Factors associated with Triuridine/Tipiracil (TAS-102) effectiveness in patients with refractory metastatic colorectal cancer: real-life data from the Czech Republic.

Background: Triuridine/tipiracil (TAS-102) is effective in refractory metastatic colorectal cancer (mCRC). Currently, no predictive biomarkers are established and used in clinical practice. Methods: We analyzed data of 160 patients treated with TAS-102 in real clinical practice in the Czech Republic. Different factors associated with progression-free survival (PFS) and overall survival (OS) were evaluated. Results: Median PFS was 3.3 months, and median OS 10.2 months. Factors signicantly associated with PFS and/or OS were: ECOG performance status (PS), time from diagnosis of mCRC > 24 months, initiation of treatment > 3 months from last uoropyrimidine, number of metastatic sites, baseline CRP level, WBC count, neutrophils count, monocytes count, neutrophil to lymphocyte ratio, development of neutropenia, thrombocytopenia, diarrhea, required dose reduction and cycle delay. We developed a scoring system TAScore from factors available at the beginning of treatment. One point each was assigned to the following factors (PS, diagnosis of mCRC > 24 months, initiation of TAS-102 > 3 months from uoropyrimidine, baseline CRP, WBC, monocytes count < 0.5 × 10 9 /L) and patients were divided into 3 groups: high risk group (0 to 1 point), intermediate (2 to 3), favorable with 4 or more points. OS according to risk group was: 5.7 months for high risk, 8.7 for intermediate, 12.8 for favorable (P < 0.001). TAScore was also associated with PFS (P < 0.001). Conclusions : TAS-102 is effective in patients with refractory mCRC. We propose simple scoring system TAScore to help with precise patient selection at the beginning of TAS-102 treatment. treatment, baseline laboratory values—white blood cell count, absolute neutrophil count, absolute monocyte count, absolute lymphocyte count, neutrophil to lymphocyte ratio (NLR), CEA level, CA19–9 level, C-reactive protein (CRP) level, lactate dehydrogenase (LDH) level, treatment toxicity—neutropenia, low platelets count, anemia, diarrhea, asthenia, adverse events requiring TAS–102 dose reduction, and adverse events requiring TAS–102 cycle delay. documented progression or and overall to death due to any cause. Survival curves were estimated using the Kaplan-Meier method. A log-rank test was used to test the difference between survival curves (PFS or OS) for different factors. All point estimates include 95% condence intervals (CIs). Fisher’s exact test or Chi-squared test were used for establishing the signicance of the association between categorical variables. Univariate and multivariate analyses of predictive factors were performed using Cox proportional hazard regression. All tests were performed at a signicance level of α = 0.05.

Frequency analysis and summary statistics were used to characterize the sample data set.
Progression-free survival was de ned as the time from the initiation of TAS-102 treatment to the date of rst documented progression or death due to any cause and overall survival as the time from the initiation of TAS-102 treatment to death due to any cause. Survival curves were estimated using the Kaplan-Meier method. A log-rank test was used to test the difference between survival curves (PFS or OS) for different factors. All point estimates include 95% con dence intervals (CIs). Fisher's exact test or Chisquared test were used for establishing the signi cance of the association between categorical variables. Univariate and multivariate analyses of predictive factors were performed using Cox proportional hazard regression. All tests were performed at a signi cance level of α = 0.05.

Baseline characteristics
Patient characteristics are summarized in Table 1. Median follow-up from the beginning of TAS-102 treatment was 12.4 months. The median age was 66 years (range 28-83), 106 patients were male (66.3%), ECOG performance status 0 and 1 was present in 38.1% and 61.9%, respectively, at the start of TAS-102 therapy. Primary tumor location was right colon in 15%, transversum in 5%, left colon in 50%, and rectum in 30% of patients. Almost 30% of patients had disease limited to one organ site, 48.8% had 2 metastatic sites and 21.8% had 3 or more metastatic sites. Ninety-ve patients were diagnosed with synchronous metastatic colorectal cancer (59.4%). The median number of previous treatment lines for metastatic disease was 2 (range 1-7). One hundred two patients (63.8%) were treated for metastatic colorectal cancer for more than 24 months before they started TAS-102 treatment. All patients had previously received uoropyrimidines, oxaliplatin, and irinotecan, and 28 (17.5%) had previously received regorafenib. A total of 72 (45%) patients had RAS wild-type cancers. Anti-VEGF treatment had been used in 133 (83.1%) patients and anti-EGFR treatment in 70 (43.8%) patients.

