Metronomic Capecitabine With Cyclophosphamide Regimen in Unresectable or Relapsed Pseudomyxoma Peritonei

Background: No standard treatment for advanced unresectable pseudomyxoma peritonei (PMP) has been defined so far. PMP is traditionally considered chemoresistant but nonrandomized series showed promising results with regimens for gastrointestinal tumors. Patients and Methods: We conducted a single-center prospective single-arm trial. Inclusion criteria were histologically confirmed PMP, unresectable or progressive to surgery/previous treatments. Patients received a continuous metronomic regimen with capecitabine (625 mg/m² twice per day) with cyclophosphamide (50 mg/d) until progression, unacceptable toxicity, or consent withdrawal. The primary end point was progression-free survival (PFS); secondary end points were disease control rate (DCR), overall survival (OS), and safety. Exploratory analyses were the variation of circulating tumor biomarkers and neutrophil to lymphocyte ratio (NLR). Results: Twenty-three consecutive patients were enrolled from April 2015 to October 2017. At a median follow up of 22.4 months, median PFS was 9.5 months and 1-year OS rate was 73.7%. Overall, DCR was 87% and 6 (27%) patients achieved disease control ≥12 months. The safety profile was manageable: 26% of patients reported Grade 3 drug-related adverse events and none Grade 4/5. NLR baseline < 3 versus ≥ 3 was associated with prolonged PFS (12.6 vs. 3.4 months; P =.0001). Conclusion: Metronomic capecitabine with cyclophosphamide is a well tolerated regimen in unresectable/recurrent PMP, and its safety profile favorably compares with previously investigated regimens.