Restricted Mean Survival Times to Improve Communication of Evidence from Cancer Randomized Trials and Observational Studies

Individualized survival prediction and surgery recommendation for patients with glioblastoma

Background

There is a lack of individualized evidence on surgical choices for glioblastoma (GBM) patients.

Aim

This study aimed to make individualized treatment recommendations for patients with GBM and to determine the importance of demographic and tumor characteristic variables in the selection of extent of resection.

Methods

We proposed Balanced Decision Ensembles (BDE) to make survival predictions and individualized treatment recommendations. We developed several DL models to counterfactually predict the individual treatment effect (ITE) of patients with GBM. We divided the patients into the recommended (Rec.) and anti-recommended groups based on whether their actual treatment was consistent with the model recommendation.

Results

The BDE achieved the best recommendation effects (difference in restricted mean survival time (dRMST): 5.90; 95% confidence interval (CI), 4.40-7.39; hazard ratio (HR): 0.71; 95% CI, 0.65-0.77), followed by BITES and DeepSurv. Inverse probability treatment weighting (IPTW)-adjusted HR, IPTW-adjusted OR, natural direct effect, and control direct effect demonstrated better survival outcomes of the Rec. group.

Conclusion

The ITE calculation method is crucial, as it may result in better or worse recommendations. Furthermore, the significant protective effects of machine recommendations on survival time and mortality indicate the superiority of the model for application in patients with GBM. Overall, the model identifies patients with tumors located in the right and left frontal and middle temporal lobes, as well as those with larger tumor sizes, as optimal candidates for SpTR.

Survival After Implementation of a Decision Support Tool to Facilitate Evidence-Based Cancer Treatment

PURPOSE

Decision support tools (DSTs) to facilitate evidence-based cancer treatment are increasingly common in care delivery organizations. Implementation of these tools may improve process outcomes, but little is known about effects on patient outcomes such as survival. We aimed to evaluate the effect of implementing a DST for cancer treatment on overall survival (OS) among patients with breast, colorectal, and lung cancer.

METHODS

We used institutional cancer registry data to identify adults treated for first primary breast, colorectal, or lung cancer between December 2013 and December 2017. Our intervention of interest was implementation of a commercial DST for cancer treatment, and outcome of interest was OS. We emulated a single-arm trial with historical comparison and used a flexible parametric model to estimate standardized 3-year restricted mean survival time (RMST) difference and mortality risk ratio (RR) with 95% confidence limits (CLs).

RESULTS

Our study population comprised 1,059 patients with cancer (323 breast, 318 colorectal, and 418 lung). Depending on cancer type, median age was 55-60 years, 45%-67% were racial/ethnic minorities, and 49%-69% were uninsured. DST implementation had little effect on survival at 3 years. The largest effect was observed among patients with lung cancer (RMST difference, 1.7 months; 95% CL, -0.26 to 3.7; mortality RR, 0.95; 95% CL, 0.88 to 1.0). Adherence with tool-based treatment recommendations was >70% before and >90% across cancers.

CONCLUSION

Our results suggest that implementation of a DST for cancer treatment has nominal effect on OS, which may be partially attributable to high adherence with evidence-based treatment recommendations before tool implementation in our setting. Our results raise awareness that improved process outcomes may not translate to improved patient outcomes in some care delivery settings.

Adjuvant immunotherapy in patients with high-risk muscle-invasive urothelial carcinoma: The potential impact of informative censoring

BACKGROUND

The results of 2 studies exploring adjuvant immune checkpoint inhibition (aCPI) in high-risk muscle-invasive urothelial cancer have yielded conflicting results. A trial employing placebo as the control arm demonstrated a significant prolongation in disease-free survival (DFS) whereas a trial employing observation as the control arm (IMvigor010) demonstrated no prolongation in DFS with CPI. Here, the authors aimed to estimate the aCPI benefit and to model the potential impact of informative censoring on trial results.

METHODS

Survival data from 1518 patients was reconstructed from Kaplan-Meier curves. A network meta-analysis approach was used to estimate aCPI benefit through the restricted mean disease-free survival time (RMDFST). To estimate the potential impact of informative censoring on IMvigor010, a simulation was performed. The minimum proportion of informative censoring on the observation arm that could account for the lack of observed improvement in DFS was estimated. Random variability from the time of censoring to progression was modeled using the exponential distribution.

RESULTS

Patients receiving aCPI had better DFS: ΔRMDFST at 36 months of 2.2 (95% CI, 0.6-3.7, P = .006) months relative to observation/placebo. In IMvigor010, in the observation arm, 20.5% of patients were censored due to consent withdrawal, protocol violation and/or noncompliance, or lost to follow-up versus 8.2% in the treatment arm. On simulation, it was found that the lack of observed improvement in DFS could have resulted from as few as 14% of the censored patients on observation arm not being censored at random (simulated DFS with 14% informative censoring hazard ratio, 0.83; 95% CI, 0.69-0.99; P = .049).

CONCLUSIONS

Phase 3 trials comparing adjuvant therapies to observation are at risk for informative censoring that could potentially impact interpretation of study results.

Timing of adjuvant chemotherapy initiation and mortality among colon cancer patients at a safety-net health system

Background

Prior studies reported survival benefits from early initiation of adjuvant chemotherapy for stage III colon cancer, but this evidence was derived from studies that may be sensitive to time-related biases. Therefore, we aimed to estimate the effect of initiating adjuvant chemotherapy ≤8 or ≤ 12 weeks on overall and disease-free survival among stage III colon cancer patients using a study design that helps address time-related biases.

Methods

We used institutional registry data from JPS Oncology and Infusion Center, a Comprehensive Community Cancer Program. Eligible patients were adults aged < 80 years, diagnosed with first primary stage III colon cancer between 2011 and 2017, and received surgical resection with curative intent. We emulated a target trial with sequential eligibility. We subsequently pooled the trials and estimated risk ratios (RRs) along with 95% confidence limits (CL) for all-cause mortality and recurrence or death at 5-years between initiators and non-initiators of adjuvant chemotherapy ≤8 or ≤ 12 weeks using pseudo-observations and a marginal structural model with stabilized inverse probability of treatment weights.

Results

Our study population comprised 222 (for assessing initiation ≤8 weeks) and 310 (for assessing initiation ≤12 weeks) observations, of whom the majority were racial/ethnic minorities (64–65%), or uninsured with or without enrollment in our hospital-based medical assistance program (68–71%). Initiation of adjuvant chemotherapy ≤8 weeks of surgical resection did not improve overall survival (RR for all-cause mortality = 1.04, 95% CL: 0.57, 1.92) or disease-free survival (RR for recurrence or death = 1.07, 95% CL: 0.61, 1.88). The results were similar for initiation of adjuvant chemotherapy ≤12 weeks of surgical resection.

Conclusions

Our results suggest that the overall and disease-free survival benefits of initiating adjuvant chemotherapy ≤8 or ≤ 12 weeks of surgical resection may be overestimated in prior studies, which may be attributable to time-related biases. Nevertheless, our estimates were imprecise and differences in population characteristics are an alternate explanation. Additional studies that address time-related biases are needed to clarify our findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09688-w.

Gini's mean difference and the long-term prognostic value of nodal quanta classes after pre-operative chemotherapy in advanced breast cancer

Gini's mean difference (GMD, mean absolute difference between any two distinct quantities) of the restricted mean survival times (RMSTs, expectation of life at a given time limit) has been proposed as a new metric where higher GMD indicates better prognostic value. GMD is applied to the RMSTs at 25 years time-horizon to evaluate the long-term overall survival of women with breast cancer who received neoadjuvant chemotherapy, comparing a classification based on the number (pN) versus a classification based on the ratio (LNRc) of positive nodes found at axillary surgery. A total of 233 patients treated in 1980–2009 with documented number of positive nodes (npos) and number of nodes examined (ntot) were identified. The numbers were categorized into pN0, npos = 0; pN1, npos = [1,3]; pN2, npos = [4,9]; pN3, npos ≥ 10. The ratios npnx = npos/ntot were categorized into Lnr0, npnx = 0; Lnr1, npnx = (0,0.20]; Lnr2, npnx = (0.20,0.65]; Lnr3, npnx > 0.65. The GMD for pN-classification was 5.5 (standard error: ± 0.9) years, not much improved over a simple node-negative vs. node-positive that showed a GMD of 5.0 (± 1.4) years. The GMD for LNRc-classification was larger, 6.7 (± 0.8) years. Among other conventional metrics, Cox-model LNRc's c-index was 0.668 vs. pN's c = 0.641, indicating commensurate superiority of LNRc-classification. The usability of GMD-RMSTs warrants further investigation.

Counterfactual mediation analysis in the multistate model framework for surrogate and clinical time-to-event outcomes in randomized controlled trials

In cancer randomized controlled trials, surrogate endpoints are frequently time-to-event endpoints, subject to the competing risk from the time-to-event clinical outcome. In this context, we introduce a counterfactual-based mediation analysis for a causal assessment of surrogacy. We use a multistate model for risk prediction to account for both direct transitions towards the clinical outcome and indirect transitions through the surrogate outcome. Within the counterfactual framework, we define natural direct and indirect effects with a causal interpretation. Based on these measures, we define the proportion of the treatment effect on the clinical outcome mediated by the surrogate outcome. We estimate the proportion for both the cumulative risk and restricted mean time lost. We illustrate our approach by using 18-year follow-up data from the SPCG-4 randomized trial of radical prostatectomy for prostate cancer. We assess time to metastasis as a surrogate outcome for prostate cancer-specific mortality.

Lymph Node Ratio after Neoadjuvant Chemotherapy for Stage II/III Breast Cancer: Prognostic Value Measured with Gini's Mean Difference of Restricted Mean Survival Times

Restricted mean survival time (RMST), recommended for reporting survival, lacks a tool to evaluate multilevel factors. The potential of the Gini’s mean difference of RMSTs (Δ) is explored in a comparison of a lymph node ratio-based classification (LNRc) versus a number-based classification (ypN) applied to stage II/III breast cancer patients who received neoadjuvant chemotherapy and underwent axillary dissection. Number of positive nodes (npos) classified patients into ypN0, npos = 0, ypN1, npos = [1,3], ypN2, npos = [4,9], and ypN3, npos ⩾ 10. Ratio npos/(number of nodes examined) of 0, (0,0.20], (0.20,0.65], and >0.65, classified patients into Lnr0 to Lnr3, respectively. Unadjusted and Cox-adjusted RMSTs were computed for the ypN and LNRc’s. At a follow-up time horizon of 72 months for 114 node-negative and 254 node-positive patients, unadjusted ypN0-ypN3 RMSTs were 62.4-41.4 months, Δ = 11.9 months (95%CI: 7.4-16.9), and Lnr0-Lnr3 62.4 to 36.3 months, Δ = 14.0 months (95%CI: 10.1-18.1). Cox models’ ypN1-ypN3 hazard ratios were 1.81-3.30, and Lnr1-Lnr3 1.52-4.39. Δ from Cox-fitted survival were ypN 8.1 months (95%CI: 5.9-10.5), LNRc 10.5 months (95%CI: 8.4-12.8). In conclusion, Gini’s mean difference is applicable to well established data in keeping with the literature on LNRc. It provides an alternative view on the improvement gained with a lymph node ratio-classification over using a number-classification.

Adherence to Treatment Guidelines and Associated Survival in Older Patients with Prostate Cancer: A Prospective Multicentre Cohort Study

The guidelines on prostate cancer treatment in older men recommend evaluating the patient's underlying health status before treatment selection. We aimed to evaluate the frequency of a guideline-discordant treatment (GDT), identify factors associated with GDT, and assess the relationship between GDT and overall survival. We studied patients with prostate cancer aged 70 or older included in the ELCAPA cohort between 2010 and 2019. Multivariable logistic regression assessed GDT-associated factors. The restricted mean survival time (RMST) assessed the 24- and 36-month OS using stabilized inverse probability of treatment weighting of propensity scores. We included 356 patients (median age: 81 years), and 164 (46%) received a GDT (95% confidence interval (CI) = (41-51%)). Patients with metastases were less likely to receive a GDT (adjusted odds ratio (95% CI) = 0.34 (0.17-0.69); p = 0.003). After weighting, the RMST at 24 months was shorter in the GDT group (13.9 months, vs. 17 months for compliant treatments; difference (95% CI): -3.1 months (-5.3, -1.0); p = 0.004). RMST at 36 months was 18.5 months, vs. 21.8 months (difference: -3.3 months (-6.7, 0.0); p = 0.053). GDT is common in older patients with prostate cancer and especially those with non-metastatic disease. GDT was associated with worse survival, independently of health status and tumour characteristics.

Statistical Considerations for Sequential Analysis of the Restricted Mean Survival Time for Randomized Clinical Trials

In this paper, we illustrate the method of designing a group-sequential randomized clinical trial based on the difference in restricted mean survival time (RMST). The procedure is based on theoretical formulations of Murray and Tsiatis (1999). We also present a numerical example in designing a cardiology surgical trial. Various practical considerations are discussed. R codes are provided in the Supplementary Materials. We conclude that the group-sequential design for RMST is a viable option in practice. A simulation study is performed to compare the proposed method to the Max-Combo and conventional log-rank tests. The simulation result shows that when there is a delayed treatment benefit and the proportional hazards assumption is untrue, the sequential design based on the RMST can be more efficient than that based on the log-rank test but less efficient than that based on the Max-Combo test. Compared with Max-Combo test, the RMST-based study design yield coherent estimand, statistical inference and result interpretation.

Psychotropic medication use during pregnancy and gestational age at delivery

PURPOSE

The purpose of this study was to evaluate the association between psychotropic medication use during pregnancy and gestational age at delivery, after adjusting for depressive symptom and perceived stress severity.

METHODS

We analyzed data on singleton live births from 2914 female Pregnancy Study Online participants, aged 21 to 45, with a reported conception from 6/2013 to 6/2018. Women reported psychotropic medication use at 8 to 12 weeks' and ~32 weeks' gestation. We measured depressive symptoms using the Major Depressive Inventory and perceived stress using the 10-item Perceived Stress Scale. Data on gestational age at delivery were based on self-reports and/or birth certificates. We used restricted mean survival time models, stratifying by severity of depressive symptoms (Major Depression Inventory <25 vs. ≥25) and perceived stress (Perceived Stress Scale <20 vs. ≥20).

RESULTS

Two hundred and ten (7.2%) participants reported using psychotropic medications during pregnancy. Mean gestational age at delivery among women who never used psychotropic medications was 38.2 weeks (95% confidence interval: 37.7, 38.7), whereas it was 37.3 weeks (95% confidence interval: 36.7, 37.9) among women who used psychotropic medications during pregnancy. Results were similar across strata of depressive symptoms and perceived stress.

CONCLUSIONS

Our data indicate that the association between psychotropic medication use and gestational age at delivery is not confounded by indication.

Neutron Therapy for High-Grade Salivary Carcinomas in the Adjuvant and Primary Treatment Setting

OBJECTIVES/HYPOTHESIS

Our primary objective was to compare differences in survival of patients with high-grade salivary gland carcinomas (SGCs) receiving adjuvant neutron versus photon radiotherapy using a hospital-based national cohort and restricted mean survival time (RMST) analysis. Our secondary objective was to compare survival of similar patients treated with primary neutron versus photon radiation.

STUDY DESIGN

Multicenter, retrospective population-based study of patients within the National Cancer Database from 2004 to 2014.

METHODS

One thousand eight hundred forty-four patients were selected on diagnosis of high-grade parotid and submandibular malignancies. One thousand seven hundred seventy-seven patients receiving photon and 67 patients receiving neutron therapy were identified who met inclusion criteria. Patients were then categorized as having primary surgery with adjuvant radiation or primary radiation without prior surgery. Bivariate analysis was performed to assess for differences between groups, and RMST analysis was performed at 1-, 2-, and 5-year timepoints with controlling for available covariate data.

RESULTS

There was no significant difference in RMST for patients receiving neutrons over photons at 1, 2, and 5 years in the adjuvant setting. Among patients undergoing primary radiotherapy, there was a difference in RMST of 2.29 months at 1 year and 5.05 months at 2 years for neutrons over photons, though this benefit was not observed at 5 years post-therapy.

CONCLUSIONS

For patients with high grade SGCs undergoing adjuvant photon versus neutron radiotherapy, there was no difference in RMST. There was observed to be a significant difference in RMST at 1 and 2 years among patients undergoing primary neutron therapy of up to 5 months. Given the benefit observed with primary neutron therapy, it should be considered in both the primary and adjuvant treatment setting.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:541-547, 2021.

The effect of insurance status on overall survival among children and adolescents with cancer

Background

Differences in access, delivery and utilisation of health care may impact childhood and adolescent cancer survival. We evaluated whether insurance coverage impacts survival among US children and adolescents with cancer diagnoses, overall and by age group, and explored potential mechanisms.

Methods

Data from 58 421 children (aged ≤14 years) and adolescents (15–19 years), diagnosed with cancer from 2004 to 2010, were obtained from the National Cancer Database. We examined associations between insurance status at initial diagnosis or treatment and diagnosis stage; any treatment received; and mortality using logistic regression, Cox proportional hazards (PH) regression, restricted mean survival time (RMST) and mediation analyses.

Results

Relative to privately insured individuals, the hazard of death (all-cause) was increased and survival months were decreased in those with Medicaid [hazard ratio (HR) = 1.27, 95% confidence interval (CI): 1.22 to 1.33; and −1.73 months, 95% CI: −2.07 to −1.38] and no insurance (HR = 1.32, 95% CI: 1.20 to 1.46; and −2.13 months, 95% CI: −2.91 to −1.34). The HR for Medicaid vs. private insurance was larger (pinteraction &lt;0.001) in adolescents (HR = 1.52, 95% CI: 1.41 to 1.64) than children (HR = 1.16, 95% CI: 1.10 to 1.23). Despite statistical evidence of PH assumption violation, RMST results supported all interpretations. Earlier diagnosis for staged cancers in the Medicaid and uninsured populations accounted for an estimated 13% and 19% of the survival deficit, respectively, vs. the privately insured population. Any treatment received did not account for insurance-associated survival differences in children and adolescents with cancer.

Conclusions

Children and adolescents without private insurance had a higher risk of death and shorter survival within 5 years following cancer diagnosis. Additional research is needed to understand underlying mechanisms.

Oncogenic Genomic Alterations, Clinical Phenotypes, and Outcomes in Metastatic Castration-Sensitive Prostate Cancer

PURPOSE

The genomic underpinning of clinical phenotypes and outcomes in metastatic castration-sensitive prostate cancer is unclear.

EXPERIMENTAL DESIGN

In patients with metastatic castration-sensitive prostate cancer at a tertiary referral center, clinical-grade targeted tumor sequencing was performed to quantify tumor DNA copy number alterations and alterations in predefined oncogenic signaling pathways. Disease volume was classified as high volume (≥4 bone metastases or visceral metastases) versus low volume.

