Younger Thyroid Cancer Survivors at Higher Risk for Late Effects

Brenna Blackburn

As part of our coverage of the 2017 American Society of Clinical Oncology Cancer Survivorship Symposium, held last month in San Diego, we are speaking with one of the presenters at the conference, Brenna Blackburn, a PhD candidate in public health at the Huntsman Cancer Institute at the University of Utah. Blackburn and her colleagues conducted a study that examined some of the late effects of therapy among thyroid cancer survivors who were diagnosed with the disease at a young age.

Cancer Network: First, can you talk about the frequency of thyroid cancer diagnoses annually in the United States and the proportion of patients who are diagnosed as children and young adults?

Blackburn: Thyroid cancer is the most rapidly increasing cancer in the United States, and last year it is estimated there were over 54,000 people diagnosed. There are currently over 600,000 thyroid cancer survivors within the United States.

It is a really young cancer with a median age at diagnosis of 51. When we look at the proportion of young adults, it is about 35% of all thyroid cancer patients. In our study, specifically, we looked at those diagnosed between 18 and 40, and that made up 37% of the thyroid cancer survivors in our population.

Cancer Network: Can you tell us about the study’s design? What did you seek to understand?

Blackburn: Our objective was to examine if thyroid cancer survivors diagnosed before the age of 40 experience a greater risk of late effects than those diagnosed at older ages, specifically for diseases associated with aging. In order to do this, we identified thyroid cancer survivors diagnosed in Utah between 1997 and 2012 and we matched each thyroid cancer survivor to up to five cancer-free individuals based on sex, birth year, and whether they were born in Utah or outside of Utah. This was all done within a Utah population database.

The Utah population database is an in-depth database that longitudinally links sources including Utah births, marriages, deaths, cancer records, driver licenses, and electronic medical records. So we used the electronic medical records to identify the late effects in the study population, and those medical records contained all state-wide ambulatory, surgery, and in-patient discharge data as well as electronic medical records from the University of Utah Health Sciences Center and Intermountain Healthcare, which covers a large majority of the state. We selected conditions and diseases associated with aging as delayed effects and studied these over three different time periods (1–5 years, 5–10 years, and more than 10 years after cancer diagnosis) so we could see how things changed over time. And then each model was adjusted for sex, birth year, race, baseline BMI, and baseline Charlson comorbidity index. And we looked at all of these outcomes with those diagnosed between 18 and 40 and those diagnosed at age 40 and older.

Cancer Network: What did you find when you examined these participants who had survived their thyroid cancer up to more than 10 years?

Blackburn: Overall, we found a significantly increased risk in the diseases associated with aging for both age groups when we compared them to the matched cancer-free individuals. But for the majority of the outcomes studied, the younger diagnosed population had much higher risk than those diagnosed when they were older. So some of interesting results were in the cardiovascular system. Looking at hypertension, the risk was significantly increased across all time periods for both age groups. So when we looked at those diagnosed at a younger age, for instance, from 1–5 years after cancer diagnosis, there was a 2.3-fold increased risk of hypertension compared to a 1.7-fold increased risk for those who were diagnosed with thyroid cancer at age 40 or later. Also in the cardiovascular system, swelling around the heart, those diagnosed before the age of 40 were more than 5.5 times as likely to experience this than the matched cancer-free individuals, and that remained nearly a 5-fold increase 10 years after the cancer diagnosis, so that risk remained in the long term.

A couple of other interesting outcomes were diabetes and osteoporosis. So thyroid cancer survivors diagnosed before age 40 had more than double the increased risk of diabetes across all three timeframes. It was also significantly increased for those diagnosed at age 40 and later, but it was significantly lower than for those that were diagnosed at a younger age. Looking at osteoporosis 1–5 years after cancer diagnosis, the risk was more than 7.5 times higher for patients diagnosed at a younger age compared to the matched cancer-free individuals. Again it was significant for those diagnosed at an older age (more than double, so it’s something to be aware of), but not quite as high as the 7.5 times increased risk in younger patients.

Cancer Network: What did you and your colleagues learn from this study that could be applied to the monitoring of these thyroid cancer survivors?

Blackburn: I think the biggest thing to remember is that thyroid cancer has very high survival, with a 5-year survival rate of approximately 98%. It is a population that is living a long time and it is important to be aware of how these risks are affecting these patients down the road. Many of these diseases and conditions are not thought to affect younger people, like osteoporosis, so the patients may not be screened for this as much, but knowing that thyroid cancer survivors are at increased risk for these can help with awareness for monitoring for these conditions.

Cancer Network: Thank you so much for joining us today, Brenna.

Blackburn: Thank you.