This article is more than 5 years old. Information may no longer be current.
Antineoplastic agents associated with thyroid dysfunction
Hamnvik OPR. J Natl Cancer Inst. 2011;doi:10.1093/jnci/djr373.
Click Here to Manage Email Alerts
Approximately 20% to 50% of patients taking antineoplastic agents for treatment of cancer experience thyroid dysfunction. Researchers said, however, that close monitoring and careful evaluation of patients using these therapies may mitigate the development of thyroid disease.
Although evidence links antineoplastic agents with thyroid dysfunction, physicians may often overlook the disease’s symptoms, such as fatigue, weakness, depression, memory loss and cardiovascular disease, due to the complex clinical picture of patients with cancer. Therefore, researchers at Brigham and Women’s Hospital in Boston conducted a literature review of studies involving various antineoplastic agents and thyroid dysfunction to determine how to proceed with patients at risk for disease.
Challenges in screening, management
According to the researchers’ findings, no guidelines exist on screening asymptomatic patients, and some of the preventive measures may be more toxic than the disease itself. However, they make several recommendations themselves based on the unique issues of patients with cancer. For example, whereas treatment for subclinical hypothyroidism is usually deemed unnecessary due to a lack of evidence indicating clinical benefit, patients with cancer may require a different course.
“In the cancer patient, it may be difficult to determine if mild hypothyroidism is truly asymptomatic because of the substantial overlap between symptoms of hypothyroidism with symptoms related to treatment or the underlying disease,” the researchers wrote. “Therefore, it seems reasonable to start low-dose levothyroxine therapy in these patients as a therapeutic trial, especially if they are receiving an agent associated with a high risk of hypothyroidism.”
They also suggest initiating treatment in patients with thyroid-stimulating hormone levels of more than 10 mIU/L or with low free thyroxine levels, citing a study showing improvement in at least half of patients who began levothyroxine treatment for sunitinib (Sutent, CPPI CV/Pfizer)-associated hypothyroidism. The researchers recommend a starting dose of 1.6 mcg/kg daily for patients without underlying cardiac disease, but they said a lower dose, such as 50 mcg daily, should be used during the first few weeks for patients with coronary artery disease.
Although atypical, taking levothyroxine with other medications simplifies the life of a patient with cancer, the researchers said, noting that dosage strength can be adjusted to achieve target TSH or T4 levels.
Close monitoring for hypothyroidism in patients with cancer receiving antineoplastic agents is essential but also presents a challenge, the researchers said. Central hypothyroidism associated with bexarotene (Targretin, Eisai) and ipilimumab (Yervoy, Bristol-Myers Squibb) or tremelimumab, for instance, cannot be monitored using TSH concentrations. In this case, the researchers suggest using free T4 levels instead, with normal levels ranging from 1 ng/dL to 1.5 ng/dL.
The treatment of thyrotoxicosis can be much more complex, according to the researchers. For example, patients with Graves’ disease who are initially treated with antithyroid medications cannot usually undergo ablation with radioactive iodine if they have received iodinated contrast within the past 3 months.
Future research
“As this review highlights, there are multiple areas of uncertainty in this topic, and most of the data are derived from case reports or case series, small prospective studies or laboratory-based studies,” the researchers wrote.
Therefore, to improve physicians’ ability to treat thyroid disease associated with antineoplastic agents, they said increased knowledge about biological effects of each medication, as well as large, randomized clinical trials evaluating screening and treatment in these patients, are needed.
Disclosure: The researchers report no relevant financial disclosures.
 |
Follow EndocrineToday.com on Twitter. |