When observational studies can give wrong answers: the potential of immortal time bias

Disease control of acromegaly does not prevent excess mortality in the long term: results of a nationwide survey in Italy

OBJECTIVE

This study aimed to assess the long-term outcome of patients with acromegaly.

DESIGN

This is a multicenter, retrospective, observational study which extends the mean observation period of a previously reported cohort of Italian patients with acromegaly to 15 years of follow-up.

METHODS

Only patients from the centers that provided information on the life status of at least 95% of their original cohorts were included. Life status information was collected either from clinical records or from the municipal registry offices. Standardized mortality ratios (SMRs) were computed comparing data with those of the general Italian population.

RESULTS

A total of 811 patients were included. There were 153 deaths, with 90 expected and an SMR of 1.7 (95% CI 1.4-2.0, p < 0.001). Death occurred after a median of 15 (women) or 16 (men) years from the diagnosis, without gender differences. Mortality remained elevated in the patients with control of disease (SMR 1.3, 95% CI 1.1-1.6). In the multivariable analysis, only older age and high IGF1 concentrations at last available follow-up visit were predictors of mortality. The oncological causes of death outweighed the cardiovascular ones, bordering on statistical significance with respect to the general population.

CONCLUSIONS

Mortality remains significantly high in patients with acromegaly, irrespectively of disease status, as long as the follow-up is sufficiently long with a low rate of patients lost to follow-up. Therapy strategy including radiotherapy does not have an impact on mortality. Oncological causes of death currently outweigh the cardiovascular causes.

The association between trajectory of serum cholesterol, statin dosage, and the risk of recurrent biliary stone diseases

BACKGROUND

Statins may reduce the risk of recurrent gallstone disease by decreasing bile cholesterol saturation and pathogenicity. However, limited studies have investigated this issue. This study aimed to assess whether statin doses and serum cholesterol levels were associated with a decreased risk of recurrent biliary stone diseases after the first event index, with a follow-up time of 15 years.

METHODS

Based on the Chang Gung Research Database (CGRD) between January 1, 2001, and December 31, 2020, we enrolled 68,384 patients with the International Classification of Diseases, Ninth and Tenth Revision codes of choledocholithiasis. After exclusions, 32,696 patients were divided into non-statin (<28 cDDD, cumulative defined daily doses) (n = 27,929) and statin (≥28 cDDD) (n = 4767) user groups for analysis. Serum cholesterol trajectories were estimated using group-based trajectory modeling (n = 8410).

RESULTS

The statin users had higher Charlson Comorbidity Index (CCI) scores than the non-statin users. Time-dependent Cox regression analysis showed that statin use >365 cDDD was associated with a significantly lower risk of recurrent biliary stones (adjusted hazard ratio [aHR] = 0.28, 95% CI, 0.24-0.34; p < 00.0001), acute pancreatitis (aHR = 0.24, 95% CI, 0.17-0.32, p < 00.0001), and cholangitis (aHR = 0.28, 95% CI, 0.25-0.32, p < 00.0001). Cholecystectomy was also a protective factor for recurrent biliary stones (aHR = 0.41, 95% CI, 0.37-0.46; p < 00.0001). The higher trajectory serum cholesterol group (Group 3) had a lower risk trend for recurrent biliary stones (aHR = 0.79, p = 0.0700) and a lower risk of cholangitis (aHR = 0.79, p = 0.0071).

CONCLUSION

This study supports the potential benefits of statin use and the role of cholecystectomy in reducing the risk of recurrent biliary stone diseases.

Effect of multidisciplinary care on diabetic kidney disease: a retrospective cohort study

BACKGROUND

Diabetic kidney disease (DKD) is the most common disease among patients requiring dialysis for the first time in Japan. Multidisciplinary care (MDC) may prevent the progression of kidney failure. However, the effectiveness and timing of MDC to preserve kidney function in patients with DKD is unclear. Therefore, the aim of this study was to investigate whether MDC for patients with DKD affects the preservation of kidney function as well as the timing of MDC in clinical practice.

