(ChemotherapyAdvisor) – Infants exposed to chemotherapy in utero had a lower birthweight and more complications than those not exposed; however, these differences were not clinically significant and were most likely related to premature delivery, since none was exposed in the first trimester, results from an ongoing registry of breast cancer and pregnancy published Online First in The Lancet Oncology August 16 have found.
“Delay of cancer treatment did not significantly affect disease-free survival for mothers with early breast cancer,” the investigators reported. “Because preterm birth was strongly associated with adverse events, a full-term delivery seems to be of paramount importance.”
The registry, founded in 2003 by the German Breast Group, includes data on women diagnosed with breast cancer during their pregnancy from seven European countries. Data is collected on fetal outcome 4 weeks after delivery, maternal outcome of pregnancy, breast cancer therapy applied (treatment, response to chemotherapy, type of surgery), diagnostic procedures applied (palpation, ultrasound, mammogram) and outcome of mother and child after 5 years of therapy.
The observational study reported on 447 women; median age was 33 years (range 22–51). Median gestational age was 24 weeks (range 5-40) at the time of breast cancer diagnosis. Of 413 women with early breast cancer, 197 (48%) received chemotherapy during pregnancy, including an anthracycline (n=178), cyclophosphamide, methotrexate, and fluorouracil (n=15), and a taxane (n=14). Median number of cycles was 4 (range 1-8). Primary end point was fetal health for up to 4 weeks postdelivery.
“In total, participants gave birth to 386 liveborn babies (374 patients continued with pregnancy after diagnosis, eight patients were diagnosed at birth, seven women had twins, three babies were stillbirths),” they wrote.
“Birthweight was affected by chemotherapy exposure after adjustment for gestational age (P=0.018), but not by number of chemotherapy cycles (P=0.71),” they noted. Of 386 infants, 40 (10%) had side effects, malformation, or newborn complications more common in those born before the 37th week of gestation vs later (31 vs 9 events; P=0.0002). Adverse events were more common in infants exposed to chemotherapy in utero (31 vs 7 events; P=0.00045). “Two infants died; both were exposed to chemotherapy and delivered prematurely, but both deaths were thought not to be related to treatment,” they reported.
In women who initiated chemotherapy during pregnancy, median disease-free survival was 70.6 months (95% CI 62.1–105.5) vs 94.4 months (95% CI 64.4–not yet reached) in women starting chemotherapy after delivery (unadjusted HR 1.13 [95% CI 0.76–1.69]; P=0.539).
“If our findings are confirmed by other studies, breast cancer during pregnancy could be treated as it is in nonpregnant women without putting fetal and maternal outcomes at substantially increased risk,” said Sibylle Loibl, MD, of the German Breast Group.