Prognostic impact of pregnancy after breast cancer according to estrogen receptor status: a multicenter retrospective study

Abstract

Purpose: We questioned the impact of pregnancy on disease-free survival (DFS) in women with history of breast cancer (BC) according to estrogen receptor (ER) status.

Patients and methods: A multicenter, retrospective cohort study in which patients who became pregnant any time after BC were matched (1:3) to patients with BC with similar ER, nodal status, adjuvant therapy, age, and year of diagnosis. To adjust for guaranteed time bias, each nonpregnant patient had to have a disease-free interval at least equal to the time elapsing between BC diagnosis and date of conception of the matched pregnant one. The primary objective was DFS in patients with ER-positive BC. DFS in the ER-negative cohort, whole population, and overall survival (OS) were secondary objectives. Subgroup analyses included DFS according to pregnancy outcome and BC-pregnancy interval. With a two-sided α = 5% and β = 20%, 645 ER-positive patients were required to detect a hazard ratio (HR) = 0.65.

Results: A total of 333 pregnant patients and 874 matched nonpregnant patients were analyzed, of whom 686 patients had an ER-positive disease. No difference in DFS was observed between pregnant and nonpregnant patients in the ER-positive (HR = 0.91; 95% CI, 0.67 to 1.24, P = .55) or the ER-negative (HR = 0.75; 95% CI, 0.51 to 1.08, P = .12) cohorts. However, the pregnant group had better OS (HR = 0.72; 95% CI, 0.54 to 0.97, P = .03), with no interaction according to ER status (P = .11). Pregnancy outcome and BC-pregnancy interval did not seem to impact the risk of relapse.

Conclusion: Pregnancy after ER-positive BC does not seem to reduce the risk of BC recurrence.

Fig 1.

CONSORT diagram summarizing patients eligible for the study. (*) Some patients in the comparator group had more than one reason for exclusion but were considered once. ER, estrogen receptor.

Fig 2.

Differences in disease-free survival between the pregnant group and matched nonpregnant group. (A) Estrogen receptor (ER) –positive cohort; (B) ER-negative cohort; (C) all patients. Hazard ratios (HRs) with 95% CIs are provided. P values are calculated using the log-rank test.

Fig 3.

Differences in overall survival between the pregnant group and the matched nonpregnant group. (A) Estrogen receptor (ER) –positive cohort; (B) ER-negative cohort; (C) all patients. Hazard ratios (HRs) with 95% CIs are provided. P values are calculated using the log-rank test.

Fig 4.

Forest plots of predefined subgroup analyses. Dotted lines represent a hazard ratio (HR) of 1.0, and error bars represent 95% CI. (A) Pregnancy outcome (completed pregnancy v induced abortion and miscarriage); (B) breast cancer diagnosis to pregnancy interval (< 2 v ≥ 2 years). The P value of interaction is provided.

Fig A1.

Differences in relapse-free survival according to the interval between breast cancer (BC) diagnosis and conception. (A) Patients nonpregnant after BC diagnosis; (B) patients pregnant after BC diagnosis.