Shares in a struggling oncology company have skyrocketed after a late-stage cancer patient taking one of its drugs saw her tumours apparently disappear.

Nasdaq-listed stock of Sydney-based Kazia Therapeutics surged 51.7 per cent to a five-month high of $US8.74 ($A13.43) in after-hours trading on Tuesday after the announcement.

Kazia said the patient with stage-four breast cancer has achieved what an "immune-complete response", meaning there was no indication she still had cancer.

The woman in her 40s had been treated with a combination of standard chemotherapy, Kazia's drug candidate paxalisib and Merck's Keytruda, an intravenous infusion sometimes described as miraculous for its ability to melt away tumours.

Kazia is one of a number of companies exploring treatments that could work sy

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