ThyroidCancer Epidemiology NicholasFoggia MSCC-503 Cancer Epidemiology SaintFrancis University December11, 2017 ThyroidCancer Epidemiology Abstract Thyroidcancer is a common tumor type that has increased over the years around theworld and in the United States. This tumor is found in the thyroid gland thatis located at the bottom of the throat and is known as an endocrine cancer ortumor. The reasoning behind being labeled an endocrine tumor is because of therole the thyroid has in the human body regarding growth and metabolism. Thethyroid is an important gland because of the hormones it releases that help thebody grow as well as regulate certain functions within the body. With such animportant role to the maturation and growth of a person, is it safe to assumethat thyroid cancer is an incredibly dangerous diagnosis with little chance ofsurvival? On the contrary, thyroid cancer is one of the less dangerous cancerswith a positive prognosis. While all cancer is serious, this cancer has asilver lining by its survival rate even though it seems to be growing over thepast year. This cancer has a higher incidence rate in women and minorities andthis could be because of certain risk factors that put people at a higher riskof developing thyroid cancer.
With these risk factors in mind there are certainprevention measures that can be taken in order for a person to be at adecreased risk of cancer. ThyroidCancer by the Numbers Thyroid cancer, like many other cancers has increasedover the past couple decades and in prevalence but has remained very muchsimilar in terms of the survival rate. Based off of recent statistics theprevalence of thyroid cancer is roughly around 725,000 people as of 2014. Thenumber of new cases in cancer has also increased over the past decades withroughly around 0.5 per 100,000 people being diagnosed with thyroid cancer peryear.
It is estimated that there will be upwards of 56,000 new cases of thyroidcancer diagnoses in the year 2017. This estimate would make up about 3.4% ofall new cancer diagnoses in the current year. 1 While these numbers seem daunting thyroid cancer does noteven rank in the top ten types of cancer. Thyroid cancer is the eleventh mostcommon type of cancer in the United States with breast cancer in females andlung and bronchus cancer at the top of the list. Both breast and lung andbronchus cancer have an estimated new cases in 2017 of over 200,000 diagnoses.
1,2This is almost four times the incidence of thyroid cancer (almost 57,000 newcases in 2017). While this shows that thyroid cancer is not as prominent assome other cancers it is still an area that obviously needs attention. The numbers behind thyroid cancer can be a littleconfusing because while the cancer is the eleventh most common cancer in theUnited States it actually as a positive survival rate.
The five-year survivalrate of this cancer is 98.2% which sets an optimistic outlook on this disease.However, this survival rate is not set at this positive value because thesurvival rate can be affected by stage. The further the stage of the cancer thelower the five-year survival rate in thyroid cancer. When the cancer islocalized, or has not left the thyroid, the five-year survival rate is close toabsolute at 99.9% and when the cancer has spread locally to the lymph nodewithin the area then there is a 98.0% five-year survival rate. Unfortunately,like most cancers, when the cancer cells spread to a distant region in the bodythe survival rate decreases.
Specific to thyroid cancer, when the cancer cellsmetastasize to a distant place in the body there is a 56.4% five-year survivalrate. Luckily the majority of thyroid cancers are found in early stages with68% of it staying within the thyroid and 27% of it staying in the lymph nodesaround the thyroid. 2 Like most cancers there are certain people who are at ahigher risk of being diagnosed than others and thyroid cancer is no different. Thyroidcancer is mainly diagnosed later on in life with a dramatic increase in ages45-54.
This peak range accounts for 23% of all thyroid cancer diagnoses and themean age of thyroid cancer diagnoses is 51 years of age. In addition to agebeing an increased risk factor for thyroid cancer, gender is also of increasedprevalence.2 In women there are 21.0 new cases per 100,000 people ascompared to 7.
1 new cases per 100,000 people in men. This is in all races butthere is also an increased prevalence in people who are white, Hispanic andAsian/Pacific Islander.2 While the average age of diagnoses of this cancer is 51years of age the average age of death of thyroid cancer is 73 years of age.Even though the highest age group of diagnoses is 45-54 the highest age ratefor death is 75-84 years of age.2 The number of deaths per 100,000people is actually fairly even among races. Hawaii is also atan increased prevalence and incidence because it is considered a regionalfactor. A study done in 2013 looked at the descriptive epidemiology of thyroidcancer in areas with volcanoes and found that these areas were at an increasedincidence.3 A reason that this could possibly be is because theenvironmental factors that are influenced by the volcanos can be consideredcarcinogenic.
3 These can be considered carcinogenic because they maybe endocrine disruptors which can disrupt the natural function of tissues andbecome cancerous mutations. RelativeRisk in Thyroid Cancer While there are several risk factors that are attributedto thyroid cancer certain factors have a higher risk than others. Using aliterary review several relative risks were assessed to determine theprobability of being diagnosed with thyroid cancer when exposed to these risks.According to the American Cancer Society some of the more common risk factorsthat have already been discussed have been discussed such as age and gender. Severalother exposure factors such as smoking an alcohol consumption are known to haveadverse health effects in areas other than thyroid cancer but studies have alsobeen done in order to assess how great of a risk these things have on thisspecific cancer type.
