Effect of a FIT-Based Colorectal Cancer Screening Program on Mortality Estimated by the Regression Discontinuity Design

The fecal immunochemical test (FIT) has been implemented in colorectal cancer (CRC) screening programs, but effect evaluations are lacking. We evaluated the effect of a positive FIT on all-cause and CRC mortality using the regression discontinuity design. The Danish CRC screening program invites all residents 50-74 years old, using a 20-μg hemoglobin/g feces cutoff for colonoscopy referral. In this cohort study, we followed all first-time screening participants from 2014-2019 until 2020. We estimated the local effect of screening results, of just above the cutoff vs. just below, as hazard ratios (HRs) between models fitted at each side of the cutoff. We conducted the analysis within a narrow hemoglobin range (≥17 and <23, n = 16,428) and a wider range (≥14 and <26, n = 35,353). Those screened just above the cutoff had lower all-cause mortality compared with below (HR = 0.87, 95% confidence interval: 0.69; 1.10), estimated from the narrow range. The CRC mortality analysis had few outcomes. In the wider range, those with a FIT just above the cutoff had a lower hazard of CRC mortality compared with just below the cutoff (HR = 0.49, 95% confidence interval: 0.17; 1.41). A FIT result just above the cutoff, leading to referral to colonoscopy, pointed towards reduced all-cause and CRC mortality compared with just below the cutoff.

The effect of medicare and screening guidelines on colorectal cancer outcomes

BACKGROUND

Colorectal cancer screening has been shown effective at reducing stage at presentation, but there is differential uptake of screening based on insurance status. We sought to determine the population-level effect of Medicare and screening guidelines on colorectal screening by race and region.

METHODS

Data on Black and white patients with colorectal cancer were obtained from the SEER database. Regression discontinuity was used to assess the causal effect of near-universal health insurance (represented by age 65) and United States Preventive Services Task Force guidelines (age 50) on the proportion of people presenting at advanced stage. This was stratified by race and region.

RESULTS

In the Southern United States, Black patients saw a significant decrease in advanced stage at presentation at age 65 (coefficient -0.12, p = 0.003), while white patients did not (coefficient -0.03, p = 0.09). At age 50, neither Black (coefficient 0.09, p = 0.10) nor white patients (coefficient -0.04, p = 0.1) saw a significant decrease in advanced stage. In the Western U.S., neither Black (coefficient 0.02, p = 0.72) or white patients (coefficient -0.02, p = 0.09) saw a significant decrease in advanced stage at age 65; however, both Black (coefficient -0.20, p = 0.008) and white patients (coefficient -0.05, p = 0.03) saw a significant decrease at age 50.

CONCLUSIONS

Our data highlight the significant impact that near-universal insurance has on reducing colorectal cancer stage at presentation in areas with poor baseline insurance coverage, particularly for Black patients. To reduce disparities in advanced stage at presentation for colorectal cancer, state-level insurance coverage should be addressed.

Behaviour within a Clinical Trial and Implications for Mammography Guidelines

Mammography guidelines have weakened in response to evidence that mammograms diagnose breast cancers that would never eventually cause symptoms, a phenomenon called "overdiagnosis." Given concerns about overdiagnosis, instead of recommending mammograms, US guidelines encourage women aged 40-49 to get them as they see fit. To assess whether these guidelines target women effectively, I propose an approach that examines mammography behavior within an influential clinical trial that followed participants long enough to find overdiagnosis. I find that women who are more likely to receive mammograms are healthier and have higher socioeconomic status. More importantly, I find that the 20-year level of overdiagnosis is at least 3.5 times higher among women who are most likely to receive mammograms. At least 36% of their cancers are overdiagnosed. These findings imply that US guidelines encourage mammograms among healthier women who are more likely to be overdiagnosed by them. Guidelines in other countries do not.

Effects of lower screening activity during the COVID-19 pandemic on breast cancer patient pathways: Evidence from the age cut-off of organized screening

We examined the effects of the COVID-19 pandemic on the screening, diagnosis and treatment of breast cancer in Hungary based on administrative data until June 2021, covering three pandemic waves. After correcting for trend and seasonality, the number of mammography examinations decreased by 68% in 2020q2, was around its usual level in 2020q3 and was reduced by 20-35% throughout 2020q4-2021q2. The reduction was caused by a combination of supply-side (temporary suspensions of screening) and demand-side (lower screening participation during the pandemic waves) factors. The number of new breast cancer diagnoses and mastectomy surgeries responded with a lag, and were below their usual level by 15-30% in all quarters between 2020q2 and 2021q2, apart from 2020q4, when there was no significant difference. Using a regression discontinuity framework, we found that the partial mastectomy rate (indicative of early diagnosis) dropped more substantially in 2020q2 in the 61-65 years old age group that was just below the age cut-off of organized screening than in the 66-70 years old age group, and this difference was partially offset in 2021q1. We suggest that policymakers need to motivate the target population (by providing both information and incentives) to catch up on missed screenings.

