Radioactive Iodine Treatment Increases Leukemia Risk


Research has shown that treatment with radioactive iodine for well-differentiated thyroid cancer is associated with an increased risk of two types of blood cancer: acute myeloid leukemia and chronic myeloid leukemia.

"Differentiated" thyroid cancer refers to the appearance and behavior of the cancer cells, and in a well-differentiated thyroid cancer, the cells look and act like normal thyroid cells.

Well-differentiated thyroid cancer types include papillary thyroid. carcinoma, follicular thyroid carcinoma, and Hürthle cell carcinoma (HCC).

Radioactive iodine is frequently administered as part of the treatment for thyroid cancer, typically after surgery to remove the thyroid gland. The radioactive iodine, also known as RAI, is given to help destroy any thyroid tissue remaining after surgery, as a way to prevent the recurrence of the thyroid cancer that could develop in remaining thyroid tissue.

While research has shown that thyroid cancer survivors who have undergone RAI face an increased risk of a number of secondary cancers, this is the first time that a significant and demonstrated relationship has been found between radioactive iodine for thyroid cancer and an increased risk of both acute and chronic myeloid leukemia.

About Myeloid Leukemias

Acute myeloid leukemia (AML), also known as acute myelogenous leukemia, is a serious form of blood cancer that progresses quickly and can be fatal if not treated.

AML can also spread to other parts of the body including the lymph nodes, liver, spleen, brain, spinal cord, and testicles.  The American Cancer Society estimates that there will be more than 21,000 new cases of AML in 2017, and around 10,600 deaths from AML. AML is rare before the age of 45, and the average age of an AML patient is 67.

The five-year overall survival rate for AML is 26 percent.

Chronic myeloid leukemia (CML), also known as chronic myelogenous leukemia, is a chronic form of blood cancer.  The American Cancer Society estimates that around 9,000 new cases of CML will be diagnosed in 2017, with almost 1,110 deaths. The average age at diagnosis is 64. The five-year overall survival rate for CML is around 75 percent.

The researchers identified a study group of patients well-differentiated thyroid cancer in order to calculate their risks of secondary blood cancers. In the study, a total of 148,215 patients with well-differentiated thyroid cancer were evaluated. For a total of 53 percent of the patients, their only treatment was thyroidectomy, a surgery to remove the thyroid gland. A total of 47 percent had a thyroidectomy, as well as radioactive iodine remnant ablation treatment.

Among the patient group studied, a total of 783 patients developed a secondary blood cancer over the study timeframe of 6.5 years.

Compared to patients who had only a thyroidectomy, the patients who also had radioactive iodine had a significantly increased early risk of developing either acute myeloid leukemia or chronic myeloid leukemia.

The risk was similar whether the patient had a low, medium- or high-risk tumor.

Among those thyroid cancer survivors who developed AML, the media survival of 1.2 years was also significantly less than the 2.9-year median in people who have not had radioactive iodine treatment.

A Word From Verywell

This research shows that patients who have well-differentiated thyroid cancer such as papillary, follicular, or Hurthle cell cancer, and receive radioactive iodine remnant ablation treatment, have an increased early risk of developing acute myeloid leukemia and chronic myeloid leukemia. Acute myeloid leukemia also has a poor prognosis in patients after radioactive iodine treatment.

The researchers recommend that only patients with very high-risk disease characteristics be treated with radioactive iodine for well-differentiated thyroid cancers.

If you are diagnosed with a well-differentiated thyroid cancer and your doctor recommends radioactive iodine treatment, consider getting a second opinion from another practitioner.

If you have had radioactive iodine in the past, or have it in the future, be sure that periodic monitoring and surveillance for these blood cancers is part of your ongoing health care. You can be periodically monitored with blood tests, as well as chromosomal and genetic testing.

Also, be on the looking for symptoms of acute and chronic myeloid leukemia, which can include fatigue, feeling rundown, reduced ability to exercise, recurrent infections, easy bruising, fever, loss of appetite, shortness of breath, weight loss, night sweats, dizziness, bleeding gums, frequent nosebleeds, skin rashes


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