A recipient of the 2025 Foundation for Surgery Research Scholarship from the Royal Australasian College of Surgeons (RACS), Dr Zexi Allan is working on a problem that could change how doctors treat some of the deadliest upper gastrointestinal cancers.

Her research focuses on peritoneal tumour DNA in gastric and gastroesophageal junctional cancers. Peritoneal tumour DNA or ptDNA consists of tiny fragments of tumour DNA found within the abdominal cavity. By studying these fragments, Dr Allan hopes to enable earlier identification of high-risk cancer patients and more accurate treatment decisions in the future.

“It’s definitely a great honour to receive the RACS Foundation for Surgery Research Scholarship,” she says. “It was very encouraging to see the surgical community recognising the value of this work.”

One of the biggest challenges in upper gastrointestinal cancer, Dr Allan says, is that current scans and staging tests can still miss tiny traces of cancer that have already spread within the abdominal cavity.

At present, doctors rely on scans, gastroscopy and staging laparoscopy to determine how far the cancer has spread. But within the abdominal cavity – a place where gastric and gastroesophageal cancer can often spread to – microscopic disease can still go undetected.

“Unless it’s gross peritoneal disease, the scans tend to miss it. Cytology also carries a high false negativity rate.”

That gap in diagnosis became the focus of her research.

Currently in the final year of her PhD through the University of Melbourne and Peter MacCallum Cancer Centre, Dr Allan is analysing patient samples and outcomes as part of a real-time study into tumour DNA and cancer recurrence.

Using ptDNA, Dr Allan and her team analyse fluid from the peritoneal cavity to detect even the smallest traces of tumour DNA. Their results so far have been striking.

“We saw a really high proportion of patients being ptDNA-positive, despite having negative scans and negative cytology. That was an alarming result. It means ptDNA is predicting a large cohort of patients with high risk of peritoneal recurrence that is actually missed by conventional staging.”

The implications could be significant. In the future, ptDNA testing may help identify patients who are more likely to experience peritoneal recurrence, allowing doctors to offer more targeted treatment earlier and potentially avoid ineffective or unnecessary procedures.

“We are hoping that one day it will become part of routine clinical care. The next project is to use it to identify high-risk patients and offer more targeted treatment.”

While tumour DNA testing in the blood, or circulating tumour DNA, is already becoming more common overseas, particularly in the United States, Dr Allan says research in ptDNA remains critical because each marker represents disease state from different body compartments and we know little about the role of ptDNA in upper gastrointestinal cancer in the western population.

“Upper GI cancer has been studied a lot in Asian populations. But in Australia we are now seeing a higher incidence, particularly for gastroesophageal cancer. The disease biology and treatment guidelines are different, so we need to understand our own population and provide better care locally.”

Dr Allan’s path into surgery began long before her PhD.

Born in Henan province, China, she moved to Queensland during junior high school and later studied medicine at the University of Melbourne. Even as a child, she says she was drawn to hands-on work and problem-solving.

“Surgery always appealed to me because of the practical and technical aspects,” she says.

During training, upper GI surgery stood out not only because of the complexity of the disease, but also because of the people she worked with.

“I was fortunate to work with a team that was welcoming, supportive and encouraging. That really strengthened my interest in pursuing upper GI surgery.”

Although her days are now dominated by research, Dr Allan says the mindset required for surgery and scientific work overlaps closely.

“As clinicians, we are diligent. We work long hours. We love problem-solving. The resilience you build from surgical training definitely applies to PhD study as well.”

Her research is highly translational, something she finds deeply rewarding because she can already see how it may eventually shape patient care.
“I can see the next stage of this molecular marker being translated into clinical care and where it can make a difference.”

Outside the lab, Dr Allan says life during a PhD is different from the intensity of full-time surgical training. The flexibility has allowed her to reconnect with family and friends and return to activities she enjoys, including badminton, tennis and swimming.

“You feel you have more control of when you plan things.”

Still, her focus remains firmly on improving outcomes for patients facing gastric and oesophageal cancer.

“It means a lot to me. I feel that I am doing something meaningful in the bigger picture of patient care.”