Evaluating comparative effectiveness with observational data: endoscopic ultrasound and survival in pancreatic cancer

Use of endoscopic ultrasound for pancreatic cancer from 2000 to 2016

Background and study aims  Pancreatic cancer (PC) is the fourth most common cause of cancer death in the United States. Previous studies have suggested a survival benefit for endoscopic ultrasound (EUS), an important tool for diagnosis and staging of PC. This study aims to describe EUS use over time and identify factors associated with EUS use and its impact on survival. Patients and methods  This was a retrospective review of the Surveillance, Epidemiology and End Results (SEER) database linked with Medicare claims. EUS use, clinical and demographic characteristics were evaluated. Chi-squared analysis, Cochran-Armitage test for trend, and logistic regression were used to identify associations between sociodemographic and clinical factors and EUS. Kaplan-Meier and Cox proportional hazard ratios were used for survival analysis. Results  EUS use rose during the time period, from 7.4 % of patients in 2000 to 32.4 % in 2015. Patient diversity increased, with a rising share of older, non-White patients with higher Charlson comorbidity scores. Both clinical (receipt of other therapies, PC stage) and nonclinical factors (region of country, year of diagnosis) were associated with receipt of EUS. While EUS was associated with a survival improvement early in the study period, this effect did not persist for PC patients diagnosed in 2012 to 2015 (median survival 3 month ± standard deviation [SD] 9.8 months without vs. 4 months ± SD 8 months with EUS). Conclusions  Our data support previous studies, which suggest a survival benefit for EUS when it was infrequently used, but finds that benefit was attenuated as EUS became more widely available.

Comparative Effectiveness of Chemotherapy, Rituximab, and Bendamustine in Medicare Beneficiaries With Mantle-Cell Lymphoma

BACKGROUND

Over the past 2 decades, rituximab, bortezomib, and bendamustine have been approved to treat mantle-cell lymphoma (MCL). To date, few studies have evaluated the comparative effectiveness of these novel agents. Therefore, this study evaluated the comparative effectiveness of those novel agents in elderly patients newly diagnosed with MCL.

PATIENTS AND METHODS

All newly diagnosed MCL patients aged 66 or older were identified from Surveillance, Epidemiology, and End Results Program (SEER)-Medicare databases from 1999 to 2013. Patients were categorized into 4 groups on the basis of their first-line treatment regimens: chemotherapy alone, rituximab ± chemotherapy, bortezomib ± chemotherapy, and bendamustine ± chemotherapy. Multivariable proportional hazard regressions with 1-year follow-up from treatment were performed to compare the all-cause, MCL-specific, and noncancer mortality rates. Sensitivity analyses using propensity score-adjusted and instrumental variable-adjusted regressions were also conducted.

RESULTS

A total of 1215 MCL patients were included. The bortezomib group was not included in the primary analyses because of the small sample size (n = 24). On multivariable analyses, the rituximab group showed significant decrease in both 1-year all-cause mortality (hazard ratio [HR] = 0.38, 95% confidence interval [CI], 0.25-0.59) and MCL-specific mortality (HR = 0.38; 95% CI, 0.24-0.60) compared to the chemotherapy-alone group. The bendamustine group showed significant decrease in 1-year MCL-specific mortality (HR = 0.49; 95% CI, 0.24-0.99) compared to the chemotherapy-alone group. The results from sensitivity analyses were similar to those from primary analyses.

CONCLUSION

For elderly patients with newly diagnosed MCL, rituximab-based regimen and bendamustine-based regimen as first-line treatment significantly decreased 1-year mortality rates compared to chemotherapy alone.

Medicare savings from conservative management of low back pain

OBJECTIVES

Low back pain (LBP) is a common and expensive clinical problem, resulting in tens of billions of dollars of direct medical expenditures in the United States each year. Although expensive imaging tests are commonly used, they do not improve outcomes when used in the initial management of idiopathic LBP. We estimated 1-year medical costs associated with early imaging of Medicare beneficiaries with idiopathic LBP.

STUDY DESIGN

We used a 5% random sample of Medicare fee-for-service enrollees between 2006 and 2010 to determine 12-month costs following a diagnosis of idiopathic LBP. We analyzed costs of care and patient outcomes according to whether or not the patients had been referred for early imaging following their initial diagnosis.

METHODS

We employed an instrumental variables analysis using risk-adjusted physician-level propensity to order imaging for patients without LBP as an instrument for imaging use among patients with LBP. We selected this approach to adjust for confounding by indication when estimating the relative costs of early imaging of LBP compared with conservative management.

RESULTS

Early imaging is strongly associated with increased costs of care in the first year following LBP diagnosis. Patients receiving an early magnetic resonance imaging scan accrued $2500 more in Medicare expenditures than conservatively managed patients, and patients who received computed tomography accrued $19,900 more.

