Explanatory Notes

Definitions, inclusion criteria and explanations for trust results

Volume of care

Why this fact is important:

The volume of care is the number of oesophago-gastric cancer procedures conducted by a surgeon or NHS organisation.

A low volume does not mean that a surgeon is inexperienced in the procedure as he or she might have performed a lot of operations in the past.  A surgeon will also be performing other procedures (not for cancer) on the stomach and its connecting organs.

In general, as the volume of procedures increases, the mortality rates get closer to the national average. With higher volumes, there is more certainty about the outcomes of the surgeon or trust because the results will be less affected by chance.

Things to note:

Because of the effect of volume on outcomes, we do not report outcomes for surgeons who performed fewer than ten procedures in the reporting period.

Interpretation of results:

When the number of operations is low, rates are often unreliable due to the influence of random events.  Moreover, the observed rates cannot represent a low underlying risk precisely.  For example, although the underlying risk of an operation may be 2%, surgeons who perform just 10 operations could equally have observed mortality rates of 0%, 10%, etc.

Things to consider about the data source:

The Audit used data reported by the surgeons and NHS organisations.  The figures on this website were reviewed and verified by both NHS trusts and individual surgeons prior to publication.

Considerable care should be taken in making comparisons between surgeons on the basis of the data reported here, as outcomes may vary due to random variation, case-mix or data quality. Every effort has been made to ensure the accuracy of the information in this section.  The NOGCA does not accept any liability arising from errors or omissions, or the use of, or reliance on, the information contained in this website and reserve the right to change the information and descriptions when required.

In looking at this information, it is important to remember that the outcomes of NHS trusts and surgeons may vary because of patient characteristics and the influence of random variation.  We recommend that patients discuss the likely outcomes of their treatment with their surgeon before an operation, so that they can understand the expected outcomes given their own circumstances.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


30 day mortality postoperative surgery following oesophagectomy or gastrectomy (risk-adjusted)

Why this fact is important:

30-day postoperative mortality addresses the time immediately following the surgery. Complications may occur in this time window which are beyond the control of the consultant and the multidisciplinary team. This outcome is highly dependent on the patient’s fitness, but also on the surgical skill and the intensive care support available at the Specialist Cancer Centres in the event that complications occur.

Things to note:

The mean national 30 day postoperative mortality rate is 1.8 %. For individual surgeons these percentages may vary largely simply because of chance. For example, a surgeon operating on 50 patients would usually experience one patient death within 30 days after surgery, but if during the time period two patients die just by chance then the mortality rate among patients for this surgeon would be double the national average. In practice, these chance findings can explain three or four fold variations in mortality rates without these rates indicating that the surgeons or trust performance is below average.

Because of the effect of volume on outcomes, we do not report outcomes for surgeons who performed fewer than ten procedures in the reporting period.

Interpretation of results:

When the number of operations is low, rates are often unreliable due to the influence of random events.  Therefore outcomes should always be interpreted in combination with the number of procedures performed by the surgeon.

Some surgeons may operate on patients who are on average sicker than the patients of other surgeons, for whom surgery may be higher risk. Our statistical approach adjusts outcomes to take into account the case mix of patients. Postoperative mortality figures for NHS trusts and surgeons have been adjusted for patient age, sex, site of tumour, performance status, overall fitness (ASA grade), the number of comorbidities, and overall TNM stage.  In practice, however, risk-adjustment is never perfect and higher mortality rates may still mean that a highly experienced surgeon operates on sicker patients. Therefore, the data cannot be interpreted as a definitive judgement on the performance of the surgeon.

Things to consider about the data source:

To ensure accuracy, the Audit used mortality data reported by the surgeons and from the Office for National Statistics.  The figures on this website were reviewed and verified by both NHS trusts and individual surgeons prior to publication.