METHODS

In this retrospective cohort study, we identified patients with type 2 diabetes mellitus and DKD from April 2012 to January 2020 using a nationwide Japanese healthcare record database. The fee code for medical guidance to prevent dialysis in patients with diabetes was used to distinguish between the MDC and non-MDC groups. The primary outcome was a 40% decline in the estimated glomerular filtration rate, and secondary outcomes were death, hospitalization, permanent dialysis, kidney failure with replacement therapy, and emergency temporary catheterization. Propensity score matching was performed, and Kaplan-Meier and multivariable Cox regression analyses were performed.

RESULTS

Overall, 9,804 eligible patients met the inclusion criteria, of whom 5,614 were matched for the main analysis: 1,039 in the MDC group, and 4,575 in the non-MDC group. The primary outcome did not differ between the groups (hazard ratio: 1.18, [95% confidence interval: 0.99-1.41], P = 0.07). The groups also did not differ in terms of the secondary outcomes. Most patients with DKD received their first MDC guidance within 1 month of diagnosis, but most received guidance only once per year.

CONCLUSIONS

Although we could not demonstrate the effectiveness of MDC on kidney function in patients with DKD, we clarified the characteristics of such patients assigned the fee code for medical guidance to prevent dialysis related to diabetes.

Methodological biases in observational hospital studies of COVID-19 treatment effectiveness: pitfalls and potential

Introduction

This study aims to discuss and assess the impact of three prevalent methodological biases: competing risks, immortal-time bias, and confounding bias in real-world observational studies evaluating treatment effectiveness. We use a demonstrative observational data example of COVID-19 patients to assess the impact of these biases and propose potential solutions.

Methods

We describe competing risks, immortal-time bias, and time-fixed confounding bias by evaluating treatment effectiveness in hospitalized patients with COVID-19. For our demonstrative analysis, we use observational data from the registry of patients with COVID-19 who were admitted to the Bellvitge University Hospital in Spain from March 2020 to February 2021 and met our predefined inclusion criteria. We compare estimates of a single-dose, time-dependent treatment with the standard of care. We analyze the treatment effectiveness using common statistical approaches, either by ignoring or only partially accounting for the methodological biases. To address these challenges, we emulate a target trial through the clone-censor-weight approach.

Results

Overlooking competing risk bias and employing the naïve Kaplan-Meier estimator led to increased in-hospital death probabilities in patients with COVID-19. Specifically, in the treatment effectiveness analysis, the Kaplan-Meier estimator resulted in an in-hospital mortality of 45.6% for treated patients and 59.0% for untreated patients. In contrast, employing an emulated trial framework with the weighted Aalen-Johansen estimator, we observed that in-hospital death probabilities were reduced to 27.9% in the "X"-treated arm and 40.1% in the non-"X"-treated arm. Immortal-time bias led to an underestimated hazard ratio of treatment.

Conclusion

Overlooking competing risks, immortal-time bias, and confounding bias leads to shifted estimates of treatment effects. Applying the naïve Kaplan-Meier method resulted in the most biased results and overestimated probabilities for the primary outcome in analyses of hospital data from COVID-19 patients. This overestimation could mislead clinical decision-making. Both immortal-time bias and confounding bias must be addressed in assessments of treatment effectiveness. The trial emulation framework offers a potential solution to address all three methodological biases.

Is male gynaecomastia associated with an increased risk of death? A nationwide register-based cohort study

OBJECTIVE

Recent evidence supports that gynaecomastia may predict long-term morbidity, but evidence on the association with death and causes of death in males with gynaecomastia is lacking. The objective of this work is to estimate the risk of death in men diagnosed with gynaecomastia and evaluate whether this was conditional on underlying aetiologies of gynaecomastia.

DESIGN

A nationwide register-based cohort study.

SETTING

Nationwide Danish national health registries.

PARTICIPANTS

Males were diagnosed with incident gynaecomastia (n=23 429) from 1 January 1995 to 30 June 2021, and each was age and calendar matched to five randomly population-based males without gynaecomastia (n=117 145).

INTERVENTIONS

Not applicable.

PRIMARY AND SECONDARY OUTCOMES

Gynaecomastia was distinguished between males without (idiopathic) and males with a known pre-existing risk factor. Cox regression models and Kaplan-Meier analyses estimated associations between gynaecomastia and death (all cause/cause specific).

