Resistance to single-agent chemotherapy and its risk factors in low-risk gestational trophoblastic neoplasms

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.

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.

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.

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.