Restricted mean survival time as a summary measure of time-to-event outcome.

Many clinical research studies evaluate a time-to-event outcome, illustrate survival functions, and conventionally report estimated hazard ratios to express the magnitude of the treatment effect when comparing between groups. However, it may not be straightforward to interpret the hazard ratio clinically and statistically when the proportional hazards assumption is invalid. In some recent papers published in clinical journals, the use of restricted mean survival time (RMST) or τ-year mean survival time is discussed as one of the alternative summary measures for the time-to-event outcome. The RMST is defined as the expected value of time to event limited to a specific time point corresponding to the area under the survival curve up to the specific time point. This article summarizes the necessary information to conduct statistical analysis using the RMST, including the definition and statistical properties of the RMST, adjusted analysis methods, sample size calculation, information fraction for the RMST difference, and clinical and statistical meaning and interpretation. Additionally, we discuss how to set the specific time point to define the RMST from two main points of view. We also provide developed SAS codes to determine the sample size required to detect an expected RMST difference with appropriate power and reconstruct individual survival data to estimate an RMST reference value from a reported survival curve.

Determination of hazard ratio for progression-free survival considering the tumor assessment schedule in sample size calculation.

Progression-free survival is recognized as an important endpoint in oncology clinical trials. In clinical trials aimed at new drug development, the target population often comprises patients that are refractory to standard therapy with a tumor that shows rapid progression. This situation would increase the bias of the hazard ratio calculated for progression-free survival, resulting in decreased power for such patients. Therefore, new measures are needed to prevent decreasing the power in advance when estimating the sample size. Here, I propose a novel calculation procedure to assume the hazard ratio for progression-free survival using the Cox proportional hazards model, which can be applied in sample size calculation. The hazard ratios derived by the proposed procedure were almost identical to those obtained by simulation. The hazard ratio calculated by the proposed procedure is applicable to sample size calculation and coincides with the nominal power. Methods that compensate for the lack of power due to biases in the hazard ratio are also discussed from a practical point of view.

Relationship Between Thymidine Kinase 1 Expression and Trifluridine/Tipiracil Therapy in Refractory Metastatic Colorectal Cancer: A Pooled Analysis of 2 Randomized Clinical Trials.

BACKGROUND: High thymidine kinase 1 (TK1) activity increases the incorporation of trifluridine (FTD) into DNA; thus, FTD antitumor activity is likely to increase in patients with high tumoral TK1 activity. To date, no established predictive biomarker to indicate the clinical benefit of FTD/tipiracil (TPI) has been identified. We aimed to determine the relationship between TK1 expression and FTD/TPI efficacy in refractory metastatic colorectal cancer. PATIENTS AND METHODS: Individual patient data from 2 randomized placebo-controlled trials were analyzed. We measured TK1 protein expression in tumor tissue samples and its relationship with FTD/TPI clinical efficacy using overall survival (OS), progression-free survival, and disease control rate. RESULTS: This study comprised 329 patients (FTD/TPI, 224; placebo, 105). FTD/TPI significantly improved OS versus placebo in the high-expression (cutoff ≥ 15%) TK1 group (median OS, 7.8 vs. 6.8 months; hazard ratio = 0.65; 95% confidence interval, 0.46-0.93; P = .018). The low-expression (cutoff < 15%) TK1 group experienced a smaller OS benefit (9.3 vs. 7.4 months; hazard ratio = 0.88; 95% confidence interval, 0.63-1.23; P = .45). For patients who received placebo, the high-expression TK1 group had a slightly worse prognosis than the low-expression TK1 group. The tendency of FTD/TPI efficacy concerning progression-free survival and disease control rate was not similar to that concerning OS between groups. CONCLUSION: Patients with high TK1 expression showed an improvement in OS when treated with FTD/TPI. Further investigations are warranted to confirm this relationship.

A Proposal for Progression-Free Survival Assessment in Patients with Early Progressive Cancer.

BACKGROUND/AIM: Progression-free survival (PFS), which is evaluated in oncology clinical trials, is determined based on tumor progression evaluated according to an assessment schedule. There is possibly a bias in median PFS and hazard ratio (HR) for PFS depending on the assessment schedule referring to randomized controlled trials (RCTs) in patients with metastatic colorectal cancer. MATERIALS AND METHODS: We re-analyzed the PFS in the FTD/TPI phase 2 trial by changing the assessment schedule. To assess biases in median PFS and HR for PFS resulting from different assessment schedules, we performed a computational simulation. RESULTS: The reanalysis of FTD/TPI phase 2 trial and the simulation results showed that there were biases in median PFS and HR for PFS. CONCLUSION: In RCTs for early progressive cancer, median PFS is dependent on the assessment schedule; however, HR for PFS can be assessed without clinically-meaningful differences between assessment schedules, regardless of biomarker assumptions.

Trabectedin monotherapy after standard chemotherapy versus best supportive care in patients with advanced, translocation-related sarcoma: a randomised, open-label, phase 2 study.

