PUTTING off going to the dentist could mean that oral cancer goes unnoticed, the British Dental Association warned patients yesterday. Early diagnosis can increase a patient's chance of surviving the disease for another five years from 50% to 80%.

Dentists are able to detect tumours, which can start as whitish or reddish patches or ulcers in the mouth that fail to heal. Treatment of the cancer is more effective if lesions are detected before they have a chance to spread. Oral cancer kills about 16,000 people in the UK each year, the same number as are killed by cervical cancer.

Another survey yesterday revealed that 90% of men know nothing about a blood test which can reveal a risk of prostate cancer. Only one in five of the 968 questioned in the Mori survey for the Institute of Cancer Research said they knew ''a great deal or a fair amount'' about either prostate or testicular cancer.