Table 4. Risks of breast cancer after supradiaphragmatic radiotherapy in relation to age at menopause.
Risk factor | Cases | Controls | Total | ORa (95% CI) | P-value |
---|---|---|---|---|---|
Menopause before age 40 | |||||
No | 103 | 598 | 701 | 1.00 | |
Yes | 49 | 454 | 503 | 0.65 (0.44–0.94) | 0.02 |
Unknown |
32 |
168 |
200 |
1.09 (0.69–1.73) |
0.70 |
Menopause within 5 years of start of treatment | |||||
No | 205 | 1399 | 1604 | 1.00 | |
Yes | 26 | 357 | 383 | 0.55 (0.35–0.85) | 0.01 |
Unknown |
34 |
337 |
371 |
0.92 (0.61–1.38) |
0.68 |
Premenopausal years after start of treatment | |||||
Less than 1 | 10 | 103 | 113 | 1.00 | |
1–4 | 7 | 98 | 105 | 0.96 (0.34–2.69) | 0.94 |
5–9 | 7 | 84 | 91 | 1.02 (0.36–2.87) | 0.97 |
10–14 | 19 | 277 | 296 | 1.49 (0.63–3.55) | 0.36 |
15–24 | 49 | 281 | 330 | 1.62 (0.76–3.44) | 0.21 |
25 or over | 25 | 40 | 65 | 3.56 (1.50–8.45) | 0.004 |
Unknown | 52 | 294 | 346 | 1.74 (0.84–3.64) | 0.14 |
Ptrend=0.003 |
Abbreviations: CI=confidence interval; OR=odds ratio; sRT=supradiaphragmatic radiotherapy.
Odds ratios are adjusted for age and year of treatment, duration between treatment and questionnaire completion, calendar year of birth, sRT field.