Risk and outcome of subsequent malignancies after radioactive iodine treatment in differentiated thyroid cancer patients

Efficacy assessment of repeat iodine-131 treatment in patients with papillary thyroid carcinoma assessed as biochemical incomplete response

PURPOSE

Although most patients with Papillary Thyroid Carcinoma (PTC) have a favorable prognosis, some continue to have elevated serum Thyroglobulin (Tg) levels after surgery and ¹³¹I treatment, classified as a Biochemical Incomplete Response (BIR). According to the 2015 American Thyroid Association (ATA) guidelines, 20% of these patients will develop a Structural Incomplete Response (SIR). Doctors often recommend ¹³¹I retreatment without imaging evidence, hoping for benefits. However, the effectiveness of this treatment strategy is still not supported by evidence. The aim of this study is to explore the potential benefits by comparing Tg levels and their changes in patients who were retreated with 131I and combining them with the results of follow-up assessment using Dynamic Risk Stratification (DRS).

METHODS

This retrospective study collected clinical data from patients with PTC who underwent ¹³¹I therapy after surgery at two medical centers. All of them were evaluated for Biochemical Incomplete Response (BIR) after initial treatment. Based on whether they received ¹³¹I retreatment, they were divided into two groups: the retreatment group and the no-retreatment group. Our primary outcome measures included basic clinical data, suppressed Tg, change in Tg levels, and DRS stratification at the last follow-up. The potential benefits of ¹³¹I retreatment were analyzed by comparing the changes in Tg levels and the DRS distribution at the end of follow-up between the two groups.

RESULTS

Patients with PTC assessed for BIR after initial therapy showed a greater reduction in Tg at short-term follow-up after ¹³¹I retreatment compared to the no retreatment group (0.84 ng/mL vs. 0.72 ng/mL). The one-sample Wilcoxon signed-rank test results were T = 6.001, p < 0.001 and T = 1.378, p = 0.168, respectively. At the end of follow-up, this treatment did not alter the DRS strata composition ratio (R = 3.06, p = 0.39). The area under the receiver operating characteristic curve for pre-ablation stimulated thyroglobulin (Ps-Tg) predicting non-remission status was 0.64 (95% CI: 0.55-0.73), with the highest Youden index (0.26) at a Ps-Tg cutoff of 20.5 ng/mL, corresponding to a sensitivity of 62.6% and a specificity of 63.3%. For the first suppressed Tg (sup-Tg) predicting non-remission, the AUC was 0.75 (95% CI: 0.67-0.84). The highest Youden index (0.40) was achieved at a sup-Tg cutoff of 1.85 ng/mL, corresponding to a sensitivity of 68.9% and a specificity of 70.8%.

CONCLUSION

For patients with PTC who received 131I therapy after surgery and are classified as BIR, 131I retreatment may accelerate the decline in Tg levels over time but does not change the DRS distribution. Only few of patients have structural and/or functional lesions detected on the whole-body scan after 131I retreatment. The Ps-Tg and first sup-Tg values after the first ¹³¹I treatment can help predict a non-remission state, with cutoff values of 20.5 ng/mL and 1.85 ng/mL, respectively.

The Interplay Between High Cumulative Doses of Radioactive Iodine and Type 2 Diabetes Mellitus: A Complex Cardiovascular Challenge

Starting from the metabolic profile of type 2 diabetes mellitus (T2DM), we hypothesized that the mechanisms of ¹³¹I-induced cardiotoxicity differ between patients diagnosed with differentiated thyroid cancer (DTC) with/without T2DM, with metformin potentially acting as a cardioprotective agent by mitigating inflammation in patients with T2DM. To address this hypothesis, we quantified, using ELISA, the serum concentration of several key biomarkers that reflect cardiac injury (NT-proBNP, NT-proANP, ST2/IL-33R, and cTn I) in 74 female patients with DTC/-T2DM and 25 with DTC/+T2DM treated with metformin. All patients received a cumulative oral dose of 131I exceeding 150 mCi (5.55 GBq) over approximately 53 months. Our results showed the following: (i) In DTC/-T2DM patients, high-cumulative 131I doses promote a pro-inflammatory state that accelerates the development of cardiotoxicity. Monitoring NT-proBNP, ST2/IL-33R, and cTn I in these patients may help identify those at risk of developing cardiac complications. (ii) In patients with DTC/+T2DM, high-cumulative 131I doses lead to the release of NT-proANP (r = 0.63), which signals that the atria are under significant stress. (iii) In patients with DTC/+T2DM, metformin suppresses inflammation, leading to a dose-dependent reduction in cTn I (r = -0.59). Monitoring cTn I and NT-proANP, and considering the use of metformin as part of the therapeutic strategy, could help manage cardiotoxicity in T2DM patients undergoing 131I therapy.

