The Influence of Tumour Grade on Radiotherapy Results

Histological grading, based on the degree of tumour differentiation and mitotic activity, is used to try and classify patients with cancer according to the potential malignancy and likely rate of progress of their tumours. The value of grading may be considered for cancer at sites where a detailed system of clinical staging is wellestablished (e.g. breast, cervix, bladder, larynx); where there is a limited method of staging based on whether the regional lymph nodes are involved or not (e.g. oral cavity, vulva, penis, skin, thyroid); where staging depends largely upon operative findings (e.g. kidney, ovary, endometrium, rectum), and in sites where no system of staging has been developed (e.g. bone, brain, soft tissues). In some sites, where information is lacking regarding histological tumour grade in relation to radiotherapy, it has been necessary to draw on the results of surgery and of combined treatments in order to draw attention to the possible value of grading in radiotherapy studies. A more accurate assessment of results of treatment in, for example, cancer of the breast, cervix, oral cavity, kidney, endometrium and rectum can be achieved by classifying patients according to both tumour stage and grade than by either factor alone. Grade of bladder cancer, although itself related to survival, failed to give additional information concerning prognosis in cases already grouped by stage. In patients with tumours of bone, soft tissue sarcoma and brain gliomas grading is indispensable for classification and prognosis. This was illustrated by survival rates in osteosarcoma, chondrosarcoma and giant cell tumour, in soft tissue fibrosarcoma, and in cerebral astrocytoma and ependymoma. Certain histological features such as round cell infiltration of the tumour and sinus histiocytosis in the regional lymph nodes may represent host resistance factors, and the degree to which they are present may, in some cases, modify the prognosis based on tumour grade alone. By ignoring histological grade and classifying cancer cases by stage alone heterogeneous groups of patients may be produced in which a true comparison of treatment results is often not possible. The wider use of grading is likely to lead, in many instances, to a more accurate evaluation of treatment, such as ancillary irradiation in operable cancer of the breast, and radical surgery versus irradiation for early carcinoma of the cervix.