Post-molar gestational trophoblastic neoplasia — structured SAQ (15 marks)

(a) The FIGO criterion and the diagnosis (2 marks)

• The FIGO hCG-plateau criterion — a sustained hCG level within 10 per cent (plus or minus 10 per cent) across four values over a three-week duration (days 1 to 7, 8 to 14, 15 to 21, 22 to 28). Her four values (820, 845, 810, 830) all fall within 10 per cent of each other across four weekly measurements.^[4]
• The diagnosis is post-molar gestational trophoblastic neoplasia (GTN). ^[1]

One mark for the correct criterion named and applied to her values, one mark for the diagnosis. ^[1]

(b) Steps before starting any chemotherapy (4 marks)

One mark per step, maximum four. ^[2][4]

• Register her with the regional trophoblast centre (the Queensland Trophoblast Centre coordinates ANZ care) before starting treatment.^[2]
• Exclude phantom hCG and a new pregnancy — check a urine pregnancy test (a positive serum with a negative urine is phantom hCG, never treated) and a pelvic ultrasound.^[4]
• Stage and risk-stratify — pelvic ultrasound, chest radiograph (count lung metastases), CT chest-abdomen-pelvis and brain MRI if lung metastases of 1 cm or more or a high score is suspected; assign the FIGO stage and WHO score.^[2]
• Document baseline bloods before chemotherapy — full blood count, renal and hepatic function, body surface area and performance status; counsel on the cure rate, fertility preservation, and the need for reliable contraception throughout.^[4]

(c) FIGO 2000 staging and the WHO risk-score cut-off (4 marks)

One mark for each correct stage (max 3) and one mark for the WHO cut-off. ^[1][5]

• Stage I — disease confined to the uterine corpus.^[1]
• Stage II — GTN extends outside the uterus but is limited to the genital structures (adnexa, vagina, broad ligament).^[1]
• Stage III — GTN extends to the lungs with or without genital tract involvement.^[1]
• Stage IV — all other metastatic sites.^[1]
• WHO prognostic score — eight variables each scored 0, 1, 2 or 4; a total of 6 or below is low-risk (single-agent) and 7 or above is high-risk (multi-agent EMA-CO); the stage and score are written together as one figure.^[5]

(d) First-line chemotherapy for low-risk disease and the switch rule (5 marks)

Two marks for the regimen with drug, dose, route, timing; one mark for the repeat interval and consolidation; two marks for the switch-on-resistance rule. ^[3][4]

• Methotrexate 50 mg intramuscularly on days 1, 3, 5 and 7, with folinic acid 15 mg orally on days 2, 4, 6 and 8 — the 8-day low-dose methotrexate-folinic acid regimen.^[3]
• Repeated every two weeks until hCG normalises, then three consolidation cycles after the first normal hCG.^[3][4]
• Switch-on-resistance rule: if methotrexate resistance develops (hCG plateau or rise during treatment) and hCG is low, switch to pulsed actinomycin-D 1.25 mg per square metre intravenously every two weeks; if hCG is high or rising on a single agent, escalate to multi-agent EMA-CO.^[4]