In the fourth instalment of a six-part Health Matters wellness series on cancer in Hong Kong, Elizabeth Cheung examines how city researchers are developing new blood tests to detect the disease earlier, and what they could mean for screenings and diagnoses.Retired Hong Kong businessman Peter Wan Ying-keung still remembers the uncertainty and discomfort of his months-long journey to a prostate cancer diagnosis 13 years ago.It began with a routine blood test in 2013 that showed elevated levels...