Effects of the Colorectal Cancer Control Program

Although colorectal cancer (CRC) screening is highly effective, screening rates lag far below recommended levels, particularly for low-income people. The Colorectal Cancer Control Program (CRCCP) funded $100 million in competitively awarded grants to 25 states from 2009-2015 to increase CRC screening rates among low-income, uninsured populations, in part by directly providing and paying for screening services. Using data from the 2001-2015 Behavioral Risk Factor Surveillance System (BRFSS) and a difference-in-differences strategy, we find no effects of CRCCP on the use of relatively cheap fecal occult blood tests (FOBT). We do, however, find that the CRCCP significantly increased the likelihood that uninsured 50-64-year-olds report ever having a relatively expensive endoscopic CRC screening (sigmoidoscopy or colonoscopy) by 2.9 percentage points, or 10.7%. These effects are larger for women, minorities, and individuals who did not undertake other types of preventive care. We do not find that the CRCCP led to significant changes in CRC cancer detection. Our results indicate that the CRCCP was effective at increasing CRC screening rates among the most vulnerable.

The Effect Of The Affordable Care Act On Cancer Detection Among The Near-Elderly

During the period 2014-16 the Affordable Care Act (ACA) dramatically reduced rates of uninsurance and underinsurance in the United States. In this study we estimated the effects of these coverage increases on cancer detection among the near-elderly population (ages 60-64). Using 2010-16 Surveillance, Epidemiology, and End Results (SEER) Program data, we estimated that the ACA increased cancer detection among this population. We found that 45 percent of the jump in cancer detection that occurs when people reach Medicare eligibility age was eliminated by the ACA coverage expansions. The ACA coverage expansions had large effects on cancers with and without routine screening tests, and 68 percent of newly detected cancers were early- and middle-stage cancers. In addition, the empirical strategy used to identify the effects of the ACA on cancer detection confirmed the role of health insurance as the key mechanism to explain Medicare's effects on health care use and health outcomes as described in the prior literature. Our results highlight the importance of the ACA, Medicare, and health insurance coverage generally for disease detection.

Screening and Selection: The Case of Mammograms

We analyze selection into screening in the context of recommendations that breast cancer screening start at age 40. Combining medical claims with a clinical oncology model, we document that compliers with the recommendation are less likely to have cancer than younger women who select into screening or women who never screen. We show this selection is quantitatively important: shifting the recommendation from age 40 to 45 results in three times as many deaths if compliers were randomly selected than under the estimated patterns of selection. The results highlight the importance of considering characteristics of compliers when making and designing recommendations.

Strategies for evaluating the assumptions of the regression discontinuity design: a case study using a human papillomavirus vaccination programme

Background

The regression discontinuity design (RDD) is a quasi-experimental approach used to avoid confounding bias in the assessment of new policies and interventions. It is applied specifically in situations where individuals are assigned to a policy/intervention based on whether they are above or below a pre-specified cut-off on a continuously measured variable, such as birth date, income or weight. The strength of the design is that, provided individuals do not manipulate the value of this variable, assignment to the policy/intervention is considered as good as random for individuals close to the cut-off. Despite its popularity in fields like economics, the RDD remains relatively unknown in epidemiology where its application could be tremendously useful.

Methods

In this paper, we provide a practical introduction to the RDD for health researchers, describe four empirically testable assumptions of the design and offer strategies that can be used to assess whether these assumptions are met in a given study. For illustrative purposes, we implement these strategies to assess whether the RDD is appropriate for a study of the impact of human papillomavirus vaccination on cervical dysplasia.

Results

We found that, whereas the assumptions of the RDD were generally satisfied in our study context, birth timing had the potential to confound our effect estimate in an unexpected way and therefore needed to be taken into account in the analysis.

Conclusions

Our findings underscore the importance of assessing the validity of the assumptions of this design, testing them when possible and making adjustments as necessary to support valid causal inference.

When public health intervention is not successful: Cost sharing, crowd-out, and selection in Korea's National Cancer Screening Program

This study investigates the impact of and behavioral responses to cost sharing in Korea's National Cancer Screening Program, which provides free stomach and breast cancer screenings to those with an income below a certain cutoff. Free cancer screening substantially increases the screening take up rate, yielding more cancer detections. However, the increase in cancer detection is quickly crowded out by cancer detection through other channels such as diagnostic testing and private cancer screening. Further, compliers are much less likely to have cancer than never takers. Crowd-out and selection help explain why the program has been unable to reduce cancer mortality.