Chronic myeloid leukaemia (CML) patients are often required to take tyrosine kinase inhibitors (TKIs) indefinitely.
But 93% of those in a new study stayed cancer-free after stopping or reducing treatment.
Cancer Research UK said the results were "promising" but dosages should not be changed without a doctor's advice.
In 2000, trials of TKIs proved successful in controlling the rare disease, but also had side-effects,  including an increased risk of infection, skin rashes, nausea, hair loss and in some cases hormone disorder and a build of fluid around the heart.
The follow-up study, led by the University of Liverpool and involving consultants from Newcastle's Freeman Hospital, saw patients being given half the standard dose for the first 12 months. If leukaemia levels remained low, the drug was then stopped completely.
So far, out of 174 patients tested, 93% have shown no evidence of their leukaemia relapsing one year after reducing their dosage and many reported a significant decrease in side-effects within the first three months.
Source: CML Support
Dr Wendy Osborne, who is leading the Destiny study in Newcastle, said: 'We've gone from having patients with a potentially incurable disease and requiring toxic chemotherapy and transplantation, to now selecting some patients, again in a clinical trial setting, to stop the drug completely to remove any side-effects they have.
"This in itself is moving towards saying we've cured some patients and this is all because of research."
Dr Ã
New research could see patients with a rare blood cancer live longer without the side-effects of drugs, doctors say.