Table 2. Crude rate ratio for the univariate association between each variable and invasive epithelial ovarian/tubal cancer risk, overall and by Type I/II.
| Variable | Overall | All invasive epithelial ovarian/tubal cancer | Type I** | Type II** | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| n | HR (95% Cl) | P value | n | HR (95% Cl) | P value | n | HR (95% Cl) | P value | ||
| Total | n (%) | 1176 (100) | 178 (15.1) | 890 (75.7) | ||||||
| Hysterectomy | ||||||||||
| Yes | 41 912 (20.7) | 231 (0.55) | 0.98 (0.85−1.14) | 0.819 | 39 (0.09) | 1.13 (0.79−1.62) | 0.493 | 173 (0.41) | 0.91 (0.77−1.07) | 0.252 |
| No | 160 594 (79.3) | 945 (0.59) | 139 (0.09) | 717 (0.45) | ||||||
| Tubal ligation | ||||||||||
| Yes | 43 100 (21.3) | 199 (0.46) | 0.78 (0.67−0.91) | 0.002 | 27 (0.06) | 0.66 (0.44−0.99) | 0.047 | 151 (0.35) | 0.78 (0.65−0.93) | 0.006 |
| No | 159 406 (78.7) | 977 (0.61) | 151 (0.09) | 739 (0.46) | ||||||
| Use of HRT at recruitment | ||||||||||
| Yes | 37984 (18.8) | 248 (0.65) | 1.23 (1.07−1.42) | 0.004 | 42 (0.11) | 1.28 (0.90−1.81) | 0.173 | 189 (0.50) | 1.24 (1.05−1.46) | 0.01 |
| No | 164522 (81.2) | 928 (0.56) | 136 (0.08) | 701 (0.43) | ||||||
| Ever use of OCP | ||||||||||
| Yes | 120 669 (59.6) | 579 (0.48) | 0.74 (0.66−0.84) | <0.0001 | 94 (0.08) | 0.72 (0.52−0.98) | 0.038 | 438 (0.36) | 0.74 (0.64−0.85) | <0.0001 |
| No | 81 837 (40.4) | 597 (0.73) | 84 (0.10) | 452 (0.55) | ||||||
| Pregnancies <6 months | ||||||||||
| 0 | 137 941 (68.1) | 831 (0.60) | ref | − | 129 (0.09) | ref | − | 619 (0.45) | ref | − |
| 1+ | 61 913 | 327 (0.52) | 0.87 (0.75−1.01) | 0.085 | 37 (0.07) | 0.79 (0.57−1.11) | 0.176 | 256 (0.41) | 0.93 (0.81−1.09) | 0.398 |
| Pregnancies >6 months | ||||||||||
| 0 | 23 482 (11.6) | 153 (0.65) | ref | − | 33 (0.14) | ref | − | 110 (0.47) | ref | − |
| 1+ | 178 430 | 1016 (0.57) | 0.85 (0.72−1.01) | 0.06 | 142 (0.08) | 0.67 (0.39−0.83) | 0.003 | 776 (0.43) | 0.90 (0.74−1.10) | 0.306 |
| Family history of ovarian cancer | ||||||||||
| Yes | 9177 (4.5) | 79 (0.86) | 1.53 (1.22−1.92) | <0.0001 | 1.13 (0.58−2.22) | 0.714 | 1.65 (1.28−2.13) | <0.0001 | ||
| No | 193 329 (95.5) | 1097 (0.57) | ||||||||
| Family history of breast cancer | ||||||||||
| Yes | 44 983 (22.2) | 288 (0.64) | 1.14 (1.00−1.31) | 0.049 | 36 (0.08) | 0.89 (0.62−1.29) | 0.539 | 220 (0.49) | 1.15 (0.99−1.35) | 0.062 |
| No | 157 523 (77.8) | 888 (0.56) | 142 (0.09) | 670 (0.43) | ||||||
| Infertility treatment | ||||||||||
| Yes | 6627 (3.3) | 36 (0.54) | 1.04 (0.75−1.46) | 0.799 | 1.2 (0.56−2.57) | 0.633 | 1.07 (0.74−1.57) | 0.709 | ||
| No | 195 879 (96.7) | 1140 (0.58) | ||||||||
| Quantitative variables | ||||||||||
| OCP use (years)* | 5 (2−10)*** | 4 (2_9)*** | 0.96 (0.95−0.97) | <0.0001 | 6 (2−10)*** | 0.99 (0.96−1.02) | 0.421 | 5 (2_9)*** | 0.96 (0.94−0.97) | <0.0001 |
| Duration of HRT | 8.11 (4.5−12.0)*** | 9.89 (5.22−12.93)*** | 1.00 (1.00−1.00) | 0.002 | 9.58 (5.9−12.1)*** | 1.03 (0.97−1.08) | 0.325 | 9.62 (4.9−12.9)*** | 1.01 (0.98−1.03) | 0.516 |
| use for users at randomisation (years) | ||||||||||
| BMI (kg/m2) | 25.7 (23.3−29.1)*** | 25.6 (23.4−29.0)*** | 0.99 (0.98−1.01) | 0.412 | 27.0 (23.7−30.7)*** | 1.03(1.01−1.06) | 0.017 | 25.4 (23.2−28.6)*** | 0.90(0.97−1.00) | 0.038 |
| Time since last period at randomisation (years) | 11.35 (5.29−18.47)*** | 13.4 (6.33−19.8)*** | 1.02 (0.97−1.08) | 0.409 | 11 (5−18)*** | 0.90 (0.78−1.03) | 0.128 | 11 (5−18)*** | 1.05 (0.99−1.11) | 0.124 |
(%), % of ovarian/tubal cancer cases in each variable group.
Bold denotes the crude association of hysterectomy and ovarian cancer risk.
*
Includes non-users.
**
Ovarian/tubal cancer diagnoses of uncertain type n = 108 (9.2%).
***
Median (IQR) for women with ovarian/tubal cancer diagnosis.
****
Unreported because of the small number of events.