Table 7.
Multivariable-adjusted associations of relaxer use and characteristics of use with breast tumor clinicopathologic features among Black breast cancer casesa
| Regular relaxer useb | Duration of relaxer useb |
Early relaxer useb |
Typical relaxer applicationc |
Joint use of hair dye and relaxerd | ||||
|---|---|---|---|---|---|---|---|---|
| ≤10 Years | >10 Years | Did not use before age 12 | Used before age 12 | Home kit | Combination | |||
|
| ||||||||
| Tumor feature | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) |
|
| ||||||||
| Tumor grade | ||||||||
| Well differentiated | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Moderately differentiated | 0.86 (0.53–1.42) | 0.86 (0.52–1.41) | 0.74 (0.29–1.89) | 0.88 (0.53–1.45) | 0.79 (0.32–1.97) | 1.03 (0.54–1.96) | 0.89 (0.51–1.54) | 0.72 (0.38–1.39) |
| Poorly differentiated | 0.79 (0.48–1.30) | 0.79 (0.48–1.30) | 0.71 (0.28–1.78) | 0.82 (0.50–1.36) | 0.72 (0.29–1.77) | 0.85 (0.44–1.63) | 1.02 (0.59–1.77) | 0.69 (0.36–1.32) |
| Ptrend = 0.69 | Ptrend = 0.66 | Ptrend = 0.86 | Ptrend = 0.68 | Ptrend = 0.76 | Ptrend = 0.75 | Ptrend = 0.78 | Ptrend = 0.53 | |
| Tumor size | ||||||||
| <1.0 cm | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| 1.0–2.0 cm | 1.16 (0.83–1.61) | 1.13 (0.81–1.57) | 1.75 (0.98–3.13) | 1.31 (0.94–1.83) | 1.60 (0.91–2.82) | 1.31 (0.85–2.03) | 1.37 (0.94–1.99) | 1.16 (0.76–1.75) |
| >2.0 cm | 0.89 (0.65–1.23) | 0.89 (0.64–1.22) | 0.95 (0.52–1.72) | 1.03 (0.74–1.43) | 0.93 (0.52–1.65) | 1.43 (0.90–2.27) | 1.81 (1.22–2.68)* | 0.64 (0.42–0.97) |
| Ptrend = 0.47 | Ptrend = 0.62 | Ptrend = 0.024 | Ptrend = 0.20 | Ptrend = 0.050 | Ptrend = 0.24 | Ptrend = 0.15 | Ptrend = 0.75 | |
| ER status | ||||||||
| Negative | 1.16 (0.84–1.60) | 1.19 (0.87–1.65) | 0.74 (0.42–1.31) | 1.22 (0.89–1.69) | 0.77 (0.44–1.33) | 0.90 (0.59–1.36) | 0.81 (0.57–1.15) | 1.12 (0.75–1.70) |
| Positive | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Ptrend = 0.52 | Ptrend = 0.96 | |||||||
| HER2 status | ||||||||
| Negative | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Positive | 1.07 (0.75–1.56) | 1.07 (0.74–1.56) | 1.36 (0.72–2.58) | 1.08 (0.75–1.58) | 1.41 (0.76–2.64) | 0.95 (0.59–1.53) | 0.84 (0.56–1.27) | 1.27 (0.79–2.09) |
| Ptrend = 0.81 | Ptrend = 0.53 | |||||||
| Lymph node status | ||||||||
| Negative | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| Positive | 1.07 (0.77–1.49) | 1.07 (0.77–1.49) | 1.13 (0.65–1.98) | 1.06 (0.77–1.49) | 1.06 (0.61–1.84) | 0.96 (0.63–1.46) | 0.85 (0.59–1.23) | 0.92 (0.61–1.40) |
| Ptrend = 0.91 | Ptrend = 0.11 | |||||||
| Tumor subtype | ||||||||
| Luminal A | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) | 1.00 (REF) |
| HER2-positive | 1.07 (0.73–1.57) | 1.08 (0.73–1.59) | 1.06 (0.54–2.09) | 1.10 (0.75–1.63) | 1.07 (0.55–2.08) | 0.90 (0.54–1.50) | 0.81 (0.52–1.27) | 1.32 (0.80–2.19) |
| Triple-negative | 1.09 (0.74–1.61) | 1.13 (0.76–1.66) | 0.63 (0.32–1.35) | 1.16 (0.79–1.71) | 0.65 (0.33–1.26) | 0.79 (0.47–1.32) | 0.79 (0.52–1.22) | 1.18 (0.72–1.94) |
| Ptrend = 0.85 | Ptrend = 0.77 | |||||||
a
The multivariable-adjusted model included the following covariates: 1) family history of breast cancer, 2) oral contraceptive use, 3) education, 4) BMI, 5) age and 6) mode of detection.
b
Never-users of chemical relaxers/straighteners composed the referent group.
c
Those reporting salon application as the typical application of relaxers composed the referent group.
d
Those reporting no regular hair dye use and no regular relaxer use (i.e., never-users of both products) composed the referent group.
*
Significant after correction for multiple comparisons (Bonferroni correction, P <0.01).