Abstract 249P
Background
Patients with MBC prefer convenient treatments with low toxicity but without compromised efficacy. Metronomic chemotherapy (MCT), which involves oral low dose continuous administration, is used in selected cases. However, evidence of efficacy with different chemotherapies used in MCT is limited. Here we provide evidence specifically on MCT-CX (Capecitabine 500 mg x 3 and Cyclophosphamide 50 mg x 1).
Methods
This is an open single-armed prospective phase II trial at one site in Sweden. A Fleming two stage design with first analysis after 20 evaluable cases was applied. If ≤8 responders (ineffective) or ≥13 responses (effective) the study would be terminated. Otherwise, treatment was considered effective if in total ≥18 (45 %) responded. Primary endpoint was Clinical benefit rate (CBR); proportion of cases with Complete response (CR), Partial Response (PR) or Stable Disease (SD) ≥ 24 weeks. Secondary endpoints included Over all response rate (ORR; CR or PR), Progression free survival (PFS), Overall survival (OS), safety and Quality of Life.
Results
In total, 40 patients were included between 2019-2023. Ages ranged between 49-86 years. 82% had endocrine resistant Luminal MBC. Seven patients presented with bone-only disease, and 50% had liver metastasis. In 58% treatment was given beyond second-line. First analysis after 20 evaluable cases showed eleven responders which warranted further investigation. Final analysis showed an CBR of 45%; 8 PR, 10 SD ≥ 24 weeks. ORR was 20%, however 15 participants had non-measurable disease and could reach SD as best outcome. Median PFS was 17 months and median OS 20 months. Low grade hand-foot syndrome and diarrhoea were the most reported toxicities.
Conclusions
Almost half of participants with far advanced MBC responded to treatment with MCT-CX and presented with mild toxicities. This provides a feasible treatment option applicable to patients commonly seen by oncologists in daily practice. Randomized trials comparing MCT not only to standard dosing chemotherapy but also to best supportive care are needed.
Clinical trial identification
NCT04350021.
Legal entity responsible for the study
Västra Götalands Regionen.
Funding
Bröstcancerförbundet, Anna-Lisa och Bror Björnssons stiftelse, SU-fonden Sahlgrenska University hospital, ALF Västra Götalands Regionen.
Disclosure
K. Larsson: Financial Interests, Personal, Advisory Board: Pfizer; Financial Interests, Personal, Other, Second opinions: Canser. B.K. Linderholm: Financial Interests, Personal, Advisory Board: Pfizer, AstraZeneca, Daiichi Sankyo, Gilead, Eli Lilly, Novartis.