Considerable care should be taken in making comparisons between surgeons on the basis of the data reported here, as outcomes may vary due to random variation, case-mix or data quality. Every effort has been made to ensure the accuracy of the information in this section.  The NOGCA does not accept any liability arising from errors or omissions, or the use of, or reliance on, the information contained in this website and reserve the right to change the information and descriptions when required.

In looking at this information, it is important to remember that the outcomes of NHS trusts and surgeons may vary because of patient characteristics and the influence of random variation.  We recommend that patients discuss the likely outcomes of their treatment with their surgeon before an operation, so that they can understand the expected outcomes given their own circumstances.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


90 day mortality postoperative surgery following oesophagectomy or gastrectomy (risk-adjusted)

Why this fact is important:

90-day postoperative mortality covers an extended period of follow-up after surgery and will give a better understanding for assessing the long-term outcomes after surgery. This outcome reflects not just the quality of the surgical intervention but the contribution of the multidisciplinary teams at the Specialist Cancer Centres.

Things to note:

The mean national 90 day mortality rate is  3.3%. For individual surgeons these percentages may vary largely simply because of chance. For example, a surgeon operating on 25 patients would usually experience one patient death within 90 days after surgery, but if during the time period two patients die just by chance then the mortality rate among patients for this surgeon would be double the national average. In practice, these chance findings can explain three or four fold variations in mortality rates without these rates indicating that the surgeons or trust performance is below average, given the small volumes of operations performed.

Because of the effect of volume on outcomes, we do not report outcomes for surgeons who performed fewer than ten procedures in the reporting period.

Interpretation of results:

When the number of operations is low, rates are often unreliable due to the influence of random events.  Therefore outcomes should always be interpreted in combination with the number of procedures performed by the surgeon.

Some surgeons may operate on patients who are on average sicker than the patients of other surgeons, for whom surgery may be higher risk. Our statistical approach adjusts outcomes to take into account the case mix of patients. Postoperative mortality figures for NHS trusts and surgeons have been adjusted for patient age, sex, site of tumour, performance status, overall fitness (ASA grade), the number of comorbidities, and overall TNM stage.  In practice, however, risk-adjustment is never perfect and higher mortality rates may still mean that a highly experienced surgeon operates on sicker patients. Therefore, the data cannot be interpreted as a definitive judgement on the performance of the surgeon.

Things to consider about the data source:

To ensure accuracy, the Audit used mortality data reported by the surgeons and from the Office for National Statistics.  The figures on this website were reviewed and verified by both NHS trusts and individual surgeons prior to publication.

Considerable care should be taken in making comparisons between surgeons on the basis of the data reported here, as outcomes may vary due to random variation, case-mix or data quality. Every effort has been made to ensure the accuracy of the information in this section.  The NOGCA does not accept any liability arising from errors or omissions, or the use of, or reliance on, the information contained in this website and reserve the right to change the information and descriptions when required.

In looking at this information, it is important to remember that the outcomes of NHS trusts and surgeons may vary because of patient characteristics and the influence of random variation.  We recommend that patients discuss the likely outcomes of their treatment with their surgeon before an operation, so that they can understand the expected outcomes given their own circumstances.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


Unadjusted proportion of patients with adequate lymph nodes examined for oesophagectomy and gastrectomy

Why this fact is important:

Lymph nodes are removed from the patient during surgery to assess the stage of tumour. This may be important in determining whether the patient needs to have further treatment after surgery. The adequate number of lymph nodes examined has been defined as 15 for both oesophagectomy and gastrectomy by the Association of Upper Gastrointestinal Surgeons (AUGIS): www.augis.org/wp-content/uploads/2016/06/Provision-of-Services-June-2016.pdf.

Things to note:

The national average for the unadjusted proportion of patients with adequate lymph nodes examined is 82.5%. It is important to note that the number of lymph nodes examined can vary due to patient characteristics, the type of treatment they had before surgery and the type of operation.

