Cancer Biology and Survival Analysis in Cancer Trials: Restricted Mean Survival Time Analysis versus Hazard Ratios

The Impact of Sequence of Therapy for Older Patients With Follicular Lymphoma: SEER-Medicare Analysis

BACKGROUND

One key clinical challenge remains in how to sequence treatments in follicular lymphoma (FL). The chemoimmunotherapy rituximab cyclophosphamide, doxorubicin, vincristine (Oncovin), and prednisone (R-CHOP) has been a standard treatment option for two decades. However, there are limited data to suggest in which line R-CHOP should be used for older patients.

PATIENTS AND METHODS

We leveraged population-based surveillance, epidemiology, and end results-medicare data and identified 675 patients aged ≥65 years newly diagnosed with FL from 2000 to 2009 who received R-CHOP in either the first or second line. We estimated restricted mean survival time using Kaplan-Meier curves, propensity scores (PS), and regression models comparing patients who received R-CHOP as a first versus second line.

RESULTS

We found that patients who received R-CHOP as first line had significantly longer 9-year RMST than those who received R-CHOP in the second line using Kaplan-Meier curves (P = .01), PS stratification (P = .002), PS matching (P = .005), and the inverse of PS as the treatment weight (P < .0001). The subgroup analyses using linear regression models showed that the 9-year restricted mean survival time of patients who received R-CHOP as the first line was longer in patients aged ≥80 years (P = .002) and with histological grade 1 or 2 (P = .02), compared to those who received R-CHOP as second line.

CONCLUSION

R-CHOP given in the first line was associated with longer overall survival compared to R-CHOP given as second line for older patients with FL.

Impact of postoperative chemotherapy on survival for oesophagogastric adenocarcinoma after preoperative chemotherapy and surgery

BACKGROUND

Perioperative chemotherapy is widely used in the treatment of oesophagogastric adenocarcinoma (OGAC) with a substantial survival benefit over surgery alone. However, the postoperative part of these regimens is given in less than half of patients, reflecting uncertainty among clinicians about its benefit and poor postoperative patient fitness. This study estimated the effect of postoperative chemotherapy after surgery for OGAC using a large population-based data set.

METHODS

Patients with adenocarcinoma of the oesophagus, gastro-oesophageal junction or stomach diagnosed between 2012 and 2018, who underwent preoperative chemotherapy followed by surgery, were identified from a national-level audit in England and Wales. Postoperative therapy was defined as the receipt of systemic chemotherapy within 90 days of surgery. The effectiveness of postoperative chemotherapy compared with observation was estimated using inverse propensity treatment weighting.

RESULTS

Postoperative chemotherapy was given to 1593 of 4139 patients (38.5 per cent) included in the study. Almost all patients received platinum-based triplet regimens (4004 patients, 96.7 per cent), with FLOT used in 3.3 per cent. Patients who received postoperative chemotherapy were younger, with a lower ASA grade, and were less likely to have surgical complications, with similar tumour characteristics. After weighting, the median survival time after postoperative chemotherapy was 62.7 months compared with 50.4 months without chemotherapy (hazard ratio 0.84, 95 per cent c.i. 0.77 to 0.94; P = 0.001).

CONCLUSION

This study has shown that postoperative chemotherapy improves overall survival in patients with OGAC treated with preoperative chemotherapy and surgery.

Prediction of long-term survival after gastrectomy using random survival forests

BACKGROUND

No well validated and contemporaneous tools for personalized prognostication of gastric adenocarcinoma exist. This study aimed to derive and validate a prognostic model for overall survival after surgery for gastric adenocarcinoma using a large national dataset.

METHODS

National audit data from England and Wales were used to identify patients who underwent a potentially curative gastrectomy for adenocarcinoma of the stomach. A total of 2931 patients were included and 29 clinical and pathological variables were considered for their impact on survival. A non-linear random survival forest methodology was then trained and validated internally using bootstrapping with calibration and discrimination (time-dependent area under the receiver operator curve (tAUC)) assessed.

RESULTS

The median survival of the cohort was 69 months, with a 5-year survival of 53.2 per cent. Ten variables were found to influence survival significantly and were included in the final model, with the most important being lymph node positivity, pT stage and achieving an R0 resection. Patient characteristics including ASA grade and age were also influential. On validation the model achieved excellent performance with a 5-year tAUC of 0.80 (95 per cent c.i. 0.78 to 0.82) and good agreement between observed and predicted survival probabilities. A wide spread of predictions for 3-year (14.8-98.3 (i.q.r. 43.2-84.4) per cent) and 5-year (9.4-96.1 (i.q.r. 31.7-73.8) per cent) survival were seen.

CONCLUSIONS

A prognostic model for survival after a potentially curative resection for gastric adenocarcinoma was derived and exhibited excellent discrimination and calibration of predictions.