Incidence and pattern of second primary cancer in patients diagnosed with primary cancer

The long survival of patients with primary cancer increases the chance of such patients developing second primary cancer (SPC). The development of SPC in cancer survivors exerts a large psychological, social and economic burden on patients and their families. The aim of the present study was to assess the risk of cancer survivors developing SPC. The study included patients who had been diagnosed with a first primary cancer in five organs (stomach, colorectum, lung, breast and thyroid), which are the five most common sites of cancer in patients from Korea, at the regional cancer center in Jeonbuk National University Hospital between January 2007 and December 2009. The standardized incidence ratio (SIR) of SPC according to sex and site was calculated from 5,209 patients who were followed up to September 2017. General incidence was acquired from the National Cancer Registry of Republic of Korea. SPC occurred in 6.2% (323/5,209) of patients, and the incidence of SPC among the five major types of cancer was in the order of breast (8.8%, 46/524), colorectum (8.6%, 86/1,003), gastric (6.6%, 89/1,358), thyroid (4.7%, 67/1,437) and lung cancer (3.9%, 35/887). When all SPC sites were included, the SIRs of SPC in patients with colorectal cancer and breast cancer were >1.0 (1.21 and 1.66, respectively). Breast cancer and thyroid cancer exhibited a high site relationship (P<0.05), and colorectal cancer had a high site relationship with gastric cancer (P<0.05). The present study analyzed the incidence and pattern of SPC in patients with cancer who were diagnosed with primary carcinoma in five organs. The results of the study may be useful for effective follow-up and early detection of SPC in patients with cancer.

Risk of Subsequent Primary Cancers in Thyroid Cancer Survivors according to the Dose of Levothyroxine: A Nationwide Cohort Study

BACKGRUOUND

Current research has not investigated the effect of thyroid-stimulating hormone suppression therapy with levothyroxine on the risk for developing subsequent primary cancers (SPCs). This study aimed to investigate the association between levothyroxine dosage and the risk for SPCs in thyroid cancer patients.

METHODS

We conducted a nationwide population-based retrospective cohort study form Korean National Health Insurance database. This cohort included 342,920 thyroid cancer patients between 2004 and 2018. Patients were divided into the non-levothyroxine and the levothyroxine groups, the latter consisting of four dosage subgroups according to quartiles. Cox proportional hazard models were performed to evaluate the risk for SPCs by adjusting for variables including cumulative doses of radioactive iodine (RAI) therapy.

RESULTS

A total of 17,410 SPC cases were observed over a median 7.3 years of follow-up. The high-dose levothyroxine subgroups (Q3 and Q4) had a higher risk for SPC (adjusted hazard ratio [HR], 1.14 and 1.27; 95% confidence interval [CI], 1.05-1.24 and 1.17- 1.37; respectively) compared to the non-levothyroxine group. In particular, the adjusted HR of stomach (1.31), colorectal (1.60), liver and biliary tract (1.95), and pancreatic (2.48) cancers were increased in the Q4 subgroup. We consistently observed a positive association between high levothyroxine dosage per body weight and risk of SPCs, even after adjusting for various confounding variables. Moreover, similar results were identified in the stratified analyses according to thyroidectomy type and RAI therapy, as well as in a subgroup analysis of patients with good adherence.

CONCLUSION

High-dose levothyroxine use was associated with increased risk of SPCs among thyroid cancer patients regardless of RAI therapy.

Second Primary Malignancy After Radioiodine Therapy in Thyroid Cancer Patient: A Nationwide Study

Objective

This study aimed to investigate the risk of second primary malignancy after radioiodine (RAI) therapy in patients with thyroid cancer, using the National Health Insurance Service (NHIS) database.

Methods

We extracted data from the NHIS database of South Korea, which covers the entire population of the nation. Risk of second primary malignancy in the thyroid cancer patients who received RAI therapy were compared with the thyroid cancer patients who received surgery only.

