28 February 2022, Monday

Cancer Grading Vs. Cancer Staging

‘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 about the nature of the disease, especially about its tendency to metastasize. 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 of 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 bone tumor; ‘Patient A’ and ‘Patient B’. A biopsy revealed that both have Chondrosarcoma. The pathologist further added that the tumor was ‘Low Grade’ in both patients.

In conclusion, both patients have identical disease, i.e. Low Grade Chondrosarcoma; 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 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 disease with identical Grades, ‘Patient B’ with ‘Stage IV’ disease is at a higher risk as compared to ‘Patient A’ with ‘Stage I’ 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.

At this point it is important to have a clear idea that ‘grading’ and ‘staging’ is meant for primary malignant tumors only (As already described in the section on bone metastases, a metastatic bone disease is considered as a part of the cancer of the tissue or organ from where it had first started, and in effect, represents stage ‘IV” of that cancer.).

Further Reads:

1. What is Cancer Grading?

2. What is Cancer Staging?

3. What is importance of Biopsy in Cancer?