Reassuring news for women who receive a diagnosis of breast cancer during pregnancy: Pregnancy-induced alterations in the pharmacokinetics of chemotherapy do not appear to compromise outcomes for the mother.
That’s according to investigators who reviewed registry data on 662 pregnant women and 2,081 nonpregnant women with a diagnosis of breast cancer. After a median follow-up of 66 months, there were no significant differences in either disease-free survival (DFS) or overall survival (OS), and women who received more than 60% of their chemotherapy doses during pregnancy had survival comparable to that of nonpregnant women, reported Frédéric Amant, MD, PhD, of University Hospitals Leuven (Belgium).
“These results support initiation of chemotherapy for breast cancer during pregnancy where indicated for oncological reasons,” they reported in a poster discussion session at the American Society of Clinical Oncology annual meeting. (Abstract 515).
Although in general a diagnosis of breast cancer during pregnancy does not appear to affect the mother’s prognosis when standard therapy is used, “caution is warranted as gestational changes in pharmacokinetics with respect to the distribution, metabolism, and excretion of drugs may lead to reduced chemotherapy concentration in pregnant patients,” the authors wrote.
To get a better picture of the prognosis for women diagnosed with breast cancer during pregnancy, the investigators created a cohort of patients from two multicenter registries: the International Network of Cancer, Infertility, and Pregnancy and the German Breast Group. Both registries collect data retrospectively and prospectively,
They used propensity scoring to smooth out differences in the baseline characteristics of pregnant women and nonpregnant controls.
The median age at diagnosis was 34 year for pregnant women, and 38 years for controls. Pregnant women were more likely than were controls to have stage II disease (60.1% vs. 56, 1%, P = .035), grade 3 tumors (74% vs. 62.2%, P < .001), hormone receptor–negative breast tumors (48.4% vs. 30%), and triple-negative breast cancer (38.9% vs. 26.9%, P < .001).
In Cox proportional hazard regression analysis controlling for age, stage, grade, hormone receptor status, HER2 status and histology, there were no significant differences between pregnant women and controls in either DFS (hazard ratio [HR] 1.02, P = .83) or OS (HR 1.08, P = .57).
As noted before, a subgroup analysis of 339 women who received more than 60% of their assigned chemotherapy doses during pregnancy also showed that survival was not significantly different from that of nonpregnant women (HR for DFS 0,71, P = .13; HR for OS 0.85, P = .39).
Termination does not benefit the mother
“Thanks to the important work of Dr. Amant in the INCIP [International Network on Cancer, Infertility, and Pregnancy] network and others around the world, we now have sufficient data to know that it’s safe to treat breast cancer during pregnancy, and that the prognosis of breast cancer during pregnancy is comparable to nonpregnant controls if we adjust for certain characteristics such as age and others,” said Fatima Cardoso, MD, of Champalimaud Clinical Center in Lisbon, Portugal, the invited discussant.
“With this and other studies, we can come to the conclusion that pregnancy-induced alterations in the chemotherapy concentration due to altered pharmacokinetics does not seem to affect maternal prognosis, and therefore we should initiate treatment of breast cancer during wherever it’s indicated for oncological reasons, knowing that you can only use chemotherapy during the second or third trimester,” she said.
Dr. Cardoso emphasized that breast cancer during pregnancy is a rare situation requiring that treatment be given in a specialized center by an experienced multidisciplinary team, and that interrupting the pregnancy does not improve the mother’s prognosis.
“We have to spread the word to all health professionals who come across these women to stop advising them to immediately terminate pregnancy. For the children, the most important take-home message is avoid prematurely delivery,” she said.
Treatment for women with a diagnosis of breast cancer during pregnancy should be similar to that for nonpregnant women, with the exception of endocrine therapy and anti-HER2 agents, which should be withheld until after delivery, she added.
The study was supported by the European Research Council, Research Foundation Flanders, and Kom op tegen kanker (Stand Up to Cancer). Dr. Amant disclosed a consulting or advisory role for AstraZeneca and Clovis Oncology. Dr. Cardoso disclosed consulting or advisory roles and travel support from multiple companies.