Girl, 11, first kid here with eye tumour to get invasive radiation therapy

When 11-year-old Kristal Yong was diagnosed with a rare and aggressive cancer of the muscle in her right eye in late 2020, her parents said yes to the best available radiation therapy the doctors proposed.

Interstitial brachytherapy allows radioactive material to be delivered directly inside a tumour or very near it through a catheter or similar device. Surrounding healthy tissues are less affected by the radiation than with conventional external beam radiation, a non-invasive method in which a machine delivers radiation to a particular part of the body.

But interstitial brachytherapy had not been done in Singapore on the eye before, and Kristal would be only the second child here to have brachytherapy at all.

Kristal completed six months of cancer treatment, including chemotherapy, in April last year. She is the first child cancer patient with orbital rhabdomyosarcoma in Singapore and South-east Asia to receive interstitial brachytherapy.

At a media briefing yesterday, Clinical Associate Professor Joyce Lam Ching Mei, a senior consultant at the haematology/oncology service at KK Women's and Children's Hospital (KKH), said she and the team working on Kristal's case proposed interstitial brachytherapy because they wanted to save her eyesight.

The method would also minimise Kristal's risk of developing a second cancer from the exposure of normal tissues to low-dose radiation, said another team member, Clinical Assistant Professor Kiattisa Sommat, a senior consultant in the department of breast and gynaecology at the National Cancer Centre Singapore's radiation oncology division.

The first child to have brachytherapy in Singapore was an 11-month-old Vietnamese boy, who came here for treatment for a prostate tumour in 2020.

Both children are doing well today, with no active cancer cells detected, Prof Lam said.

During her brachytherapy treatment in February last year, Kristal was confined to a hospital bed with six plastic catheters inserted into her right eye. For a week, radiation doses were delivered twice a day, for 10 minutes each time.

Prof Kiattisa said the multidisciplinary team, which also included Clinical Associate Professor Sunny Shen, a senior consultant and head of the Oculoplastic Department at the Singapore National Eye Centre, consulted an Italian expert on the treatment, and held dry runs where they practised inserting the catheters in fruit.

Only a few centres in the world have the capability to use interstitial brachytherapy on paediatric tumours, though it has been used here to treat adult gynaecological and prostate cancers for about four or five years, said Prof Kiattisa. This is partly because of the rarity of childhood cancers. KKH, which handles around 80 per cent of such cases here, sees about 100 cases a year.

Prof Kiattisa said the cost is highly dependent on the site of treatment and the level of technical expertise needed.

Kristal's mother, Madam Lim Hwee Ping, 43, a housewife, said she first discovered what seemed to be a small "pimple" near Kristal's eye. She thought it was linked to puberty but the pimple got bigger, sparking alarm.

She and her husband talked about their options and decided to trust the doctors.

"Our main concern is, is it safe for her? Second, is the team confident enough to do it because we don't want her to be a guinea pig," said Madam Lim, who also has an eight-year-old son.

"We just want her to have the best chance in life because she has a long runway and brachytherapy is the best available option."