First Orally Administered Paclitaxel Shown to Be More Effective than Intravenous Paclitaxel for Metastatic Breast Cancer

According to the results of a phase 3 trial presented at the San Antonio Breast Cancer Symposium, patients with metastatic breast cancer (MBC) who received an oral formulation of the chemotherapy drug palitaxel (Taxol) had a better response and survival and less neuropathy than patients who received intravenous (IV) paclitaxel.

Researchers evaluated an oral form of paclitaxel in combination with encequidar, a p-glycoprotein pump inhibitor that allows the oral formulation of paclitaxel to be absorbed into the bloodstream. The trial included 402 patients with MBC, who were randomly assigned in a 2:1 ratio, to receive either 205 mg/m² of oral paclitaxel plus encequidar (Pac + E) for 3 days per week or 175 mg/m² paclitaxel IV (IV Pac) every 3 weeks. The participants’ tumors were evaluated for response and confirmed at 2 consecutive evaluations by a blinded, independent radiology company.

The primary endpoint was radiologically confirmed tumor response rate at 2 consecutive timepoints. Secondary endpoints were progression-free survival (PFS) and overall survival (OS).

Results from the trial showed that 35.8% of the Pac+E group had a confirmed tumor response, compared with 23.4% in the IV Pac group. The response rate was 40.4% for the Pac+E group and 25.6% for the IV Pac group when evaluating the pre-specified modified intention to treat population.

Researchers found that 51% of patients in the Pac+E group had a response that lasted more than 150 days, compared with 38% of the IV Pac group. PFS analysis showed a median of 9.3 months for the Pac+E group and 8.3 months for the IV Pac group. In the OS analysis, the Pac+E group showed a median of 27.9 months and 16.9 months for the IV Pac group.

Higher rates of neutropenia, infection, and gastrointestinal adverse effects were reported in the Pac+E group. Lower incidence of severity of neuropathy was reported, with 17% in the Pac+E group compared with 57% in the IV Pac group.

Grade 3 neuropathic symptoms were experienced by 1% of patients in the Pac+E group and 8% in the IV Pac group.

According to Gerardo Antonio Umanzor Funez, MD, medical oncologist with Centro Oncologico Integral and one of the researchers in the study, the next step will be testing for tolerability of oral paclitaxel in patients at high risk of developing peripheral neuropathy. In addition, the oral formulation may also be studied in other cancers either as a monotherapy or in combination with other agents.

REFERENCE

Oral paclitaxel yielded better outcomes than intravenous paclitaxel for metastatic breast cancer patients in phase III trial [news release]. San Antonio, TX; San Antonio Breast Cancer Symposium: December 13, 2019. https://aacr.ent.box.com/s/8ocddnlefz4wej5ljfuo4k06ve7h83ls. Accessed December 5, 2019.