The Trophoblastic Tower of Babel: Classification Systems for Metastatic Gestational Trophoblastic Neoplasia

Abstract

There are presently three classifications of metastatic gestational trophoblastic tumors (MGTM). The first is that of low-risk and high-risk neoplasia devised by Hammond, now designated the National Cancer Institute classification. The second is that of FIGO that attempts to conform to the staging of other gynecologic malignancies by that organization. The third is a scoring system adopted by World Health Organization (WHO) from the original devised by Bagshawe. This scoring system is finding the widest acceptance and is increasingly being used for treatment planning. However, different investigators not only define risk groups differently from the WHO recommendation, but also modify the WHO scoring system in novel, individualistic ways that changes the total score and outcome assessment. This results in patients with the same risk factors being placed in different WHO risk groups. Comparison of therapy between center is then invalidated. Furthermore, it would appear preferable that the WHO scoring system is restricted to metastatic neoplasia. To achieve a uniform scoring system for MGTN there needs to be consensus (i) whether lung metastases should be detected by chest X ray or CAT scan; (ii) whether the size of metastases should be measured clinically or radiologically (including ultrasound, CAT scan, and MRI); (iii) are multiple lung or brain metastases counted by CAT scan or MRI; (iv) are ABO blood groups to be included so that the number of points is uniform for different centers; and (v) that idiosyncratic and individual categories are not added or omitted from the score.