Researchers at the National Institute of Radiological Sciences have developed a method to predict how prone a cancer patient may be to radiation side effects based on minor genetic differences, possibly paving the way for customized radiation treatment, a senior researcher in the project said Monday.

Clinical studies are set to be held on more than 1,000 patients at the institute's heavy particle radiotherapy center in Chiba and five universities across the nation as early as April, according to Mayumi Iwakawa, leader of one of the research groups in the project.

The researchers traced a gene cluster that determines sensitivity to radiation by irradiating mice and analyzing the condition of skin damage against genetic differences, Iwakawa said.

The project, headed by Takashi Imai, was conducted at the Frontier Center at the National Institute of Radiological Sciences. The center is based in Chiba.

Iwakawa said the researchers sought cooperation from about 30 medical facilities around the country to check through blood tests the genes of about 1,700 breast cancer, uterus cancer and prostate cancer patients -- both those who suffered side effects from radiation treatment and those who did not.

They then identified 57 types of DNA sequence variations that occur when a single nucleotide in the genome sequence is altered, but only among those who experienced side effects.

Radiation therapy, one of three major methods of treating cancer along with surgery and chemotherapy, involves killing cancerous cells using X-rays or gamma rays. Its side effects can include fatigue, anemia, skin inflammation and functional impairment of the lungs, kidneys and other organs.