Ki-67 immunostain could potentially generate a preoperative risk stratification for gastrointestinal stromal tumors (GISTs), according to a new study recently published in Cancer Cytopathology.

“The added value of Ki-67 may help improve clinical management for GIST patients,” the authors wrote.

This retrospective study evaluated 50 GIST cell blocks from the stomach (90%), duodenum (8%), and esophagus (2%), with a mean tumor size of 5.4 cm. All samples underwent immunostain with Ki-67 to later calculate the Ki-67 index on the areas identified as “hot spots.”


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Overall, the samples that exhibited a higher Ki-67 index also had an increased mitotic rate (3.5%) compared to those with a low mitotic rate (1%).

The further confirmatory analysis demonstrated a sensitivity of 70% and specificity of 92% for the prediction capacity of Ki-67 on mitotic rate when using a cutoff value of 2.5%. A receiver operating characteristic curve yielded an area under the curve of 0.839.

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Among the included samples, most of them (74%) had a low mitotic rate, and the remaining 26% had a high mitotic rate. The spindle cell type was the most common, present at 60% of the cases, followed by the mixed type with 26%, and finally, the epithelioid type accounting for 14% of the samples.

These findings suggest a potential mechanism for the mitotic count, and hence, the risk stratification could be obtained before surgery. This possibility will likely translate into a great benefit for patients with GISTs since not all cases are candidates for surgery, and a limited biopsy or cytology taken through fine needle aspiration may be the only sample available to determine the risk, which could, in turn, modify the therapeutic approach.

“This study demonstrates good correlations between Ki-67 index and mitotic count or risk stratification, suggesting that Ki-67 index evaluated on cytology specimens may offer a promising approach to preoperatively predict the mitotic rate and risk of GIST,” the authors concluded.

Reference

Wang X, Abi‐Raad R, Tang H, Cai G. Ki‐67 index assessment on FNA specimens of gastrointestinal stromal tumor: correlation with mitotic rate and potential predictive value for risk stratification. Cancer Cytopathol. Published online July 25, 2022. doi:10.1002/cncy.22630