Results

Between January 1, 2004, and December 31, 2018, we identified 363,155 patients who underwent thyroid surgery due to thyroid cancer for analysis. The surgery only cohort was 215,481, and the RAI cohort was 147,674 patients. A total of 19,385 patients developed second primary malignancy (solid cancer, 18,285; hematologic cancer, 1,100). There was no significant increase in the risk of second primary malignancy in patients who received a total cumulative dose of 100 mCi or less (hazard ratio [HR], 1.013; 95% confidence interval [CI], 0.979-1.049). However, a statistically significant increase in the risk of second primary malignancy was observed in patients who received 101-200 mCi (HR, 1.214; 95% CI, 1.167-1.264), 201-300 mCi (HR, 1.422; 95% CI, 1.258-1.607), and > 300 mCi (HR, 1.693; 95% CI, 1.545-1.854).

Conclusion

Total cumulative doses of 100 mCi or less of RAI can be safely administered without concerns about second primary malignancy. However, the risk of second primary malignancy increases in a dose-dependent manner, and the risk-benefit needs to be considered for doses over 100 mCi of RAI therapy.

A long-term retrospective cohort-based risk-benefit analysis of augmenting total cumulative I-131 activity to 37GBq in differentiated thyroid cancer patients with skeletal metastases

OBJECTIVE

Skeletal metastases in differentiated thyroid cancer (DTC) patients are associated with poor prognosis. The objective was to determine the maximum I-131 cumulative activity that could be safely administered without compromising efficacy. The secondary objective was to identify other prognostic factors affecting survival outcomes.

MATERIALS AND METHODS

This was a retrospective cohort study done at a tertiary-care institution comprising of data from January 1990-June 2020. 489 DTC patients having skeletal metastases with ≥12 months follow-up were included. Ninety-six percent of patients had thyroidectomy followed by radioiodine therapy for skeletal metastases. All patients were on oral suppressive levothyroxine tablets. External beam radiotherapy (EBRT) and oral tyrosine kinase inhibitors were used whenever indicated. The main outcome measures were overall survival (OS), progression-free survival (PFS), and adverse-events.

RESULTS

There were 347 (71%) females and 324 (66%) had follicular carcinoma thyroid. Median follow-up was 78 (interquartile range, IQR: 37-153) months. 333 patients (68%) received ≤37GBq I-131 cumulative activity (group 1) and 156 patients (32%) received >37GBq cumulative RAI activity (group 2). Overall median OS and PFS were 74 (95% confidence interval (CI): 62.2-85.8) and 48 (95%CI: 40.5-55.4) months, respectively. The 5-, 10-, 15- and 20-year estimated overall survival probabilities were 55.7%, 28.4%, 14% and 8.3%, respectively. On multivariate analysis, age(<55years) (p<0.001), female gender(p = 0.01), cumulative I-131 activity >37GBq (p<0.001) and EBRT(p = 0.001) were favourably associated with OS; no factors were significantly associated with PFS. The median OS for groups 1 & 2 were 51 versus 90 months (p<0.001) & median PFS for groups 1 & 2 were 45 versus 53 months respectively (p = 0.9). However, cumulative activity >37GBq resulted in more adverse events (2.4%), particularly bone marrow suppression (3.5%).

CONCLUSION

For better survival outcomes, cumulative I-131 activity upto 37GBq could be administered with acceptable toxicity to DTC patients with skeletal metastases.

Radiation and leukaemia: Which leukaemias and what doses?

The cause(s) of most cases of leukaemia is unknown. Save for several rare inherited disorders the most convincingly-identified causes of leukaemia are exposures to ionizing radiations, to some chemicals and to some anti-cancer drugs. Data implicating ionizing radiations as a cause of leukaemias come from several sources including persons exposed to the atomic bomb explosions in Japan, persons receiving radiation therapy for cancer and other disorders, persons occupationally exposed to radiation such as radiologists and nuclear facility workers, cigarette smokers, and others. Although ionizing radiations can be a cause of almost all types of leukaemias, some are especially sensitive to induction such as acute and chronic myeloid leukaemias (AML and CML) and acute lymphoblastic leukaemia (ALL). Whether chronic lymphocytic leukaemia can be caused by radiation exposure is controversial. The mechanism(s) by which ionizing radiations cause leukaemia differs for different leukaemia types. I discuss these issues and close with a hypothesis which might explain why haematopoietic stem cells are localized to the bone marrow.

