Better cure eye cancer with personalized radioactive implants

This content is produced by Laval University.

Uveal melanoma, or eye cancer, is the most common type of melanoma after skin cancer, with 350 new diagnoses each year. The treatment of this disease poses several challenges that Marc-André Fortin, professor in the Department of Mining, Metallurgy and Materials Engineering, wants to overcome.

“It’s a project that is close to my heart,” he says. It’s practically an orphan disease for which there hasn’t been much development in the last 30 years and for which we could have a significant impact.” He presented his research work on radioactive implants at a general public conference organized by the Continuing Education of the Faculty of Science and Engineering.

Professor Fortin explains that eye cancer is currently treated using a circular metal plate which contains radioactive grains. This episcleral plate is surgically inserted into the eye to kill tumor cells. The approach of radiation therapy directly inside the body, called brachytherapy, however, poses risks to healthy tissue surrounding the tumor.

“For 30 to 45% of patients treated, particularly when the plaque is located too close to the optic nerve or the retina, there will be eye damage and a reduction in visual acuity, a pathology called radiation-induced retinopathy. », underlines Marc-André Fortin, also a researcher at the Research Center of the CHU de Québec – Université Laval.

Depending on the shape of the tumor and how deep it is in the eye, it is more difficult to treat. The plaque must be larger, which causes more damage to healthy tissue. “Elongated or deep tumors account for 25% of cases,” he explains. And for 5% of patients, the damage caused leads to enucleation, or removal of the eye.

Improve treatment

With his research group, Professor Fortin wishes to improve treatment technology by improving the episcleral plaque. Researchers are using 3D printing to make plates with a more personalized shape and distribution of radioactivity. “As an engineer, this is by far the most interesting type of radioactive object, because it is small. This is therefore associated with a design and manufacturing challenge.”

In his laboratory, Théophraste Lescot, a former master’s student and research professional, worked on the digital design of the plate and its printing. “Precision is the main challenge in 3D printing. It was therefore necessary to find a way to verify the conformity of the plate by comparing it to the initial diagram,” reports Professor Fortin.

His team notably collaborated with Claudine Bellerive, clinical professor at the Faculty of Medicine and researcher at the CHU de Québec – Université Laval, to ensure that the plates are easy to use. “If an implant is too different from what surgeons expect, they may not use it.”

In addition to the shape of the plaque, Professor Fortin’s team customized the arrangement of the radioactivity to better treat deep tumors, often in the form of fungus, in the eye. Doctoral student Souheib Zekhraoui has developed a new way to transform radioactive sources. Usually in the form of grains of rice which radiate in all directions, they instead take the form of small channels which contain the radioactivity. This configuration allows radiation to be projected in one direction to preserve surrounding healthy tissue.

These radioactive channels can be positioned in the plaque according to the prescribed dose. To validate this arrangement, a dose profile is necessary to determine the extent of the radiation. Doctoral student Mahdokht Akbari designed a hydrogel that solidifies slightly in the presence of radiation. These zones, called polymerized, are used to map the radiation.

Professor Fortin and his team test their technology using real case data, from prescription to validation of the printed implant. They wish to submit an application to Health Canada for a clinical study permit.

According to Marc-André Fortin, advances related to eye cancer can be transferred to other types of cancer, including that of the throat, esophagus or genitals. “It can be used in all types of treatments that would involve the design of a personalized implant.”