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National trends in hospital-acquired preventable adverse events after major cancer surgery in the USA

Objectives While multiple studies have demonstrated variations in the quality of cancer care in the USA, payers are increasingly assessing structure-level and process-level measures to promote quality improvement. Hospital-acquired adverse events are one such measure and we examine their national trends after major cancer surgery. Design Retrospective, cross-sectional analysis of a weighted-national estimate from the Nationwide Inpatient Sample (NIS) undergoing major oncological procedures (colectomy, cystectomy, oesophagectomy, gastrectomy, hysterectomy, lung resection, pancreatectomy and prostatectomy). The Agency for Healthcare Research and Quality Patient Safety Indicators (PSIs) were utilised to identify trends in hospital-acquired adverse events. Setting Secondary and tertiary care, US hospitals in NIS Participants A weighted-national estimate of 2 508 917 patients (>18 years, 1999–2009) from NIS. Primary outcome measures Hospital-acquired adverse events. Results 324 852 patients experienced ≥1-PSI event (12.9%). Patients with ≥1-PSI experienced higher rates of in-hospital mortality (OR 19.38, 95% CI 18.44 to 20.37), prolonged length of stay (OR 4.43, 95% CI 4.31 to 4.54) and excessive hospital-charges (OR 5.21, 95% CI 5.10 to 5.32). Patients treated at lower volume hospitals experienced both higher PSI events and failure-to-rescue rates. While a steady increase in the frequency of PSI events after major cancer surgery has occurred over the last 10 years (estimated annual % change (EAPC): 3.5%, p<0.001), a concomitant decrease in failure-to-rescue rates (EAPC −3.01%) and overall mortality (EAPC −2.30%) was noted (all p<0.001). Conclusions Over the past decade, there has been a substantial increase in the national frequency of potentially avoidable adverse events after major cancer surgery, with a detrimental effect on numerous outcome-level measures. However, there was a concomitant reduction in failure-to-rescue rates and overall mortality rates. Policy changes to improve the increasing burden of specific adverse events, such as postoperative sepsis, pressure ulcers and respiratory failure, are required.


GENERAL COMMENTS
In the current manuscript Sukumar et al. undertook a national assessment of the quality of major surgical oncology care within a standardized framework of preventable adverse events to examine trends in patient safety within the United States. The authors also evaluated the hypothesis explaining the volume-complicationmortality relationship, which states that higher mortality rates for patients undergoing surgery at lowvolume hospitals is preferentially explained by higher failure-to-rescue rates. The results of the current analyses demonstrates there has been a substantial increase in the national frequency of potentially avoidable adverse-events after major cancer surgery, while there was a concomitant reduction in failure-to-rescue rates and overall-mortality rates. These observations seem to be related with hospital volume.
The authors should be applauded for their effort to systematically analyze the outcomes of 8 major cancer surgeries within the United States. Overall the manuscript is well written, the methodology appropriate, and the results clearly explained. However, it would be of interest to the reviewer to better understand why the rate of adverse outcomes is increasing through years. With the improvements of surgical techniques, one would expect a decrease of post-operative complications. Accordingly, an hypothesis for this apparent "paradox" should be stated in the discussion section.

GENERAL COMMENTS
This is an excellent study that I honestly do not have much to add. It is extremely well written and comprehensive analysis of trends in preventable events following cancer surgery. It provides enlightening statistics that lead one to ponder who to improve care for our patients. Additionally, it does pose questions regarding CMS' potential policy of penalizing institutions for increased mortality/complication rate when realistically a higher failure-torescue rate seems more appropriate.
My one comment would be to see if the authors could add surgeon volume to the analysis. I understand that this may be beyond the scope of an already comprehensive work, however I wonder if they would explore this in the future of if they already have. The graphs are difficult to read and need a different scale or format to be clearer. Can authors comment on the impact of cancer center accreditation, hospital volume of surgery and present on admission diagnoses. Otherwise, paper is well written and conclusions sound.

GENERAL COMMENTS
The paper is a retrospective cross-sectional. The objective of the paper is to estimate Hospital-acquired-adverse events after major cancer surgery.
The introduction is good and talks about the fact of multiple studies have demonstrated that significant variation exists in cancer incidence rates and in access to quality cancer care, but variations in the actual quality of surgical oncology care remain unclear.
About methodology, the variables are correct defined. The statistical analysis is the suitable one. The statistical meaning of the results is defined. The information of the results answers to the aims of the study and reflects the findings more relevant. The presentation is clear and suitable. It seems to me a good manuscript, correctly developed and with a suitable methodology, and that it supposes an interesting contribution to the knowledge of the health quality improvement.