Second Primary Malignancies in Patients with Differentiated Thyroid Cancer after Radionuclide Therapy: A Retrospective Single-Centre Study

Second primary malignancies (SPM) are described as any primary, not synchronous, malignancy arising in a different anatomical district, with confirmed histological diagnosis. Age at diagnosis, previous non-thyroidal primary malignancy, and radioactive iodine (RAI) therapy have been proposed as independent risk factors for SPM. RAI therapy is a standard treatment for moderate-high risk differentiated thyroid cancer (DTC), and its effect on the development of SPM has become a critical topic in DTC treatment. The purpose of this retrospective single-center study was to investigate the occurrence and the possible association of non-thyroidal SPM diagnosed after DTC and RAI therapy in a cohort of 1326 consecutive DTC patients referred at our Institution for RAI treatment from 1993 to 2009. Eighty-nine patients with ages ≤ 18 years at the time of DTC diagnosis or with a follow-up of ≤12 months were excluded from the final analysis. All patients underwent a complete clinical and hematological follow-up every 6 months for a minimum of 12 months. During follow-up (mean 89 ± 73 months), 25 patients (2%) had an SPM diagnosis (mean 133 ± 73 months). The most common site of the second malignancy was the breast, accounting for 32% of all SPM, followed by colon-rectal cancer (16%), leukemia, and gynecological and kidney cancer (4%). At Cox univariable regression analysis, age at DTC diagnosis (p < 0.001), age ≥55 years (p < 0.001) and follow-up duration (p < 0.004) were associated with SPM onset, while no significant association was observed with the administered activity of radioiodine. In conclusion, our data suggest that the older a person gets, the more sharply the likelihood of developing additional diseases, such as PMS, increases. Similarly, for follow-up, the more a patient is followed up clinically over time, the higher the risk of new diagnoses increases.

2022 European Thyroid Association Guidelines for the management of pediatric thyroid nodules and differentiated thyroid carcinoma

At present, no European recommendations for the management of pediatric thyroid nodules and differentiated thyroid carcinoma (DTC) exist. Differences in clinical, molecular, and pathological characteristics between pediatric and adult DTC emphasize the need for specific recommendations for the pediatric population. An expert panel was instituted by the executive committee of the European Thyroid Association including an international community of experts from a variety of disciplines including pediatric and adult endocrinology, pathology, endocrine surgery, nuclear medicine, clinical genetics, and oncology. The 2015 American Thyroid Association Pediatric Guideline was used as framework for the present guideline. Areas of discordance were identified, and clinical questions were formulated. The expert panel members discussed the evidence and formulated recommendations based on the latest evidence and expert opinion. Children with a thyroid nodule or DTC require expert care in an experienced center. The present guideline provides guidance for healthcare professionals to make well-considered decisions together with patients and parents regarding diagnosis, treatment, and follow-up of pediatric thyroid nodules and DTC.

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.

Risk of primary breast cancer in patients with differentiated thyroid cancer undergoing radioactive iodine therapy: a systematic review and meta-analysis

PURPOSE

Although it has been proven that radioactive iodine (RAI) treatment is an effective and well-tolerated procedure in patients with differentiated thyroid cancer (DTC), there is still some concern regarding the risk of developing a second primary malignancy after RAI administration. We performed a systematic review and meta-analysis to investigate the risk of primary breast cancer in patients with DTC undergoing RAI therapy.

METHODS

A comprehensive literature search of the PubMed, Scopus, and Web of Science databases was conducted according to the PRISMA statement.

RESULTS

The final analysis included 14 studies accounting for a total of 200,247 patients with DTC (98,368 treated with RAI and 101,879 not treated with RAI). The relative risk of primary breast cancer in patients with DTC treated with RAI to those not treated with RAI among studies ranged from 0.45 to 2.55, the pooled relative risk was 0.83 (95% confidence interval, 0.70-0.99), and the heterogeneity was 71.5%.

CONCLUSION

The present meta-analysis indicates that patients with DTC treated with RAI do not have a higher risk of primary breast cancer compared to those not treated with RAI. These findings suggest that RAI therapy does not increase the risk of breast cancer.