Contrary to what most physicians believe, the most common forms of thyroid cancer are no more serious in pregnant women than they are in other women, new research shows.
The Ohio State University study also showed that delaying treatment until after delivery had no identifiable negative effects on patients who decided to wait.
Surgery Can Be Safely Postponed
A pregnant woman can now choose to postpone surgery for the disease until after delivery without fear of worsening her outcome. This is the first large group study to look at this question.
Prior to this study, doctors suspected that thyroid cancer might be more dangerous in pregnant women. Some evidence had suggested that human chorionic gonadotropin might hasten tumor progression. Doctors therefore often recommended that surgery take place soon after tumor diagnosis.
“We can now tell women they have a choice,” said Ernest Mazzaferri, professor of internal medicine and a clinical researcher at Ohio State’s Comprehensive Cancer Center. “We can reassure them that just because they are pregnant and have this malignancy, it’s not a more vicious disease. We can also now give patients the choice of postponing surgery until after delivery with little fear of worsening their outcome,” he said. “Surgery for this disease during pregnancy isn’t highly dangerous, but it does carry some risk, and now we can give our patients the option of waiting.”
An estimated 14,000 new cases of thyroid cancer occur annually, with about 1,000 people dying of the disease each year. The disease occurs more commonly in women, afflicting about 1 in 1,000 pregnant women.
Retrospective Study
The retrospective study appeared recently in the Journal of Endocrinology and Metabolism. Mazzaferri and coworkers examined the treatment and follow-up records of 61 pregnant women with differentiated papillary or follicular thyroid cancer, which comprise about 80% of thyroid cancers in the United States.
The 61 pregnant women were matched with 528 nonpregnant women with thyroid cancer. Both groups averaged 26 years of age. When the researchers compared tumor characteristics of the pregnant women with those of the nonpregnant women, they found no differences.
“Tumors from pregnant women had none of the features of a more aggressive malignancy,” said Mazzaferri. The tumors of the pregnant women were no larger than those of the nonpregnant women and were no more likely to have metastasized to lymph nodes.
Next, the researchers looked at the timing of surgery in the pregnant women, comparing women treated during pregnancy with those treated after delivery. The average follow-up for the women was about 15 years after treatment.
Of the 61 pregnant women with cancer, 14 underwent surgery during their pregnancy and 47 waited until after delivery. The average time from discovery of the tumor until the first treatment was about 1 month for those operated on while pregnant and was about 16 months for those who had surgery after delivery.
No Difference in Recurrence Rate
The researchers found that cancer recurred in 2 (14%) of the 14 women who underwent surgery during pregnancy and in 8 (17%) of those who waited until after delivery to have surgery. There was no significant difference between the two groups.
“The fear was that high levels of human chorionic gonadotropin would potentially stimulate the growth of thyroid tumors. The thought that pregnant women might be subject to a much more aggressive tumor caused a lot of anxiety in people who treated this disease. These results allow us to worry less about pregnant women we see who have thyroid cancer.”
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