RESULTS

We identified a total of 16 253 males with idiopathic gynaecomastia and 7176 with gynaecomastia and a known pre-existing risk factor. Of these, 1093 (6.7%) and 1501 (20.9%) died during follow-up, respectively. We detected a 37% increased risk of all-cause death in males with gynaecomastia in the entire cohort (HR 1.37; 95% CI 1.31 to 1.43). Death risk was highest in males diagnosed with gynaecomastia and a known pre-existing risk factor (HR 1.75; 95% CI 1.64 to 1.86) compared with males with idiopathic gynaecomastia (HR 1.05; 95% CI 0.98 to 1.13). Specific causes of increased death were malignant neoplasms and circulatory, pulmonary and gastrointestinal diseases. Of the latter, an over fivefold risk of death from liver disease was detected (HR 5.05; 95% CI 3.97 to 6.42).

CONCLUSIONS

Males diagnosed with gynaecomastia are at higher risk of death, observed mainly in males with a known pre-existing risk factor of gynaecomastia. These findings will hopefully stimulate more awareness among healthcare providers to potentially apply interventions that aid in alleviating underlying risk factors in males with this condition.

Association between immune-related adverse events and survival in patients with renal cell carcinoma treated with nivolumab plus ipilimumab: immortal time bias-corrected analysis

BACKGROUND

Immune-related adverse events (irAEs) in patients treated with immune check inhibitors are associated with favourable response rate and survivals in multiple cancers, including renal cell carcinoma (RCC). The aim of this study was to investigate how irAEs were associated with improved survivals in advanced RCC patients treated with nivolumab plus ipilimumab.

MATERIALS AND METHODS

This retrospective study included patients who received nivolumab plus ipilimumab at six centres, institutions, or hospitals between September 2018 and February 2022. We assessed associations of the development and the number of irAEs with overall survival (OS) and progression-free survival (PFS). To eliminate immortal time bias, landmark analysis and a Cox model with time-dependent variables were used.

RESULTS

This study included 129 patients with a median follow-up of 12.3 months. The 2-year OS and PFS rates were 55% and 42%, respectively. Ninety six patients experienced irAEs. The development of irAEs was positively associated with OS and PFS rates (hazard ratio [HR] 0.328, 95% confidence interval [CI] 0.165-0.648, p = 0.001; HR 0.334, 95% CI 0.151-0.737, p = 0.007). Patients who experienced multiple irAEs had longer OS (HR 0.507, 95% CI 0.235-1.097, p = 0.085 or HR 0.245, 95% CI 0.110-0.544, p < 0.001) and PFS (HR 0.572, 95% CI 0.316-1.036, p = 0.085 or HR 0.267, 95% CI 0.113-0.628, p = 0.002) compared with those who experienced single or zero irAE.

CONCLUSIONS

Developing irAEs, particularly multiple irAEs, is associated with favourable survivals in advanced RCC patients treated with nivolumab plus ipilimumab.

Competing risks analysis of external versus internal radiation in patients with hepatocellular carcinoma after controlling for immortal time bias

PURPOSE

In cohort studies on liver cancer, there are often immortal time bias and interference of competing risk events. This study proposes to explore the role of internal and external radiotherapy for hepatocellular carcinoma using SEER data, using a competing risk model and controlling immortal time bias.

METHODS

Data of SEER from 2004 till 2015 was included. To analyze whether there was a difference in survival between HCC (hepatocellular carcinoma) patients receiving external radiation and internal radiation, we used a competing risk analysis after excluding immortal time bias, and created a nomogram to assess the risk of cancer-specific death (CSD) in hepatocellular carcinoma patients receiving radiotherapy.

RESULTS

Potential confounding factors adjusted, there was no significant difference in CSD between external and internal radiation therapy [HR and its 95% CI = 1.098 (0.874-1.380)]. The constructed nomogram performed better than the traditional AJCC model. The AUC and calibration curve results showed that this well-calibrated nomogram could be used to make clinical decisions regarding the prognosis and personalized treatment of hepatocellular carcinoma treated. There was no difference in the cumulative risk of death between patients with liver cancer treated with external radiation therapy and internal radiation therapy.

CONCLUSION

There is no difference in the cumulative risk of death between patients with liver cancer treated with external radiation therapy and internal radiation therapy. The nomogram predicts the results more accurately. These results can be used to guide the choice of treatment options for patients with HCC and to predict their survival prognosis.

