Lymph node metastasis in 72% of thyroid cancers, invasive in 47%: Experts call for long-term studies

Prof. Shinichi Suzuki of Fukushima Medical University spoke at an international symposium in Fukushima City on February 3, 2020. He has been performing most of the surgeries for people who were 18 years old or younger at the time of the 2011 Fukushima nuclear accident and diagnosed with thyroid cancer via the Fukushima Health Management Survey.

He reported that of the 180 cases of surgery for thyroid cancer from 2012 to 2018, 72% were found to have lymph node metastasis and 47% were invasive, but that very low-risk cases where follow-up observation was recommended were not included in those numbers.

It was also revealed that 6% of the patients had a relapse after surgery and required repeat surgery. The male-to-female ratio for those 180 individuals was 1:1.7 (this includes 1:1.4 for the second round of surgery, and 1:0.7 for the third round), and while the male-to-female ratio for thyroid cancer is typically 1:7 or 1:8 (weighted heavily toward females), this study found the ratio of males to be greater than females.

Prof. Suzuki emphasized the need for long-term studies. The Fukushima Health Management Survey, found that 231 people had or were suspected of having thyroid cancer, and 172 underwent surgery (as reported by the prefecture as of October 2019). Even though the Review Committee found this to be tens of orders of magnitude higher than the number of cases that would be estimated from thyroid cancer morbidity statistics, paradoxically it also stated that “It is difficult to consider these numbers to be due to the (nuclear) accident.”