Systemic therapy for breast cancer and risk of subsequent contralateral breast cancer in the WECARE Study

Breast Cancer Research

Table 7 Risk ratios of contralateral breast cancer associated with different combinations of breast cancer treatment

Treatment for first breast cancer^a	CBC cases	UBC controls
Treatment for first breast cancer^a	N (%)	N (%)	RR^b (95 % CI)	Overall P value^d
Surgery alone	249 (16)	156 (7)	1.00 (Referent)
Chemotherapy alone	209 (14)	197 (9)	0.68 (0.49–0.93)
Tamoxifen alone	81 (5)	58 (3)	1.06 (0.69–1.64)
Radiotherapy alone	244 (16)	470 (21)	1.13 (0.88–1.47)	<0.0001
Chemotherapy + tamoxifen	81 (5)	83 (4)	0.70 (0.47–1.05)
Chemotherapy + radiotherapy	319 (21)	569 (26)	0.82 (0.62–1.09)
Tamoxifen + radiotherapy	107 (7)	208 (9)	0.83 (0.60–1.16)
Chemotherapy + tamoxifen + radiotherapy	142 (9)	329 (15)	0.54 (0.39–0.76)
Other endocrine therapy^c ± other treatment	89 (6)	141 (6)	0.49 (0.33–0.72)
One treatment or more unknown	0 (0)	1 (0.05)

^aAll treatment categories include surgery
^bAdjusted for all variables in the Table plus age at first breast cancer diagnosis (continuous), first-degree family history of breast cancer (yes, no, unknown), histology (lobular, other, unknown), stage (local, regional, unknown), and estrogen receptor/progesterone receptor status (positive for either, negative, unknown) at first breast cancer diagnosis
^cIncludes aromatase inhibitors (67 cases and 99 controls) and other anti-estrogens
^d P value overall = 0.002 if the category “Radiotherapy alone” is removed from the model
CBC contralateral breast cancer, CI confidence interval, RR risk ratio, UBC unilateral breast cancer

ISSN: 1465-542X