Table I.
Distribution of baseline characteristics in nested case control studies of advanced colorectal adenoma and colorectal cancer in the PLCO Cancer Screening Trial
| Adenoma | Cancer | ||||||
| Characteristic | Cases (n = 1205)a | Controls (n = 1386)a | Pb | Cases (n = 364)a | Controls (n = 394)a | Pb | |
| Age (years) | 63.1±5.2 | 62.6±5.3 | 0.02 | 67.6±6.5 | 67.5±6.3 | 0.81 | |
| Sex, n (%) | 0.83 | 0.71 | |||||
| Male | 776 (64.4) | 887 (64.0) | 216 (59.3) | 239 (60.7) | |||
| Female | 429 (35.6) | 499 (36.0) | 148 (40.7) | 155 (40.3) | |||
| Ethnicity, n (%) | 0.23 | 0.97 | |||||
| Non-Hispanic white | 1136 (94.3) | 1284 (92.6) | 311 (90.9) | 357 (90.6) | |||
| Non-Hispanic black | 29 (2.4) | 46 (3.3) | 18 (5.0) | 21 (5.3) | |||
| Other | 40 (3.3) | 56 (4.0) | 15 (4.1) | 16 (4.1) | |||
| First degree family history of colorectal cancer, n (%) | 157 (13.1) | 136 (9.9) | 0.01 | 56 (15.6) | 45 (11.6) | 0.11 | |
| Smoking status, n (%) | |||||||
| Never | 462 (38.4) | 657 (47.4) | <0.01 | 157 (43.1) | 164 (41.6) | 0.90 | |
| Former cigarette smoker | 165 (13.7) | 94 (6.8) | 167 (45.9) | 187 (47.5) | |||
| Current cigarette smoker | 577 (47.9) | 635 (45.8) | 40 (11.0) | 43 (10.9) | |||
| B[a]P (ng/day) | |||||||
| median (IQR) | 7.0 (1.3, 36.1) | 6.9 (1.2, 35.9) | 0.17 | 5.5 (1.2. 23.8) | 5.4 (1.0, 36.4) | 0.74 | |
| PhIP (ng/day) | |||||||
| Median (IQR) | 65.4 (24.6, 132.6) | 61.1 (23.3, 132.3) | 0.69 | 50.0 (21.0. 127.5) | 53.8 (22.8, 135.8) | 0.23 | |
| MeIQx (ng/day) | |||||||
| Median (IQR) | 22.7 (9.75, 43.2) | 20.5 (8.94, 41.8) | 0.20 | 18.0 (9.1. 38.7) | 18.9 (9.0, 39.6) | 0.59 | |
| DiMeIQx (ng/day) | |||||||
| Median (IQR) | 1.02 (0.23, 2.47) | 0.95 (0.27, 2.2) | 0.39 | 0.80 (0.18, 2.22) | 0.90 (0.22, 2.22) | 0.35 | |
| Combined nitrate and nitrite (ng/day) | |||||||
| Median (IQR) | 0.32 (0.13, 0.61) | 0.28 (0.12, 0.59) | 0.10 | 0.31 (0.13, 0.61) | 0.28 (0.12, 0.55) | 0.36 | |
Data are means ± standard deviations unless otherwise indicated. IQR, Interquartile range; NSAIDs, non-steroidal anti-inflammatory drugs.
aNumbers may not sum due to total due to missing values.
b P-values derived from t-test or chi-square test.