CHEOPS trial: a GINECO group randomized phase II assessing addition of a non-steroidal aromatase inhibitor to oral vinorelbine in pre-treated metastatic breast cancer patients.

Background: The objective of the CHEOPS trial was to assess the benefit of adding aromatase inhibitor (AI) to metronomic chemotherapy, oral vinorelbine, 50 mg, three times a week for pre-treated, HR + /HER2- metastatic breast cancer patients.

Methods: In this multicentric phase II study, patients had to have progressed on AI and one or two lines of chemotherapy. They were randomized between oral vinorelbine (Arm A) and oral vinorelbine with non-steroidal AI (Arm B).

Results: 121 patients were included, 61 patients in Arm A and 60 patients in Arm B. The median age was 68 years. 109 patients had visceral metastases. They all had previously received an AI. The study had been prematurely stopped following the third death due to febrile neutropenia. Median PFS trend was found to be different with 2.3 months and 3.7 months in Arm A and Arm B, respectively (HR 0.73, 95%CI 0.50-1.06, p value = 0.0929). No statistical difference was shown in OS and better tumor response. 56 serious adverse events corresponding to 25 patients (21%) were reported (respectively, 12 (20%) versus 13 (22%) for arms A and B) (NS).

Conclusion: The addition of AI to oral vinorelbine over oral vinorelbine alone in aromatase inhibitor-resistant metastatic breast cancer was associated with a non-significant improvement of PFS. Several unexpected serious adverse events were reported. Metronomic oral vinorelbine schedule, at 50 mg three times a week, requires close biological monitoring. The question of hormonal treatment and chemotherapy combination remains open.