In patients with combined clavicle and multiple rib fractures, does fracture fixation of the clavicle improve clinical outcomes? A multicenter prospective cohort study of 232 patients

BACKGROUND

Clavicle and rib fractures are often sustained concomitantly. The combination of injuries may result in decreased stability of the chest wall, making these patients prone to (respiratory) complications and prolonged hospitalization. This study aimed to assess whether adding chest wall stability by performing clavicle fixation improves clinical outcomes in patients with concurrent clavicle and rib fractures.

METHODS

A prospective multicenter study was performed including all adult patients admitted between January 2018 and March 2021 with concurrent ipsilateral clavicle and rib fractures. Patients treated operatively versus nonoperatively for their clavicle fracture were matched using propensity score matching. The primary outcome was hospital length of stay (HLOS). Secondary outcomes were intensive care unit length of stay, duration of mechanical ventilation, pain, complications, and quality of life at 6 weeks and 12 months of follow-up.

RESULTS

In total, 232 patients with concomitant ipsilateral clavicle and rib fractures were included. Fifty-two patients (22%) underwent operative treatment of which 39 could be adequately matched to 39 nonoperatively treated patients. No association was observed between clavicle plate fixation and HLOS (mean difference, 2.3 days; 95% confidence interval, -2.1 to 6.8; p = 0.301) or any secondary endpoint. Eight of the 180 nonoperatively treated patients (4%) had a symptomatic nonunion, for which 5 underwent secondary clavicle fixation.

CONCLUSION

We found no evidence that, in patients with combined clavicle and multiple rib fractures, plate fixation of the clavicle reduces HLOS, pain, or (pulmonary) complications, nor that it improves quality of life.

STUDY TYPE

Therapeutic/Care Management; Level III.

Real-world outcomes among patients with metastatic colorectal cancer treated first line with a bevacizumab biosimilar (bevacizumab-awwb)

Background

Bevacizumab-awwb (MVASI®) was the first U.S. Food and Drug Administration-approved biosimilar to Avastin® (reference product [RP]) for the treatment of several different types of cancers, including metastatic colorectal cancer (mCRC), an indication approved based on extrapolation.

Objectives

Evaluate treatment outcomes in mCRC patients who received first-line (1L) bevacizumab-awwb at treatment initiation or as continuing bevacizumab therapy (switched from RP).

Design

A retrospective chart review study.

Methods

Adult patients who had a confirmed diagnosis of mCRC (initial presentation of CRC on or after 01 January 2018) and initiated 1L bevacizumab-awwb between 19 July 2019 and 30 April 2020 were identified from the ConcertAI Oncology Dataset. A chart review was conducted to evaluate patient baseline clinical characteristics and effectiveness and tolerability outcomes during the follow-up. Study measures were reported stratified by prior use of RP: (1) naïve patients and (2) switchers (patients who switched to bevacizumab-awwb from RP without advancing the line of therapy).

Results

At the end of study period, naïve patients (n = 129) had a median 1L progression-free survival (PFS) of 8.6 months [95% confidence interval (CI), 7.6-9.9] and a 12-month overall survival (OS) probability of 71.4% (95% CI, 61.0-79.5%). Switchers (n = 105) had a median 1L PFS of 14.1 months (95% CI, 12.1-15.8) and a 12-month OS probability of 87.6% (95% CI, 79.1-92.8%). During treatment with bevacizumab-awwb, 20 events of interest (EOIs) were reported in 18 naïve patients (14.0%) and 4 EOIs reported in 4 switchers (3.8%), of which the most commonly reported events were thromboembolic and hemorrhagic events. Most EOIs resulted in emergency department visit and/or treatment hold/discontinuation/switch. None of the EOIs resulted in death.

Conclusion

In this real-world cohort of mCRC patients who were treated 1L with a bevacizumab biosimilar (bevacizumab-awwb), the clinical effectiveness and tolerability data were as expected and consistent with previously published findings from real-world studies of bevacizumab RP in mCRC patients.

Trends in incidence and mortality risk for acromegaly in Norway: a cohort study

PURPOSE

Recent data have shown a decreasing overall mortality in acromegaly over the last decades. However, cancer incidence and cancer-related mortality still appear to be increased. Our aim was to obtain updated epidemiological data from Norway in a clinically well-defined cohort with complete register-based follow-up.

