Systematic review of fetal and placental metastases among pregnant patients with cancer

Introduction: Little is known about placental and fetal metastases among pregnant women with cancer. Therefore, we conducted a systematic review to identify the clinical and pathological characteristics, treatment trends and prognosis of this entity.

Methods: We searched PubMed and EMBASE to identify the publications reporting on placental and fetal metastases through September 2021, according to the PRISMA statement. Cases of fetal and/or placental metastases among pregnant women diagnosed with metastatic cancer during pregnancy were eligible for this review. The collected information included the patients and tumor characteristics, treatment during pregnancy and prognosis including the pregnancy outcomes.

Results: We identified 72 eligible cases among which placental and fetal metastases occurred in 61 (84.7%) and 24 cases (33.3%), respectively. Gestational melanoma and lung cancers were the main culprits of placental and fetal metastases. Two-thirds of the patients were diagnosed during the third trimester and only 2.7% have received cancer-specific therapy. The median maternal survival was 1 (95% CI 0.7-1.3) months post-partum and the one-year infant survival rate was 51.1%. The median gestational age was 28 weeks and the median infant age at diagnosis was 150 days. The most common fetal metastatic sites were the lungs (21.7%), scalp (17.4%), and liver (8.7%).

Conclusion: Fetal metastasis occurred mainly in patients with placental metastases of melanoma and lung cancer primaries and was associated with a dismal prognosis. Collecting cases from multiple institutions using a standardized case report form is necessary to increase our awareness of the occurrence of fetal metastases and the role of systemic therapies.