Influence of tumour differentiation on survival after resection for rectal cancer in a series of 1296 patients.

The influence of differentiation grade on tumour staging, local recurrence and long term survival prospects has been evaluated in a series of patients managed by resection for rectal cancer. Differentiation was known in 1095 of 1296 patients. Well-differentiated tumours were over-represented among Dukes' stage A cases and poorly differentiated among those with disseminated disease (P less than 0.001). Local recurrence was twice as common (31%) after curative resection of poorly differentiated tumours than of well (14%) or moderately (17%) differentiated. Five year cancer specific survival rates after resection (curative and palliative combined) of tumours of good, average or poor differentiation were 68%, 59% and 33%, respectively. After potentially curative resection, survival was also significantly worse in patients with poorly differentiated tumours (P less than 0.001); 5 year survival rates of patients with tumours of good, average or poor differentiation were 75%, 71% and 51%, respectively. Survival prospects beyond 5 years in patients with Dukes' stage A tumours were significantly reduced when the tumour was poorly differentiated; 5 and 10 year survival rates were 76% and 40%, respectively. However, patients with Dukes' stage C tumours of poor differentiation had an identical 5 and 10 year cancer specific survival, 26%. Patients with mucoid type tumours had worse survival prospects than those with non-mucoid type (P less than 0.02).