Estimation of the average causal effect among subgroups defined by post-treatment variables

Duration of and time to response in oncology clinical trials from the perspective of the estimand framework

Duration of response (DOR) and time to response (TTR) are typically evaluated as secondary endpoints in early-stage clinical studies in oncology when efficacy is assessed by the best overall response and presented as the overall response rate. Despite common use of DOR and TTR in particular in single-arm studies, the definition of these endpoints and the questions they are intended to answer remain unclear. Motivated by the estimand framework, we present relevant scientific questions of interest for DOR and TTR and propose corresponding estimand definitions. We elaborate on how to deal with relevant intercurrent events which should follow the same considerations as implemented for the primary response estimand. A case study in mantle cell lymphoma illustrates the implementation of relevant estimands of DOR and TTR. We close the paper with practical recommendations to implement DOR and TTR in clinical study protocols.

Estimating conditional vaccine effectiveness

Vaccine effectiveness for COVID-19 is typically estimated for different outcomes that often are hierarchical in severity (e.g. any documented infection, symptomatic infection, hospitalization, death) and subsets of each other. Conditional effectiveness for a more severe outcome conditional on a less severe outcome is the protection offered against the severe outcome (e.g. death) among those who already sustained the less severe outcome (e.g. documented infection). The concept applies also to the protection offered by previous infection rather than vaccination. Formulas and a nomogram are provided here for calculating conditional effectiveness. Illustrative examples are presented from recent vaccine effectiveness studies, including situations where effectiveness for different outcomes changed at different pace over time. E(death | documented infection) is the percent decrease in the case fatality rate and E(death | infection) is the percent decrease in the infection fatality rate (IFR). Conditional effectiveness depends on many factors and should not be misinterpreted as a causal effect estimate. However, it may be used for better personalized communication of the benefits of vaccination, considering also IFR and epidemic activity in public health decision-making and communication.

A culturally adapted depression intervention for African American adults experiencing depression: Oh Happy Day

The purpose of this article is to describe development of a culturally adapted depression intervention (Oh Happy Day Class, OHDC) designed for African American adults experiencing major depressive disorder (MDD). This project included 2 pilot studies testing the feasibility and acceptability of the OHDC and examining short-term effects of the OHDC in reducing symptoms of MDD. The OHDC is a 2.5-hr weekly, culturally specific, cognitive behavioral, group counseling intervention for 12 weeks. Cultural adaptations of the OHDC are based on the ecological validity and culturally sensitive framework, along with an Afrocentric paradigm. Fifty African American participants with MDD were enrolled (15 in Pilot I and 35 in Pilot II). All participants in Pilots I and II received the 12-week intervention and completed assessments at baseline, mid-intervention, end-intervention, and 3 months postintervention. General linear mixed modeling for assessment of pre-post longitudinal data analysis was conducted. Results for Pilot I showed 73% of participants completed the full OHDC, a statistically significant decline in depression symptoms from pre- to postintervention, and a 0.38 effect size. Participants were very satisfied with the OHDC. In Pilot II, 66% of participants completed the full OHDC, and there was a significant pre-post intervention decrease in depression symptoms. For men, the OHDC showed a 1.01 effect size and for women, a 0.41 effect size. Both men and women were very satisfied with the OHDC based on the satisfaction measure. These promising findings are discussed with a focus on future plans for examining efficacy of the OHDC in a large-scale, randomized, control trial.

The effectiveness of Stepping Stones Triple P parenting support in parents of children with borderline to mild intellectual disability and psychosocial problems: a randomized controlled trial

BACKGROUND

Children with borderline to mild intellectual disability (BMID) have been shown to be at increased risk for psychosocial problems. The presence of these psychosocial problems leads to parenting stress. Stepping Stones Triple P (SSTP) is a parenting support program to support parents with children with BMID and psychosocial problems. The aim of this study was to evaluate the effectiveness of SSTP compared to Care as Usual (CAU) in reducing psychosocial problems in children with BMID.

METHOD

We conducted a randomized controlled trial in the Northern provinces of the Netherlands. Parents of children aged 5 to 12 with borderline (IQ 70 to 85) or mild (IQ 70 to 50) ID and psychosocial problems were invited. Psychosocial problems were identified using the Strengths and Difficulties Questionnaire (SDQ) parent report (≥14). Measurements were assessed before the intervention (T0), immediately after the intervention (T1) and after a follow-up of six months (T2). SSTP takes 8 to 10 individual sessions of 40-90 minutes, provided over 10 to 12 weeks. CAU concerned any service, except SSTP. Primary outcomes were the child's psychosocial problems (SDQ parent and teacher forms and the Eyberg Child Behavior Inventory, ECBI). Secondary outcomes were parenting stress (Parenting Stress Index, PSI) and parenting skills (Alabama Parenting Questionnaire, APQ).

RESULTS

In total 209 parents of children aged 5 to 12 with BMID were allocated blindly to either SSTP (n =111) or CAU (n =98). In the intention to treat analyses, SSTP achieved no significantly better effect than CAU for the SDQ parent report, the ECBI and the APQ on the short- and long- term. In the short term, SSTP was significantly more effective than CAU for the SDQ teacher report (B = -2.25, 95% CI -3.79 to -0.71) and the PSI (B = -7.06, 95% CI -12.11 to -2.01). For both SDQ teacher report and PSI, there was no statistically significant effect in the long term. Dropout from SSTP was considerable (49%), with the effects being solely found in the adherent SSTP subgroup.

CONCLUSIONS

SSTP had some short-term advantages over CAU, but not in the longer term.

TRIAL REGISTRATION

Dutch Trial Register NTR2624. Registered 26 November 2010.

Kaplan-Meier curves for survivor causal effects with time-to-event outcomes

BACKGROUND

In clinical trials, an outcome of interest may be undefined for individuals who die before the outcome is evaluated. One approach to deal with such issues is to consider the survivor causal effect (SCE), which is defined as the effect of treatment on the outcome among the subpopulation that would have survived under either treatment arm. Although several methods have been presented to estimate the SCE with time-to-event outcomes, they are difficult to implement in practice.

PURPOSE

We present a simple method to create Kaplan-Meier curves and to estimate the hazard ratio (HR) for the SCE with time-to-event outcomes.

METHODS

To develop such a method, we applied the weighted average method presented for the SCE to outcomes with no censoring, where weights are calculated using the probability that a patient would have survived had the patient been in the other treatment arm. By multiplying the weight to each patient, Kaplan-Meier curves can be created for the SCE to outcomes with censoring. The HR is then calculated using a weighted proportional hazard model. For this method, two assumptions need to be introduced to achieve unbiasedness.

RESULTS

The proposed method is illustrated using data from a randomized Phase II clinical trial, comparing two chemotherapy treatments with radiotherapy in patients with esophageal cancer. Here, we focus on the loco-regional control rate, which is calculated from the time after randomization until recurrence in the radiation field. The duration is undefined for patients who died without recurrence. The proposed method yielded a HR of 1.026 (95% confidence interval (CI): 0.627, 1.677). The standard method, where data of patients who died without progression were regarded as censored at the time of death, yielded a HR of 1.121 (95% CI: 0.688, 1.827).

LIMITATIONS

The proposed method requires two assumptions. As a general problem, unfortunately, whether these assumptions hold cannot be confirmed from the observed data. Thus, we cannot confirm whether the Kaplan-Meier curves and the HR are unbiased.

CONCLUSION

We have proposed a simple method for the SCE with time-to-event outcomes, which is easy to implement in practice. The proposed method is a potentially valuable supplement to the standard method.