In women undergoing treatment for low-risk gestational trophoblastic neoplasia (GTN), one dose of dactinomycin (Cosmegen) every 2 weeks results in a higher complete response rate than a weekly dose of methotrexate (Trexall, generics), the more commonly used drug.
Whereas cervical or endometrial cancers develop from uterine cells, GTNs start in cells that would normally develop into the placenta during pregnancy. These highly curable tumors include hydatidiform moles, which are caused by overproduction of placental tissue, and choriocarcinoma, a fast-growing form of cancer in the uterus. With no consensus on the best regimen for the primary treatment of low-risk GTNs, a research team compared the two commonly used single-drug regimens in 216 patients over the course of 8 years.
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Both regimens were well-tolerated, but biweekly IV dactinomycin 1.25 mg/m2 was statistically superior to weekly intramuscular methotrexate 30 mg/m2, with complete response rates of 70% and 53%, respectively, in women without choriocarcinoma and with a risk score of 0 to 4. The investigators noted that both regimens were less effective if the risk score was 5 or 6 or if the diagnosis was choriocarcinoma (J Clin Oncol. 2011;29[7]:825).
“Both chemotherapy drugs are effective in treating this kind of neoplasia, but this trial proved that dactinomycin is the best first-line regimen,” remarked coinvestigator David Scott Miller, MD, head of gynecologic oncology at the University of Texas Southwestern Medical Center in Dallas.
Nevertheless, “The study … does not change standard practice at this time,” according to an accompanying editorial (J Clin Oncol. 2011;29[7]:786). “Most treating physicians will continue to use single-agent methotrexate … and will reserve the use of dactinomycin … for methotrexate resistance or toxicity.” ONA
