Histological profile of thyroid cancer
between 1975-2009.Chernobyl effect and
universal iodine fortification of salt
THYROID CANCER
EVOLUTION OF THE DISEASE EVALUATED IN
ONE SETTING
VOICHIŢA MOGOŞ1. EUGEN TIRCOVEANU2
1. Clinic of Endocrinology, 1st Surgery Clinici University
of Medicine and Pharmacy “Gr.T Popa” Iasi
PURPOSE
To evaluate the evolution in time of
incidence, clinical and histological profile
in our setting from 1975 to 2009 taking into
account two main events:
• The accident from Chernobyl
• The role of iodine prophylaxis
Data from literature
• There was noticed a steady increase of thyroid
cancer all over the world
• External irradiation in the only well documented
cause in papillary thyroid cancer leading to
RET/PTC re-arrangements
• Iodine deficiency may play a role in the
development of follicular cancer and may favor
the development of anaplastic carcinoma
• Iodine repletion is associated with increased
incidence of papillary carcinoma with excellent
prognosis
There was noticed a steady increase of thyroid
cancer all over the world
Davies L et al. JAMA 2006, 295, 2164-2167
Between 1973-2002:
• 2.4 times increase in thyroid cancer incidence
• All thyroid cancer: 3.6/105 to 8.7/105/year (with 5.1/105)
• Papillary cancer: 2.7/105 to 7.7/105/year
• Small papillary cancer account for 87 % of the cancer
• Mortality decreased from 0.57 to 0.47/105/year
– External irradiation stopped after 1961
– Most data show that precocious diagnosis by ultrasound and FNB
leads to increased incidence but stable mortality
– Papillary cancer has a long evolution and excellent survival
– Over diagnosis increased the number of radical surgery and its
complications
Davies L., Welch HG.JAMA 2006,295, 2164-2167
Davies L., Welch HG.JAMA 2006,295, 2164-2167
There was noticed a steady increase of thyroid
cancer all over the world
Schottenfeld D et al. CA Cancer J.Clin. 1978, 28, 66-86
USA:Connecticut Tumor registry
• 1949-1969: 1.4/105/year to 1970-1983: 4/105/year
– Papillary: 64 %
– Follicular: 18 %
– Medullary: 3 %
• New York a study on autopsies:
– 16.4 /1000 all study
– 19.6/1000 in women
– 10.4/1000 in men
• Microcarcinomas:
– USA: 1- 5.7 %
– Japan: 17.9-24%
There was noticed a steady increase of thyroid
cancer all over the world
Scheiden P.et al. BMC Cancer 2006, 6, 102-109
Evaluation in an European country – Luxembourg 30 years after Chernobyl in 2
cohorts: 1990-1994 (a) and 1995-1999 (b)
• 310 new cases out of which 124 microcarcinomas < 1cm. After 1997
• Increased microcarcinomas from 7 % to 16.6 %
–
–
–
•
•
•
46.5 % papillary
13.3 % follicular
27.3 % medullary
Increased incidence from 6.4 to 8.6/105/year
Increased incidence in women from 7.4 to 10.1/105/year
Increased incidence in men from 2.3 to 3.6 /105/year
Mahoney MC et al. Int.Epidemiol. 2005, 34, 714-722 (1970-2001)
• Severe exposure: increase incidence in males + 775%, in females:+1925%
• Low exposure: increased incidence in males:+54 %, in females: + 250 %
Luxembourg
Scheider R et al. BMC Cancer 2006, 6, 102-116
There was noticed a steady increase of thyroid
cancer all over the world
Leehardt L et al. Thyroid 2004, 14, 1056-1060
• FRANCE: 1998-2001
• Increased incidence of thyroid cancer
• Increased prevalence of cancer operated among thyroid
nodules submitted to surgery due to
• increased assessment with ultrasound from 3 to 84 5
• Increased assessment through FNB from 8 to 36 %
• In France there was notice no association between cancer
incidence and nuclear accident from Chernobyl
There was noticed a steady increase of thyroid
cancer all over the world
Reynolds RM et al. Clin.Endocrinol. (Oxf) 2005, 62, 156-162
Scotish Cancer Registry 1960-2000:
• Incresed incidence of thyroid cancer from 1.76 to 3.54/105/year
in women
• Increased incidence from 0.82 to 1.25/105/year in men
• Decreased mortality from 1.05 to 0.28 % in women and from
0.73 to 0.34 in men
• Decreased follicular cancer
• Stable incidence of medullary carcinoma
