The classification of gestational trophoblastic disease: a critical review

Gestational trophoblastic disease defines a group of conditions which arises from the fetal chorion. Two of the most important advances in the management of gestational trophoblastic disease have been the standardisation of terminology, and the concept of risk assignment based on classification or staging systems which allows rationalisation of treatment. Gestational trophoblastic disease is unique as the prognosis is dependent not only on the anatomic extent but also the presence of prognostic factors. A staging system similar to that used for other cancers does not apply to this disease because in most cases diagnosis is bases not on histology but on clinical or biochemical parameters. Metastatic spread to distant organs can occur early, even in the absence of disease in the uterus or pelvis. Staging in gestational trophoblastic disease must include prognostic factors in addition to anatomic extent of disease. Broadly there are two categories of classification in current use. The first is based on the usual staging system as in other cancers, with four stages of disease, but at the same time prognostic factors are incorporated. This has the important advantages of simplicity and uniformity with other staging systems. However the main pitfall is that no recommendations are made for treatment. The other broad category consists of risk tables, based on anatomic spread as well as prognostic factors. Here patients are assigned varying risk scores, with guidelines for multiagent chemotherapy at the outset in high-risk patients to minimise drug resistant disease. The ideal system would be one which has four stages of disease, so that comparison is easier, with recommendations for combination chemotherapy beyond a certain stage of disease.