Oral Paclitaxel With P-Glycoprotein Pump Inhibitor in Metastatic Breast Cancer
Posted: Wednesday, January 8, 2020
Patients with metastatic breast cancer who received oral paclitaxel with encequidar had improved overall response rates and lower rates of peripheral neuropathy compared with patients receiving intravenous paclitaxel, according to Gerardo Umanzor, MD, a medical oncologist with Centro Oncologico Integral, and colleagues. Encequidar is an inhibitor of the intestinal P-glycoprotein pump, to which the low bioavailability of paclitaxel is owed. Dr. Umanzor and colleagues presented the findings of their phase III trial at the 2019 San Antonio Breast Cancer Symposium (SABCS; Abstract GS6-01).
“We were pleasantly surprised that responses were durable, conferring an early survival advantage with minimal neuropathy,” commented Dr. Umanzor in an American Association for Cancer Research press release.
In this open-label, multicenter study, a total of 402 patients with metastatic breast cancer were randomly assigned to receive a higher dose of oral paclitaxel (205 mg/m2) with encequidar for 3 consecutive days per week or a lower dose of intravenous paclitaxel (175 mg/m2) once every 3 weeks. The primary endpoint was tumor response rate at two consecutive time points.
The confirmed tumor response rates for patients in the intention-to-treat population, compared with patients receiving intravenous paclitaxel, were 35.8% and 23.4%. In the modified intention-to-treat population, the confirmed tumor response rates were 40.4% and 25.6%, respectively. Progression-free and overall survival rates from ongoing analyses were 9.3 and 27.9 months versus 8.3 and 16.9 months for the oral and intravenous paclitaxel treatment groups, respectively.
The toxicity profile of both treatments was similar. Patients who received oral paclitaxel with encequidar reported lower rates of all-grade and grade 3 peripheral neuropathy versus patients treated with intravenous paclitaxel (17% and 1%, vs. 57% and 8%, respectively). However, patients on the oral taxane regimen experienced higher rates of neutropenia, infection, and gastrointestinal adverse events.
Disclosure: Dr. Umanzor reported no conflicts of interest. For full disclosures of the other study authors, visit abstractsonline.com.