• Increased survival
External irradiation was the only well
documented cause in papillary thyroid
cancer leading to RET/PTC rearrangements
Data from internal irradiation are related to
the best studied nuclear plant accident from
Chernobyl
Thyroid irradiation
The role of external irradiation in induction of thyroid cancer was
first noticed by Duffy and Fitzgerald in 1953, in those who
received external irradiation for different diseases. 36 % of
children who developed thyroid cancer had neck irradiation in
their personal history
The role of radioiodine was largely studied after Chernobyl
Contamination:
• Internal irradiation by inhalation or ingestion of: radioactive
iodine 131I, 132I, 135I, 131mTe (tellurium). 133 Te
• External irradiation X ray, gamma Irradiation due to radioactive
material deposits on the ground1
• Belarus: cancer in children: 1/106 before and 100/106 after
Chernobyl2. The risk in children less than 1 year is 30 fold
greater3
Cardis E et al. J.Natl.Cancer Inst. 2005, 97, 724-732
Nagatachi S et al. Thyroid 2002, 12, 899-896
Boltze C et al. Oncology 2009, 22, 459-467
Thyroid irradiation
Questions:
• Which is the role of the previous iodine intake in the
contaminated area
• Which are the factors that modify the risk of thyroid cancer
after exposure to irradiation:
– contamination level
– individual factors
Total dose of exposure:
– 365 mGy in Belarus (7- 3109 mGy)
– 40 mGy Rusian Federation (max. 10.2Gy)
– Dose of exposure to radioiodine: 1-2 mGy
Cardis E et al. J.Natl.Cancer Inst. 2005, 97, 724-732
Thyroid irradiation
• The risk to develop thyroid cancer after irradiation in individual
who previously consumed stable iodine after an exposure to 1
Gy is reduced 5 fold
• Low level of iodine in the soil is correlated with a 3 fold
increase of risk to develop cancer compared with residents in
areas with naturally more iodine in soil
• At doses of contamination between 1.5-2 Gy there is no linear
correlation between exposure and risk of cancer
• Previously ingestion of iodine reduces radioactive iodine intake
• Increased iodine supply reduces thyroid volume and
multiplication of thyroid cell and risk of occurrence of
mutations
Cardis E et al. J.Natl.Cancer Inst. 2005, 97, 724-732
Cardis E et al. J.Natl.Cancer Inst. 2005, 97, 724-732
Cardis E et al. J.Natl.Cancer Inst.2005, 97, 724-732
Thyroid irradiation
1986-1995 in Bellarus 472 patients among which 97.7 were
differentiated cancers
• median age: les than 14 years
• median age at exposure: 4.4 in children and 8.9 in adolescents
Italy and France after Chernobyl: 369 patients
Mean age in children more than 14 years
Follicular cancer: 15.2 % compared with 5.3 % in Bellarus
Most effected children were exposed at less than 5 years1
Most cancers occur 5-30 years after irradiation but the risk last to 50
years2
Pacini F. et al. J.Clin.Endocrinol.Metab. 1997, 82, 3563-3569
Greenspan FS JAMA 1977, 237, 2089-2091
Thyroid irradiation
Differences among cancers developed after Chernobyl and those developed in
Italy1
• Extrathyroidal extension: 49.1% vs 24.9 %
• Lymph node involvement: 64% vs 53.9 %
• Distant metastasis: 7.8 % vs 17.3 %
• For more latent forms of papillary cancer a new pick of incidence may be
expected
20 years after Chernobyl accident 5000 cases of thyroid cancer were
diagnosed. 60-70 % had N1 and 10-15 had M12
1. Pacini F. et al. J.Clin.Endocrinol.Metab. 1997, 82, 3563-3569
2. Tuttle RM et al. Clin.Oncolocy 2011, 23, 268-275
Relationship between the degree of iodine contamination and number and
percentage of new cases of thyroid cancer in children and adolescents after
Chernobyl nuclear reactor accident
Pacini F et al. J.clin.Endocrinol.Metab. 1997, 82, 3563-3569
Pacini F et al. J.clin.Endocrinol.Metab. 1997, 82, 3563-3569
Iodine deficiency may play a role in the
development of follicular cancer and may
favor the development of anaplastic
carcinoma
Iodine and thyroid cancer
