Men with advanced prostate cancer can take highly targeted hormone therapies at home instead of coming into hospital for chemotherapy, NHS England says.
Experts say it will relieve pressure on the NHS, which wants all urgent and essential cancer treatments to continue during the coronavirus pandemic.
The drugs are also smarter, kinder treatments and could extend the lives of many more patients, they say.
This precision-medicine approach is already used to treat other cancers.
Diagnosed with advanced prostate cancer in February, Stuart Fraser, 66, from Ashtead, in Surrey, will now take four enzalutamide tablets a day.
"Being diagnosed was a huge shock," he said.
"What made it even more worrying was that, because of coronavirus, I was told I couldn't have the usual treatment of chemotherapy, which would have affected my immune system.
"When I heard about other possible treatments like abiraterone and enzalutamide, I launched a petition to try to make sure men like me could get hold of it.
"That's why it's such great news that now no-one will be in the same position I was at the beginning of all this."
Enzalutamide blocks the effect of the testosterone hormone on prostate-cancer cells, preventing them from growing.
Patients intolerant to enzalutamide, will be given abiraterone, which stops the body producing testosterone.
Until now, in England and Wales, the drugs were available only to patients for whom other hormone therapy had stopped working, although abiraterone was recommended in Scotland as a first-line treatment earlier this year.
Now, doctors can prescribe them when a patient is first diagnosed.
Prof Nick James, of the Institute of Cancer Research, in London, who has led major trials into targeted prostate cancer drugs, said: "I'm pleased and relieved that many more men should now benefit from targeted hormone therapies right from when they are first diagnosed.
"It will greatly lower the risk of exposing vulnerable patients to the coronavirus and lightens the load on our hard-pressed hospitals.
"Men can take their tablets at home and have their bloods checked by their GP.
"And, unlike chemotherapy, enzalutamide and abiraterone have no significant effects on patients' immune system."
National clinical director for cancer Prof Peter Johnson said: "The NHS has been working hard to ensure the safety of cancer patients during the pandemic.
"Switching from chemotherapy to hormone treatments for prostate cancer is just one example of how we are adapting our approach to help thousands of cancer patients across the country continue to access the care they need."