Large Differences in Survival According to Hospital Risk-Adjusted Margin Positivity Rate Status in Rectal Cancer Surgery


Key Points

  • Treatment at higher-performing hospitals was associated with reductions in 5-year mortality of 31% vs hospitals performing at expected levels and 39% vs poorer-performing hospitals.
  • Treatment at poorer-performing hospitals was associated with an increase of 12% in 5-year mortality vs hospitals performing at expected levels.

Risk-adjusted margin positivity rate has been suggested for use as a rectal cancer surgery quality metric. In an observational cohort study reported in the Journal of Clinical Oncology, Massarweh et al from The University of Texas MD Anderson Cancer Center identified risk-adjusted margin positivity rate status of U.S. hospitals at which rectal cancer surgery was performed and found marked differences in survival according to such status.

Study Details

In the study, patients undergoing rectal cancer surgery between 2003 and 2005 were identified from the National Cancer Data Base. Hospital performance with regard to surgical margin positivity was categorized as low outlier (better than expected), high outlier (worse than expected), or nonoutlier (expected) using standard observed-to-expected methodology. Logistic regression used to calculate the expected number of margin positive events for each hospital and the observed-to-expected ratio and P value for each hospital were calculated by dividing the observed number of events by model-derived expected number of events.

Risk-Adjusted Margin Positivity Rate Status

A total of 32,354 patients (mean age, 64 years; 57% male; 87% white) were treated at 1,349 hospitals. Among the hospitals, 4.9% were high outliers and 0.7% were low outliers. Among patients, 5.6% were treated at high-outlier hospitals (worse than expected) and 3.0% were treated at low-outlier hospitals (better than expected). The overall rate of margin positivity was 5.3%, including 17.1% in high outliers, 4.8% in nonoutliers, and 0.8% in low outliers (P < .001).

Factors Associated With Risk-Adjusted Margin Positivity Rate Status

Overall, 29.8% of patients were treated at academic institutions, which accounted for 26.0% of high-outlier hospitals, 28.2% of nonoutliers, and 84.3% of low outliers (P < .001 for trend), and 53.4% received treatment at high-volume centers, which accounted for 51.8% of high-outlier hospitals, 52.1% of nonoutliers, and 96.7% of low outliers (P < .001 for trend). Totals of 46.8% of patients had at least 12 lymph nodes evaluated, and 25.3% received neoadjuvant radiation therapy. Evaluation of at least 12 nodes occurred in 46.4% of patients treated at high-outlier hospitals, 46.3% of those treated at nonoutliers, and 60.8% of those treated at low outliers (P < .001 for trend), and neoadjuvant radiation therapy was received by 23.5%, 23.9%, and 34.6%, respectively (P < .001 for trend).

Similarly, there were significant trends favoring low-outlier hospitals for rates of sphincter preservation (69.4%, 70.9%, and 75.0%, respectively, P = .02 for trend), lower readmission rates (11.0%, 9.7%, and 8.0%, respectively, P = .01 for trend), and lower 30-day mortality rates (2.2%, 1.8%, and 0.7%, P = .007) for trend.

5-Year Overall Survival

Unadjusted 5-year overall survival was 79.9% at low-outlier hospitals, 68.9% at nonoutliers, and 64.9% at high outliers (P < .001), with a significant difference persisting when T4 tumors were excluded from analysis (81.1%, 70.4%, and 66.9%, P < .001).

On multilevel modeling adjusting for age, sex, race, year of diagnosis, income, education, insurance, rurality, comorbidity, disease stage, and tumor size, histology, grade, and location,  patients treated at low-outlier hospitals had a 31% reduction in risk of death at 5 years vs those treated at nonoutlier hospitals (hazard ratio [HR] = 0.69, 95% confidence interval [CI] = 0.57–0.83) and a 39% reduction vs those treated at high outliers (HR = 0.61, 95% CI = 0.50–0.75). Patients treated at high-outlier hospitals had a significant 12% increase in risk of death at 5 years vs those treated at nonoutliers (HR = 1.12, 95% CI = 1.03–1.23).

In an analysis excluding T4 tumors, treatment at a low outlier was associated with a significant 30% reduction in risk of death vs treatment at nonoutliers and a significant 38% reduction in risk vs treatment at high outliers, and treatment in a high outlier was associated with a significant 11% increase in risk vs those treated at nonoutliers.

The investigators concluded, “Hospital [risk-adjusted margin positivity rate] outlier status is a rectal cancer surgery composite metric that reliably captures hospital quality across all levels of care and could be integrated into existing quality improvement initiatives for hospital performance.”

George J. Chang, MD, MS, of The University of Texas MD Anderson Cancer Center, is the corresponding author for the Journal of Clinical Oncology article.

The study was supported by grants from the National Institutes of Health/National Cancer Institute. The authors indicated no potential conflicts of interest.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.