15 November 2021, Monday

What is the Difference Between ‘Grade’ of the Disease and ‘Stage’ of the Disease?

‘Grade’ of the tumor tells us how aggressive the disease is; especially about its tendency to metastasize (spread to other regions of the body). However, it does not tell us anything about the extent of its presence in the patient and the actual threat it poses to the patient, at any given time.

‘Staging’ on the other hand, is a system that helps in understanding the extent of cancer in the patient and the level of risk to the patient due to it. ‘Stage of the cancer at diagnosis’, is the best predictor of survival and is a powerful guide to the optimal treatment of the disease.

As described earlier, ‘Grade’ of the tumor is a value allotted to the tumor by a pathologist based on its appearance under the microscope (sometimes, in certain borderline cases, clinical and radiological information may also be used while allotting the grade to the disease).

It tells us how aggressive the disease is; especially about its tendency to metastasize (spread to other regions of the body). However it does not tell us anything about the extent of its presence in the patient and the actual threat it poses to the patient at any given time.

Grade of the disease is just one of the criteria used in the staging cancer. Staging systems take into account several other details to designate the ‘Stage’ of the disease.

For example, let us consider the situation of two patients with Soft Tissue Sarcoma; ‘Patient A’ and ‘Patient B’. A biopsy revealed that both have Ewing’s Sarcoma. (There is no grading system for Ewing’s sarcoma as it is always a high-grade disease).

Thus, both patients have identical disease, i.e. Soft Tissue Ewing’s sarcoma; in which case it is logical to assume that both ‘Patient A’ and ‘Patient B’ will receive the same treatment.

However, that is not correct. We still do not have the complete information necessary for formulating the right treatment plan. We know that cancer can spread to other organs and tissues.

It is for this reason, staging investigations are done. Staging investigations revealed that ‘Patient A’ has no metastasis (i.e. he has localized disease only) whereas ‘Patient B’ has metastases in the lungs; which means ‘Patient A’ has ‘Stage II’(for a high grade tumor, there is no ‘Stage I’) disease while ‘Patient B’ has ‘Stage IV’ disease.

Clearly, the same treatment strategy will not work for both patients as the extent of disease in both patients is different. So, despite having the same high grade disease, ‘Patient B’ with ‘Stage IV’ disease is at a higher risk as compared to ‘Patient A’ with ‘Stage II ’ disease, and therefore needs a different treatment approach. This is essentially the difference between ‘Grade’ and ‘Stage’ of the disease.

Thus, staging is a system that helps in understanding the extent of the cancer in the patient and the level of risk to the patient due to it. Stage of the cancer at diagnosis, is the best predictor of survival and is a powerful guide to the optimal treatment of the disease.