METHODS

Patients diagnosed with acromegaly from South-Eastern Norway between 1999-2019 (n = 262) and age and sex matched population controls (1:100) were included (n = 26,200). Mortality and cancer data were obtained from the Norwegian Cause of Death and Cancer Registry. Mortality and cancer incidence were compared by Kaplan-Meier analyses and Cox regression; we report hazard ratios (HRs) with 95% confidence intervals (95% CI).

RESULTS

Median age at diagnosis was 48.0 years (interquartile range (IQR): 37.6-58.0). Mean annual acromegaly incidence rate was 4.7 (95% CI 4.2-5.3) cases/10⁶ person-years, and the point prevalence (2019) was 83 (95% CI 72.6-93.5) cases/10⁶ persons. Overall mortality was not increased in acromegaly, HR 0.8 (95% CI 0.5-1.4), cancer-specific and cardiovascular-specific mortality was also not increased (HR: 0.7 (95% CI 0.3-1.8) and 0.8 (95% CI: 0.3-2.5) respectively). The HR for all cancers was 1.45 (1.0-2.1; p = 0.052).

CONCLUSION

In this large cohort study, covering the period 1999-2019, patients were treated with individualized multimodal management. Mortality was not increased compared to the general population and comparable with recent registry studies from the Nordic countries and Europe. Overall cancer risk was slightly, but not significantly increased in the patients.

Non-operative vs. operative treatment for multiple rib fractures after blunt thoracic trauma: a multicenter prospective cohort study

BACKGROUND

Patients with multiple rib fractures without a clinical flail chest are increasingly being treated with rib fixation; however, high-quality evidence to support this development is lacking.

METHODS

We conducted a prospective multicenter observational study comparing rib fixation to non-operative treatment in all patients aged 18 years and older with computed tomography confirmed multiple rib fractures without a clinical flail chest. Three centers performed rib fixation as standard of care. For adequate comparison, the other three centers performed only non-operative treatment. As such clinical equipoise formed the basis for the comparison in this study. Patients were matched using propensity score matching.

RESULTS

In total 927 patients with multiple rib fractures were included. In the three hospitals that performed rib fixation, 80 (14%) out of 591 patients underwent rib fixation. From the nonoperative centers, on average 71 patients were adequately matched to 71 rib fixation patients after propensity score matching. Rib fixation was associated with an increase in hospital length of stay (HLOS) of 4.9 days (95%CI 0.8-9.1, p = 0.02) and a decrease in quality of life (QoL) measured by the EQ5D questionnaire at 1 year of 0.1 (95% CI - 0.2-0.0, p = 0.035) compared to non-operative treatment. A subgroup analysis of patients who received operative care within 72 h showed a similar decrease in QoL. Up to 22 patients (28%) who underwent surgery experienced implant-related irritation.

CONCLUSIONS

We found no benefits and only detrimental effects associated with rib fixation. Based on these results, we do not recommend rib fixation as the standard of care for patients with multiple rib fractures.

TRIAL REGISTRATION

Registered in the Netherlands Trial Register NTR6833 on 13/11/2017.

Prognostic value of dysnatremia for survival in neuroendocrine neoplasm patients

OBJECTIVE

Hyponatremia and hypernatremia are common electrolyte abnormalities in patients with malignancy and have been independently associated with worse survival outcomes. To date, there are no data on the impact of dysnatremia on survival outcomes in patients with neuroendocrine neoplasms (NENs).

DESIGN

This study involves retrospective cohort analysis from a tertiary care center of NEN patients treated with peptide receptor radionuclide therapy (PRRT) with a cumulative activity of at least 3.7 GBq 177Lu-DOTATATE between the years 2000 and 2015.

METHODS

Comparison of overall survival of patients with the occurrence of hyponatremia (serum sodium < 135 mmol/L) or hypernatremia (serum sodium > 145 mmol/L) before starting or during PRRT was perfomed.

RESULTS

A total of 649 patients were included. Hyponatremia occurred in 57 patients during the observation period and was associated with a shorter median overall survival (95% CI) of 25 months (14-36) compared to 55 months (48-61) of the 512 normonatremic patients (P < 0.001), adjusted hazard ratio (HR): 1.48 (95% CI: 1.04-2.12). Overall survival time was reduced regardless of whether hyponatremia was present at baseline or during PRRT. In contrast, hypernatremia occurred in 80 patients and was associated with a longer median overall survival (95% CI) of 94 months (47-140) compared with the 512 normonatremic patients (P = 0.018), adjusted HR: 0.61 (95% CI: 0.40-0.92). This association was driven by the patients with hypernatremia during PRRT. No association between dysnatremia and progression-free survival after PRRT was observed.

