Mitotic Rate and Tumor Size Shown to Be Prognostic Factors for Some GISTs

Mitotic rates and tumor sizes were found to be significant prognostic factors for the progression of gastrointestinal stromal tumors (GISTs) located in the colon or esophagus, according to a new study.

Tumors in these locations that were larger than 5 cm and tumors with greater than 5 mitoses per 5 mm² (5/5mm²) had hazard ratios (HR) of 1.10 (P =.013) and 18.81 (P <.0001) for disease progression, respectively. These results were published in Modern Pathology.

The study also looked at another rare form of GISTs, those located in the appendix. However, none of these tumors progressed during follow-up after resection surgery (median, 39 months; range, 1-156 months) and therefore were not included in statistical analysis.

The study included information from 265 patients with GISTs located in either the esophagus (n=102), colon (n=136), or appendix (n=27). Patients were identified from 47 institutions across the US and Canada.

Read more about GIST epidemiology

The study also found that the tumors with mitotic rates less than 5/5mm² but size greater than 5.0 cm had a moderate risk of progression. GISTs of the esophagus or colon ≤5.0 cm and with mitotic rates ≤5/5mm² had a very low risk of progression, as none of the 71 esophageal or 102 colonic patients meeting this criteria progressed.

“Our data show that mitotic rate and tumor size are significant prognostic factors for both esophageal and colonic GISTs, as with GISTs arising in more common locations. Furthermore, our results indicate that esophageal, colonic, and appendiceal GISTs with size ≤5.0 cm and mitotic rate ≤5/5 mm² are unlikely to progress,” the authors concluded.

Stratification of risk for the patients in this study found that esophageal and colonic GISTs appear to fall between the risk level associated with small bowel and gastric GISTs. This was found in the table published by the College of American Pathologists (CAP) in their Protocol for the Examination of Resection Specimens From Patients With Gastrointestinal Stromal Tumors.

Reference

Hu S, Alpert L, Cates JMM, et al. Gastrointestinal stromal tumors (GISTs) arising in uncommon locations: clinicopathologic features and risk assessment of esophageal, colonic, and appendiceal GISTs. Mod Pathol. Published online October 26, 2021. doi:10.1038/s41379-021-00949-w