Empirical power comparison of statistical tests in contemporary phase III randomized controlled trials with time-to-event outcomes in oncology

BACKGROUND

More than 95% of recent cancer randomized controlled trials used the log-rank test to detect a treatment difference making it the predominant tool for comparing two survival functions. As with other tests, the log-rank test has both advantages and disadvantages. One advantage is that it offers the highest power against proportional hazards differences, which may be a major reason why alternative methods have rarely been employed in practice. The performance of statistical tests has traditionally been investigated both theoretically and numerically for several patterns of difference between two survival functions. However, to the best of our knowledge, there has been no attempt to compare the performance of various statistical tests using empirical data from past oncology randomized controlled trials. So, it is unknown whether the log-rank test offers a meaningful power advantage over alternative testing methods in contemporary cancer randomized controlled trials. Focusing on recently reported phase III cancer randomized controlled trials, we assessed whether the log-rank test gave meaningfully greater power when compared with five alternative testing methods: generalized Wilcoxon, test based on maximum of test statistics from multiple weighted log-rank tests, difference in t-year event rate, and difference in restricted mean survival time with fixed and adaptive τ.

METHODS

Using manuscripts from cancer randomized controlled trials recently published in high-tier clinical journals, we reconstructed patient-level data for overall survival (69 trials) and progression-free survival (54 trials). For each trial endpoint, we estimated the empirical power of each test. Empirical power was measured as the proportion of trials for which a test would have identified a significant result (p value < .05).

RESULTS

For overall survival, t-year event rate offered the lowest (30.4%) empirical power and restricted mean survival time with fixed τ offered the highest (43.5%). The empirical power of the other types of tests was almost identical (36.2%-37.7%). For progression-free survival, the tests we investigated offered numerically equivalent empirical power (55.6%-61.1%). No single test consistently outperformed any other test.

CONCLUSION

The empirical power assessment with the past cancer randomized controlled trials provided new insights on the performance of statistical tests. Although the log-rank test has been used in almost all trials, our study suggests that the log-rank test is not the only option from an empirical power perspective. Near universal use of the log-rank test is not supported by a meaningful difference in empirical power. Clinical trial investigators could consider alternative methods, beyond the log-rank test, for their primary analysis when designing a cancer randomized controlled trial. Factors other than power (e.g. interpretability of the estimated treatment effect) should garner greater consideration when selecting statistical tests for cancer randomized controlled trials.

A systematic review of observational studies of trifluridine/tipiracil (TAS-102) for metastatic colorectal cancer

Background: The treatment options for patients with therapy refractory metastatic colorectal cancer (mCRC) are sparse. TAS-102 (FTD/TPI) is a new oral anti-tumour agent composed of a nucleoside analogue, trifluridine, and a thymidine phosphorylase inhibitor, tipiracil, indicated for patients with mCRC who are refractory to standard therapies. This study summarizes published and unpublished experience with FTD/TPI in clinical practice settings. Patients and methods: The Medline/PubMed, Embase and Cochrane Library databases were searched to identify observational studies on FTD/TPI monotherapy for mCRC. Papers describing use of FTD/TPI monotherapy outside clinical trials in series of patients evaluable for effectiveness were eligible. The outcomes of interest were median progression free survival (mPFS), median overall survival (mOS) as well as mean PFS time restricted to six months (PFS_6m) and mean OS time restricted to one year (OS_1y). Results of the pooled analyses of observational studies were compared to the results of the Japanese phase II trial and the two phase III trials, RECOURSE and TERRA. Results: Seven published and two unpublished studies with 1008 patients from 64 centres were included for analysis. The pooled mPFS was 2.2 months (95% CI 2.1 to 2.3 months), and the pooled mOS was 6.6 months (95% CI 6.1 to 7.1 months). PFS_6m was 2.9 months (95% CI 2.6 to 3.1 months) and OS_1y was 6.8 (95% CI 6.0 to 7.5) months. While these results all reflect RECOURSE, the pooled mOS is lower than in the phase II trial and the OS_1y is inferior to both the phase II trial and TERRA. Conclusion: This systematic review and a meta-analysis indicates that in real life settings, the survival benefit of FTD/TPI monotherapy in patients with therapy refractory mCRC reflects the outcomes in RECOURSE but is inferior to outcomes in the two Asian efficacy trials. What is already known TAS 102 (Lonsurf) is an oral fixed dose combination of trifluridine (FTD) and tipiracil (TPI) indicated as salvage-line treatment in patients with therapy refractory metastatic colorectal cancer (mCRC). A Japanese phase II trial and two phase III trials, RECOURSE and TERRA, demonstrated that FTD/TPI prolonged overall survival. What this study adds This systematic review and meta-analysis of real life data from 64 sites indicates that the effectiveness in daily clinical practice settings of FTD/TPI monotherapy in late stage mCRC reflects the outcomes in RECOURCE but is inferior to the outcomes in the Japanese phase II trial and TERRA.