11-year-old girl with rare eye cancer is the first in Singapore to receive invasive radiation therapy

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

Called interstitial brachytherapy, the treatment delivers radioactive material directly into or very close to a tumor through a catheter or similar device. Surrounding healthy tissue is less affected by the radiation than with conventional external radiation, a non-invasive method in which a machine delivers radiation to a particular part of the body.

However, in Singapore, brachytherapy had never been performed on the eye before, and Kristal would only be the second child to benefit from brachytherapy.

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

At a press conference on Tuesday June 21, Associate Professor Joyce Lam Ching Mei, Senior Consultant in the Department of Hematology/Oncology at KK Women’s and Children’s Hospital (KKH) said that she and the team working on the case de Kristal had offered interstitial brachytherapy because they wanted to preserve his sight.

This method would also minimize the risk of her developing a second cancer due to the exposure of normal tissue to low-dose radiation, said another member of the team, clinical assistant professor Kiattisa Sommat, senior consultant in the department. Breast and Gynecology at the National Cancer Division of Radiation Oncology Center in Singapore.

The first child to have brachytherapy in Singapore was an 11-month-old Vietnamese boy, who came here for treatment for a prostate tumor in 2020. Both children are doing well today, with no active cancer cells detected , said Professor Lam.

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, doses of radiation were delivered in the morning and afternoon, for 10 minutes each time.

Prof Kiattisa said the multidisciplinary team, which also included clinical associate professor Sunny Shen, senior consultant and head of the department of oculoplasty at the Singapore National Eye Centre, consulted an Italian expert on the treatment. They did a lot of testing and practiced inserting the catheters on a few fruits, including a pomelo, to make sure they got the best entry route and placement of the device for example, while minimizing potential eye injuries.

Professor Shen said they were also concerned about the effects of the treatment. “The lens inside the eye is very sensitive to radiation therapy and such treatment can cause premature cataracts,” he said. Fortunately, Kristal did not develop such a complication.

Only a few centers in the world have the capacity to use the interstitial brachytherapy method on pediatric tumors, although it has been used here to treat gynecological and prostate cancers in adults for about four or five years, a said Professor Kiattisa.

This is not only because it is difficult, but also because of the rarity of childhood cancers. KKH, which handles about 80% of these cases here, sees about 100 cases a year.

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

Kristal’s mother, Madame Lim Hwee Ping, a 43-year-old stay-at-home mom, said she first discovered what appeared to be a small “pimple” near Kristal’s eye. She thought it was related to puberty, but the pimple got bigger, setting off the alarm.

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