They warned delays in operation could lead to cancer progression and potentially more cancer deaths, as they called upon authorities around the world to set up systems to avoid delay or cancellation of planned surgery amid the pandemic.

The surgeons and anesthetists, including those from Chinese University's medical school, worked together as part of the CovidSurg Collaborative to analyze data from the 15 most common cancer types in 20,000 patients across 466 hospitals in 61 countries.

The analysis published in The Lancet Oncology recently said the researchers compared cancellations and delays for cancer surgery during lockdowns to those during times with light restrictions only.

During lockdowns, 15 percent of patients did not receive their planned operation for an average of more than five months from diagnosis, all because of the pandemic. Delays were also seen in surgery under lockdowns.

One in four cancer patients had to wait for more than three months from diagnosis to surgery during full lockdown, double the proportion of one in 10 during moderate lockdown or even looser restrictions.

Researchers from the Chinese University said despite the reduction in diagnostic services and fewer operating theaters available during the peak of previous Covid-19 outbreaks in Hong Kong, cancer patient treatments were still handled with priority.

Some cancer patients who feared going to hospitals during Covid-19 had their diagnosis delayed.

Even though Hong Kong did not experience a full lockdown, some of the planned operations had to be delayed.

Chinese University's surgical assistant professor, Kaori Futaba, said: "We have been implementing more stringent infectious control measures and operation arrangements during Covid-19. Balancing the capacity of urgent and planned surgeries has been one of the biggest medical challenges during the pandemic."