Routine pathology tests could miss out on tiny cancer cells, the error proving costly for the patient, particularly so in esophagal cancer. Additional sectioning of the lymph nodes could help.
Dr Sarah Thompson, a surgeon and PhD candidate in the University of Adelaide, points out half of patients given the "all-clear" signal tend to die within five years therafter.
In a study of 250 oesophageal cancer patients in Adelaide over the past 10 years, Dr Thompson found that of the 119 people given a clean bill of health, only 62 were still alive five years later.
"If you tell people they are totally clear of cancer and then a year later they come back with secondary cancer, that is a devastating result," she says.
More than 1000 people are diagnosed with cancer of the oesophagus in Australia each year. There are two types: squamous cell carcinoma, occurring in the top part of the esophagus; and adenocarcinoma, which is closer to the stomach. The latter has increased by 400% in Australia since the 1970s.
Dr Thompson's study showed that oesophageal tumour cells are being missed in the lymph nodes in conventional pathological tests.
"Pathologists normally take just one cut from a lymph node when testing for cancer and this is usually sufficient. But our research has shown that in one third of cancer patients with negative nodes, small cancer cells will be present. These are only visible with special stains and at least three cuts of the node," Dr Thompson says.
"A controversy in the medical world, as far as predicting cancer survival rates, is whether or not those tiny, single cancer cells mean anything. Some medical experts believe these cells are just in transit and passing through our blood stream. Others think if they are present in the lymph nodes these patients should be offered chemotherapy as a matter of course."
Dr Thompson says the oesophageal cancer patients who have the most to gain are those who have had surgery without chemotherapy or radiation beforehand to shrink the tumour.
"Chemotherapy after surgery might improve their survival."
"I think there is also merit in changing the existing pathology guidelines for esophageal cancer patients to ensure a more accurate diagnosis. Further sectioning and staining of the lymph nodes should be carried out if the lymph nodes are negative after only one cut to rule out the presence of isolated tumour cells," Dr Thompson says.
Her findings have been published in the Annals of Surgery
in an article co-authored by Dr Thompson's PhD supervisor Professor Glyn Jamieson, the Dorothy Mortlock Professor of Surgery at the University of Adelaide.