CONCLUSIONS

The occurrence of hypo- or hypernatremia in PRRT-treated NET patients is associated with opposing outcomes with regard to overall survival. Sodium levels might have a prognostic role in these patients.

Immortal time bias for life-long conditions in retrospective observational studies using electronic health records

Background

Immortal time bias is common in observational studies but is typically described for pharmacoepidemiology studies where there is a delay between cohort entry and treatment initiation.

Methods

This study used the Clinical Practice Research Datalink (CPRD) and linked national mortality data in England from 2000 to 2019 to investigate immortal time bias for a specific life-long condition, intellectual disability. Life expectancy (Chiang’s abridged life table approach) was compared for 33,867 exposed and 980,586 unexposed individuals aged 10+ years using five methods: (1) treating immortal time as observation time; (2) excluding time before date of first exposure diagnosis; (3) matching cohort entry to first exposure diagnosis; (4) excluding time before proxy date of inputting first exposure diagnosis (by the physician); and (5) treating exposure as a time-dependent measure.

Results

When not considered in the design or analysis (Method 1), immortal time bias led to disproportionately high life expectancy for the exposed population during the first calendar period (additional years expected to live: 2000–2004: 65.6 [95% CI: 63.6,67.6]) compared to the later calendar periods (2005–2009: 59.9 [58.8,60.9]; 2010–2014: 58.0 [57.1,58.9]; 2015–2019: 58.2 [56.8,59.7]). Date of entry of diagnosis (Method 4) was unreliable in this CPRD cohort. The final methods (Method 2, 3 and 5) appeared to solve the main theoretical problem but residual bias may have remained.

Conclusions

We conclude that immortal time bias is a significant issue for studies of life-long conditions that use electronic health record data and requires careful consideration of how clinical diagnoses are entered onto electronic health record systems.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01581-1.

A real-world analysis of nanoliposomal-irinotecan with 5-fluorouracil and folinic acid as third- or later-line therapy in patients with metastatic pancreatic adenocarcinoma

Background:

Nanoliposomal encapsulation of irinotecan (nal-IRI) with 5-fluorouracil and leucovorin (5-FU/LV) has shown a survival benefit for gemcitabine-pretreated patients with metastatic pancreatic adenocarcinoma (mPAC). The aim of this study was to evaluate the effectiveness and safety of nal-IRI with 5-FU/LV for use beyond second-line treatment after standard frontline therapy for mPAC.

Method:

This multicenter, retrospective, non-comparative observational study included mPAC patients who received nal-IRI plus 5-FU/LV as third- or later-line therapy after disease progression on first-line FOLFIRINOX (FFX) or gemcitabine plus nab-paclitaxel.

Results:

In all, 128 patients who received nal-IRI plus 5-FU/LV beyond second-line treatment between October 2017 and July 2021 were analyzed. Most patients (82%) received nal-IRI plus 5-FU/LV as a third-line treatment. The median overall survival (OS) was 4.9 months and the median progression-free survival (PFS) was 2.4 months. Patients with better Eastern Cooperative Oncology Group (ECOG) performance status experienced significantly longer OS (ECOG 0, 8.7 months; ECOG 1, 4.8 months; ECOG 2, 2.9 months; p < 0.001) and PFS (3.9 months; 2.1 months; 1.5 months; p = 0.019). Patients who had not been previously treated with FFX or had a time to progression of 7 months or more on FFX experienced longer OS and PFS than those who did not (6.1 months and 5.6 versus 4.1 months, p = 0.053; 3.6 months and 2.4 versus 2.1 months, p = 0.002). The most common adverse events were neutropenia (56%) and anemia (51%).

Conclusion:

Our real-world data indicated that nal-IRI plus 5-FU/LV can be effective not only as second-line therapy, but also as third-line or later-line treatment in selected patients. Nal-IRI plus 5-FU/LV may be particularly beneficial for the survival of patients that maintain good general condition or those with favorable prior experience to irinotecan.