BACKGROUND: Trabectedin binds to the minor groove of DNA and blocks DNA repair machinery. Preclinical data have shown that trabectedin also modulates the transcription of the oncogenic fusion proteins of translocation-related sarcomas. We aimed to assess the efficacy and safety of trabectedin as second-line therapy or later for patients with advanced translocation-related sarcoma. METHODS: We did a multicentre randomised open-label study in Japan. Eligible patients had pathological diagnosis of translocation-related sarcoma, were aged 19 years or older, were unresponsive or intolerant to standard chemotherapy regimens, no more than four previous chemotherapy regimens, Eastern Cooperative Oncology Group performance status 0 or 1, adequate bone marrow reserve, renal and liver functions, and had measurable lesions. Patients were randomly assigned (1:1) by the minimisation method to receive either trabectedin (1·2 mg/m(2) given via a central venous line over 24 h on day 1 of a 21 day treatment cycle) or best supportive care, which was adjusted centrally by pathological subtype. Investigators, patients, and the sponsor were unmasked to the treatment assignment. Progression-free survival and objective responses were assessed by a masked central radiology imaging review. Efficacy was assessed by masked central radiology imaging review. The primary endpoint was progression-free survival for the full analysis set population. Follow-up is ongoing for the patients under study treatment. The study is registered with Japan Pharmaceutical Information Center, number JapicCTI-121850. FINDINGS: Between July 11, 2012, and Jan 20, 2014, 76 patients were enrolled and allocated to receive either trabectedin (n=39) or best supportive care (n=37). After central review to confirm pathological subtypes, 73 patients (37 in the trabectedin group and 36 in the best supportive care group) were included in the primary efficacy analysis. Median progression-free survival of the trabectedin group was 5·6 months (95% CI 4·1-7·5) and the best supportive care group was 0·9 months (0·7-1·0). The hazard ratio (HR) for progression-free survival of trabectedin versus best supportive care was 0·07 (90% CI 0·03-0·14 and 95% CI 0·03-0·16) by a Cox proportional hazards model (p<0·0001). The most common drug-related adverse events for patients treated with trabectedin were nausea (32 [89%] of 36), decreased appetite (21 [58%]), decreased neutrophil count (30 [83%]), increased alanine aminotransferase (24 [67%]), and decreased white blood cell count (20 [56%]). INTERPRETATION: Trabectedin significantly reduced the risk of disease progression and death in patients with advanced translocation-related sarcoma after standard chemotherapy such as doxorubicin, and should be considered as a new therapeutic treatment option for this patient population. FUNDING: Taiho Pharmaceutical Co., Ltd.

TAS-102 monotherapy for pretreated metastatic colorectal cancer: a double-blind, randomised, placebo-controlled phase 2 trial.

BACKGROUND: Treatments that confer survival benefit are needed in patients with heavily pretreated metastatic colorectal cancer. The aim of this trial was to investigate the efficacy and safety of TAS-102-a novel oral nucleoside antitumour agent. METHODS: Between August 25, 2009, and April 12, 2010, we undertook a multicentre, double-blind, randomised, placebo-controlled phase 2 trial in Japan. Eligible patients were 20 years or older; had confirmed colorectal adenocarcinoma; had a treatment history of two or more regimens of standard chemotherapy; and were refractory or intolerant to fluoropyrimidine, irinotecan, and oxaliplatin. Patients had to be able to take oral drugs; have measurable lesions; have an Eastern Cooperative Oncology Group performance status of between 0 and 2; and have adequate bone-marrow, hepatic, and renal functions within 7 days of enrolment. Patients were randomly assigned (2:1) to either TAS-102 (35 mg/m(2) given orally twice a day in a 28-day cycle [2-week cycle of 5 days of treatment followed by a 2-day rest period, and then a 14-day rest period]) or placebo; all patients received best supportive care. Randomisation was done with minimisation methods, with performance status as the allocation factor. The randomisation sequence was generated with a validated computer system by an independent team from the trial sponsor. Investigators, patients, data analysts, and the trial sponsor were masked to treatment assignment. The primary endpoint was overall survival in the intention-to-treat population. Safety analyses were done in the per-protocol population. The study is in progress and is registered with Japan Pharmaceutical Information Center, number JapicCTI-090880. FINDINGS: 112 patients allocated to TAS-102 and 57 allocated to placebo made up the intention-to-treat population. Median follow-up was 11·3 months (IQR 10·7-14·0). Median overall survival was 9·0 months (95% CI 7·3-11·3) in the TAS-102 group and 6·6 months (4·9-8·0) in the placebo group (hazard ratio for death 0·56, 80% CI 0·44-0·71, 95% CI 0·39-0·81; p=0·0011). 57 (50%) of 113 patients given TAS-102 in the safety population had neutropenia of grade 3 or 4, 32 (28%) leucopenia, and 19 (17%) anaemia. No patient given placebo had grade 3 or worse neutropenia or leucopenia; three (5%) of 57 had grade 3 or worse anaemia. Serious adverse events occurred in 21 (19%) patients in the TAS-102 group and in five (9%) in the placebo group. No treatment-related deaths occurred. INTERPRETATION: TAS-102 has promising efficacy and a manageable safety profile in patients with metastatic colorectal cancer who are refractory or intolerant to standard chemotherapies.