NRI: CDC Activities

Study of Military Personnel

The Department of Veterans Affairs evaluated whether 1,214 NRI-exposed World War II submariners were at an increased risk of death compared to 3,176 untreated submariners (Kang et al, 2000). In this study, researchers found a small increased risk of death for the NRI-exposed veterans due to cancers, including cancers of the head and neck. However, these findings were no statistically significant.

Epidemiologic Studies of Health Effects

Maryland Study

On the basis of a cohort study of 904 exposed and 2021 unexposed persons during 1943-1960 (conducted by Sandler et al. in Maryland in 1982), showed a slight increased risk of head and neck cancers among exposed persons, but this was not statistically significant. A follow-up study of this cohort was conducted in 2001 (Yeh et al, 2001). In this study researchers found an elevated but statistically non-significant risk of developing certain cancers (brain, thyroid). However, they also found that the rates for other types of cancers (breast, endometrium, ovary, and prostate) were lower in the exposed population than in the non-exposed population. None of these findings was statistically significant.

Netherlands Study

A cohort study of 2510 exposed and 2199 unexposed persons (conducted by Verduijn et al. in the Netherlands) did not document a statistically significant increase in head and neck cancers in the exposed group.

Follow-up Investigators assessed whether cancer mortality of the Netherlands cohort was higher among 5,358 NRI-exposed individuals compared to 5,265 non-exposed patients (Ronckers et al, 2001). At the time of the study, they had been followed for an average of 31.6 years. The investigators found no increased risk of death from cancers of the head and neck, nor from brain tumors. They did, however, find evidence of a marginally statistically significant increase in death from non-Hodgkin lymphoma. They concluded that their study did not indicate that NRI-exposure in childhood was associated with an increased risk of cancer mortality.

In an analysis of the cancer incidence among 4,339 NRI-treated Dutch patients in the same Netherlands cohort (Ronckers et al, 2002b), the investigators found no elevated risk of cancer in general, nor of tumors of the head and neck in particular, compared to the 4,109 untreated participants. The same researchers (Ronckers et al, 2002a) evaluated the occurrence of nonmelanoma skin cancer, benign tumors, and hormonal disorders in the same Dutch cohort. They found that the exposed population (3,440 patients) was not at increased risk of thyroid disorders or benign head and neck tumors, including pituitary adenomas and salivary gland tumors. However, they did find a marginally statistically significant increased risk of infertility in exposed men compared to the unexposed men.

Conclusions

Current studies do not indicate substantial increases in risks for neoplastic or other disease among those who received NRI treatments. Although these studies identify possible associations between NRI treatment and health effects, the findings are not consistent and thus no clear link between NRI exposure and cancer risk has been established.

CDC Recommendations

Because the diseases that could be associated with this treatment are rare and the treatment may confer a modest additional risk of those diseases, CDC does not recommend screening for all patients who received the treatment. However, physicians may consider performing thorough head and neck examinations of patients with a history of NRI treatments. In addition, physicians who provide care for patients born before 1960 with head and neck complaints should ask the patients whether they have a history of NRI or other head and neck radiation treatments. Persons who recall being treated or believe they were treated with NRI should inform their physicians of the exposure. Some patients who received this treatment will be worried about it, and need the reassurance that is offered by a thorough and caring examination.