Comparison of radioiodine utilization in adolescent and young adult and older thyroid cancer patients

Association Between Radioactive Iodine Treatment for Pediatric and Young Adulthood Differentiated Thyroid Cancer and Risk of Second Primary Malignancies

PURPOSE

Since the 1980s, both the incidence of differentiated thyroid cancer (DTC) and use of radioactive iodine (RAI) treatment increased markedly. RAI has been associated with an increased risk of leukemia, but risks of second solid malignancies remain unclear. We aimed to quantify risks of second malignancies associated with RAI treatment for DTC in children and young adults, who are more susceptible than older adults to the late effects of radiation.

METHODS

Using nine US SEER cancer registries (1975-2017), we estimated relative risks (RRs) for solid and hematologic malignancies associated with RAI (yes v no or unknown) using Poisson regression among ≥ 5- and ≥ 2-year survivors of nonmetastatic DTC diagnosed before age 45 years, respectively.

RESULTS

Among 27,050 ≥ 5-year survivors (median follow-up = 15 years), RAI treatment (45%) was associated with increased risk of solid malignancies (RR = 1.23; 95% CI, 1.11 to 1.37). Risks were increased for uterine cancer (RR = 1.55; 95% CI, 1.03 to 2.32) and nonsignificantly for cancers of the salivary gland (RR = 2.15; 95% CI, 0.91 to 5.08), stomach (RR = 1.61; 95% CI, 0.70 to 3.69), lung (RR = 1.42; 95% CI, 0.97 to 2.08), and female breast (RR = 1.18; 95% CI, 0.99 to 1.40). Risks of total solid and female breast cancer, the most common cancer type, were highest among ≥ 20-year DTC survivors (RR_solid = 1.47; 95% CI, 1.24 to 1.74; RR_breast = 1.46; 95% CI, 1.10 to 1.95). Among 32,171 ≥ 2-year survivors, RAI was associated with increased risk of hematologic malignancies (RR = 1.51; 95% CI, 1.08 to 2.01), including leukemia (RR = 1.92; 95% CI, 1.04 to 3.56). We estimated that 6% of solid and 14% of hematologic malignancies in pediatric and young adult DTC survivors may be attributable to RAI.

CONCLUSION

In addition to leukemia, RAI treatment for childhood and young-adulthood DTC was associated with increased risks of several solid cancers, particularly more than 20 years after exposure, supporting the need for long-term surveillance of these patients.

Decreasing Use of Radioactive Iodine for Low-Risk Thyroid Cancer in California, 1999 to 2015

CONTEXT

Routine radioactive iodine (RAI) ablation for low-risk differentiated thyroid cancer (DTC) is not supported by current practice guidelines.

OBJECTIVE

To assess recent stage-specific trends in use of RAI ablation.

DESIGN, SETTING, AND PATIENTS

Retrospective study of patients with DTC (1999 to 2015) identified from the California Cancer Registry. Statistical analysis included standardized differences, P values, and multivariable analyses using RAI as the predictor variable.

MAIN OUTCOME MEASURES

Trends and drivers of RAI ablation for low-risk DTC.

RESULTS

Of 46,906 patients with DTC who underwent near-total or total thyroidectomy [mean age 48.2 ± 15.5 (standard deviation) years, 77% female), 25,457 (54%) received RAI. The proportion of patients with regional/distant disease who received RAI remained stable at 68%. Use of RAI for patients with localized disease (no extrathyroidal extension, lymph node, or distant metastases) decreased from 55% (1999) to 30% (2015), with the most substantial change occurring in tumors <1 cm (39% to 11%). The rate also decreased for localized tumors between 1 and 2 cm (62% to 34%) and 2 and 4 cm (67% to 49%) and remained stable at 59% for tumors >4 cm. In multivariable analyses, patients with localized disease were less likely to receive RAI if they were >65 years old [odds ratio (OR) 0.77, 95% confidence interval (CI): 0.71 to 0.83], had tumors <1 cm (OR 0.33, 95% CI: 0.31 to 0.35), or were treated in an academic hospital (OR 0.71, 95% CI: 0.67 to 0.75).

CONCLUSIONS

The rate of RAI ablation decreased over time, mainly attributable to decreased use for localized DTCs <2 cm. Many patients with low-risk DTC still receive RAI unnecessarily.

