ON a day turned frigid by an intense winter monsoon, more than 2,000 students and staff members of the Chinese University, Government officials, commercial leaders and celebrities gathered to spread their warmth at the Sha Tin sports ground. Participants shared their generosity and enthusiasm in a recent charity walk to help those suffering from cancer, which is believed to cause more deaths than any other disease in Hongkong. The Chinese University of Hongkong Anniversary Walkathon raised money for the Hongkong Cancer Institute of the Chinese University of Hongkong. ''There is a pressing need for the most effective diagnosis and treatment so that more lives can be saved,'' said Professor Charles Kao Kuen, vice-chancellor of the university, which started its 30th anniversary celebrations with the charity walkathon. The donations will help strengthen cancer research and treatment of cancer patients at the Prince of Wales Hospital, including bone marrow transplant and other treatments for cancer in children, cancer outpatient treatment, counselling and public education. In addition to the funds raised in a walkathon, the Cancer Institute received a major boost with $20 million contributed by two sources - $10 million each from the Mrs Cheng Suen Man-shook Foundation and Mr Thomas Chen. Starting at Lingnan Stadium of the Chinese University's Chung Chi College and finishing at Sha Tin Central Park, the walk was about seven kilometres. Catherine Wong Ka-man, said she participated in the walk in the hope of helping those less fortunate than herself. Although Ka-man said it was difficult to face the chilly winds during the walk, she felt ''a strong responsibility to do so''. A student at CUHK FAA Thomas Cheung Secondary School, she said many of her friends and relatives had sponsored her and she did not want to disappoint them. Her schoolmate, Tang Wing-yan, said she was not put off by the chilly weather. ''I am very happy to have collected more than $200 for the Cancer Institute.'' ''Helping the others is the best means to help myself as well. This way I gain experience that will come in useful later,'' the first former said. ''By taking part in an event like this, I learn to understand the significance of charity and social action.'' The walkathon also marked the beginning of a year of activities commemorating the 30th anniversary of the university, whose student population has grown six-fold from 1,600 in three faculties in 1963 to more than 10,000 in seven faculties in 1993.