RelativeRisks Cigarette Smoking Study Relative Risk Current or Former Smoker Mack 0.6 Current Mack 0.9 Former Rossing 0.
5 Current Rossing 0.7 Former Kabat 0.57 Current Kabat 1.16 Former Table 1. CigaretteSmoking and Relative Risk Alcohol Consumption Study Relative Risk Study Type Seung-Hee Hang 0.74 Observational Seung-Hee Hang 0.
77 Case-Control Seung-Hee Hang 0.70 Cohort Study Seung-Hee Hang 0.82 Cross Sectional Wang Inverse Relationship – Mack Inverse Relationship – Rossing 0.7 – Kabat 0.67-0.97 – Table 2. AlcoholConsumption and Relative Risk Caffeine Consumption Study Relative Risk Han 0.88/0.
59 Mack 0.6 Table 3. CaffeineConsumption and Relative Risk Diet Factors Study Relative Risk Cho 1.43* Table 4. Dietary Factors and Relative Risk(* denotes a significant relative risk) Hormonal and Goiter Factors Study Relative Risk Menopause Schonfield 1.22 Surgical 1.00 Natural 1.
29 >55 years at Natural Menopause 1.26 45-49 years at Surgical Menopause 1.26-1.63 MHT Use 1.47 Benign Breast Disease Goiter-Truong 4.2 Goiter Table 5. Hormonal Factorsand Relative Risk Age: Age is a common risk factor among several types of cancerand thyroid cancer is no different. It is very common that the older a persongets the more likely it is that they are at risk for thyroid cancer.
4,5A study done in 2015 showed that risk of multinodularity risk of thyroid cancerincreased by 1.6% each year with a relative risk of 1.022.5 Gender: As mentioned before, women have a greater risk ofdeveloping thyroid cancer as compared to men. The overall relative risk forthyroid cancer in both men and women in the United States has been calculatedto be 2.9 but the risk for women is four times greater than it is for men.5It is not completely clear as to why thyroid cancer is more common in women asto men but with this knowledge more preventative measures can be taken for thisspecified group at risk.
Hormonal Effects andGoiter Effects: Hormonal effects are one of the most common risk factorsfor those who develop thyroid cancer. It is shown that some of these riskfactors include; age at natural menopause, age at surgical menopause and statusof menopausal hormone therapy. Table 5 describes the relative risk within theserisk factors.6,7 Another important but not common risk factor is theeffect a goiter can have on a person’s risk of thyroid cancer.
Goiters are anabnormal growth of the thyroid gland that can be visible from a person’s neckarea. This growth of the thyroid can be explained by an imbalance of hormonesin the thyroid that causes it to grow. () While goiters are not overly commonit still can place a person at a higher risk of developing thyroid cancer. Astudy was done that examined this risk based on the history of people who had agoiter. Those who had a goiter had a significant relative risk of a 4.2.17,18This means that a person with a history of a goiter is more than 4 timeslikely to have thyroid cancer than someone who does not share this samehistory.
These studies show that hormonal effects play a major role in the riskof thyroid cancer and should not be taken lightly.17 Smoking in ThyroidCancer: While smoking has adverse health effects in differentareas of human life it is not always the case with specific types of disease.While greater risk factors in thyroid cancer such as age and gender exist therehave been several studies done to assess the relative risk of smoking andthyroid cancer.11,12,13 The studies found in Table 1 all representan analysis of the different studies that have been done in order to assessthis risk.
Many of these studies separated the risk by those who are currentsmokers, previous smokers and some even by those who have not smoked before.Within this review it was shown that smoking does not have a high relative riskin terms of thyroid cancer. Looking at the table the ranges of relative risk incurrent smokers is an RR of 0.5-0.6 and former smokers is 0.7-1.
16. This showsthat there is not a strong relative risk among those who smoke and those whoare diagnosed with thyroid cancer. Alcohol in ThyroidCancer: Very much like smoking, alcohol has been known to have anegative effect in certain areas of health related disease and outcomes. Theseveral studies that have been done about alcohol and the relative risk ofthyroid cancer have shown similar results to that of the smoking and evensuggest that alcohol may serve as a protective factor to the risk of thyroidcancer.8,12,13 Table 2 shows that these relative risks of thealcohol are all below 1.
This suggests that there may even be aprotective factor between alcohol and thyroid cancer. Coffee/Caffeine inThyroid Cancer: When examining if coffee drinking or caffeine intakemakes one a greater risk of developing thyroid cancer a similar finding toalcohol and smoking is found once again. In Table 3 it shows that in these twostudies the relative risk of caffeine intake was 0.59-0.88, meaning that itdoes not put a person at greater risk of developing this cancer.9,10 Diet/Diabetic/ PhysicalActivity factors in Thyroid Cancer: Diet and lifestyle habits can also have an effect onwhether or not someone is at an increased effect of being diagnosed withcancer. Some dietary factors included a diet that involves aniodine-deficiency. A study that was conducted showed that there was anincreased risk of thyroid cancer with an iodine deficiency, RR= 1.