VERSION 1 -AUTHOR RESPONSE
Reviewer: Marco Bianchi, MD; San Raffaele hospital, Department of Urology; Urological Research Institute; Milan; Italy In the current manuscript Sukumar et al. undertook a national assessment of the quality of major surgical oncology care within a standardized framework of preventable adverse events to examine trends in patient safety within the United States. The authors also evaluated the hypothesis explaining the volume-complication-mortality relationship, which states that higher mortality rates for patients undergoing surgery at lowvolume hospitals is preferentially explained by higher failure-to-rescue rates. The results of the current analyses demonstrates there has been a substantial increase in the national frequency of potentially avoidable adverse-events after major cancer surgery, while there was a concomitant reduction in failure-to-rescue rates and overall-mortality rates. These observations seem to be related with hospital volume.
The authors should be applauded for their effort to systematically analyze the outcomes of 8 major cancer surgeries within the United States. Overall the manuscript is well written, the methodology appropriate, and the results clearly explained. However, it would be of interest to the reviewer to better understand why the rate of adverse outcomes is increasing through years. With the improvements of surgical techniques, one would expect a decrease of post-operative complications. Accordingly, an hypothesis for this apparent "paradox" should be stated in the discussion section.
-We thank the reviewer for this helpful comment.
To comply, we added the following to our discussion: "The increase may be attributed to changes in case-mix, including an aging population. Conversely, the emergence of multi-resistant bacteria may contribute to the recorded trends […] Nonetheless, alternate explanations include refinements in coding practices, which may have led to better recognition and recording of non-lethal adverse events, thereby resulting in an apparent decrease in mortality rates." Reviewer: Keith Kowalczyk, MD Instructor of Surgery Department of Urology Lombardi Comprehensive Cancer Center Georgetown University Hospital Washington, DC, USA This is an excellent study that I honestly do not have much to add. It is extremely well written and comprehensive analysis of trends in preventable events following cancer surgery. It provides enlightening statistics that lead one to ponder who to improve care for our patients. Additionally, it does pose questions regarding CMS' potential policy of penalizing institutions for increased mortality/complication rate when realistically a higher failure-to-rescue rate seems more appropriate.
My one comment would be to see if the authors could add surgeon volume to the analysis. I understand that this may be beyond the scope of an already comprehensive work, however I wonder if they would explore this in the future of if they already have.
-We thank the reviewer for his comment. Unfortunately the Nationwide Inpatient Sample does not provide reliable information on surgeon volume. The information is not provided by many states, and oft miscoded in others: some surgical units are identified with a single ID. Therefore, these analyses cannot be performed in the Nationwide Inpatient Sample. As suggested, our research team will pursue this topic in future projects analyzing datasets that provide this information, such as SEER-Medicare.
Reviewer: John Morton, MD, MPH Associate Professor Stanford University no competing interests Paper is well done and essentially replicates the following study confining it to oncologic surgeryclearly needs to be cited. Downey JR, Hernandez-Boussard T, Banka G, Morton JM. "Is patient safety improving? National trends in patient safety indicators: 1998-2007," Health Serv Res, 47 (1 Pt 2): 414-30, 2012 This is an important comment.
To comply, we cited the suggested paper.
The graphs are difficult to read and need a different scale or format to be clearer.
-We thank the reviewer for this comment and have reformatted several figures.
Can authors comment on the impact of cancer center accreditation, hospital volume of surgery and present on admission diagnoses. Otherwise, paper is well written and conclusions sound.
-We did not analyze the impact of cancer center accreditation, as hospital attributes to identify those centers is not provided consistently for all states. To perform such an analysis would have required the exclusion of a significant number of states, and therefore would not have allowed us to provide nationally representative figures. In contrast, hospital volume of surgery is accounted for in all of our multivariable analyses. Diagnoses at admission are adjusted for using the Charlson Comorbidity Index, which is also included in our multivariable analyses.
Reviewer: 4 If you have any further comments for the authors please enter them below. The paper is a retrospective cross-sectional. The objective of the paper is to estimate Hospitalacquired-adverse events after major cancer surgery.
The introduction is good and talks about the fact of multiple studies have demonstrated that significant variation exists in cancer incidence rates and in access to quality cancer care, but variations in the actual quality of surgical oncology care remain unclear.
About methodology, the variables are correct defined. The statistical analysis is the suitable one. The statistical meaning of the results is defined. The information of the results answers to the aims of the study and reflects the findings more relevant. The presentation is clear and suitable. It seems to me a good manuscript, correctly developed and with a suitable methodology, and that it supposes an interesting contribution to the knowledge of the health quality improvement.
-We thank the reviewer for his kind assessment of our manuscript. To answer the last question, we cannot directly share our dataset as per NIS data-use agreement. However, any independent research group can assess the raw dataset for a nominal fee and perform subset or alternate examinations on the same topic.