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, punadjusted = 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.

Birthweight and Chemotherapy Exposure in Women Diagnosed with Breast Cancer during Pregnancy.

OBJECTIVE: Breast cancer is one of the most frequently diagnosed cancers in pregnancy and is commonly treated with chemotherapy. To date, studies examining effects of chemotherapy during pregnancy on fetal growth have yielded conflicting results, and most are limited by small sample sizes or are nonspecific with respect to cytotoxic regimen or type of cancer treated. We sought to evaluate the effect of chemotherapy for breast cancer in pregnancy on birthweight and small for gestational age infants. STUDY DESIGN: This is a retrospective cohort study of 74 women diagnosed with pathologically confirmed breast cancer during pregnancy between 1997 and 2018 at one of three academic medical centers, who had a singleton birth with known birthweight. Forty-nine received chemotherapy and 25 did not receive chemotherapy. Linear regression modeling was used to compare birthweight (by gestational age and sex-specific z-score) by chemotherapy exposure. Subanalyses of specific chemotherapy regimen and duration of chemotherapy exposure were also performed. Placental, neonatal, and maternal outcomes were also analyzed by chemotherapy exposure. RESULTS: In the adjusted model, chemotherapy exposure was associated with lower birthweight (Δ z-score = -0.49, p = 0.03), but similar rates of small for gestational age (defined as birthweight <10th percentile for gestational age) infants (8.2 vs. 8.0%, p = 1.0; Fisher's exact test). Each additional week of chemotherapy (Δ z-score = -0.05, p = 0.03) was associated with decreased birthweight, although no association was found with specific chemotherapy regimen. Chemotherapy exposure was associated with lower median placental weight percentile by gestational age (9th vs. 75th, p < 0.05). Secondary maternal outcomes were similar between the group that did and did not receive chemotherapy. CONCLUSION: Chemotherapy for breast cancer in pregnancy in this cohort is associated with lower birthweight but no difference in the rate of small for gestational age infants. KEY POINTS: · Chemotherapy for breast cancer in pregnancy is associated with decreased birthweight but similar rates of small for gestational age infants.. · Birthweight did not differ according to chemotherapy regimen.. · There is no difference in the rate of small for gestational age infants..