Monitoring complete hydatidiform molar pregnancies after normalisation of human chorionic gonadotrophin: national retrospective population study.

Objective: To provide evidence for a reduced surveillance protocol to detect gestational trophoblastic neoplasia after normalisation of human chorionic gonadotrophin (hCG) levels following uterine evacuation of a complete hydatidiform mole.

Design: National retrospective population study.

Setting: Two UK Trophoblastic Disease Treatment Centres (Sheffield and London), 1 January 1980 to 30 November 2020.

Participants: 17 424 patients with hCG normalisation after evacuation of their complete hydatidiform mole were included. Complete hydatidiform moles were verified by centralised pathological review. Patients were excluded if lost to follow-up or required treatment before normalisation of hCG levels.

Main outcome measures: Incidence and clinical presentation of gestational trophoblastic neoplasia after normalisation of hCG levels following uterine evacuation of a complete hydatidiform mole.

Results: Of 17 424 patients whose hCG normalised after complete hydatidiform mole evacuation, 99.8% (n=17 393 of 17 424) did not subsequently develop gestational trophoblastic neoplasia. The overall risk of gestational trophoblastic neoplasia after previous normalisation of hCG levels was 0.2% (n=31 of 17 424 patients). The risk of developing gestational trophoblastic neoplasia after uterine evacuation was substantially lower if hCG levels returned to normal in <56 days rather than ≥56 days (posterior medians 0.06%, 95% credible interval 0.01% to 0.14% v 0.22%, 0.15% to 0.31%), with a posterior relative risk of 0.25 (0.06 to 0.72). Most patients who developed gestational trophoblastic neoplasia (71.0%, n=22 of 31) had received a diagnosis after the current six month surveillance protocol. The cumulative risk of developing gestational trophoblastic neoplasia in patients whose hCG levels normalised early increased minimally with time. If a patient had normal hCG levels in <56 days, a clinically relevant time point, the risk of developing gestational trophoblastic neoplasia was small (0.04%, about 1 in 2619 patients) at 39 months after normalisation. The equivalent risk for a patient who had normal hCG levels in ≥56 days was 0.16% (about 1 in 642 patients). All 31 women who developed gestational trophoblastic neoplasia achieved sustained remission after subsequent treatment.

Conclusions: The findings of the study indicate that surveillance protocols could safely change to one confirmatory normal hCG value for patients whose hCG levels return to normal in <56 days of evacuation of a complete hydatidiform mole. Patients whose hCG levels return to normal in ≥56 days should be counselled on the remaining risk of gestational trophoblastic neoplasia over time to help decide the length of subsequent follow-up.