• The relationship between thyroid cancer and dietary iodine is
controversial
• There are some data that could demonstrate that iodine deficiency
may increase thyroid cancer in some areas
• Iodine may act as adjuvant factor for carcinogensis and may have a
role in the hystological profile of thyroid cancer
• Is obvious from all statistics that increased dietary iodine is
associated with an increase of incidence of thyroid cancer1
• Sicilia:
– Thyroid malignancies: IDA – 2.96%, ISA 5.48 %
– Follicular cancer: IDA; up to 127/105,
– Anaplastic cancer: 93/105
1. Knobel M et al. Arq.Bras. Endocrinol.Metab. 2007, 51, 701-712
2. Belfiore A et al. Cancer 1987, 60, 3096-3192
Iodine and thyroid cancer
Iodine deficiency is associated with a relative risk (RR) of cancer as
follows (Sweden)1
• 0.92 for all histological types
• 0.80 for papillary cancer
• 0.87 for anaplastic carcinma
• 1.98 for follicular cancer
The risk for follicular cancer is 1.3-15 in iodine deficient areas and
depends of the time of residence in these areas2
1. Petterson B et al. Int.J.Cancer 1996, 65, 13-19
2. Galanti MR et al. Int J.Cancer 1995, 61, 615-621
Iodine and thyroid cancer
Frequency of thyroid cancer by tumor
type in Salta, Argentina before
and after iodine prophylaxis
Total number of cases
Years after iodine prophylaxis
10 years
59
11-26
85
Papillary
26
46
Follicular
15
15
Anaplastic
9
13
Ratio between Papillary and follicular
cancer
1.7
3.1
Harach C et al. Clin.Endocrinol. 1995, 61, 615-621
Iodine and thyroid cancer
Histologic pattern of thyroid tumors in
two areas of Sicily, Italy with low
and adequate iodine intake
Total number of cases submitted to
surgery
Low intake
911 (126)
High intake
2437 (419)
Papillary
11
103
Follicular
11
27
Anaplastic
5
9
Belfiore A et al. Cancer 1987, 60, 3096-3102
Iodine prophylaxis and thyroid cancer
Incidence of different forms of thyroid cancer before and after
iodine prophylaxis
Papillary: pre prophylaxis 44% vs post prophylaxis: 60 %
Papillary/follicular ratio: 1.7/1 to 3.1/1 1
Ratio papillary to follicular cancer according to iodine intake2
IDA: 0.1/1, moderate intake: 1.6/1-3.7/1, high intake: 3.4/1-6.5/1
1986-1999: 1500 new cases:
Incidence: 3.86 to 6.08/105
After prophylaxis: papillary to follicular ratio: 5.323
1. Harach H et al. Endocr.Pathiol. 2002, 13, 175-181
2. Lind p et al. Thyroid 1998, 8, 1179-1183
3. Szybinski Z et al. Wiad Lek 2001, 54, 106-116
Iodine prophylaxis and thyroid cancer
Incidence of different forms of thyroid cancer before and after
iodine prophylaxis 1974-1976 and 1992-1994
• Increased percentage of thyroid cancer on thyroidectomies
• Papillary: 54.3 %
• Follicular: 27 %
• Anaplastic: 11.1 %
• Medullary: 4.6 %
Papillary to follicular ratio:
1974-1976: 0.60
1992-1994: 6.88
Deandrea M et al. J.Endocriol.Invest. 1997, 20, 52-58
Iodine prophylaxis and thyroid cancer
iodine prophylaxis:
• Increased incidence of papillary cancer
• Decreased incidence of follicular cancer
• Decreased incidence of anaplastic cancer
• Improved prognosis
Histology of thyroid cancer in iodine deficient areas (Algeria)
Improvement of socio-econimc status from 1966-1981 and
1982-1991
Bakiri et all.Cancer 1998, 82, 1146-1153
Bakiri et all.Cancer 1998, 82, 1146-1153
Histological profile of thyroid cancers in an iodine sufficient
area ( Connecticut - USA )
Schottenfeld D, Gersman ST. Epidemiology of thyroid Cancer 2008
There is a trend to increase the incidence of thyroid cancer as well as
an increase of papillary thyroid cancer
Burges JR et al.J.Clin. Endocrinol.Metab.2000, 85, 4, 1513-1517
Histology and age are the best predictor factors for
survival
Scheiden P et al.BMC Cancer 2006, 6, 102-106
5 years survival:
• Papillary: 96 %
• Follicular: 88.9 %
• Medullary: 90.9 %
Hundahl Sa et al. Cancer 1998, 83, 2638-2648
10 years survival:
• Papillary: 93 %
• Follicular: 85 %
• Hurthle cell: 76 %
• Medullary: 75 %
• Anaplastic: 14 %
Histology and age are the best predictor
