RATIONALE: Studying samples of blood in the laboratory from patients with cancer receiving dactinomycin may help doctors learn how dactinomycin works in the body and how patients will respond to treatment.

PURPOSE: This laboratory study is evaluating the pharmacokinetics of dactinomycin in young patients with cancer.

OBJECTIVES:

• Determine the pharmacokinetics (PKs) of dactinomycin in pediatric patients with cancer.
• Determine the degree of interpatient variation in the PKs of this drug.
• Determine the influence of characteristics such as age, tumor type, and concurrent therapy on drug PKs in these patients.
• Correlate drug PKs with clinical response and toxicity observed in these patients, focusing particularly on the incidence of severe liver toxicity or veno-occlusive disease.
• Correlate pharmacogenetic variability with clinical and PK data.

OUTLINE: This is a multicenter study.

Patients undergo blood collection for pharmacokinetic sampling of dactinomycin at baseline (prior to the initiation of dactinomycin) and periodically during course 1 of chemotherapy. An additional blood sample is obtained before or after treatment for the collection of peripheral blood lymphocytes. DNA from these cells is isolated and investigated for genetic variation in genes relevant to the pharmacology of dactinomycin. Plasma concentrations of dactinomycin are determined by liquid chromatography mass spectrometry analysis.

Patients are followed for 2 years.

PROJECTED ACCRUAL: A total of 50 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Diagnosis of cancer
• Currently being treated with dactinomycin on a clinical trial at a United Kingdom Children's Cancer Study Group center

PATIENT CHARACTERISTICS:

• Single- or double-lumen central venous catheter or portacath in place

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics