Adding a new analytical procedure with clinical interpretation in the tool box of survival analysis

Association between concomitant proton pump inhibitor use and survival of patients with metastatic prostate cancer receiving abiraterone acetate: a post-hoc analysis of pooled data from three randomized controlled trials

BACKGROUND

Evidence suggests proton pump inhibitor (PPI) use may attenuate the effect of abiraterone acetate plus prednisone (AAP) in metastatic prostate cancer via the modification of gut microbiota. This study aimed to examine whether concomitant PPI use is associated with survival in patients with metastatic prostate cancer treated with androgen deprivation therapy (ADT) and AAP.

METHODS

Post-hoc analysis was conducted in patients with metastatic castration-sensitive prostate cancer (mCSPC) and metastatic castration-resistant prostate cancer (mCRPC) treated in the LATITUDE, COU-AA-301, and COU-AA-302 trials (ADT vs. ADT plus AAP). PPI users and non-users were compared for restricted mean overall survival time (RMOST) and restricted mean progression-free survival time (RMPFST) based on inverse probability of treatment weight (IPTW)-adjusted Kaplan-Meier curves. IPTW-adjusted Cox regression models were used to assess heterogeneity of treatment effect.

RESULTS

In patients treated with AAP, PPI use was associated with inferior RMOST [difference (95% confidence interval): -4.2 (-7.0 to -1.4)] and RMPFST [-3.5 (-6.6 to -0.4)] compared with non-users. However, RMOST and RMPFST were similar between PPI users and non-users in patients treated with ADT alone [RMOST, -2.6 (-5.8 to 0.6); RMPFST, -1.7 (-4.8 to 1.4)]. Interaction term analyses did not show evidence of heterogeneity in treatment effect between AAP and ADT, despite the prominent treatment effect shown in mCSPC vs. mCRPC.

CONCLUSIONS

PPI use may be associated with inferior survival in patients with metastatic prostate cancer who receive ADT plus AAP. Discontinuing unnecessary PPI use might improve those outcomes.

A Critical Analysis of All-Cause Deaths during COVID-19 Vaccination in an Italian Province

Immortal time bias (ITB) is common in cohort studies and distorts the association estimates between the treated and untreated. We used data from an Italian study on COVID-19 vaccine effectiveness, with a large cohort, long follow-up, and adjustment for confounding factors, affected by ITB, with the aim to verify the real impact of the vaccination campaign by comparing the risk of all-cause death between the vaccinated population and the unvaccinated population. We aligned all subjects on a single index date and considered the "all-cause deaths" outcome to compare the survival distributions of the unvaccinated group versus various vaccination statuses. The all-cause-death hazard ratios in univariate analysis for vaccinated people with 1, 2, and 3/4 doses versus unvaccinated people were 0.88, 1.23, and 1.21, respectively. The multivariate values were 2.40, 1.98, and 0.99. Possible explanations of this trend of the hazard ratios as vaccinations increase could be a harvesting effect; a calendar-time bias, accounting for seasonality and pandemic waves; a case-counting window bias; a healthy-vaccinee bias; or some combination of these factors. With 2 and even with 3/4 doses, the calculated Restricted Mean Survival Time and Restricted Mean Time Lost have shown a small but significant downside for the vaccinated populations.

Incidence of diabetes following COVID-19 vaccination and SARS-CoV-2 infection in Hong Kong: A population-based cohort study

BACKGROUND

The risk of incident diabetes following Coronavirus Disease 2019 (COVID-19) vaccination remains to be elucidated. Also, it is unclear whether the risk of incident diabetes after Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection is modified by vaccination status or differs by SARS-CoV-2 variants. We evaluated the incidence of diabetes following mRNA (BNT162b2), inactivated (CoronaVac) COVID-19 vaccines, and after SARS-CoV-2 infection.

METHODS AND FINDINGS

In this population-based cohort study, individuals without known diabetes were identified from an electronic health database in Hong Kong. The first cohort included people who received ≥1 dose of COVID-19 vaccine and those who did not receive any COVID-19 vaccines up to September 2021. The second cohort consisted of confirmed COVID-19 patients and people who were never infected up to March 2022. Both cohorts were followed until August 15, 2022. A total of 325,715 COVID-19 vaccine recipients (CoronaVac: 167,337; BNT162b2: 158,378) and 145,199 COVID-19 patients were 1:1 matched to their respective controls using propensity score for various baseline characteristics. We also adjusted for previous SARS-CoV-2 infection when estimating the conditional probability of receiving vaccinations, and vaccination status when estimating the conditional probability of contracting SARS-CoV-2 infection. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident diabetes were estimated using Cox regression models. In the first cohort, we identified 5,760 and 4,411 diabetes cases after receiving CoronaVac and BNT162b2 vaccines, respectively. Upon a median follow-up of 384 to 386 days, there was no evidence of increased risks of incident diabetes following CoronaVac or BNT162b2 vaccination (CoronaVac: 9.08 versus 9.10 per 100,000 person-days, HR = 0.998 [95% CI 0.962 to 1.035]; BNT162b2: 7.41 versus 8.58, HR = 0.862 [0.828 to 0.897]), regardless of diabetes type. In the second cohort, we observed 2,109 cases of diabetes following SARS-CoV-2 infection. Upon a median follow-up of 164 days, SARS-CoV-2 infection was associated with significantly higher risk of incident diabetes (9.04 versus 7.38, HR = 1.225 [1.150 to 1.305])-mainly type 2 diabetes-regardless of predominant circulating variants, albeit lower with Omicron variants (p for interaction = 0.009). The number needed to harm at 6 months was 406 for 1 additional diabetes case. Subgroup analysis revealed no evidence of increased risk of incident diabetes among fully vaccinated COVID-19 survivors. Main limitations of our study included possible misclassification bias as type 1 diabetes was identified through diagnostic coding and possible residual confounders due to its observational nature.

CONCLUSIONS

There was no evidence of increased risks of incident diabetes following COVID-19 vaccination. The risk of incident diabetes increased following SARS-CoV-2 infection, mainly type 2 diabetes. The excess risk was lower, but still statistically significant, for Omicron variants. Fully vaccinated individuals might be protected from risks of incident diabetes following SARS-CoV-2 infection.

Comparison of two diagnostic intervention packages for community-based active case finding for tuberculosis: an open-label randomized controlled trial

Two in every five patients with active tuberculosis (TB) remain undiagnosed or unreported. Therefore community-based, active case-finding strategies require urgent implementation. However, whether point-of-care (POC), portable battery-operated, molecular diagnostic tools deployed at a community level, compared with conventionally used POC smear microscopy, can shorten time-to-treatment initiation, thus potentially curtailing transmission, remains unclear. To clarify this issue, we performed an open-label, randomized controlled trial in periurban informal settlements of Cape Town, South Africa, where we TB symptom screened 5,274 individuals using a community-based scalable mobile clinic. Some 584 individuals with HIV infection or symptoms of TB underwent targeted diagnostic screening and were randomized (1:1) to same-day smear microscopy (n = 296) or on-site DNA-based molecular diagnosis (n = 288; GeneXpert). The primary aim was to compare time to TB treatment initiation between the arms. Secondary aims included feasibility and detection of probably infectious people. Of participants who underwent targeted screening, 9.9% (58 of 584) had culture-confirmed TB. Time-to-treatment initiation occurred significantly earlier in the Xpert versus the smear-microscopy arm (8 versus 41 d, P = 0.002). However, overall, Xpert detected only 52% of individuals with culture-positive TB. Notably, Xpert detected almost all of the probably infectious patients compared with smear microscopy (94.1% versus 23.5%, P = <0.001). Xpert was associated with a shorter median time to treatment of probably infectious patients (7 versus 24 d, P = 0.02) and a greater proportion of infectious patients were on treatment at 60 d compared with the probably noninfectious patients (76.5% versus 38.2%, P < 0.01). Overall, a greater proportion of POC Xpert-positive participants were on treatment at 60 d compared with all culture-positive participants (100% versus 46.5%, P < 0.01). These findings challenge the traditional paradigm of a passive case-finding, public health strategy and argues for the implementation of portable DNA-based diagnosis with linkage to care as a community-oriented, transmission-interruption strategy. The study was registered with the South African National Clinical Trials Registry (application ID 4367; DOH-27-0317-5367) and ClinicalTrials.gov (NCT03168945).

Implications of Pleural Fluid Composition in Persistent Pleural Effusion following Orthotopic Liver Transplant

Persistent pleural effusions (PPEf) represent a known complication of orthotopic liver transplant (OLT). However, their clinical relevance is not well described. We evaluated the clinical, biochemical, and cellular characteristics of post-OLT PPEf and assessed their relationship with longitudinal outcomes. We performed a retrospective cohort study of OLT recipients between 2006 and 2015. Included patients had post-OLT PPEf, defined by effusion persisting >30 days after OLT and available pleural fluid analysis. PPEf were classified as transudates or exudates (Exud^Light) by Light's criteria. Exudates were subclassified as those with elevated lactate dehydrogenase (Exud^LDH) or elevated protein (Exud^Prot). Cellular composition was classified as neutrophil- or lymphocyte-predominant. Of 1602 OLT patients, 124 (7.7%) had PPEf, of which 90.2% were Exud^Light. Compared to all OLT recipients, PPEf patients had lower two-year survival (HR 1.63; p = 0.002). Among PPEf patients, one-year mortality was associated with pleural fluid RBC count (p = 0.03). While Exud^Light and Exud^Prot showed no association with outcomes, Exud^LDH were associated with increased ventilator dependence (p = 0.03) and postoperative length of stay (p = 0.03). Neutrophil-predominant effusions were associated with increased postoperative ventilator dependence (p = 0.03), vasopressor dependence (p = 0.02), and surgical pleural intervention (p = 0.02). In summary, post-OLT PPEf were associated with increased mortality. Ninety percent of these effusions were exudates by Light's criteria. Defining exudates using LDH only and incorporating cellular analysis, including neutrophils and RBCs, was useful in predicting morbidity.

Antibiotic Therapy is Associated with Worse Outcome in Patients with Hepatocellular Carcinoma Treated with Sorafenib

Background

Antibiotic treatment (ABT) affects the outcome of cancer patients treated with immune checkpoint inhibitors (ICIs) and chemotherapy, possibly by altering the gut microbiome. We investigated the impact of ABT on overall survival (OS) and progression-free survival (PFS) in patients with advanced HCC treated with sorafenib.

Methods

HCC patients treated with sorafenib between 05/2006 and 03/2020 at the Medical University of Vienna were retrospectively analyzed. ABT was defined as antibiotic use within 30 days prior to or after sorafenib initiation.

Results

Of 206 patients, the majority was male (n=171, 83%) with a mean age of 66±9.6 years. Half of patients (n=94, 46%) had impaired liver function (Child-Pugh stage B). Median time of follow-up was 10.8 (95% CI: 9.2-12.3) months. ABT was administered in 23 (11%) patients due to different types of proven or clinically suspected bacterial infections (n=17, 74%) and hepatic encephalopathy (n=6, 26%). The median duration of ABT was 14 (IQR: 12-30) days. Penicillin (n=13, 57%), followed by rifaximin (n=6, 26%), fluoroquinolones (n=3, 13%), and cephalosporins (n=1, 4%), was administered in the ABT group. The ABT group had a significantly shorter median OS (4.7 (95% CI: 3.2-6.1) months vs 11.4 (95% CI: 9.9-12.9) months, p=0.012), which was confirmed in multivariable analysis (HR: 1.91 (95% CI: 1.1-3.2), p=0.014). Similarly, PFS trended to be shorter in the ABT group (3.5 (95% CI: 1.6-5.4) months vs 4.8 (95% CI: 3.9-5.7) months, p=0.099). None of the 10 patients with complete or partial response was found in the ABT group.

Conclusion

ABT was independently associated with worse outcomes in sorafenib-treated HCC patients. Prospective studies are needed to elucidate the underlying mechanism.

Restricted mean survival time versus conventional measures for treatment decision-making

BACKGROUND/OBJECTIVES

Restricted mean survival time (RMST) summarizes treatment effect in terms of a gain or loss in the event-free days. It remains uncertain whether communicating treatment benefit and harm using RMST-based summary is more effective than conventional summary based on absolute and relative risk reduction. We compared the effect of RMST-based approach and conventional approach on decisional conflict using an example of intensive versus standard blood pressure-lowering strategies.

DESIGN

On-line survey.

SETTING

A convenience sample of patients in the United States.

PARTICIPANTS

Two hundred adults aged 65 and older with hypertension requiring anti-hypertensive treatment (response rate 85.5%).

INTERVENTIONS

Participants were randomly assigned to either RMST-based summary or conventional summary about the benefit and harm of blood pressure-lowering strategies.

MEASUREMENTS

Decisional Conflict Scale (DCS), ranging from 0 (no conflict) to 100 (high conflict), and preference for intensive blood pressure-lowering strategy.

RESULTS

Participants assigned to RMST-based approach (n = 100) and conventional approach (n = 100) had similar age (mean [standard deviation, SD]: 72.3 [5.6] vs 72.8 [5.5] years) and proportions of female (50 [50.0%] vs 61 [61.0%]) and white race (92 [92.0%] vs 92 [92.0%]). The mean (SD) DCS score was 25.2 (15.0) for RMST-based approach and 25.6 (14.1) for conventional approach (p = 0.84). The number (%) of participants who preferred intensive strategy was 10 (10.0%) for RMST-based approach and 14 (14.0%) for conventional approach (p = 0.52). The results were consistent in subgroups defined by age, sex, education level, cardiovascular disease status, and predicted mortality risk categories.

CONCLUSION

In a sample of relatively healthy older adults with hypertension, RMST-based approach was as effective as conventional approach on decisional conflict about choosing a blood pressure-lowering strategy. This study provides proof-of-concept evidence that RMST-based approach can be used in conjunction with absolute and relative risk reduction for communicating treatment benefit and harm in a decision aid.

Time spent outside of the hospital, CKD progression, and mortality: a prospective cohort study

PURPOSE

Home time-being out of any healthcare facility-has been proposed as a patient-centered outcome. This novel measure has not been investigated in patients with chronic kidney disease (CKD). The aim of this study is to determine whether there was an association between home time and occurrence of end-stage renal disease (ESRD) or all-cause mortality during 1 year of follow-up.

METHODS

We assembled a prospective cohort of patients with CKD not requiring dialysis at the Nephrology Center of First Affiliated Hospital of Jiaxing University between May 2014 and April 2017 and followed up for 1 year. Home time was calculated as the number of days spent out of a hospital, rehabilitation facility, or skilled nursing facility. Outcomes included progression to ESRD and all-cause mortality.

RESULTS

Among 943 patients, 882 (93.5%) had complete follow-up through 1 year. Mean home time was 246.9 ± 126.7 days. In regression analysis, several patient characteristics were associated with significantly reduced home time, including diabetes mellitus, cardiovascular disease, and albuminuria. Home time was strongly correlated with time-to-event endpoints of ESRD (τ=0.324) and all-cause mortality (τ=0.785).

CONCLUSIONS

Home time is significantly reduced for patients with CKD not requiring dialysis and is highly correlated with traditional time-to-event endpoints. Home time serves as a novel, easily calculated, patient-centered outcome that may reflect effect of interventions on future CKD research.

On permutation tests for comparing restricted mean survival time with small sample from randomized trials

Between-group comparison based on the restricted mean survival time (RMST) is getting attention as an alternative to the conventional logrank/hazard ratio approach for time-to-event outcomes in randomized controlled trials (RCTs). The validity of the commonly used nonparametric inference procedure for RMST has been well supported by large sample theories. However, we sometimes encounter cases with a small sample size in practice, where we cannot rely on the large sample properties. Generally, the permutation approach can be useful to handle these situations in RCTs. However, a numerical issue arises when implementing permutation tests for difference or ratio of RMST from two groups. In this article, we discuss the numerical issue and consider six permutation methods for comparing survival time distributions between two groups using RMST in RCTs setting. We conducted extensive numerical studies and assessed type I error rates of these methods. Our numerical studies demonstrated that the inflation of the type I error rate of the asymptotic methods is not negligible when sample size is small, and that all of the six permutation methods are workable solutions. Although some permutation methods became a little conservative, no remarkable inflation of the type I error rates were observed. We recommend using permutation tests instead of the asymptotic tests, especially when the sample size is less than 50 per arm.

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.

An alternative approach for estimating the number needed to treat for survival endpoints

To investigate the issues of the NNT based on the absolute risk reduction (ARR), namely NNT_ARR; and to propose an alternative definition and an estimation procedure based on the restricted mean survival time (RMST), namely NNT_RMST, for RCTs. Three recent clinical trials with survival endpoints, representing different scenarios, were selected to compare the performance of the NNT_ARR and NNT_RMST. For each trial, both versions of NNT were estimated using the reconstructed individual-level data, and the average life gain (ALG) was derived to show the differences between the NNT_ARR and NNT_RMST. Four hypothetical scenarios were constructed to further explore the advantages and disadvantages of each definition of the NNT for survival endpoints. For the illustrative trial examples, the NNT_ARR failed to capture the profile of the treatment effect over time as it is calculated at a specific time point. Sometimes it may even result in misinterpretations of the treatment benefit. In particular, when either the observed event rates are low, the two survival curves cross, or a mixture of survival patterns exist. In contrast, the NNT_RMST based on the average survival (or event-free) time can quantify the treatment effect more accurately and its interpretation is more intuitive and clinically meaningful. The NNT_RMST can be used as an alternative measure for quantifying treatment effect in RCTs, especially so in the case of the ALG, which helps practitioners to better understand the magnitude of the benefit conferred by treatment.

Home Time as a Patient-Centered Outcome in Administrative Claims Data

BACKGROUND

Home time, the number of days alive and spent out of hospital and skilled nursing facility, has been proposed as a patient-centered outcome that can be readily calculated in administrative claims data.

OBJECTIVES

To compare home time against existing patient-centered outcome measures.

DESIGN

Retrospective cohort study.

SETTING

Community.

PARTICIPANTS

A total of 4594 Medicare beneficiaries 65 years or older with complete survey and claims data in the Medicare Current Beneficiary Survey 2010 to 2011.

MEASUREMENTS

Home time was calculated from the 2011 claims data (range, 0-365 days). The 1-year incidence of patient-centered outcomes (poor self-rated health, mobility impairment, depression, limited social activity, and difficulty in self-care) was measured. The minimum clinically important difference (MCID) was derived by contrasting the mean home time between those who experienced functional decline or death and those who did not.

RESULTS

The mean home time was 355.8 days (SD, 42.1 days); 84.1% had a home time of 365 days, and 5.7% had a home time of 336 days or fewer. The incidence of poor self-rated health ranged from 2% (home time, 365 days) to 21% (home time, less than 337 days). Similarly, the corresponding incidence risks were 11% to 59% for mobility impairment, 5% to 19% for depression, 17% to 67% for limited social activity, and 13% to 68% for difficulty in self-care. The risk of mobility impairment, depression, and difficulty in self-care increased steeply after home time loss of 15 days or greater. The MCID of home time was 18.6 days.

CONCLUSION

A loss in home time is associated with decline in several patient-centered outcome measures in community-dwelling Medicare beneficiaries. These results provide empirical evidence to promote adoption of home time and its clinical interpretation for database studies of medical interventions. J Am Geriatr Soc 67:347-351, 2019.

Pravastatin for Primary Prevention in Older Adults: Restricted Mean Survival Time Analysis

OBJECTIVES

To use restricted mean survival time, which summarizes treatment effects in terms of event-free time over a fixed time period, to evaluate the benefit of pravastatin therapy for primary prevention of cardiovascular disease in older adults.

DESIGN

Secondary analysis of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial-Lipid-Lowering Trial (ALLHAT-LLT).

SETTING

Ambulatory setting.

PARTICIPANTS

Individuals aged 65 and older (mean aged 71, 49% female) free of cardiovascular disease (N=2,867).

INTERVENTION

Pravastatin 40 mg/d (n=1,467) versus usual care (n=1,400).

MEASUREMENTS

We estimated the difference in RMST for total and coronary heart disease (CHD)-free survival between the pravastatin and usual care groups over the 6-year trial period and used parametric survival models to estimate RMST differences projected over 10 years.

RESULTS

Over 6 years, individuals treated with pravastatin lived (RMST 2,008.1 days), on average, 33.7 fewer days than those receiving usual care (RMST 2,041.8 days) (difference -33.7 days, 95% confidence interval (CI)=-67.0 to -0.5 days, p=.047). Pravastatin-treated individuals lived RMST 2,088.1 days), on average, 18.7 more days free of CHD over 6 years than those receiving usual care (RMST 2,069.4 days), but this difference was not statistically significant (difference 18.7 days, 95% CI=-10.4-47.8 days, p=.21). The 10-year projection showed that pravastatin-treated individuals would live 108.1 fewer days (95% CI=-204.5 to -14.1, p=.03) than those receiving usual care, although treated individuals would gain 77.9 days (95% CI=3.8-159.6, p=.046) of CHD-free survival.

CONCLUSION

RMST provides an intuitive and explicit way to express the effect of pravastatin therapy on CHD-free and overall survival in older adults free of cardiovascular disease. This measure allows a more personalized interpretation than hazard ratios of the benefits and risks of a medical intervention for decision-making.