title: Resistance to single-agent chemotherapy and its risk factors in low-risk gestational trophoblastic neoplasms.
abstract: OBJECTIVE
  Gestational trophoblastic neoplasm (GTN) is a rare disease which is classified into high- and low-risk groups. While the high-risk patients require combination therapy, the low-risk groups respond to single-agent chemotherapy. We studied resistance to single-agent chemotherapy and its risk factors among the low-risk GTN patients in Iran.
  
  
  METHODS
  We followed 168 low-risk GTN patients who were treated between 2001 and 2011 in Valiasr Hospital, Tehran, Iran. We used a case-control design and studied odds ratios (OR) and corresponding 95% confidence intervals (CI) to evaluate association between drug resistance and different personal and clinical variables.
  
  
  RESULTS
  Resistance to sequential single-agent chemotherapy was 19%, although all patients had a complete remission after a combination of chemotherapy and/or surgery. Patients who had International Federation of Gynecology and Obstetrics scores of 5-6 - considered as, the intermediate risk group - had a 14-fold higher resistance compared with the low score patients (OR = 14.28, 95% CI = 5.54-36.81). We found higher risk of resistance among patients with metastasis (OR = 8.42, 95% CI = 2.44-29.07), large tumor size (>3 cm) (OR = 7.73, 95% CI = 1.93-30.91), high β-hCG (>100 000 IU/L) (OR = 5.86, 95% CI = 1.07-32.02) and/or a diagnosis more than 4 months after pregnancy (OR = 3.30, 95% CI = 1.08-10.02), compared with their reference group. We found no priority for the different chemotherapy regimens.
  
  
  CONCLUSIONS
  Intermediate risk GTN patients had a higher risk of resistance to chemotherapy compared with low-risk patients. Clinical trials and cost-effectiveness studies are needed to suggest a better treatment program for the intermediate risk group.
authors.affiliation: Gynecology Oncology Department, Valiasr Hospital, Faculty of Medicine, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, I.R of Iran.
authors.forename: Azam Sadat
authors.initials: AS
authors.lastname: Mousavi
authors.forename: Ashraf
authors.initials: A
authors.lastname: Zamani
authors.forename: Faezeh
authors.initials: F
authors.lastname: Khorasanizadeh
authors.forename: Mitra Modarres
authors.initials: MM
authors.lastname: Gilani
authors.forename: Kazem
authors.initials: K
authors.lastname: Zendehdel
mesh_terms: D000293:Adolescent; D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D016022:Case-Control Studies; D003520:Cyclophosphamide / Q000627:therapeutic use; D003609:Dactinomycin / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm; D005047:Etoposide / Q000627:therapeutic use; D005260:Female; D031901:Gestational Trophoblastic Disease / Q000188:drug therapy*; D006801:Humans; D007492:Iran; D008727:Methotrexate / Q000627:therapeutic use; D008875:Middle Aged; D011247:Pregnancy; D012307:Risk Factors; D014750:Vincristine / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D003609:Dactinomycin; D014750:Vincristine; D005047:Etoposide; D003520:Cyclophosphamide; D008727:Methotrexate
keywords: International Federation of Gynecology and Obstetrics; chemotherapy; gestational trophoblastic disease; resistance