Immortal Time Bias in the Analysis of Time-to-Event Data in Orthopedics

Many outcomes in arthroplasty research are analyzed as time-to-event outcomes using survival analysis methods. When comparison groups are defined after a time-delayed exposure or intervention, a period of immortal time arises and can lead to biased results. In orthopedics research, immortal time bias often arises when a minimum amount of follow-up is required for study inclusion or when comparing outcomes in staged bilateral vs unilateral arthroplasty patients. We present an explanation of immortal time and the associated bias, describe how to correctly account for it using proper data preparation and statistical techniques, and provide an illustrative example using real-world arthroplasty data. We offer practical guidelines for identifying and properly handling immortal time to avoid bias. Please visit the followinghttps://youtu.be/58p8w5o-ci4for a video that explains the highlights of the paper in practical terms.

Association Between Testosterone Treatment and Risk of Incident Cardiovascular Events Among US Male Veterans With Low Testosterone Levels and Multiple Medical Comorbidities

Background

Testosterone treatment is common in men, although risks for major cardiovascular events are unclear.

Methods and Results

A study was conducted in US male veterans, aged ≥40 years, with low serum testosterone and multiple medical comorbidities and without history of myocardial infarction, stroke, venous thromboembolism, prostate cancer, or testosterone treatment in the prior year. For the primary outcome, we examined if testosterone treatment was associated with a composite cardiovascular outcome (incident myocardial infarction, ischemic stroke, or venous thromboembolism). Testosterone use was modeled as intramuscular or transdermal and as current use, former use, and no use. Current testosterone users were compared with former users to reduce confounding by indication. The cohort consisted of 204 857 men with a mean (SD) age of 60.9 (9.9) years and 4.7 (3.5) chronic medical conditions. During follow‐up of 4.3 (2.8) years, 12 645 composite cardiovascular events occurred. In adjusted Cox regression analyses, current use of transdermal testosterone was not associated with risk for the composite cardiovascular outcome (hazard ratio [HR], 0.89; 95% CI, 0.76–1.05) in those without prevalent cardiovascular disease, and in those with prevalent cardiovascular disease was associated with lower risk (HR, 0.80; 95% CI, 0.70–0.91). In similar analyses, current use of intramuscular testosterone was not associated with risk for the composite cardiovascular outcome in men without or with prevalent cardiovascular disease (HR, 0.91; 95% CI, 0.80–1.04; HR, 0.98; 95% CI, 0.89–1.09, respectively).

Conclusions

In a large cohort of men without a history of myocardial infarction, stroke, or venous thromboembolism, testosterone treatment was not associated with increased risk for incident composite cardiovascular events.

Adjuvant platinum-based chemotherapy in radically resected adrenocortical carcinoma: a cohort study

BACKGROUND

After radical resection, patients with adrenocortical carcinoma (ACC) frequently experience recurrence and, therefore, effective adjuvant treatment is urgently needed. The aim of the study was to investigate the role of adjuvant platinum-based therapy.

METHODS

In this retrospective multicentre cohort study, we identified patients treated with adjuvant platinum-based chemotherapy after radical resection and compared them with patients without adjuvant chemotherapy. Recurrence-free and overall survival (RFS/OS) were investigated in a matched group analysis and by applying a propensity score matching using the full control cohort (n = 268). For both approaches, we accounted for immortal time bias.

RESULTS

Of the 31 patients in the platinum cohort (R0 n = 25, RX n = 4, R1 n = 2; ENSAT Stage II n = 11, III n = 16, IV n = 4, median Ki67 30%, mitotane n = 28), 14 experienced recurrence compared to 29 of 31 matched controls (median RFS after the landmark at 3 months 17.3 vs. 7.3 months; adjusted HR 0.19 (95% CI 0.09-0.42; P < 0.001). Using propensity score matching, the HR for RFS was 0.45 (0.29-0.89, P = 0.021) and for OS 0.25 (0.09-0.69; P = 0.007).

CONCLUSIONS

Our study provides the first evidence that adjuvant platinum-based chemotherapy may be associated with prolonged recurrence-free and overall survival in patients with ACC and a very high risk for recurrence.