factors for survival
Passler G et all.Endocrine-Related Cancer 2004,11, 131-139
Radioactive elements release after CHERNOBYL 1986
What happened in Romania? It partially remains in the area of suppositions
CONTAMINAREA RADIOACTIVA DUPA
CERNOBIL 1986 - ROMANIA
RET/PTC in the key
mutation seen in
radiation-induced
thyroid cancer and
activation of BRAF is
associated with
sporadic forms of
differentiated thyroid
carcinoma
Xing s et al Endocrine
reviews 2007, 28, 742762
Data from literature
• Elisei has demonstrated that clinical and histological profile of
thyroid cancers was modified during the last 35 years through:
• Increased incidence of papillary cancers from 80,5 % to 91% during
these years
• Decreased follicular cancers from 19,5 % to 9 %;
• Increased incidence of cancer with diameter of less than 1 cm. from
7,9% in the firs half of the interval to 28,7 % in the second
• Reduced incidence of macro-invasive cancers from 7 % to 1,9 %;
• Reduced incidence of cancers with distant metastases from 5,4 la 2
%;
• Reduced incidence of cases with lymph node metastases from 34,2
% to 22, 4%;
• Reduced incidence of cases in advanced stages according to TNM
VI, for stage III 10,8 to 7,4 % and for stage IV from 4,2% to 1,7 %.
Elisei R., et all.J.Clin. Endocrinol.Metab. 2010,
MATHERIAL AND METHOD
• Data from files of patients with thyroid tumors submitted
to surgery between 1975-2009 (35 years) were divided
into 5 years intervals and analyzed for:
• New cases for each interval
• Histology
• Clinical appearance
• Stage of the disease according to TNM classification and
tumor stage grouping TNM VI
• Ratio between papillary and follicular cancer as indirect
signs for the role of supposed external irradiation and
modification due to iodine prophylaxis
MATHERIAL AND METHOD
• From 1981 most patients were assessed
based on fine needle biopsy performed
within the Department of Endocrinology of
our hospital
• Our data were compared with data from
the Department of Endocrinology analyzed
between 1971 and 2000 for patients
admitted in this setting including those
operated in other surgery clinics
Algorithm of diagnosis for thyroid nodules used after
1981 in the
Clinic of Endocriology IASI
THYROID NODULE
CYST
ULTRASOUND
SOLID OR MIXED LESSION
FNB
BENIGN
ABC
SCINITIGRAPHY
FOLLICULAR
NEOPLASM
MALIGN
EVACUAATION,
SCLEROZING
SOLVED
T4
WARM
COLD
LOW RISK
RECURREN
CE
HIGH
RISK
THIROIDECTOMY
FOLLOW-UP
E.Zbranca et.al.Symp.Nat.Endocrinol.1995,
Endocrinologie Clinica 1997
EPIDEMIOLOGICAL BACKGROUND
Moldova is situated in the northern part of Romania
Different studies provided data that show a decrease of
prevalence of goiter and a mild to moderate iodine deficiency
assessed by urinary iodine determination, except for same
areas where urinary iodine is still low
Urinary
Goiter %
Iodine
g/dL
1975
Suceava
6.55
60
Botosani
8.62
COUNTY
Neamt
Iasi
<5
9.93
1986
1999
Thyroid ultrasound
examination
53.7
33.3
30.4
30.7
22.2
24.7
31.8
16.1
23.4
6.4
Interval
Number of
cases
Age
Females
Males
1975 - 1979
19
45.7 ± 10.9
18
1
1980 - 1984
18
52.9 ± 14.9
15
3
1985 - 1989
17
49.5 ± 15.6
13
4
1990 - 1994
37
48.6 ± 16.8
32
5
1995 - 1999
52
51.5 ± 15.8
43
9
2000 -2004
71
53.1 ± 15
53
18
2005-2009
131
51.8 ± 14.2
109
22
1975 - 2009
345
51.3 ± 14.8
283
62
Demographic data of patients with thyroid tumors admitted in the Ist
Surgery Clinic of Iasi
RESULTS: thyroid tumors submitted to surgery
between 1975-2009 in the 1st Surgery Clinic of Iasi-
345 cases
Mumber of thyroid tumors operated between 19752009
131
140
120
100
80
60
40
20
0
71
52
37
19
18
17
1975- 1980- 1985- 1990- 1995- 2000- 200509
05
99
94
89
84
79
interval
New cases of thyroid tumors operated for each 5
years interval in the 1st Surgery clinic of Iasi
140
Nr.of tumors
%
120
100
80
60
37.97
40
20
5.5
5.2
4.9
10.72
15.1
20.57
0
1975-79 1980-84 1985-89 1990-94 1995-99 2000-05 2005-09
WHAY WE FOCUSED OUR RESEARCH ON
CHANGES OF HYSTOLOGICAL PROFILE OF
TUMORS DURING TIME?