TAS-102 treatment
The median number of administered TAS-102 cycles was 3 (range 1-27). At the time of analysis 24 (15%) patients continued on TAS-102 treatment. One hundred eighteen (73.8%) patients discontinued treatment due to disease progression, 11 (6.9%) due to treatment toxicity, 6 patients (3.8%) decided to discontinue treatment (mostly for subjective poor treatment tolerance), in 1 (0.6%) patient was treatment changed per physician decision. After progression on TAS-102, about 50% of patients received another systemic oncologic treatment.

Outcomes and toxicity
The best overall response was stable disease in 34 patients (21.3%), disease progression as the best response was recorded in 108 patients (67.5%). In 18 (11.3%) patients, the response could not be precisely assessed. There were no partial or complete responses, ORR was 0%.
Any grade toxicity was recorded in 88.1% of patients ( Table 2). The most common toxicities included neutropenia, asthenia, and nausea. Any grade ≥ 3 toxicity was recorded in 65 patients (40.6%). Most common grade ≥ 3 toxicity was neutropenia in 56 patients (35%) ( Table 2). Febrile neutropenie was recorded in 4 patients (2.5%). One patient died due to infectious complication during the treatment. TAS-102 dose reduction was performed in 48 (30%) and the next treatment cycle was delayed in 84 (52.5%) patients.

Prognostic and predictive factors
Various patient and tumor characteristics in association with survival parameters were analyzed (these results are summarized in Table 3). Factors signi cantly associated with prolonged PFS in univariate analysis were: patient's ECOG performance status 0, time from diagnosis of metastatic disease to initiation of TAS-102 treatment more than 24 months, initiation of TAS-102 treatment more than 3 months from last uoropyrimidine therapy, normal baseline CRP level, baseline WBC, normal baseline neutrophils count, baseline monocytes count, NLR < 3, number of metastatic sites, neutropenia ≥ grade 2 during TAS-102 treatment, diarrhea grade ≥ 1 or more, required TAS-102 dose reduction, required TAS-102 next cycle delay.
Factors signi cantly associated with prolonged OS in univariate analysis were: time from diagnosis of metastatic disease to initiation of TAS-102 treatment more than 24 months, initiation of TAS-102 treatment more than 3 months from last uoropyrimidine therapy, normal baseline CRP level, baseline WBC, baseline neutrophils count, NLR < 3, baseline monocytes count, neutropenia ≥ grade 2 during TAS-102 treatment, thrombocytopenia ≥ grade 2 during TAS-102 treatment, required TAS-102 dose reduction, required TAS-102 cycle delay. The trend to prolonged OS was in patients with ECOG performance status 0.
The main reason for TAS-102 dose reduction and the next cycle delay was neutropenia during TAS-102 treatment and dose reduction and cycle delay were signi cantly associated with the occurrence of neutropenia grade 2 (P < 0.001).
Based on the ndings of factors associated with better survival of patients, we have developed a scoring system (TAScore) to select patients who will bene t most from TAS-102 treatment. One point each was assigned to the following criteria: ECOG performance status 0, time from diagnosis of metastatic disease to initiation of TAS-102 treatment more than 24 months, initiation of TAS-102 treatment more than 3 months from last uoropyrimidine therapy, normal baseline CRP level, normal baseline WBC, baseline monocytes count < 0.5 × 10 9 /L, Table 6). The overall score was the sum of these points. Based on the overall score patients were divided into 3 groups: high risk group with 0 to 1 point, intermediate risk group with 2 to 3 points and favorable risk group with 4 or more points. In our cohort the median OS according to risk group was: 5.7 months (95% CI, 2.4 to 6.5 months) for the high risk group (11 patients