43. Studieshave also taken a glance at physical activity levels of individuals and havebeen back and forth on the results of whether or not physical activity levelshave a significant reduction or attribution to risk.14 When diabeteswas observed it was found that certain studies showed a statistical relativerisk while others did not.15 (Table 4). Studies have also been donein order to assess possible risk factors of physical activity and thyroidcancer. While physical activity has a great effect on many areas of health anddisease prevention there was no significant risk or even reduction of risk thatwas found between the two.14,15 Radiation in ThyroidCancer Risk: Radiation is also listed as a significant risk factor forthyroid cancer. This risk can be separated between certain age groups at thetime of radiation.
Studies have also observed the risk of radiation exposureand other neck and chest cancers.16 In a specific study in 2005 itwas observed that with thyroid cancer the older a person was when they wereexposed the more likely they were to get thyroid cancer.16 Thisstudy also took a look at thyroid cancer as a second primary cancer diagnosesas a result of the treatments of other cancers.
Those who have receivedradiation therapy to combat and treat other types of cancer have a significantincreased risk of developing thyroid cancer in the future. This analysis of specific risk factors for thyroid cancerhas shown that this specific disease has different and specified risk factors.Many diseases have a greater risk factor when it comes to age and even gender andthyroid cancer is no different, as these risk factors are two of their greatercontributors. Other significant risk factors in this disease include dietarylifestyle habits, hormones and radiation and can increase the likelihood of aperson being diagnosed.
Some risk factors that have been studied but have notproven to be significant risk factors include; caffeine intake, alcoholconsumption and smoking. These factors may have a significant risk in otherdiseases but in thyroid cancer it has not been proven to be a risk factor.Epidemiologically, alcohol and caffeine intake has actually had a low enoughrelative risk to be possibly considered a protective mechanism of thyroidcancer. With the knowledge of what puts people at a higher risk of thyroid cancer,preventative measures can be implemented in daily living to avoid a possiblefuture diagnoses.
Preventionof Thyroid Cancer: Thyroid cancer has several risks associated with it andbecause of this there can be certain steps that are taken to reduce a person’srisk. There will be certain risk factors that can be modified and changed andthere are certain risks that cannot be changed. Even though there are factorsthat cannot be changed there is still preventative measures that one can takein order to decrease the risk of developing thyroid cancer. The risk factors that are non-modifiable for thyroidcancer include age and gender. A person cannot change their age, nor theirgender so it is not something that a person can attempt to adapt to in order toavoid risk. Other risk factors that cannot be controlled for are also heredityconditions and family history of thyroid disease.
These factors put certainpeople at a predisposed increased risk of thyroid cancer and cannot be changed.Because these risks cannot be changed or decreased then the risk factors thatare modifiable should be taken seriously and lifestyle habits can be changed. Some of the risk factors that can be changed in order toreduce the risk of thyroid cancer include dietary factors, hormonal factors andradiation. There are several dietary factors that go into thyroid cancer risksuch as obesity and iodine deficiency. Preventative measures that could aid inthis could be weight loss programs that could not only decrease risk of thyroidcancer but also decrease the risk of other chronic diseases.
These programs caninclude group exercise classes with dietary seminars that can improve bodycomposition and overall health. The iodine deficiency risks could be handled byalso holding dietary seminars that show the importance of eating foods that aresufficient in iodine. These foods can include the healthier areas of the foodgroups such as vegetables and fruits. Another option for this could be iodinesupplementation for those who have the knowledge that they are iodinedeficient.
These risk factors are some of the more feasible ones that can befixed and altered to reduce risk. One of the more important risk factors that can reducedis the radiation exposure factor. Because radiation is a very high risk factorin thyroid cancer it is important to reduce the exposure of it throughout thelifetime of a person. According to the United States Nuclear RegulatoryCommission (U.S.
NRC) the top two causes of exposure of radiation in the UnitedStates comes from Radon exposure, 37%, and from medical procedure, 36%.19Because these exposures are so high it is important that individuals andnations are taking the proper steps in order to reduce these risks. Radon is aradioactive chemical that is toxic to the human body especially after prolongedperiods of time. It is found greatly in homes because it escapes rocks and soiland traps itself in closed spaces like houses.20 There are severalagencies such as the International Radon Project and the World HealthOrganization that are looking to increase the awareness of radon levels andexposure so that homeowners can be aware of the risk and be conscious ofpreventing these levels to increase. Conclusion: Thyroid cancer prevalence and incidence has beenincreasing of the years but there are ways that this cancer can be beat.
Thisspecific cancer has a very good survival rate which brings hope to those whohave been diagnosed with this cancer. Taking preventative measures such asdietary regulation and avoiding radiation exposure when possible can helpreduce the risk that one has at coming down with this cancer.