CONCLUSIONS

Medicare beneficiaries with low-risk LBP frequently receive early imaging studies. Early imaging was associated with greater long-term costs than a conservative diagnostic strategy; Medicare expenditures could be reduced by $362 million annually by managing newly diagnosed LBP in accordance with clinical guidelines.

A systematic review of instrumental variable analyses using geographic region as an instrument

BACKGROUND

Instrumental variables analysis is a methodology to mitigate the effects of measured and unmeasured confounding in observational studies of treatment effects. Geographic area is increasingly used as an instrument.

METHODS

We conducted a literature review to determine the properties of geographic area in studies of cancer treatments. We identified cancer studies performed in the United States which incorporated instrumental variable analysis with area-wide treatment rate within a geographic region as the instrument. We assessed the degree of treatment variability between geographic regions, assessed balance of measured confounders afforded by geographic area and compared the results of instrumental variable analysis to those of multivariable methods.

RESULTS

Geographic region as an instrument was relatively common, with 22 eligible studies identified, many of which were published in high-impact journals. Treatment rates did not vary greatly by geographic region. Covariates were not balanced by the instrument in the majority of studies. Eight out of eleven studies found statistically significant effects of treatment on multivariable analysis but not for instrumental variables, with the central estimates of the instrumental variables analysis generally being closer to the null.

CONCLUSIONS

We recommend caution and an investigation of IV assumptions when considering the use of geographic region as an instrument in observational studies of cancer treatments. The value of geographic region as an instrument should be critically evaluated in other areas of medicine.

Surveillance and Outcomes of Nonresected Presumed Branch-Duct Intraductal Papillary Mucinous Neoplasms: A Meta-analysis

OBJECTIVES

Guidelines regarding the surveillance of intraductal papillary mucinous neoplasms (IPMNs) are controversial because of uncertain risk of malignancy, agnosticism regarding the use of endoscopic ultrasound, and their recommendation to stop surveillance after 5 years. We present a systematic review and meta-analysis of the risk of malignancy and other end points and estimate the value of endoscopic ultrasound for surveillance.

METHODS

We systematically searched MEDLINE for studies with a cohort of patients with presumed branch-duct IPMN who initially were managed nonsurgically. Data regarding study characteristics, surveillance, and outcomes were extracted. Incidence rates of morphologic progression, malignancy, surgery, and death were calculated with a random effects model.

RESULTS

Twenty-four studies with 3440 patients and 13,097 patient-years of follow-up were included. Rates of morphologic progression, surgery, malignancy, and death were 0.0379, 0.0250, 0.0098, and 0.0043 per patient-year, respectively. Endoscopic ultrasound was not associated with significantly different rates of these outcomes.

CONCLUSIONS

The risk of malignancy calculated in this study was low and in line with recent systematic reviews. Endoscopic ultrasound does not have marginal use in surveillance. Given the limitations of a systematic review of nonrandomized studies, further studies are needed to determine the optimal surveillance of branch-duct IPMNs.

Utilization of preoperative endoscopic ultrasound for pancreatic adenocarcinoma

BACKGROUND

Endoscopic ultrasound (EUS) is used for pancreatic adenocarcinoma staging and obtaining a tissue diagnosis. The objective was to determine patterns of preoperative EUS and the impact on downstream treatment.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) Medicare-linked database was used to identify patients with pancreatic adenocarcinoma. The staging period was the first staging procedure within 6 months of surgery until surgery. Logistic regression was used to determine factors associated with preoperative EUS. The main outcome was EUS in the staging period, with secondary outcomes including number of staging tests and time to surgery.

RESULTS

2782 patients were included, 56% were treated at an academic hospital (n = 1563). 1204 patients underwent EUS (43.3%). The factors most associated with receipt of EUS were: earlier year of diagnosis, SEER area, and a NCI or academic hospital (all p < 0.0001). EUS was associated with a longer time to surgery (17.8 days; p < 0.0001), and a higher number of staging tests (40 tests/100 patients; p < 0.0001).

CONCLUSIONS

Factors most associated with receipt of EUS are geographic, temporal, and institutional, rather than clinical/disease factors. EUS is associated with a longer time to surgery and more preoperative testing, and additional study is needed to determine if EUS is overused.

Evaluating different physician's prescribing preference based instrumental variables in two primary care databases: a study of inhaled long-acting beta2-agonist use and the risk of myocardial infarction

PURPOSE

Instrumental variable (IV) analysis with physician's prescribing preference (PPP) as IV is increasingly used in pharmacoepidemiology. However, it is unclear whether this IV performs consistently across databases. We aimed to evaluate the validity of different PPPs in a study of inhaled long-acting beta2-agonist (LABA) use and myocardial infarction (MI).

METHODS

Information on adults with asthma and/or COPD and at least one prescription of beta2-agonist, or muscarinic antagonist was extracted from the CPRD (UK) and the Mondriaan (Netherlands) databases. LABA exposure was considered time-fixed or time-varying. We measured PPPs using previous LABA prescriptions of physicians or proportion of LABA prescriptions per practice. Correlation (r) and standardized difference (SDif) were used to assess assumption of IV analysis.