Discussion
Our analysis con rmed the TAS-102 e cacy in heavily pretreated group of patients with metastatic colorectal cancer. The PFS and OS results in the present cohort were slightly better compared to outcomes in the RECOURSE study and to those reported in studies on "real-world" TAS-102 e cacy from Japan Spain, Italy, and Netherland [4][5][6][7]. The likely reason for these differences is conceivably patient selection. Patients in our cohort had less extensive disease with approximately 80% of patients in our study having only 1 or 2 metastatic sites compared to 61% in RECOURSE [3], 59% in the Spanish TERRA trial [5], or 38% and 23% in other studies [6,7]. Treatment-related toxicity in our analysis was similar to other studies with TAS-102 therapy and no new adverse events have emerged. The treatment has favorable toxicity pro le with asymptomatic neutropenia as the most common adverse event.
We found several factors associated with better prognosis on TAS-102 treatment. Some of these factors are probably associated not only with the outcomes of TAS-102 therapy but with CRC prognosis in general. For example, lower monocyte count is associated with better prognosis of localized CRC and metastatic disease [8][9][10][11] and was also con rmed as positive prognostic factor for TAS-102 in a study published by Kwakman and collaborators [7]. Similarly, elevated CRP levels are associated with poor prognosis of non-metastatic and metastatic CRC [12][13][14][15][16]. In our analysis, normal white blood count, neutrophil count, monocyte count, and lower NLR were associated with better treatment results. In general, it can be proposed that the in ammatory state re ected in elevated CRP and high white blood counts is associated with higher disease burden and/or biologically aggressive disease and thus poor prognosis. It is possible that only group of patients with slowly progressing and less aggressive disease can bene t from TAS-102 monotherapy. We did not con rm the association between LDH level and treatment outcomes reported in two previously published studies [6,7]. However different cut-off for LDH levels was used in these studies. Baseline tumor characteristic including RAS and BRAF mutational status or tumor localization were not prognostic in our analysis. Patients with or without previous regorafenib had similar results.
The TAS-102 component tri uridine is a uoropyrimidine derivate. Currently available data of TAS-102 e cacy were acquired in clinical studies enrolling patients pretreated with, and refractory to 5-uorouracil or capecitabine. It can be assumed that patients not pretreated with a uoropyrimidine or with a longer interval from the last uoropyrimidine treatment could have better response to TAS-102. Indeed, in our study, patients who started TAS-102 treatment more than 3 months from the last uoropyrimidine had better outcomes.
TAS-102 has a relatively favorable toxicity pro le. Several groups have described that the occurrence of toxicity, in particular neutropenia, was associated with better outcomes of TAS-102 therapy [17,18]. In our study, patients who developed grade 2 or higher neutropenia during the treatment had much better prognosis and more than doubled OS than those without this adverse event. Similarly, thrombocytopenia and diarrhea, although not as frequently observed, were also associated with longer OS and PFS. It is possible that slower drug metabolism or higher effective drug doses could lead to higher TAS-102 blood levels and higher drug concentrations in the tumor, resulting in better outcomes and simultaneously higher risk of toxicities.
Based on prognostic factors in univariate and multivariate analyses, we de ned the TAScore which could be helpful for decision-making prior to TAS-102 therapy. The TAScore consists of six clinical and laboratory parameters that are measurable prior to treatment initiation: performance status, time from diagnosis of metastatic disease, time from last uoropyrimidine therapy, normal baseline CRP level, normal baseline WBC, and baseline monocytes count. Using this very simple tool, we have been able to separate patients into 3 different prognostic groups. The high-risk group (score 0 or 1) achieved OS of only 5.4 months which is similar to the outcome in the placebo arm of phase III clinical trial with TAS-102. These patients may not bene t from TAS-102 and other treatment options or best supportive care should be considered. On the contrary, patients with TAScore of 4 or more have excellent outcomes with median OS of more than one year. If we take into account good toxicity pro le, TAS-102 therapy could be the preferred regime for this group of patients.
Several tools for predicting the survival of patients with metastatic colorectal cancer have been proposed.
A similar tool for predicting survival of patient with refractory metastatic CRC was created by Pietrantonio et al. by de ning a nomogram for predicting of 12-week death probability ("Colon Life") [19]. This nomogram includes performance status, primary tumor resection, LDH value, and peritoneal involvement and identify patients with a poor prognosis in general. This nomogram was validated by Cremolini et al. in patients treated with TAS-102. However, the nomogram is less practical to use than our TAScore scoring system that was validated speci cally in patients with TAS-102 treatment and dividing patients into 3 prognostic groups. Another group utilized modi ed a Glasgow prognostic score (mGPS) consisting of CRP and albumin values [20]. This score was prognostic for PFS an OS in patients with metastatic CRC treated with TAS-102 or regorafenib. No signi cant differences in OS and PFS were observed between treatment groups in each mGPS group. This mGPS is simple to use but it does not take into account previous patient treatment and the overall clinical condition of the patient which are important factors in physician decision making.
The present study has several limitations. The group of patients was relatively small for establishing robust prognostic factors. The retrospective character of our analysis can contribute to selection bias. We are currently analyzing the identi ed prognostic model for other therapies in later lines of treatment, such as regorafenib in order to select patients who will bene t from any treatment.
In summary, in the current study, we con rmed the moderate e cacy of TAS-102 in heavily pretreated patients with metastatic colorectal cancer. We found several factors associated with prolonged survival and de ned the TAScore as a very simple and useful tool for patient selection before initiation of TAS-102 treatment.  BRAF mutation was analyzed in 54 patients, 5 (9.3%) patients had BRAF mutation. Mismatch protein deficiency was analyzed in 33 patients, one (3%) had MMR deficient tumor.   Table 6 Factors involved in TAScore scoring system in relation to progression-free survival and overall survival Progression-free survival Progression-free survival in patients treated with TAS-102. Median PFS for the whole group was 3.3 months (95% CI, 3.0 to 3.5), and the estimated 6-months PFS rate was 20.3%