Birth rates after radioactive iodine treatment for differentiated thyroid cancer

Treatment with radioactive iodine (RAI) for differentiated thyroid cancer has been associated with alterations in gonadal function in women, including changes in menstrual function and an earlier age at menopause. Our objective was to evaluate associations between RAI and postdiagnosis live birth rates among thyroid cancer survivors diagnosed at ages 15-39 years. We identified women diagnosed with differentiated thyroid cancer between January 2000 and December 2013 in the North Carolina Central Cancer Registry (CCR). CCR records were linked to state birth certificate files to identify livebirths to thyroid cancer survivors through December 2014. Person-years of follow-up were accrued from 6 months after diagnosis to first birth, 46th birthday, death, or December 31, 2014, whichever came first. Cox proportional hazards regression was used to estimate hazards ratios (HR) and 95% confidence intervals (CI) for first livebirth. Among 2,360 women with a differentiated thyroid cancer diagnosis, 53% received RAI. The cumulative incidence of birth at the end of follow-up (maximum 14.5 years) was 30.0 and 29.3% among those who were and were not treated with RAI, respectively. Overall, first birth rates did not significantly differ between groups (HR = 1.00; 95% CI: 0.82, 1.23). In our observational cohort, treatment with RAI was not associated with a reduced birth rate. Our findings add to the evidence available for counseling thyroid cancer patients with concerns about future fertility.

Sociodemographic disparities in differentiated thyroid cancer survival among adolescents and young adults in California

BACKGROUND

Few studies have focused on prognostic factors among adolescents and young adults (AYAs) 15 to 39 years of age when diagnosed with differentiated thyroid cancer (DTC). Our study expands upon prior work by including an evaluation of survival among AYA men and by neighborhood socioeconomic status, health insurance, and clinical factors to identify subgroups of young DTC patients at higher risk of mortality.

METHODS

Data for 16,827 AYA DTC patients diagnosed between 1988 and 2010 were obtained from the California Cancer Registry. Survival, through 2010, by sociodemographic and clinical factors was analyzed using Cox proportional hazards regression.

RESULTS

Of the 2.1% of AYAs who died, 16.7% died from thyroid cancer and 21.4% died from a subsequent cancer. In multivariate analyses, older AYAs 35 to 39 year of age (versus 15- to 29-year-olds), men (hazard ratio [HR] 2.77, 95% confidence interval [CI] 1.62-4.72), and AYAs of African American or Hispanic race/ethnicity (versus non-Hispanic whites) had worse thyroid cancer specific survival. In addition, residing in low socioeconomic status neighborhoods (HR 3.11 [CI 1.28-7.56]) and nonmetropolitan areas (HR 5.53 [CI 2.07-14.78]) was associated with worse thyroid cancer-specific survival among AYA men, but not AYA women.

CONCLUSIONS

Despite the generally good prognosis among AYAs with DTC, we identified subgroups of AYA patients at risk for poor outcomes. Further study of the factors underlying these associations, including possible barriers to receiving high-quality treatment and follow-up care, as well as lifestyle factors, are critical to reducing these disparities.

Initial treatment patterns in younger adult patients with differentiated thyroid cancer in California

BACKGROUND

Differentiated thyroid cancer (DTC) is among the most common malignancies in the adolescent and young adult (age 15-39 years) population, and its incidence is rising. Younger age (<45 years) is an important prognostic indicator and is incorporated into the TNM classification system. This study hypothesized that this would result in distinct treatment patterns for younger and older patients.

METHODS

Using the California Cancer Registry, 24,362 patients with DTC from 2004 to 2011 were identified, and they were divided into younger (<45 years) and older (≥45 years) cohorts. Demographic and clinical variables were tabulated and then compared using chi-square tests. Treatment variables included total or near total thyroidectomy, other types of thyroid surgery, and the administration of radioiodine as part of the initial treatment. Multivariable logistic regression was used to identify independent predictors of treatment administered.

RESULTS

Younger patients were more likely to be Hispanic (32.5% vs. 21.2%) and female (82.7% vs. 74.7%), and to have papillary carcinoma (92.9% vs. 90.9%) and lymph node involvement (32.8% vs. 19.7%; p<0.0001). On multivariable analysis, younger patients (OR 1.20 [CI 1.11-1.30]), higher T-stage tumors, higher socioeconomic status (SES), and papillary carcinoma were predictors of undergoing total thyroidectomy versus less than total thyroid surgery. After adjustment, predictors of radioiodine administration included younger age (OR 1.12 [CI 1.05-1.18]), higher SES, total thyroidectomy, higher T stage, and lymph node positivity.

CONCLUSIONS

Younger patients with DTC in California are more likely to be female and Hispanic with papillary histology. After adjustment for disease and demographic characteristics, younger patients are more likely to undergo total thyroidectomy as their initial surgery and are more likely to receive radioiodine. Given their excellent prognosis and the potential for adverse sequelae from initial treatment for DTC, these findings warrant consideration when managing younger patients with DTC.