CANCER cases are on the rise in Hongkong with 30 per cent of all deaths now attributable to the disease. And the Hongkong Anti-Cancer Society says the majority of the public remains ignorant about treatment. Dr Poon Yeuk-foo, chairwoman of the society's education sub-committee, said the majority of cancer patients were unaware that many forms of cancer were curable, particularly if detected and treated early. She said they delayed seeking modern treatment, instead clinging to traditional Chinese remedies. The society now plans a series of free lectures to raise public awareness. ''With rapid advances in medical technology, cancer is no longer the invariably fatal disease that it used to be. ''Many cancers can be cured, especially when detected early and treated properly. Many can be prevented,'' she said. ''The general reaction to the diagnosis is still extreme fear with a feeling of doom. The ignorance and pessimism have resulted in delay in treatment and the loss of a chance of cure, for no amount of treatment facilities can do any good if people will not come forward for treatment.'' Dr Poon said cancer had been the leading cause of death in Hongkong for decades. Although the death rate is now stabilising, the number of new cases is growing along with the territory's ageing population. Dr Poon said more than 16,000 new cases of cancer were diagnosed each year with the latest available figures showing 16,464 new cases in 1989 compared with 14,527 in 1987. The most recent available figures show 8,814 people died from cancer in 1991 compared with 6,810 deaths in 1982, while the mortality rate in that time has grown from 154.1 men and 102.6 women per 100,000 of population in 1982 to 183.4 men and 122.1 womenper 100,000 people in 1991. Free lectures in Cantonese will be given every month by leading Hongkong cancer experts and start on April 15.