• Pashtoon M Kasi, Daisuke Kotani, Michael Cecchini, Kohei Shitara, Atsushi Ohtsu, Ramesh K Ramanathan, Howard S Hochster, Axel Grothey, and Takayuki Yoshino.
• Division of Medical Oncology, Mayo Clinic, 200 First St SW, Rochester, 55905, MN, USA. kasi.pashtoon@mayo.edu.
• Bmc Cancer. 2016 Jul 13; 16: 467.

BackgroundTAS-102 (trifluridine and tipiracil hydrochloride; a novel combination oral nucleoside anti-tumor agent) has recently received regulatory approval for patients with refractory metastatic colorectal cancer (mCRC). Internal review of data at a single-institution showed a trend towards better overall survival (OS) for patients who experienced chemotherapy-induced neutropenia at 1-month (CIN-1-month). To explore this finding further, a cohort study was designed based on outcome data from three centers in United States and one from Japan.MethodsCIN-1-month after starting TAS-102 was defined by the Common Terminology Criteria for Adverse Events (CTCAE), version 4.03 as a neutrophil count decrease of ≥ grade 2 (absolute neutrophil count < 1500/mm(3)). Patients had confirmed mCRC that was refractory to standard therapies. Patient demographics and clinical characteristics were compared between patients with CIN-1-month (CIN-1-month positive) versus those who did not have CIN-1-month (CIN-1-month negative); with the median progression-free survival (PFS) and OS were calculated using the Kaplan-Meier method, and differences evaluated using the Log-rank test.ResultsOur cohort study had a total of 149 patients with data regarding their neutrophil assessment at 1-month mark. Patients who developed ≥ grade 2 CIN-1-month had a both longer PFS (median 3.0 months versus 2.4 months; Log-rank P-value = 0.01), as well as OS (14.0 versus 5.6 months; Log-rank P-value < 0.0001). Only CIN-1-month (adjusted HR: 0.21 (95 % CI: 0.11-0.38) and higher baseline CEA levels (adjusted HR: 2.00 (95 % CI: 1.22-3.35) were noted to be independent predictors of OS. Furthermore, the CIN-1-month was noted to be a statistically significantly predictor of OS over a wide range of cutoffs.ConclusionsOur observations are novel and hypothesis generating. Neutropenia after starting TAS-102 was associated with better prognosis in patients with refractory mCRC. It can be postulated that the dosage of TAS-102 potentially may need to be increased to achieve better outcomes in patients not experiencing any neutropenia. Further pharmacologic investigations should help elucidate these issues.

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