Drug Repurposing, an Attractive Strategy in Pancreatic Cancer Treatment: Preclinical and Clinical Updates

Pancreatic cancer (PC) is one of the deadliest malignancies worldwide, since patients rarely display symptoms until an advanced and unresectable stage of the disease. Current chemotherapy options are unsatisfactory and there is an urgent need for more effective and less toxic drugs to improve the dismal PC therapy. Repurposing of non-oncology drugs in PC treatment represents a very promising therapeutic option and different compounds are currently being considered as candidates for repurposing in the treatment of this tumor. In this review, we provide an update on some of the most promising FDA-approved, non-oncology, repurposed drug candidates that show prominent clinical and preclinical data in pancreatic cancer. We also focus on proposed mechanisms of action and known molecular targets that they modulate in PC. Furthermore, we provide an explorative bioinformatic analysis, which suggests that some of the PC repurposed drug candidates have additional, unexplored, oncology-relevant targets. Finally, we discuss recent developments regarding the immunomodulatory role displayed by some of these drugs, which may expand their potential application in synergy with approved anticancer immunomodulatory agents that are mostly ineffective as single agents in PC.

What Is the Optimal Duration of Adjuvant Mitotane Therapy in Adrenocortical Carcinoma? An Unanswered Question

A relevant issue on the treatment of adrenocortical carcinoma (ACC) concerns the optimal duration of adjuvant mitotane treatment. We tried to address this question, assessing whether a correlation exists between the duration of adjuvant mitotane treatment and recurrence-free survival (RFS) of patients with ACC. We conducted a multicenter retrospective analysis on 154 ACC patients treated for ≥12 months with adjuvant mitotane after radical surgery and who were free of disease at the mitotane stop. During a median follow-up of 38 months, 19 patients (12.3%) experienced recurrence. We calculated the RFS after mitotane (RFSAM), from the landmark time-point of mitotane discontinuation, to overcome immortal time bias. We found a wide variability in the duration of adjuvant mitotane treatment among different centers and also among patients cared for at the same center, reflecting heterogeneous practice. We did not find any survival advantage in patients treated for longer than 24 months. Moreover, the relationship between treatment duration and the frequency of ACC recurrence was not linear after stratifying our patients in tertiles of length of adjuvant treatment. In conclusion, the present findings do not support the concept that extending adjuvant mitotane treatment over two years is beneficial for ACC patients with low to moderate risk of recurrence.

Prophylactic placement of inferior vena cava filters and the risk of death or venous thromboembolism in severe trauma patients: a retrospective study comparing two hospitals with different approaches

Background

Prophylactic use of inferior vena cava filters to prevent pulmonary embolism in trauma is controversial. The practice varies between hospitals and countries, in part due to conflicting evidence and guidelines.

Purpose

To compare the effects of pulmonary embolism, deep venous thrombosis and mortality in two hospitals using prophylactic inferior vena cava filter placement or prophylactic anticoagulation alone.

Material and Methods

Patients presenting with severe trauma were recruited from two level-1 trauma centres between January 2008 and December 2013. Recruited patients from an US hospital having prophylactic inferior vena cava filter inserted were compared to a Scandinavian hospital using prophylactic anticoagulation alone. Inclusion criteria were age >15 years, Injury Severity Score >15 and survival >24 h after hospital admission. Patients with venous thromboembolism diagnosed prior to inferior vena cava filter placement were excluded. A Cox proportional hazard regression model was used with adjustment for immortal time bias and predictor variables.

Results

In total, 951 patients were reviewed, 282 from an US hospital having inferior vena cava filters placed and 669 from a Scandinavian hospital without inferior vena cava filters. The mean age was 45.9 vs. 47.4 years and the mean Injury Severity Score was 29.8 vs. 25.9, respectively. Inferior vena cava filter placement was not associated with the hazard of pulmonary embolism (Hazard ratio=0.43; 95% confidence interval (CI) 0.12, 1.45; P=0.17) or mortality (Hazard ratio=1.16; 95% CI 0.70, 1.95; P=0.56). However, an increased rate of deep venous thrombosis was observed with inferior vena cava filters in place (Hazard ratio=3.75; 95% CI 1.68, 8.36; P=0.001).

Conclusion

In severely injured trauma patients, prophylactic inferior vena cava filter placement was not associated with pulmonary embolism or mortality. However, inferior vena cava filters were associated with increased rate of deep venous thrombosis.