People with lung, stomach, skin, bladder, pancreatic and ovarian cancer appear to beat their disease with a common chemotherapy called platinum treatment.
However, the diseases often return after they appear to develop resistance to the drug. Sometimes they are put on second-line therapies, but these often do not perform as well.
But, a team at the Ovarian Cancer Action in the UK now found that cancers do not become resistant over the time.
Instead, minute traces of cancers that were always resistant to platinum therapy remain there and cause the relapse of the disease, the Daily Telegraph reported.
This discovery helped them identify four or five different molecular "targets" that could be the focus of new drugs, Prof Hani Gabra, director of the UK charity's research centre, said.
"These cancers look like they are platinum-resistant, but in fact they were there from the outset and they were never touched by the drugs," he said.
Unaffected, they had simply taken their time to grow, he explained.
That step-change in understanding meant they were able to concentrate on what exactly was different about the tumours which appeared later, the researchers reported in the journal Cancer Research.
