Thank you..

Thank you again..

The reasons behind why the incidence of thyroid cancer is rising substantially are difficult to account for.  Increased use of diagnostic imaging capable of exposing subclinical disease is considered the most parsimonious explanation for this reported rise. The location of the thyroid gland places it within the window of many diagnostic-imaging studies. In addition, cross-sectional imaging studies have contributed to a 2.4-fold increase in the reported incidence of thyroid nodules over the past 30 years. 

The use of ultrasound for the screening of thyroid cancer has also been considered as a contributing factor.  This is believed to be the key factor in South Korea’s abrupt increase in thyroid cancer incidence.  A study based on the 2009 Korean National Cancer Screening Survey revealed that 13.2% of South Koreans undergo thyroid cancer screening with ultrasound. The link between imaging studies and increased incidence is supported by a correlation with access to healthcare, and the incidence is rising more rapidly in countries where healthcare expenditure is driven by the private sector than the public.

Contrary to the hypothesis that diagnostic imaging is the main cause of the increased incidence of small thyroid cancer, the incidence of large thyroid cancers has not declined, and is also increasing.  Moreover, higher rates of aggressive PTCs are being detected, including those with extrathyroidal extension and distant metastases.

Risk factors, not yet identified, may also be contributing to this increase in incidence.  Studies have also suggested that this may be due to high levels of ionizing radiation exposure. Moreover, hormonal, nutritional, and menstrual and reproductive factors may be causing this surge of incidence. The worldwide rise as well as the differing rates of thyroid cancer between countries suggests multiple factors may have a role in the incidence and warrant further investigation.

Thank you Salem I Noureldine. True, ultrasound might have added a little more in the early detection of tiny nodules. Do increased used of  isodised salt (fortified) added to the risk? Because, use of iodised salt has become routine practice in our ountry, with the intention to prevent hypothyroidism. Is this one of the factors responsible for rise in malignant thyroid lesions?

Also, the rise is seen in Follicular/Papillary carcinoma. Not in Medullary ca..

There are many molecules known as endocrine disruptors, some of them are present in substances used very commonly on daily basis. these endocrine disruptors are definitely a threat to an overall endocrinopathies. One common example is Bis-phenol A (BPA) present as an additive to many plastic products. There are many potehr chemicals as insecticides and pesticides, PTFE coating on non-stick utensils and many more. You can have a look on these chemicals and could correlate them clinically with thyroid malignancies. 

Thanks you Dr Zakaria and Dr Kumar.. Environmental radiations need to be addressed i feel, but most of the electronic gadgets emit non- ionizing radiations, which are unlikely to break bonds. are they really worrisome as ionizing ones?

Great discussion, all. Ingestion of and exposure to increasing levels of radiation, coupled with changes in body morphology and epigenomics may help us better understand this alarming rise.

Hello Dr. Bhat,

The reasons exposed by Dr. Noureldine are probably the correct answer to your question. This increase in incidence in thyroid cancer is correlated to access to health care and is not associated with increased morbi-mortality from thyroid cancer. What happens is probably a epidemic of overdiagnosis of thyroid cancer and not a epidemic of real malignant disease (even though they are malignancies by their pathologic definition). There is a great reservoir of subclinical disease that would never cause any harm to the patient (i.e. would never become symptomatic) had the patient not been submitted to screening diagnostic imaging studies. There are a lot of articles (and also books and conferences) discussing the problem of overdiagnosis, evidence of its existence and possible solutions (a few of these references are below).

Hope to have contributed to the discussion!

Rodrigo Olmos

http://jnci.oxfordjournals.org/content/102/9/605.abstract

http://www.amazon.com/Overdiagnosed-H-Gilbert-Welch-ebook/dp/B004C43EW6

http://www.nejm.org/doi/full/10.1056/NEJMoa1206809

http://jama.jamanetwork.com/article.aspx?articleid=1722196

http://www.preventingoverdiagnosis.net/

Dear colleagues,

Just to complement my previous comentary!

I don´'t believe that other risk factors (environmental, hormonal, nutritional, etc) play an important role in the rise in incidence of thyroid cancer, even though these factors might contribute in some ways. Most of the evidence concerning this rise relates it to the non-evidence-based screening  procedures perfomed through out the world, particularly in places with health care systems regulated by the market and/or in places where the health care is not primary-care-based and the direct access (first contact) to specialists is frequent.  The Korean case is an excellent example of the problem of non-evidence based screening programs . Two recent publications (Lancet and New Englan Journal of Medicine) discusses these issues.

All the best

Rodrigo Olmos

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2814%2962242-X/fulltext?rss%3Dyes

http://www.nejm.org/doi/full/10.1056/NEJMp1409841

Thank you Dr Rodrigo Díaz Olmos for your inputs. The point is well taken. Its the advance in the diagnostic gadgets that might have been added to the new load of Thyroid malignancies, which is otherwise has an indolent course. The one suitable example I experienced is an 80 year old female with history of Follicular neoplasm Thyroid, disgnosed as Nodular goitre at 60 yeras of age and Follicular neoplasm in her seventeen. She reached us at the age of 80, when she had Pulmonary metastasis. So, the early diagnosis helps in people who live longer?

I agree with Dr. Noureldine´s answer. The main reason for this increase is the widespread use of imaging techniques.

Other environmental factors? Maybe, probably not only one, but in my opinion non-ionizing radiation from domestic devices has none, or very few, influence  in the rising incidence of differentiated thyroid carcinoma.

I'm totally agree with Noureldine!

Currentley the increase of thyroid cancer is most likely due to the accuracy diagnostic cytological and histological.

Evidences show that the most important reason for a surge in thyroid malignancy rate, is more accessibility to thyroid imaging modalities especially ultra-sonography. This issue results in more thyroid nodule detection and more neoplasm finding. A nice randomized clinical trial followed up the patients with micro papillary carcinoma in their thyroid gland as an incidental finding with and without any further treatment and interestingly found no significant difference in clinical outcome between these two groups.

TNM staging also shows reduction in tumor size of DTC patients at the time of diagnosis which is another evidence that supports the above hypothesis.

I believe that we face with more "detection rate" not increasing in "true incidence".

Over-screening is not limited to thyroid cancer, but also a dilemma in prostate, melanoma, lung malignacies etc.

I think we need a multifactor-causal model to analyse this topic.

Major factors should be included in are:

- Mass screening with optimized diagnostic modalities specially ultrasound and FNAB

- Optimizing cencer registry (most countries and even some developed countries such as Germany have started with optimizing cancer registry during recent years)

- the role of enviormental radiation or diagnostic radiation (CT, Nuclear Medicine etc.) are still discussed controversial.

Dear Narjess-Khatoun Ayati 

Would you have the reference of the randomised trial you mentioned on your commentary? I couldnt find any randomised trial dealing with this subject.

Thank you very much.

Rodrigo

Does anyone know if there have been other studies attempting to answer the increase in thyroid cancers?

Does anyone know if there have been other studies attempting to answer the increase in thyroid cancers?

Does anyone know if there have been other studies attempting to answer the increase in thyroid cancers?

Does anyone know if there have been other studies attempting to answer the increase in thyroid cancers?