Updated analysis: Effect of biweekly dosing schedule of trifluridine-tipiracil (TAS-102) on rates of myelosuppression and maintenance of therapeutic efficacy in patients (pts) with previously treated metastatic colorectal cancer (mCRC).

95 Background: For surgically unresectable metastatic colorectal cancer pts, a continuum of treatment is required to improve the OS of our pts. Oral trifluridine-tipiracil (TAS-102) is FDA approved in refractory mCRC per the RECOURSE trial. As per the FDA insert, the recommended dose is 35 mg/m 2 twice daily (maximum = 80 mg/day) on Days 1-5 and Days 8-12 of 28-day cycles commonly resulting in Grade 3-4 neutropenia (38%), dose delays (53%), dose reductions (14%) and requiring G-CSF support (9%). To maintain efficacy and to potentially reduce toxicity, we analyzed an alternative biweekly dosing (Days 1-5 and Days 15-19 q28 days). Methods: A retrospective analysis was completed (2019-2022) at Vanderbilt-Ingram Cancer Center in pts with refractory mCRC and appendiceal cancer (CA) who completed ≥ 12 days of TAS-102 therapy and underwent surveillance imaging every 8-12 weeks. Patient data was assessed for ECOG performance status (PS), prior lines of therapy, the use of bevacizumab and CTCAE grade of treatment-related myelotoxicity. Evaluation of progression-free survival (PFS) was completed in mCRC pts. Results: Forty-three patients met the inclusion criteria, with a mCRC:appendiceal CA ratio of 39:4. The median age = 50 y/o (range 30-80); male:female 23:20; median ECOG PS = 1; median number of prior therapies = 3; and median duration of therapy = 97 days (range: 12-396). Associated grade 3/4 hematologic toxicities included: Neutropenia 39% [Grade 3 (12.2%), Grade 4 (2.4%)]; anemia 36.5% [Grade 3 (12.2%)]. No pts required G-CSF. No incidences of neutropenic fever were reported. Five pts (11.6%) required a dose delay and 3 pts (7%) required a dose reduction due to myelosuppression. In mCRC pts, the median PFS was 2.53 months. To date, 6 pts remain on treatment (range: 97-331). Conclusions: In our updated analysis, biweekly dosing of TAS-102 (35 mg/m 2 twice daily; Days 1-5 and Days 15-19 of 28-day cycles) for pts with refractory mCRC and appendiceal CA demonstrated tolerable myelosuppression, while preserving PFS in pts with mCRC. With an improved toxicity profile, this alternative TAS -102 dosing schedule may potentially broaden utilization of TAS-102 in patients with borderline PS and may be a more favorable option for future combination studies. Additional prospective data are needed to validate these findings. To our knowledge, this remains the first analysis of biweekly TAS-102 in a US patient population.