Key message: When CT scan shows a pancreatic or periampullary cancer that looks like it can be removed by surgery, having diagnostic laparoscopy may decrease the The speed or frequency of occurrence of an event, usually expressed with respect to time. For instance, a mortality rate might be the number of deaths per year, per 100,000 people. of unnecessary surgery by giving more information about whether this is likely to be so.
Pancreatic Cancer Awareness Month is drawing to a close. It’s been an opportunity for Pancreatic Cancer Action to raise awareness of a disease which is the fifth leading cause of cancer death here in the UK, where survival rates are among the worst in Europe and have not changed in over 40 years. The good news is that a new Cochrane review from the Cochrane Upper Gastrointestinal and Pancreatic Diseases (UGPD) Group has just been published with evidence that a diagnostic technique, laparoscopy, may help to reduce the number of people undergoing surgery unnecessarily.
What’s the problem?
Surgery is generally thought to be the only Something done with the aim of improving health or relieving suffering. For example, medicines, surgery, psychological and physical therapies, diet and exercise changes. that can cure pancreatic cancer but only about one in five patients have surgery, as in many cases the person is considered to be unfit for major surgery or a CT (computed tomography) scan has shown that the cancer has spread. A CT scan is used to ‘stage’ the disease (this is a means of defining how far a disease has progressed) but despite this as many as a quarter of patients then have a laparotomy, surgery to open up the abdomen and remove the cancer (called a ‘resectable cancer’ if it can be removed), only to find that the cancer can’t all be cut out as hoped (unresectable cancer). The new Cochrane review tells us that diagnostic laparoscopy may enable doctors to more accurately diagnose which patients have resectable cancers and so reduce the number of people who have an unnecessary laparotomy.
Diagnostic laparoscopy involves putting a telescope into the abdomen through a small cut, to look at the organs and to take a sample of the diseased tissue, which can then be examined in the laboratory. There is currently no standard procedure for diagnosing pancreatic cancer and periampullary cancers (which include cancer of the head and neck of the pancreas and part of the bile duct and duodenum) but most people will have a CT scan and this may be the only test before they have a laparotomy, though other tests, such as MRI scan, may be used.
What’s the evidence?
The review team looked for evidence on the The ability of an intervention (for example a drug, surgery, or exercise) to produce a desired effect, such as reduce symptoms. of diagnostic laparoscopy as an add-on test to the CT scan to find which patients had resectable cancers and which had unresectable cancers. Diagnostic laparoscopy was considered positive if the cancer was unresectable, with cancer spread confirmed by laboratory examination of a tissue sample (paraffin section was the ‘gold standard’ test used). If the sample was negative (or if the results of diagnostic laparoscopy couldn’t be interpreted), the patient went on to have a laparotomy. The cancer was then found to be resectable (a true negative result – the diagnostic test correctly identified a resectable cancer) or unresectable ( a In diagnostic tests, a conclusion that a person does not have the disease or condition being tested, when they actually do. result – the diagnostic test result was wrong, as it indicated a resectable cancer that was found to be unresectable). The reviewers found 15 studies with 1015 patients which could help answer their question; results were combined in a The use of statistical techniques in a systematic review to combine the results of included studies. Sometimes misused as a synonym for systematic reviews, where the review includes a meta-analysis. . Here’s what they found:
- Adding diagnostic laparoscopy to CT scanning reduces the likelihood of unresectable cancer from 40% to 17%. This means that for every 100 people who have CT plus diagnostic laparoscopy, 23 people will avoid laparotomy compared to CT scanning alone.
How good was the evidence?
- The results are based on low quality studies and in particular there are concerns about selection Any factor, recognised or not, that distorts the findings of a study. For example, reporting bias is a type of bias that occurs when researchers, or others (e.g. drug companies) choose not report or publish the results of a study, or do not provide full information about a study. as it wasn’t clear how patients were chosen and whether patients were inappropriately excluded
- There were lots of differences between studies and some poor reporting. However, diagnostic laparoscopy appeared to reduce the number of unnecessary laparotomies in 14 of the 15 studies
- Inappropriate delay between laparoscopy and laparotomy can result in patients who had resectable cancer developing unresectable cancer.This will underestimate the accuracy of diagnostic laparoscopy
- Reliance on the surgeon’s judgement that a cancer is unresectable at laparotomy could cause an error in the estimation of diagnostic accuracy
So where does that leave us?
The reviewers conclude that, despite the shortcomings of the evidence, diagnostic laparoscopy appears to be useful in avoiding unnecessary laparotomies, and there is a low A way of expressing the chance of an event taking place, expressed as the number of events divided by the total number of observations or people. It can be stated as ‘the chance of falling were one in four’ (1/4 = 25%). This measure is good no matter the incidence of events i.e. common or infrequent. of complications from the procedure. Cost-effectiveness needs to be formally assessed to help decide whether it should be offered routinely in state funded health systems like ours.There is a need for further well-designed studies to reliably estimate the accuracy of diagnostic laparoscopy and comparison with other tests for staging pancreatic and periampullary cancers.
For those wanting to read more about A measure of a screening or diagnostic test’s ability to correctly detect people who have the disease. and A measure of a screening or diagnostic test’s ability to correctly identify people who do not have the disease. and sort out their true and false positives and negatives, there’s a good blog on this topic on the Students for Best Evidence website here.
Allen VB, Gurusamy KS, Takwoingi Y, Kalia A, Davidson BR. Diagnostic accuracy of laparoscopy following computed tomography (CT) scanning for assessing the resectability with curative intent in pancreatic and periampullary cancer. Cochrane Database of In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. 2013, Issue 11. Art. No.: CD009323. DOI: 10.1002/14651858.CD009323.pub2.