Semiautomatic analysis of tumor proportion in colon cancer: Lessons from a validation study

The tumor stroma ratio (TSR) is a promising histopathologic prognostic biomarker, which could allow for more accurate risk stratification and improved patient management in colorectal cancer. The purpose of our research was to validate the results of a previous study, which had suggested that not only a low but also a high tumor proportion (TP) might be an independent risk factor for occurrence of distant metastasis and worse overall survival using a semiautomatic image analysis approach with the open-source software ImageJ. We investigated 253 pT3 and pT4 adenocarcinomas of no special type. The previously established thresholds (PES-cut-offs) used to classify the patients (previous 3-tiered-classification) according to the tumor proportion (TP) in a highTP (TP >= 54%), a mediumTP (TP < 54% boolean AND TP >15%) and a lowTP (TP <= 15%) group did not show a significant risk stratification. Even the adjustment of these threshold revealed no significant results. Therefore, a receiver operating characteristic (ROC) analysis was performed to establish the cut-off with the most significant predictive power and a new 2-tiered-classification using this cut-off (40% at MinTP) showed a significantly shorter absence of metastasis for patients with a low TP (p = 0.007). These results confirm that a low TP is associated with an adverse prognosis. This study did not confirm the previous assumption that a high TP might also be a risk factor for occurrence of metastasis. Furthermore, it demonstrates that this semiautomatic technique is not superior to the established method, so that approaches to enhance prognostic techniques should continue.

Automated summary

Based on the investigation of 253 cases of pT3 and pT4 colorectal adenocarcinomas, the study confirmed that a low tumor proportion is associated with an adverse prognosis, while the previous assumption that a high tumor proportion might also be a risk factor for metastasis was not confirmed. Furthermore, the study showed that the semiautomatic technique used was not superior to the established method, suggesting the need for continued improvement in prognostic techniques.