Outcomes after treatment of breast cancer during pregnancy including taxanes and/or granulocyte colony-stimulating factor use: findings from a multi-institutional retrospective analysis.

Background: Guidelines support comparable treatment for women diagnosed with breast cancer during pregnancy (PrBC) and nonpregnant women with limited case-specific modifications to ensure maternal-fetal safety. Experience during pregnancy with modern agents, such as taxanes or granulocyte colony-stimulating factors (GCSF), is limited.

Patients And Methods: We retrospectively identified a multi-institutional cohort of PrBC between 1996 and 2020. Propensity score analyses with multiple imputation for missing variables were applied to determine the associations between chemotherapy exposures during pregnancy, with or without taxanes or GCSF, and a compound maternal-fetal outcome including spontaneous preterm birth, preterm premature rupture of membranes, chorioamnionitis, small for gestational age newborns, congenital malformation, or 5-min Apgar score < 7.

Results: Among 139 PrBC pregnancies, 82 (59.0%) were exposed to chemotherapy, including 26 (31.7%) to taxane and 18 (22.0%) to GCSF. Chemotherapy use, in general, and inclusion of taxane and/or GCSF, specifically, increased over time. Pregnancies resulting in live singleton births (n = 123) and exposed to chemotherapy were as likely to reach term as those that were not (59.5% vs. 63.6%, respectively, p = 0.85). Among women treated with chemotherapy, propensity score-matched odds ratios (OR) for the composite maternal-fetal outcome were not significantly increased with taxane (OR 1.24, 95% CI 0.27-5.72) or GCSF (OR 2.11, 95% confidence interval (CI) 0.48-9.22) with similar effects in multiple imputation and sensitivity models.

Conclusion: The judicious increased use of taxane chemotherapy and/or growth factor support during pregnancy was not associated with unfavorable short-term maternal-fetal outcomes. While these findings are reassuring, case numbers remain limited and continued surveillance of these patients and progeny is warranted.