Researchers in the UK and US have discovered that a new experimental drug can stop the growth of and even shrink an advanced form of cancerous tumour.

The treatment, known as PEN-221, has been shown to stabilise neuroendocrine tumours (NETs) in almost 90% of patients and reduce the size of tumours in almost 40%.

NETs are rare types of cancer which are usually found in the pancreas, bowel or lungs but can also develop in other parts of the body, with 4,000 cases being diagnosed each year in the UK.

They arise from cells found throughout the body which form a link between the nervous system and the endocrine system, a collection of glands which produce hormones.

The treatment combines an anti-cancer molecule with a hormone to deliver the drug direct to the tumour site.

It is given to a patient via a drip over the course of an hour, repeated every three weeks until clinicians decide whether or not it is reducing or stabilising the tumour.

Hampshire-based charity Planets at University Hospital Southampton, led by Dr Judith Cave, was among sites across the UK and US which tested the new medication.

Dr Cave, who was involved in trials with 32 patients, said: “We are also hugely grateful to our patients as, without them, this research would not be possible.”

Layla Stephen, a co-founder of Planets, which helps patients with pancreatic, liver, colorectal, abdominal and neuroendocrine cancer by funding patient support groups, innovative treatments and research, took part in the study as a NET patient herself.

She said that she had seen a 20% reduction in her tumour burden following the treatment and added: “I am now quietly confident that this new drug could be a potential game-changer for certain NET patients in the near future if the continued next stage trials go well.”

The results of the study, led by the University of Texas and funded by Tarveda Therapeutics, were presented on Friday at the 2021 American Society for Clinical Oncology (ASCO) annual meeting.

They showed that the drug stopped the growth of tumours in 88.5% of patients, while 38% saw their tumours shrink.

Brian Roberts, president and chief executive of Tarveda, said: “We are encouraged by the safety and efficacy results of our Phase Two trial, which showed that PEN-221 was well tolerated and exceeded its clinical efficacy goals in patients with GI mid-gut neuroendocrine tumours.”