Radioactive iodine treatment increases risk of new cancers, more at risk in younger adults

Weighing the pros and cons of treatment modalities is an eternal topic in clinical practice, especially in this era of precision medicine and personalized treatment

In the past 10 years, with the deepening of the understanding of the disease, for some thyroid cancers with a lower degree of malignancy, such as differentiated thyroid cancer (DTC), the treatment concept has changed from invasive to mild, not only including surgical resection

Currently, it has become a consensus that radioactive iodine therapy is not required for patients with differentiated thyroid cancer with unifocal microcarcinomas (≤10 mm in diameter) [2]

For other low-risk differentiated thyroid cancer patients, the latest clinical studies have shown that the long-term prognosis of patients not receiving RAI is not worse than that of patients receiving RAI [3]

However, the effect of RAI on the risk of solid second primary malignancies (SPM) remains uncertain

Recently, Prof.

The findings showed that RAI treatment was associated with a 23% increased risk of solid SPM, with younger age being associated with greater future risk of solid SPM

Since the 1940s, RAI has become one of the main treatments for thyroid cancer due to its high tissue specificity, improving the prognosis of patients with thyroid cancer [7]

Compared with traditional radiotherapy, patients have better tolerance to RAI, but in the long run, many patients still have complications such as salivary gland dysfunction, conjunctivitis, infertility [8], and secondary radiation exposure.

Therefore, exploring the risk of RAI on secondary malignancies in the young differentiated thyroid cancer population will help to balance the benefits and risks of RAI therapy

Professor Cari M.

A total of 36,311 young patients with non-metastatic differentiated thyroid cancer were included in the study, 81% of whom were women and 45% received RAI therapy

Overall, RAI usage rose from 9% to 55% between 1975-2009, and then gradually declined, dropping to 39% in 2017

The researchers mainly analyzed the risk of developing solid thyroxine m after 5 years in patients with differentiated thyroid cancer (27,050 patients with analyzable data)

The cumulative incidence of solid thyroid particles was 5.

This difference increased with follow-up time, and the cumulative incidence of solid SPM was 12.

Among organs with high radiation exposure (≥0.
5 Gy), salivary gland cancer (RR=2.
15, 95%CI: 0.
91-5.
08), gastric cancer (RR=1.
61, 95%CI: 0.
70-3.
69) and renal cancer (RR=1.
61, 95%CI: 0.
70-3.
69) 1.
34) There is a higher risk of SPM associated with RAI treatment
.

 Organs with relatively low radiation exposure (<0.
5 Gy), uterine cancer (RR=1.
55, 95%CI: 0.
99-1.
40), breast cancer (RR=1.
18, 95%CI: 0.
99-1.
40), lung cancer (RR=1.
18, 95%CI: 0.
99-1.
40), 1.
42, 95%CI: 1.
03-2.
32) with higher risk
.

Except for bladder cancer, cervical cancer and liver cancer, the rr of other solid SPMs were all greater than 1
.
 

Compared with older patients, the RR of solid SPM was higher in younger patients (P=0.
07)
.
The RR was 1.
60 (95% CI, 1.
07-2.
40) for patients before age 25 years and 1.
16 (95% CI, 1.
02-1.
33) for patients aged 35-45 years
.

After the diagnosis of differentiated thyroid cancer, the RR of solid thyroid granules increased with the extension of follow-up time (P=0.
07)
.
 

Professor Cari M.
Kitahara's team also analyzed the effect of RAI treatment on the risk of hematological tumors in patients with differentiated thyroid cancer
.

Two years after the diagnosis of differentiated thyroid cancer, 146 patients were diagnosed with hematologic SPM during the follow-up period (median follow-up time 13 years)
.
 

RAI treatment increased the risk of leukemia (RR=1.
92, 95%CI: 1.
04 to 3.
56), especially non-lymphocytic leukemia (RR=2.
17, 95%CI: 1.
03 to 4.
55)
.
RAI treatment did not increase the risk of Hodgkin lymphoma or non-Hodgkin lymphoma
.

 Although this study has certain limitations, such as the interaction of RAI therapy with cancer risk factors such as smoking and obesity, and patients with differentiated thyroid cancer over the age of 45, it still shows that RAI therapy leads to more good result
.
High risk associated with solid thyroxine m, especially in patients with differentiated thyroid cancer aged <25 years
.

 The results of this study have important reference value for doctors to weigh whether to give RAI therapy to patients with differentiated thyroid cancer
.

On the basis of correctly identifying which patients are most likely to benefit from RAI treatment, it is also necessary to consider whether the treatment will bring adverse effects on patients, comprehensive analysis and medical decision-making, this is the real precision medicine and personalized treatment
.

Taking into account previous findings in the New England Journal of Medicine, RAI treatment did not improve outcomes in patients with low-risk differentiated thyroid cancer, and RAI increased the risk in patients with SPM
.

The answer is close, and RAI therapy will gradually cease to be the main treatment for patients with low-risk differentiated thyroid cancer, and its indications will be further strictly controlled
.

Quote:

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8.
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