Interpretation of results:

The results should be interpreted cautiously because at this initial stage we are trying to understand the differences in surgical practices in England that may contribute towards the variation in these results.  Hence, we have not benchmarked the trusts against the national average as our aim is to drive standardisation in surgical practices and pathological interpretation, so that eventually this indicator can be used for benchmarking.

Things to consider about the data source:

We have used data from the National Oesophago-Gastric Cancer Audit to derive the indicator.  The figures were reviewed and verified by the NHS trusts. It is important to note that the completeness of data may affect the result. If a NHS trust submitted data for less than 50% of cases, N/A (Not Available) has been recorded against it.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


Proportion of patients with positive circumferential margins for oesophagectomy   (risk adjusted for overall TNM stage and neo-adjuvant treatment)

Why this fact is important:

A positive circumferential margin after oesophageal cancer surgery indicates that the patient could require further treatment and monitoring, as the tumour may not have been removed completely. Hence, it is important for NHS trusts to review the proportion of patients with positive circumferential margins as a marker of the efficiency of surgery.

Things to note:

The national average for the proportion of patients with positive circumferential margins for oesophagectomy is 25.1%. It is important to note that the proportion of patients with positive circumferential margins for oesophagectomy  may vary due to patient characteristics, the type of treatment they had before surgery and the type of operation. We have adjusted the published figures for the factors that we know influence the risk of a positive margin being found, but there may be other factors that differ from trust to trust which we have not captured in the data.

Interpretation of results:

The results should be interpreted cautiously because at this initial stage we are trying to understand the differences in surgical practices in England that may contribute towards the variation in these results.  Hence, we have not benchmarked the trusts against the national average as our aim is to drive standardisation in surgical practices and pathological interpretation, so that eventually this indicator can be used for benchmarking.

Things to consider about the data source:

We have used data from the National Oesophago-Gastric Cancer Audit to derive the indicator. The figures were reviewed and verified  by the NHS trusts. It is important to note that the completeness of data may affect the result. If a NHS trust submitted data for less than 50% of cases, N/A (Not Available) has been recorded against it.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


Length of stay

Why this fact is important:

An oesophagectomy or gastrectomy is a major procedure that involves certain risks. Patients need to stay in hospital after surgery to assess the immediate outcomes of the procedure and ensure recovery. We provide information on the median length of stay, to inform patients about what they can expect when admitted to the hospital for an operation.

Things to note:

The median length of stay for patients undergoing an oesophagectomy or gastrectomy for cancer was 11 days.

Interpretation of results:

Length of stay depends on the patient’s general level of fitness and social situation,  as well as whether complications occur after the surgery, and to some extent, on the hospital policy for the post-treatment period. This indicator does not allow any definitive judgement on the performance of the surgery, but provides important information for patients and their family to inform them about what is to be expected after the procedure.

Things to consider about the data source:

The Audit used data reported by the surgeons and NHS organisations.  The figures on this website were reviewed and verified by both NHS trusts and individual surgeons prior to publication.

Considerable care should be taken in making comparisons between surgeons on the basis of the data reported here, as outcomes may vary due to random variation, case-mix or data quality. Every effort has been made to ensure the accuracy of the information in this section.  The NOGCA does not accept any liability arising from errors or omissions, or the use of, or reliance on, the information contained in this website and reserve the right to change the information and descriptions when required.

In looking at this information, it is important to remember that the outcomes of NHS trusts and surgeons may vary because of patient characteristics and the influence of random variation.  We recommend that patients discuss the likely outcomes of their treatment with their surgeon before an operation, so that they can understand the expected outcomes given their own circumstances.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


Proportion of patients with positive longitudinal margins for oesophagectomy (risk adjusted for overall TNM stage and neo-adjuvant treatment)

Why this fact is important:

A positive longitudinal margin after oesophageal cancer surgery indicates that the patient could require further treatment and monitoring, as the tumour may not have been removed completely. Hence, it is important for NHS trusts to review the proportion of patients with positive longitudinal margins as a marker of the efficiency of surgery.

