Thyroid cancer spike fuels Fukushima fears but cause could be over-diagnosis

In March, two fathers spoke via Skype at a news conference, with their voices masked electronically and their faces not shown. They did not want to reveal their identities.

The men, whose children have been diagnosed with thyroid cancer, were speaking at an event to mark the launch of 311 Thyroid Cancer Family Group.

One of the men said his teenage daughter had a hoarse voice after having half of her thyroid gland removed, leaving her with a temporary speech disorder and deep depression.

But for the patients and their families, the bigger agony is that they feel they must remain quiet about their illness.

Despite the many worries and questions surrounding possible radiation exposure, they fear they will be criticized, that their speaking out will be taken as linking the illness to the Fukushima disaster — a link that has yet to be scientifically established. Sensitivity runs high among residents of the prefecture over negative news that could increase the stigma they already bear.

“I couldn’t tell anyone that my child had cancer. My child was also unable to tell her friends,” one of the fathers said, adding that they had to keep such talk within the family.

What is worse, amid possible over-diagnosis from the mass screenings underway, some patients may have had surgery for a condition that would not cause them trouble in their lifetime if left untreated. Medical science, so far, cannot prove it one way or the other.

“They were completely at a loss after being told their children had cancer and given little explanation,” Motomi Ushiyama, a doctor at Sagami Seikyo Hospital in Kanagawa Prefecture and a member of the support group, told The Japan Times.

“They were blaming themselves,” he said. “It’s heart-wrenching to listen to such voices.”

Girls who had undergone surgery were constantly covering scars on their neck, and their parents were worried they would have a relapse in the future, Ushiyama said.

As Fukushima Prefecture continues to conduct thyroid screening for some 380,000 children who were aged 18 and under at the time the Fukushima crisis began, the list of thyroid cancer patients is getting longer.

As of December, 166 children were diagnosed with suspected thyroid cancer. Of them, 116 were confirmed to have the cancer after undergoing surgery. Some 300,000 children voluntarily received the checks in the program’s first round of screening, and another 230,000 by the end of last year in a second round, according to the prefectural government.

The accumulated data have shown that thyroid cancer was unlikely to be radiation-induced, given that the radiation release was lower than in the 1986 Chernobyl accident, according to an interim report released by a panel of experts through the Fukushima Prefectural Government at the end of March.

Even though younger children are more vulnerable to radiation exposure, no cancer was found among those under age 5 at the time of the nuclear disaster.

But the report also pointed out that a link to the nuclear disaster cannot be ruled out.

Scientists say the screening of an unprecedented number of children without prior symptoms may be the reason why the thyroid cancer rate was found to be higher than the national average.

Moreover, as ultrasonogram technology improves, over-diagnosis of thyroid cancer has become a concern worldwide, experts said.

In South Korea, the thyroid cancer rate in women spiked by 15 times in 2011 compared with that observed in 1993 after the nation added screening to other regular cancer-screening tests in 1999. And yet the number of deaths from thyroid cancer in South Korea remained unchanged.

Shoichiro Tsugane, a director at the National Cancer Center’s research arm on cancer screening, said over-diagnosis is highly likely to be the reason behind the sudden rise in Fukushima.

“There are no data to support the assumption that the rise is due to exposure to radiation. … And there are no data to confirm it is due to over-diagnosis,” Tsugane said. “But based on scientific knowledge on thyroid cancer that we have, it is natural to think it is due to over-diagnosis.”

Even so, quitting the screening program midway through is not an option, experts say.

The figures are the results of screening some 300,000 people, noted Kazuo Shimizu, a thyroid surgeon at Kanaji Hospital and professor emeritus at Nippon Medical School.

“There are no data in the world relating to symptomless children examined on this scale at one time,” he said. “This will be the basic data for future use.”

As the data are drawing global attention, “we have the responsibility to continue the examinations in Fukushima and release the data,” Shimizu said.

Thyroid cancer usually causes no symptoms, and papillary thyroid cancer, the most common type diagnosed in Fukushima children, is known for its generally slow growth and very low fatality, Shimizu said.

According to a report released by Tokyo’s Cancer Institute Hospital in January, the 10-year survival rate for thyroid cancer patients topped 90 percent, while the average rate of all cancers stood at 58.2 percent.

Given such characteristics for thyroid cancer, some patients have opted for observation rather than immediate surgery. Shimizu said he has been observing such patients for two or three years, and their tumors often have not grown.

In some patients who opted to be observed, the size of their nodules shrank with time, according to a report by Kuma Hospital, which is well known for its thyroid specialists, in Kobe.

But whatever the reason, the agony of the patients and their families continues.

If the cancer diagnosis can be chalked up to over-diagnosis, it may mean some children underwent unnecessary surgery. If their thyroid cancer is related to the nuclear disaster, the news would be even more devastating for them.

“It’s a tragedy,” Tsugane of the National Cancer Center said.

What the patients and their families really want to know is the truth.

“If those cancers were found due to the screening effect, then if they didn’t have to go through surgery. … If that’s the case, then we really want to know,” Ushiyama of the 311 family group said.