years1,607 (24)1,707 (25.6)3,314 (24.8)
 ≥35 smoking years514 (7.7)497 (7.4)1,011 (7.6)
 Unknown32 (0.5)32 (0.5)64 (0.5)
Smoking intensity (B, L, C, E)
 None3,707 (55.3)3,612 (54.1)7,319 (54.7)
 1 pack/day2,008 (29.9)2,069 (31)4,077 (30.5)
 >1 packs/day968 (14.4)972 (14.5)1,940 (14.5)
 Unknown24 (0.4)28 (0.4)52 (0.4)
5-Year breast cancer risk (Bd)
 ≤2%1,682 (25.1)1,677 (25.1)3,359 (25.1)
 >2% and ≤5%3,895 (58.1)3,823 (57.2)7,718 (57.6)
 >5%1,130 (16.8)1,181 (17.7)2,311 (17.3)
Family cancer history (number of family members who developed cancer; L, C, E)
 None759 (11.3)731 (10.9)1,490 (11.1)
 12,709 (40.4)2,717 (40.7)5,426 (40.5)
 >13,183 (47.5)3,182 (47.6)6,365 (47.5)
 Unknown56 (0.8)51 (0.8)107 (0.8)
Menstrual period stopped (B, L, C, E)
 No2,254 (33.6)2,159 (32.8)4,449 (33.2)
 Yes4,453 (66.4)4,486 (67.2)8,939 (66.8)
Estrogen use (B, L, C, E)
 Never used1,619 (24.1)1,542 (23.1)3,161 (23.6)
 Ever used5,088 (75.9)5,139 (76.9)10,227 (76.4)
Age at menarche (years; E)
 7–10567 (8.5)576 (8.6)1,143 (8.5)
 11–134,868 (72.6)4,902 (73.4)9,770 (73)
 ≥141,243 (18.5)1,180 (17.7)2,423 (18.1)
 Unknown29 (0.4)23 (0.3)52 (0.4)
Ever had diabetes (B, E)
 No6,443 (96.1)6,402 (95.8)12,845 (95.9)
 Yes264 (3.9)279 (4.2)543 (4.1)
Past pregnancy (E)
 No1,011 (15.1)1,009 (15.1)2,020 (15.1)
 Yes5,690 (84.8)5,669 (84.9)11,359 (84.8)
 Unknown6 (0.1)3 (0)9 (0.1)
Current regular aspirin use (C)
 No5,651 (84.3)5,610 (84.0)11,261 (84.1)
 Yes1,056 (15.7)1,071 (16.0)2,127 (15.9)
Personal history of tuberculosis (L)
 No6,629 (98.8)6,581 (98.5)13,210 (98.7)
 Yes78 (1.2)100 (1.5)178 (1.3)
  • aCharacteristic included in disease site models in parentheses: breast (B), lung (L), colon (C), and endometrial (E).

  • bOverweight/obesity was included in secondary analyses for models with significant effects of physical activity. These were the models for breast and endometrial cancers.

  • cIncludes former smokers who indicated 0 years of smoking history.

  • dEstimated breast cancer risk is included as a continuous variable in models.