RESULTS

Among 424 patients (88% white), 213 (50%) had high-volume disease and 211 (50%) had low-volume disease, 275 (65%) had de novo metastatic disease, and 149 (35%) had metastatic recurrence of nonmetastatic disease. Rates of castration resistance [adjusted hazard ratio, 1.84; 95% confidence interval (CI), 1.40-2.41] and death (adjusted hazard ratio, 3.71; 95% CI, 2.28-6.02) were higher in high-volume disease. Tumors from high-volume disease had more copy number alterations. The NOTCH, cell cycle, and epigenetic modifier pathways were the highest-ranking pathways enriched in high-volume disease. De novo metastatic disease differed from metastatic recurrences in the prevalence of CDK12 alterations but had similar prognosis. Rates of castration resistance differed 1.5-fold to 5-fold according to alterations in AR, SPOP (inverse), and TP53, and the cell cycle, WNT (inverse), and MYC pathways, adjusting for disease volume and other genomic pathways. Overall survival rates differed 2-fold to 4-fold according to AR, SPOP (inverse), WNT (inverse), and cell-cycle alterations. PI3K pathway alterations were not associated with prognosis once adjusted for other factors.

CONCLUSIONS

This study identified genomic features associated with prognosis in metastatic castration-sensitive disease that may aid in molecular classification and treatment selection.

Impact of age at diagnosis of de novo metastatic prostate cancer on survival

BACKGROUND

An older age at the diagnosis of prostate cancer has been linked to worse prostate cancer-specific survival (PCSS). However, these studies were conducted before the approval of many life-prolonging drugs. This study was aimed at describing outcomes in a contemporary cohort of men diagnosed with de novo metastatic prostate cancer (mPCa) and assessing associations with the age at diagnosis while controlling for known prognostic factors.

METHODS

The Surveillance, Epidemiology, and End Results registry was used to identify men diagnosed with mPCa from 2004 to 2014. Men were classified by 4 age groups: ≤54, 55 to 64, 65 to 74, and ≥75 years. The median overall survival, PCSS, and restricted mean survival times for any-cause mortality and prostate cancer-specific mortality (PCSM) were calculated. Multivariable and subdistribution hazard ratios for PCSM according to age group and with controlling for race, marital status, and income were estimated.

RESULTS

Compared with men aged ≤54 years, men aged ≥75 years experienced a mean PCSS at 5 years that was 6.7 months shorter (95% confidence interval [CI], 5.5-7.8 months). In multivariable analyses, men aged ≥75 years had a 49% increase in the rate of PCSM in comparison with those aged ≤54 years (95% CI, 1.39-1.60). The subdistribution hazard ratio for PCSM between these groups was 1.41 (95% CI, 1.32-1.50).

CONCLUSIONS

Age was found to be an independent predictor of shorter PCSS in men diagnosed with de novo mPCa even in an era with more effective therapies. Further work is needed to determine the reason for poor outcomes in older men with mPCa.

Early Mortality of Prostatectomy vs. Radiotherapy as a Primary Treatment for Prostate Cancer: A Population-Based Study From the United States and East Germany

Objective: To assess the extent of early mortality and its temporal course after prostatectomy and radiotherapy in the general population.

Methods: Data from the Surveillance, Epidemiology, and End Results (SEER) database and East German epidemiologic cancer registries were used for the years 2005–2013. Metastasized cases were excluded. Analyzing overall mortality, year-specific Cox regression models were used after adjusting for age (including age squared), risk stage, and grading. To estimate temporal hazards, we computed year-specific conditional hazards for surgery and radiotherapy after propensity-score matching and applied piecewise proportional hazard models.

Results: In German and US populations, we observed higher initial 3-month mortality odds for prostatectomy (USA: 9.4, 95% CI: 7.8–11.2; Germany: 9.1, 95% CI: 5.1–16.2) approaching the null effect value not before 24-months (estimated annual mean 36-months in US data) after diagnosis. During the observational period, we observed a constant hazard ratio for the 24-month mortality in the US population (2005: 1.7, 95% CI: 1.5–1.9; 2013: 1.9, 95% CI: 1.6–2.2) comparing surgery and radiotherapy. The same was true in the German cohort (2005: 1.4, 95% CI: 0.9–2.1; 2013: 3.3, 95% CI: 2.2–5.1). Considering low-risk cases, the adverse surgery effect appeared stronger.

Conclusion: There is strong evidence from two independent populations of a considerably higher early to midterm mortality after prostatectomy compared to radiotherapy extending the time of early mortality considered by previous studies up to 36-months.