Tumor grade employed for colorectal cancer has long been based on the degree of differentiation, which is difficult to judge objectively.
Dr Hideki Ueno and colleagues determined whether the extent of the poorly differentiated component could be a valuable criterion for a grading system.
A total of 1075 patients with advanced colorectal cancer were pathologically reviewed.
Poorly differentiated component was newly defined as a region in which a cancer has no glandular formation, irrespective of a mucin-producing or invasive pattern.
The research team quantitatively classified the poorly differentiated component into 6 degrees using the microscopic field of an objective lens as a standard.
|Survival was 86% for Grade 2|
|Annals of Surgery|
Survival analyses of the extent of poorly differentiated component demonstrated that a 3-category grading system provides the most efficient survival stratification.
Grade 3 was applied to 339 tumors for which the poorly differentiated component fully occupied the microscopic field of a 40x objective lens.
For tumors having a smaller poorly differentiated component, cancer clusters without a gland structure composed of 5 or more cancer cells, termed ‘clusters‘.
These ‘clusters' were counted in the microscopic field of a 4x objective lens, where they were observed most intensively.
The team graded 161 tumors with less than 10 'clusters' as Grade 1, and 575 tumors with 10 'clusters' as Grade 2.
Patients classified as Grade 1 demonstrated a very favorable prognosis, with a 99% cancer-related 5-year survival rate.
However, the researchers observed that the survival was 86% for Grade 2, and 69% for Grade 3.
Multivariate analysis demonstrated that the grades of poorly differentiated component function as an independent prognosticator, as do T-stage and N-stage.
Dr Ueno's team commented, "The grading system utilizing poorly differentiated component is distinctive in terms of the simplicity of judgment based on its quantification."
"The ability to determine which patients will likely be cured by surgery alone."
"It will aid in selecting postoperative treatment strategies."