• Histology, age and stage at diagnosis are the best
predictive prognostic factors for thyroid cancers
• All these factors are influenced by at least two major
events that happen in Romania:
• Hypothetical external irradiation after Chernobyl with
increase of papillary forms
• Important modification of iodine supply due to active and
universal salt iodination also with increase of papillary
form and decrease of incidence of goiter that may mask
a carcinoma
Survival in thyroid cancers acording to histology
Clinic of Endocirnology Iasi 1993
120
100
80
Papillary
Follicular
Medullary
60
Anaplastic
40
20
0
0
5 years
10 years
15 years
Survival in thyroid cancers acording to age
at diagnosis
Clinic of Endocrinology Iasi
120
100
80
<45 years
60
> 45 years
40
20
0
0
5 years
10 years
15 years
Survival in thyroid cancers acording to tumor
staging
Clinic of Endocirnology Iasi
120
100
80
Stage
Stage
Stage
Stage
60
40
20
0
0
5 years
10 years
15 years
I
II
III
IV
Histological profile of thyroid cancers Ist Surgery Clinic
Iasi
6.08
21
%
Anaplasic
4.05
14
Nr.of cases
MTC
4.05
14
Foll less dif
6.66
Other
23
17.97
Foll
62
4.92
17
Pap/Foll
56.23
Papill
0
50
194
100
150
200
250
Cancers derived from follicular epithelium
(1st.Surgery Clinic)
100
All
4.32
Anaplasic
4.32
MTC
%
7.09
Foll less dif
Nr.of cases
19.13
Follicular
5.24
Papil/foll
59.9
Papillary
0
50
100
150
200
250
300
350
Taking into account only cancers derived from follicular epithelium the
percentage of papillary and follicular cancers in more obvious among al
tumors
Others
5.82
Anaplastic
8.7
MTC
6.14
Foll less dif
15.21
Follicular
14.88
23.62
Pap/fol
Papilary
25.56
0
5
10
15
20
25
30
Histological profile of thyroid tumors in the Clinic of Endocrinology
of Iasi % 1975 - 2000
Expectation after external irradiation and
improved iodine supply
• Increased incidence of papillary carcinomas in younger
age, but the risk after exposure persists long life after
exposure
• Increased incidence of aggressive forms in children and
young adult immediately after irradiation
• Normal iodine intake is associated also with increase of
papillary cancers with good prognosis even in advanced
forms and increased papillary to follicular ratio
• Decrease incidence of follicular cancer with a less good
prognosis
• Decrease incidence of anaplastic carcinoma
• Diagnosis made in less advanced stages of the disease
Interval
Papillary
19751979
21.05
Pap/fol
19801984
19851989
19901994
19951999
20002004
20052009
33.3
23.5
21.6
30.76
61.97
85.5
11.1
11.7
2.7
17.3
2.8
0.8
3.81
Follicular
63.2
44.5
23.5
35.13
25
9.85
Foll less
dif.
