Radioactive iodine for thyroid cancer linked to risk for melanoma, other skin cancers
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Key takeaways:
- Patients with primary thyroid cancer who received radioactive iodine therapy had elevated risk for melanoma/skin cancer.
- Patients treated for thyroid cancer may benefit from subsequent skin cancer screening.
Patients with primary thyroid cancer who received radioactive iodine exhibited increased risk for melanoma and other nonkeratinocyte skin cancers, according to study results.
“Radioactive iodine therapy is a mainstay treatment for thyroid cancer, with associated reductions in all-cause and cancer-specific mortality,” Shawheen J. Rezaei, MPhil, a Knight-Hennessy Scholar from Stanford University and MD student with scholarly concentration in health services and policy research, and colleagues wrote. “Although the risks [for] subsequent cancer do not outweigh the benefits of treatment, our findings suggest that patients treated for thyroid cancer may benefit from follow-up skin cancer screening.”
Prior research showed a potential link between papillary thyroid cancer and malignant melanoma through common pathogenic variants; however, evidence for a potential relationship between melanoma and exposure to ionizing radiation is limited.
Rezaei and colleagues used SEER data to examine the risk for subsequent melanoma and other nonkeratinocyte skin cancers among patients with primary thyroid malignant neoplasms.
Researchers’ analysis utilized 17 cancer registries from the SEER database involving patients with thyroid cancer diagnosed from 2000 to 2019. Follow-up for development of subsequent cancers continued through 2020.
Investigators computed standardized incidence ratios (SIRs) and estimated risk for subsequent cancer development, then adjusted results for sex, self-reported race/ethnicity, age and year of initial diagnosis.
The study included data from 174,916 patients (78.8% women; 64.6% white), 79,576 (45.5%) of whom received first-course treatment of some form of radiation.
Researchers identified 865 nonkeratinocyte skin cancers (melanoma, n = 790) diagnosed after thyroid cancer, with 171 (19.8%) located on the head or neck.
When researchers limited analyses to cancers of the skin on the head or neck, they calculated higher-than-expected SIRs for subsequent skin cancers among patients with thyroid cancer treated with radioactive iodine. This persisted for all nonkeratinocyte skin cancers (SIR = 1.64; 95% CI, 1.32-2.02), melanoma (SIR = 1.56; 95% CI, 1.22-1.97) and other nonkeratinocyte skin cancers (SIR = 2.07; 95% CI, 1.23-3.27).
The risk for skin cancer on the head and neck did not appear elevated among patients who did not receive radioactive iodine therapy for thyroid cancer.
An analysis of patients with primary thyroid cancer who underwent treatment with any form of radiation showed a statistically significant SIR among those with the papillary subtype (SIR = 1.69; 95% CI, 1.35-2.09) but not for those with other thyroid cancer subtypes.
Researchers acknowledged study limitations, including a small sample size of patients with nonpapillary thyroid cancers, as well as limited number of non-white patients.
More research is required “to identify the mechanisms through which thyroid cancer and thyroid cancer therapy are associated with skin cancer,” Rezaei and colleagues wrote.
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