It makes cancer cells porous so more of the toxic drugs attack the tumour rather than healthy cells.
Initial results suggest the treatment reduces the amount of medicine needed and may prevent side effects such as nausea, fatigue and hair loss.
The technique, called electro-chemotherapy, has been used to treat tumours that are easily accessible, such as skin cancer.
But a team from the University of Cork has developed a probe that can do the same for tumours deep inside the body.
Trials involve patients with bowel tumours considered inoperable.
But scientists behind the experimental device, called the EndoVe, are looking at adapting it for use in cancers in the oesophagus, lungs, pancreas and prostate.
Standard treatment for bowel cancer is surgery to remove the tumour and some of the bowel, then radiotherapy and/or chemotherapy on lingering cells.
The new technique is based on the fact that when a cancer cell is bombarded with short electric pulses, the protective outer membrane that keeps it intact begins to fragment, allowing in large chemotherapy molecules.
The chemotherapy drug bleomycin is injected into the bloodstream just before the tumour is exposed to quick-fire pulses to break open the membrane on the cancer cells and absorb the drug.
The first patient to be treated with the probe had an inoperable tumour wiped out. The EndoVe is still in the early stages of clinical trials but could be available in Britain within three to five years. Cancer Research Britain said extensive trials would be needed.