SINGAPORE – When two-year-old Yanna Lui first babbled the word “mama” in August, her mother was overwhelmed with emotion.

“It was like witnessing a miracle,” said Madam Low Yoke Moi, a homemaker with three children.

Little Yanna finally hit a developmental milestone, about a year behind most of her peers, who started recognising their parents around the age of one.

It was a sign of hope and recovery for the toddler who survived a rare form of brain tumour called ependymoma.

Yanna is the youngest patient to benefit from proton beam therapy (PBT) at the National Cancer Centre Singapore (NCCS). The treatment is an advanced form of radiation therapy that targets and kills cancer cells with precision.

Diagnosed in September 2023 at just four months old, Yanna underwent a year of intensive treatment.

It included a risky seven-hour operation, eight rounds of chemotherapy and 33 sessions of PBT.

PBT is more precise than conventional radiation therapy and causes less damage to surrounding healthy cells, thereby limiting harmful side effects. It is most beneficial for patients who have cancers in sensitive areas like the head or neck, or paediatric cancers.

Singapore is the second country in South-east Asia to offer the state-of-the-art treatment, and the only facility doing so in the country’s public sector is at the National Cancer Centre Singapore (NCCS).

Since the treatment was rolled out at the NCCS Goh Cheng Liang Proton Therapy Centre in June 2023, the facility has treated 37 young patients between one and 18 years old.

Due to Yanna’s age and the complexity of her brain tumour, she was treated by a team of specialists from three public healthcare institutions – KK Women’s and Children’s Hospital (KKH), the National Neuroscience Institute (NNI) and NCCS.

At a media briefing at NCCS on Aug 27, the team of doctors detailed the treatment plan for Yanna and how they sought to save her while ensuring long-term quality of life.

The first sign of trouble came in September 2023, when Yanna started refusing to drink milk, and her neck and limbs were weak. Her parents took her to see a general practitioner, who referred her to a specialist.

Scans at KKH showed a 6.7cm tumour wrapped around Yanna’s brain stem near her neck, pressing on her vital nerves – a dangerous location for a tumour.

Dr Debbra Chong, consultant with KKH’s haematology and oncology service, said: “The brain stem is a very important structure because it controls our breathing, our blood pressure, the nerves of the face, swallowing, and the nerves that control our limbs.”

Because the tumour was compressing the brain stem significantly, as much of it had to be removed as possible.

Yanna was scheduled for surgery in late September 2023. Doctors were conservative and initially estimated that they could remove only about 20 per cent of the tumour as they did not want to damage vital nerves and organs.

Clinical Associate Professor David Low, who operated on Yanna, had good news for her parents after the surgery.

“We successfully removed 60 per cent of the tumour, including some areas around the nerves, but we had to leave portions that were wrapped around important blood vessels that supplied the brain stem, as damaging them could have caused a brain stem stroke,” said Prof Low, who is a senior consultant at NNI’s department of neurosurgery.

Madam Low and her family were awash with relief and gratitude at the results of the operation.

“All of us collapsed into a hug, and we were all so happy. It was like a miracle happened, from just being able to remove 20 per cent of the tumour to removing 60 per cent,” said Madam Low, adding that the successful surgery gave her hope.

To shrink the remaining tumour and allow her to reach a suitable age for radiotherapy, Yanna received eight cycles of chemotherapy, which she completed in May 2024.

When Yanna turned one – the minimum age for PBT – she started the treatment, which is needed to prevent the remaining tumour from growing.

Clinical Assistant Professor Gail Chua, a consultant at NCCS’ division of radiation oncology, said that as Yanna was just an infant when she was diagnosed, PBT was recommended to reduce radiation exposure to her developing brain and minimise the risk of late-onset side effects like impact on IQ, mood and memory.

PBT causes significantly less damage to healthy tissue because the radiation rays start at a low dose, spike at the tumour and stop without going further. In conventional radiation therapy, the rays start strong and diminish as they move through the tumour and outside the body – affecting healthy cells in the path of the ray.

“Young children are particularly vulnerable to late-onset side effects of radiation because their developing tissues and organs are more sensitive, and they have many years ahead for side effects to surface,” added Prof Chua.

Yanna’s PBT treatment cost about $53,000, and was fully claimable via her father’s MediSave and MediShield Life.