Inclusion Criteria

DISEASE CHARACTERISTICS:

- Diagnosis of low-risk post-molar gestational trophoblastic tumor, defined as 1 of the
following:

- Increasing human chorionic gonadotropin (hCG) levels on ≥ 3 consecutive
measurements taken over ≥ a 2-week period

- Less than 10% decrease of hCG levels on 4 measurements taken over ≥ a 3-week
period

- Persistent or recurrent disease

- Histologically confirmed complete or partial mole on initial evacuation

- Prior pregnancy ≤ 12 months ago

- No histologically confirmed choriocarcinoma or placental site trophoblastic tumor on
initial evacuation

- Failed only 1 prior dactinomycin or methotrexate therapy (with or without leucovorin
calcium)

- WHO score 2-6

- No evidence of metastatic disease, except to the lung or vagina, on physical exam,
chemistry, chest X-ray, and ultrasound

- No liver, spleen, brain, kidney, or gastrointestinal tract metastases

- No more than 8 metastatic lesions

PATIENT CHARACTERISTICS:

Age

- Any age

Performance status

- GOG 0-1

Life expectancy

- Not specified

Hematopoietic

- Absolute neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

- Granulocyte count ≥ 1,500/mm^3

Hepatic

- Bilirubin ≤ 1.5 times upper limit of normal (ULN)

- SGOT ≤ 3 times ULN

- Alkaline phosphatase ≤ 3 times ULN

Renal

- Creatinine ≤ 1.5 mg/dL

- Creatinine clearance ≥ 45 mL/min

Other

- Not pregnant or nursing

- Fertile patients must use effective contraception during and for 3 months after study
participation

- No significant infection

- No other invasive malignancy within the past 5 years except nonmelanoma skin cancer

PRIOR CONCURRENT THERAPY:

Biologic therapy

- No concurrent prophylactic filgrastim (G-CSF) unless for recurrent neutropenic
complications

- No concurrent prophylactic thrombopoietic agents unless for recurrent grade 4
thrombocytopenia

Chemotherapy

- See Disease Characteristics

- At least 7 days since prior dactinomycin or methotrexate (with or without leucovorin
calcium) and recovered

- No prior pemetrexed disodium

- No other prior chemotherapy

Endocrine therapy

- Not specified

Radiotherapy

- At least 14 days since prior radiotherapy and recovered

- No prior radiotherapy to ≥ 25% of the bone marrow

Surgery

- Recovered from prior surgery

Other

- No nonsteroidal anti-inflammatory drugs or salicylates for 2 days (or 5 days for
drugs with a long half-life) before, during, and for 2 days after pemetrexed disodium
administration

- Concurrent low-dose aspirin (≤ 325 mg/day) allowed