Cancer cells after all are aberrant forms of normal cells. Well-differentiated cancer cells (cells that look closer in appearance to their normal counterparts) generally have a lower malignant potential than poorly differentiated cells, which have a higher malignant potential. In most cancers grading is taken into account in the overall risk assessment.
The grading method in prostate cancer is known as Gleason grading named after its originator Dr Donald Gleason. Prostate cancer patients should be aware of Gleason system (also called Gleason scoring) as it plays an important role in deciding treatment, in assessing the future course of the disease. In 1960s, Dr Gleason (Minneapolis Veterans Affairs Hospital, USA) (Figure 1) devised a scoring system through his observations of the cellular architecture patterns of the cancer tissue in prostate as seen through the microscope. He and his team based his system of scoring by studying biopsies of nearly 5000 patients diagnosed with prostate cancer. One of its outstanding strengths is that it was tested in a large patient population in many countries, with long-term follow-up that included use of survival as an end point.
Each patient has a unique score depending on the pathologist’s assignment of 2 separate numerical grades. The commonly observed pattern is assigned as the ‘primary’ grade and next common is ‘secondary’ grade. There could be third common grade- it is called ‘tertiary’ grade.
How it works?
Grades range from 1 (lowest) to 5 (Highest) and scores range from 2 to 10 by adding primary and secondary grade patterns. After preparing the slides, the pathologist looks at them through the microscope particularly looking for patterns of glands and their architecture including size, shape and differentiation of glands. The primary Gleason grade has to be greater than 50% of the total pattern seen and the secondary has to be less than 50%. The sum of primary and secondary grades is called Gleason score or sum.
If the entire area has one pattern then both primary and secondary grades are reported as a same grade. For example if there is a grade 3 everywhere, it is reported as 3+3=6. Grading starts from 3 where 1 and 2 are rarely assigned. The number of grades assigned depends on tumour sample size and size of the tumour in the whole gland.
The common practice has been Gleason score 2-4 cancer as ‘low grade’ or ‘well-differentiated’ disease; Gleason 5-7 corresponding to ‘intermediate’ or ‘moderately differentiated’ disease; Gleason 8-10 corresponding to ‘high grade’ disease (Figure 2).
Importance of Gleason score
In conjunction with blood PSA, rectal examination findings, number of positive cores and radiological findings (MRI); it is a powerful predictor of behaviour of prostate cancer.
The Gleason grading is used in many settings in the management of prostate cancer. Men who have lower Gleason grades are likely to go for ‘watchful monitoring’ at least in the initial stages. Gleason grading is routinely used to check eligibility of patients for clinical trials. Patients with higher grades tend to receive more radical treatments such as surgery, radiotherapy and chemotherapy. In some patients, poorly differentiated tumours are more likely to have metastasized even before the diagnosis and are associated with a poorer prognosis. There are nomograms that incorporate Gleason grading to help doctors to decide what type of treatment is suitable for the patient.
To know more about treatment of prostate cancer and how we, at London Urologist, may be able to help you, please contact us today!