19.5
11.1
29.4
27.02
5.76
1.4
MTC
5.26
3.84
5.6
3.8
1.92
9.85
1.52
Anaplastic
11.76
13.5
Striking features noticed during the analyzed interval: increase
incidence of papillary cancers, decrease of follicular forms, decrease of
anaplastic carcinomas – all seems to be related with a better iodine
prophylaxis and perhaps to external irradiation due to Tchernobil
accident
Clinical data of thyroid cancers 1st Surgery
Clinic
Others
MNG+Lym ph node
MNG
Sol.Nod+ Lym ph node
Solitary nodule
Anaplastic
MTC
Foll less dif
Follicular
Pap/fol
Papill
0
10
20
30
40
50
60
70
80
NEW CASES OF THYROID CANCER 1971 – 2000
CLINIC OF ENDOCRINOLOGY IASI
96-2000
80
91-95
55
86-90
87
81-85
46
76-80
29
1971-75
12
0
20
40
60
80
100
70
papillary
60
follicular
mixt/pna
50
anaplastic
medullary
40
30
20
10
0
solitary.nod
SN+lymphnode
MNG
MNG+L
DM
Bmet
Interval
Unilateral
tumor
19751979
19801984
19851989
19901994
19951999
20002005
20052009
63.15
94.4
88.23
86.48
86.5
94.4
89.3
Bilateral
tumor
36.7
5.6
5.88
13.5
13.4
5.63
10.6
Lymph node
involvement
26.3
5.5
35.3
72
42.3
31
22.9
Developed
on goiter
52.6
55.5
47.05
71.8
74.46
83
16.7
The trend of thyroid cancer derived from follicular epithelium during
35 years is a slightly reduce of tumors diagnosed in later stages :
bilateral, with lymph node involvement. Only in the last 5 years the
histology did not reveal surroundings of goiter in the proximity of
tumors due to active iodine prophylaxis
1975Interval 1979
19801984
19851989
micro carcinoma
19901994
19951999
20002004
20052009
5.4
4.5
6.25
0.8
TI
31.6
27.8
5.88
18.9
20.45
35.93
34.44
T II
57.9
55.5
58.8
32.4
43.2
26.6
25.6
T III
10.5
16.7
23.5
27.2
29.5
18.8
32.8
11.76
13.5
2.27
12.5
6.4
T IV
Tumor staging at time of diagnosis show that after 1990 there were
discovered microcarcinomas, stage I tumors increase and stage IV
tumors obviously decrease (TNM classification VI)
1975Interval 1979
19801984
19851989
19901994
19951999
20002004
20052009
TI
52.7
44.4
29.4
51.35
43.18
48.43
53.6
T II
47.36
44.4
35.3
24.32
27.3
18.75
24
11.2
23.5
10.8
27.3
26.56
20.8
11.7
13.51
2.2
6.25
1.6
T III
T IV
Grouping of tumor stage according to histology, tumor extension and age
at diagnosis show that after 1990 slightly more tumors were discovered in
less advanced stages even through the mean age at diagnosis does not
change during the analyzed interval (TNM classification VI)
Papillary to follicular ratio an indirect marker of iodine
deficiency 1st Surgery Clinic
25
22.6
Pap/foll ratio
20
15
10
5
5.75
0.73
0.8
0.66
0.39
1.56
0
1975-79 1980-84 1985-89 1990-94 1995-99 2000-04 2005-09
Changen in percentage of different forms of thyroid cancers
derived of follicular cells 1975-2000
Clinic of Endocrinology Iasi
Papillary
Follicular
70
MixedFPA
62
60
50
Anaplastic
53.8
47.36
42.1
40
30
25.2
18.5
20
15.9
10.52
11.7
8.6
10
3.4
0
1971-1980
1981-1990
1991-2000
EVOLUTION of RATIO BETWEEN PAPILLARY AND
FOLLICULAR CANCER
1971 – 2000
Clinic of Endocrinology Iasi (309 cases)
3.5
3.5
3.14
3
2.5
2.21
1.86
2
1.5
1
1
0.5
0
<1980
1981-85
1986-90
Lind P. 1998: this ratio depends of iodine supply
6,5/1 - 3,8 /1: increased iodine supply;
3,7/1 - 1,6/1: moderate iodine supply
1,6/1 - 1,19/1 iodine deficiency
1991-95
1996-2000
8
7
The ratio between papilary and follicular cancer according to iodine supply in
the studied area compared with other reported data*Deandrea 1997, ** Lind
1998
1971-1980
1981-1990
6.88
1991-2000
6.5
6
5
3.7
4
3
2.48
2
1
3.4
2.9
1.78
1.4
0.88
1.7 1.6
0.6
0.19
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CONCLUSIONS
Our data on patients with thyroid cancers analyzed over a period
of 35 years indicate that:
• It is an important increase in each 5 years interval, of number of
new cases
• There is an important increase of papillary cancer and the ratio
between papillary and follicular cancer and a decrease of
anaplastic carcinoma
• There is increase of cases discovered in earlier stages of the
disease
• We cannot assume that this events are due to the external
irradiation because of lack of genetic and clinical evidence
• We believe that the afore mentioned evolution of histological
profile of thyroid cancer in our setting is due to a better iodine
prophylaxis