Levothyroxine during active surveillance of thyroid microcarcinoma may reduce tumor growth
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Key takeaways:
- Adults with papillary thyroid microcarcinoma were prescribed levothyroxine if they had a higher tumor volume doubling rate.
- The percentage of adults with tumor regression increased after levothyroxine began.
Levothyroxine therapy may help decrease tumor growth for adults with papillary thyroid microcarcinoma who are undergoing active surveillance, according to a study published in Thyroid.
Adults with papillary thyroid microcarcinoma who started levothyroxine during active surveillance (group IB) had larger tumors, Masashi Yamamoto, MD, PhD, of the department of head and neck surgery at Kuma Hospital in Japan, and colleagues wrote. “Furthermore, the incidence of tumor enlargement was higher in group IB than in group IA [no levothyroxine during active surveillance]. It is likely that when the attending physicians recognized enlargement of these tumors, they started levothyroxine administration for group IB.”
Researchers reviewed electronic medical record data from 2,509 adults aged 20 years and older who were diagnosed with low-risk papillary thyroid microcarcinoma and underwent active surveillance for more than 1 year from 2005 to 2019. The study population included 2,187 adults not receiving levothyroxine at the time active surveillance began and 322 who were receiving levothyroxine at the time of active surveillance initiation. Those not receiving levothyroxine at the start of active surveillance were divided into a group who did not receive levothyroxine during active surveillance (n = 1,935) and a group who initiated levothyroxine at some point during active surveillance (n = 252). Ultrasound was conducted and blood samples collected during follow-up one or two times annually. Disease progression was defined as tumor growth or the appearance of lymph node metastasis.
The cumulative incidence of disease progression was higher for adults who started levothyroxine during active surveillance than those who did not receive levothyroxine (13.8% vs. 5%; P < .01). Adults undergoing active surveillance who received levothyroxine had a higher tumor volume doubling rate before levothyroxine initiation than adults who underwent active surveillance but did not receive levothyroxine and adults who were using levothyroxine at active surveillance initiation (P < .01 for both).
“[This is] suggesting that patients with progression signs during active surveillance were selectively prescribed levothyroxine,” the researchers wrote.
Adults who started levothyroxine during active surveillance were more likely to have disease progression than adults who did not receive levothyroxine (adjusted OR = 3.42; 95% CI, 2.15-5.44; P < .01). Adults aged 40 to 59 years (aOR = 0.23; 95% CI, 0.14-0.38; P < .01) and those aged 60 years and older (aOR = 0.16; 95% CI, 0.1-0.27; P < .01) were less likely to have disease progression than adults younger than 40 years. Men were more likely to have lymph node metastasis than women (aOR = 4.78; 95% CI, 1.75-13.1; P < .01). Adults aged 40 to 59 years (aOR = 0.28; 95% CI, 0.1-0.78; P = .015) and those aged 60 years and older (aOR = 0.12; 95% CI, 0.03-0.43; P < .01) had lower odds for lymph node metastasis than adults younger than 40 years.
Adults who started levothyroxine during active surveillance were subdivided into five groups according to tumor growth activity as measured by tumor volume doubling rate. The proportion of adults with moderate or rapid tumor growth decreased from 26.8% before levothyroxine therapy to 12.5% after levothyroxine was initiated (P < .01). The percentage of adults with decreased tumor volume increased from 41.7% before levothyroxine therapy to 59.8% after levothyroxine began (P < .01).
“Reductions in serum thyroid-stimulating hormone levels by levothyroxine administration were associated with decreased papillary thyroid microcarcinoma growth activity during active surveillance,” the researchers wrote. “Further prospective studies are necessary to confirm these promising results and elucidate the best serum TSH target value for the prevention of papillary thyroid microcarcinoma progression, while avoiding unfavorable events caused by an overdose of levothyroxine.”
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