RESULTS

For time-fixed LABA, the IV based on 10 previous prescriptions outperformed the other IVs regarding strength of the IV (r ≥ 0.15) and balance of confounders between IV categories (SDif < 0.10). None of the IVs we considered appeared to be valid for time-varying LABA. In CPRD (n = 490,499), which included approximately 18 times more subjects than Mondriaan (n = 27,459), IVs appeared more valid. LABA was not associated with MI; hazard ratios ranged from 0.86 to 1.18 for conventional analysis, and from 0.61 to 1.24 for the IV analyses with apparent valid IVs.

CONCLUSIONS

The validity of physician's prescribing preference as IV strongly depends on how this IV is defined and in which database it is applied. Hence, general recommendations cannot be made, other than to generate several plausible IVs, assess their validity, and report the estimate(s) from apparently valid IVs.

Primary Tumor Resection Is Associated with Improved Survival in Stage IV Colorectal Cancer: An Instrumental Variable Analysis

Primary tumor resection (PTR) is recommended for patients with unresectable stage IV colorectal cancer (CRC) who present with symptoms related to their primary tumor. However, the survival benefit of PTR for asymptomatic patients is controversial. We investigated the change in PTR rates and the contribution of PTR to survival in patients with unresectable stage IV CRC over the past two decades in the United States. Clinicopathological factors and long-term survival were compared for 44 514 patients diagnosed with unresectable stage IV CRC from January 1, 1988, through December 31, 2010, who had or had not undergone PTR. Multivariable Cox regression and the instrumental variable method were used to identify independent factors for survival. Of the 44 514 patients with unresectable stage IV CRC, 27 931 (62.7%) had undergone PTR. The annual rate of PTR decreased from 74.4% to 50.2% diagnosed in 1988 and 2010, and the median overall survival increased for both PTR and non-PTR patients. Instrumental variable analyses revealed that PTR was associated with better overall, cancer-specific, and other-cause survival of patients with unresectable stage IV CRC.

Performing both propensity score and instrumental variable analyses in observational studies often leads to discrepant results: a systematic review

OBJECTIVES

Propensity score (PS) and instrumental variable (IV) are analytical techniques used to adjust for confounding in observational research. More and more, they seem to be used simultaneously in studies evaluating health interventions. The present review aimed to analyze the agreement between PS and IV results in medical research published to date.

STUDY DESIGN AND SETTING

Review of all published observational studies that evaluated a clinical intervention using simultaneously PS and IV analyses, as identified in MEDLINE and Web of Science.

RESULTS

Thirty-seven studies, most of them published during the previous 5 years, reported 55 comparisons between results from PS and IV analyses. There was a slight/fair agreement between the methods [Cohen's kappa coefficient = 0.21 (95% confidence interval: 0.00, 0.41)]. In 23 cases (42%), results were nonsignificant for one method and significant for the other, and IV analysis results were nonsignificant in most situations (87%).

CONCLUSION

Discrepancies are frequent between PS and IV analyses and can be interpreted in various ways. This suggests that researchers should carefully consider their analytical choices, and readers should be cautious when interpreting results, until further studies clarify the respective roles of the two methods in observational comparative effectiveness research.

Pancreatectomy predicts improved survival for pancreatic adenocarcinoma: results of an instrumental variable analysis

BACKGROUND AND OBJECTIVE

Pancreatic resection is the standard treatment option for patients with stage I/II pancreatic ductal adenocarcinoma (PDA), yet many studies demonstrate low rates of resection. The objective of this study was to evaluate whether increasing resection rates would result in an increase in average survival in patients with stage I/II PDA.

METHODS

SEER (Surveillance, Epidemiology, and End Results) data were analyzed for patients with stage I/II pancreatic head cancers treated from 2004 to 2009. Pancreatectomy rates were examined within Health Service Areas (HSAs) across 18 SEER regions. An instrumental variable analysis was performed, using HSA rates as an instrument, to determine the impact of increasing resection rates on survival.

RESULTS

Pancreatectomy was performed in 4322 of 8323 patients evaluated with stage I/II PDA (overall resection rate = 51.9%). The resection rate across HSAs ranged from an average of 38.6% (lowest quintile) to 67.3% (highest quintile). Median survival was improved in HSAs with higher resection rates. Instrumental variable analysis revealed that, for patients whose treatment choices were influenced by rates of resection in their geographic region, pancreatectomy was associated with a statistically significant increase in overall survival.

CONCLUSIONS

When controlling for confounders using instrumental variable analysis, pancreatectomy is associated with a statistically significant increase in survival for patients with resectable PDA. On the basis of these results, if resection rates were to increase in select patients, then average survival would also be expected to increase. It is important that this information be provided to physicians and patients so that they can properly weigh the risks and advantages of pancreatectomy as treatment of PDA.