The median progression-free survival (PFS) in the phase 2 trial showed a difference of 1.41 months favoring TT-B over C-B, but this difference was not statistically significant.
The median overall survival was 4.64 months longer with TT-B than with C-B. However, the final analysis of TASCO1 was not designed to be comparative for overall survival, “so no formal statistical analysis is presented, and survival is a secondary endpoint,” noted investigator Eric Van Cutsem, MD, PhD, of University Hospital Gasthuisberg in Leuven, Belgium.
Dr. Van Cutsem presented the final results of TASCO1 at the 2021 Gastrointestinal Cancers Symposium (abstract 14).
Prior results from the trial were reported last year (Ann Oncol. 2020 Sep;31[9]:1160-68).
About trifluridine/tipiracil
Trifluridine/tipiracil is an oral drug combining the thymidine analogue trifluridine with tipiracil, an inhibitor of trifluridine degradation. The drug was approved by the Food and Drug Administration in 2015 under the trade name Lonsurf for the treatment of refractory metastatic colorectal cancer, and in 2019 for patients with metastatic gastric cancer or gastroesophageal junction cancer that had been treated with at least two lines of chemotherapy.
Trifluridine/tipiracil was associated with a brief but statistically significant survival benefit when compared with placebo in patients with heavily pretreated metastatic gastric cancer in the TAS-102 Gastric Study (Lancet Oncol. 2018 Nov;19[11]:1437-48).
In a separate analysis of the study, trifluridine/tipiracil was associated with significantly better overall survival and PFS than placebo in patients who had undergone gastrectomy (JAMA Oncol. 2019 Oct 10;6[1]:e193531).
TASCO1 details
In TASCO1, investigators enrolled patients with colorectal cancer who had never received systemic therapy for unresectable metastatic disease, and who were judged to be ineligible for intensive therapy due to advanced age, low tumor burden, poor performance status, comorbidities, or other clinical reasons.
After stratification by RAS status, performance status, and region, patients were randomly assigned to receive TT-B (n = 77) or C-B (n = 76).
TT-B consisted of oral trifluridine/tipiracil at 35 mg/m2 twice daily on days 1-5 and 8-12 every 4 weeks plus bevacizumab at 5 mg/kg intravenously on days 1 and 15 every 4 weeks.
C-B consisted of oral capecitabine at 1,250 or 1,000 mg/m2 twice a day on days 1-14 every 3 weeks plus bevacizumab at 7.5 mg/kg IV on day 1 every 3 weeks.
Final results
The median PFS, the primary endpoint, was 9.23 months with TT-B and 7.82 months with C-B. The difference was not statistically significant, with the upper limit of the 95% confidence interval crossing 1.
The median overall survival was 22.31 months with TT-B and 17.67 months with C-B (hazard ratio, 0.78; 95% CI, 0.55-1.10).
Dr. Van Cutsem pointed out that more patients in the TT-B arm had subsequent therapies compared with patients in the C-B arm – 59.7% vs. 40.8%.
He also noted that the safety profile of TT-B “remains unchanged from the initial analysis.”
Grade 3 or greater neutropenia, decreased neutrophil count, anemia, and decreased white blood cell count were all higher among patients on TT-B, but grade 3 or greater febrile neutropenia was similar between the groups.
Patients in the TT-B arm had more frequent grade 3 or greater nausea, vomiting, and hypertension. Grade 3 or higher hand-foot syndrome and diarrhea were both more common with C-B.
At the study cutoff date in September 2020, 66 patients in each arm had died.
Dr. Van Cutsem said more data on the efficacy of TT-B vs. C-B will come from the ongoing phase 3 SOLSTICE trial. Results from this trial are expected in late 2022.
