Chapter 8: Gestational Trophoblastic Disease

INTRODUCTION

Gestational trophoblastic disease (GTD) represents a spectrum of cellular proliferations arising from the villous trophoblast of the placenta and encompasses 4 clinicopathologic entities: hydatidiform mole (complete and partial), invasive mole, choriocarcinoma (CCA), and placental site trophoblastic tumor (PSTT). The last 3 conditions are associated with more significant clinical sequelae and together comprise the general term gestational trophoblastic neoplasia (GTN). In the absence of GTD, a normal pregnancy involves functioning trophoblast that invades the endometrium and recruits a robust vasculature to develop the placenta, which supports intrauterine fetal development. In healthy trophoblastic tissue, these "cancer simulating" behaviors are highly regulated; however, in GTD, normal control mechanisms fail, leading to invasive, vascular tumors with a tendency to metastasize.¹

Historically, GTD has been associated with significant morbidity and mortality. Hydatidiform moles were typically accompanied by serious bleeding and other medical complications before the development of early detection and effective uterine evacuation in the 1970s. Over the past 50 years, advances in this field have transformed GTN from a high mortality condition to one of the most treatable of all human cancers, with a cure rate exceeding 90%.^{2,3, and 4} Collaborative global efforts and specialty care centers have promoted the development of highly predictive staging and prognostic scoring systems, which enhance individualization of therapy. Furthermore, several advances in chemotherapy afford ongoing refinement in treatment protocols.^{2,3, and 6} For women at highest risk of death, the application of multimodal therapy, including chemotherapy, radiation, and surgery, has led to high cure rates while minimizing disease and treatment-related morbidities. In this setting of potentially high cure rates, the onus to identify and appropriately treat GTD falls on the providers entrusted with the primary care of women.

EPIDEMIOLOGY

Key Points

1. The incidence of GTD is approximately 1 per 1000 pregnancies.

2. The most consistently defined risk factors for GTD include extremes of reproductive age and history of prior molar pregnancy. Of all the environmental factors associated with GTD, only low β-carotene and animal fat intake is consistently associated with GTD.

3. Complete hydatidiform molar pregnancy typically results in 1 sperm fertilizing an empty ovum, with subsequent genetic duplication; in contrast, incomplete hydatidiform molar pregnancy typically develops from dispermic fertilization of a normal ovum.

In general, studies conducted in North America, Australia, New Zealand, and Europe indicate the incidence of hydatidiform mole ranges from 0.57 to 1.1 per 1000 pregnancies. In contrast, studies from Southeast Asia and Japan suggest an incidence as high as 2.0 per 1000 pregnancies. As a result of difficulties in obtaining reliable epidemiologic data, it is unclear whether these findings represent a true difference in prevalence or are related to discrepancies between hospital- and population-based data or disparities in the availability of central pathology review.⁷ Further complicating the identification of true incidence is the uncommon diagnosis of GTD and ...