Things to note:

The national average for the proportion of patients with positive longitudinal margins is 3.6%. It is important to note that the number of lymph nodes examined may vary due to patient characteristics, the type of treatment they had before surgery and the type of operation. We have adjusted the published figures for the factors that we know influence the risk of a positive margin being found, but there may be other factors that differ from trust to trust which we have not captured in the data.

Interpretation of results:

The results should be interpreted cautiously because at this initial stage we are trying to understand the differences in surgical practices in England that may contribute towards the variation in these results.  Hence, we have not benchmarked the trusts against the national average as our aim is to drive standardisation in surgical practices and pathological interpretation, so that eventually this indicator can be used for benchmarking.

Things to consider about the data source:

We have used data from the National Oesophago-Gastric Cancer Audit to derive the indicator. The figures were reviewed and verified  by the NHS trusts. It is important to note that the completeness of data may affect the result. If a NHS trust submitted data for less than 50% of cases, N/A (Not Available) has been recorded against it.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


Proportion of patients with positive longitudinal margins for gastrectomy (risk adjusted for overall TNM stage and neo-adjuvant treatment)

Why this fact is important:

A positive longitudinal margin after gastric cancer surgery indicates that the patient could require further treatment and monitoring, as the tumour may not have been removed completely. Hence, it is important for NHS trusts to review the proportion of patients with positive longitudinal margins as a marker of the efficiency of surgery.

Things to note:

The national average for the proportion of patients with positive longitudinal  margins for gastrectomy  is 8.2%. It is important to note that the proportion of patients with longitudinal margins for gastrectomy may vary due to patient characteristics, the type of treatment they had before surgery and the type of operation. We have adjusted the published figures for the factors that we know influence the risk of a positive margin being found, but there may be other factors that differ from trust to trust which we have not captured in the data.

Interpretation of results:

The results should be interpreted cautiously because at this initial stage we are trying to understand the differences in surgical practices in England that may contribute towards the variation in these results.  Hence, we have not benchmarked the trusts against the national average as our aim is to drive standardisation in surgical practices and pathological interpretation, so that eventually this indicator can be used for benchmarking.

Things to consider about the data source:

We have used data from the National Oesophago-Gastric Cancer Audit to derive the indicator. The figures were reviewed and verified  by the NHS trusts. It is important to note that the completeness of data may affect the result. If a NHS trust submitted data for less than 50% of cases, N/A (Not Available) has been recorded against it.

Time period:

The information on surgeon outcomes was derived from data on patients diagnosed between 1 April 2014 and 31 March 2017.

 


Interpretation of funnel plots

Trust outcome information will always differ from the outcome figures published at a national level because of random variation – some NHS trusts will have higher values and some lower.  This variation is not communicated when figures are ranked.  Consequently, these NHS trusts  should not be ranked, as this would be misleading.

The variation in postoperative mortality rates was examined using a graph known as a funnel plot. The benefit of this approach is that it shows whether the outcomes for individual NHS trusts  differ from the national average by more than would be expected due to random fluctuations.  Random variation will always affect outcome information like mortality rates, and its influence is greater among small samples.

On these plots, each dot represents an NHS trust and they are centred on the national average. Example:  The national average for 30- day and 90-day postoperative mortality is approximately 1.8% and 3.3%, respectively.  The vertical axis indicates the outcome, with dots higher up the axis showing NHS trusts with a higher mortality rate. The horizontal axis shows surgical activity with dots further to the right showing the NHS trusts which perform more operations.

Funnel plots include control limits to define the range within which we would expect NHS trusts outcomes to lie.  Following convention, we use 99.8% control limits.  It is unlikely for an NHS organisation to fall beyond these limits solely because of random variation (a 1 in 500 chance).  If the outcome figures for an NHS trust fell outside the outer limits, there could be a systematic reason for the higher or lower rate, and they would be flagged as an outlier for further investigation.  The main cause of variation within the control limits is likely to be random variation.