Upper GI biopsies for Adenocarcinoma – how many biopsies should endoscopists take?

Abstract

Aims

There is evidence that 4 or 5 gastric cancer biopsies are required for accurate HER2 interpretation. However, the number of biopsies that need to be taken to reach this number of viable cancer biopsies is without evidence. This study aimed to address this gap by assessing the number of biopsies required to get at least 4 viable biopsies containing cancer

Methods and results

105 consecutive biopsy cases of gastric and oesophageal adenocarcinoma were retrieved from file. Only definite cancer diagnoses were included; missed cancers or unproven cases were not considered. The cases were reviewed and the number of biopsies taken, and the number containing viable tumour was recorded. In total, 667 biopsies were taken of which 471 had viable tumour (70.6%) 70/105 cases (67%) had 4 viable tumour biopsies but only 47/105 (45%) had 5 viable tumour biopsies. In order to have a >90% chance of having 4 viable tumour biopsies, 7 biopsies needed to be taken, while 10 or more biopsies were required for a >90% chance of 5 viable tumour biopsies. Mathematically, using a 0.7 probability for a single biopsy, 8 biopsies would be required for a 94% chance of at least 4 viable tumour biopsies.

Conclusion

In our large upper GI cancer centre, many biopsy cases do not contain sufficient material for adequate HER2 assessment. In order to meet the 4 biopsy requirement for adequate HER2 assessment in >90% of cases, at least 8 biopsies need to be taken, while 10 biopsies would be required for the 5 cancer biopsy threshold.

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