Pattern of Thyroid Cancer and Its Associated Factors Among Thyroid Patients Underwent Thyroidectomy at Jimma Medical Center, Southwest Ethiopia; A Four Years Retrospective Review

Background: Thyroid cancer is the most common malignant disease of endocrine system and its incidence is rapidly increasing globally (about three to four times higher among females and accounts the sixth most common malignancy diagnosed in women). Among the four major types of thyroid cancer, papillary thyroid cancer (PTC) accounts 85-90% from all thyroid cases, followed by follicular thyroid cancer (FTC) which accounts for 5-10% of cases. Materials and Methods: A retrospective data of 260 patients who underwent thyroid surgery from 2015 to 2019 were included in the study and the status of the disease (clinical manifestations, laboratory/pathology ndings (thyroid function tests (TFTs) and biopsy) were reviewed from patient cards. The pattern of thyroid cancer was discriminated based on histo-pathological biopsy result. Descriptive and analytical statistics were applied to express the nding and reported by tables, gures and narration. Cross tabulation and logistic regression was applied to determine the association between thyroid CA and predictors. A p-value of <0.05 was declared as statistically signicant. Results: From the total sample of 260 patients underwent thyroid surgery, majority of them were females 219(84.2%), belong to age interval of 31-40 years (34.6%), dwellers of Oromia region (91.2%) and Jimma zone (83.8%). Colloid goiter was the most prevalent (74.6%) pattern of thyroid disease followed by follicular CA (4.2%), papillary CA (1.9%) and medullary CA (0.77%) while biopsy results of 48(18.46%) patients were not known. In general, about the 194(91.5%) of the thyroid lesion was identied as benign type and malignancy accounts for 18(8.5%) from the total conducted biopsy results of 212 patients. About six variables (duration of the disease, marital status, family history of the disease, nodularity, surface and border of the thyroid mass) were the candidate variables in binary logistic regression (p-value <0.25) and nally, three variables (duration of the disease (>10 years), surface (rough) and border (irregular) of the thyroid mass) were identied as the predictors of thyroid malignancy with AOR 0.05(0.004-0.60, P-v=0.016; 1.9(1.17-5.8), P-v=0.012 and 2.5(1.13-16.16), P-v<0.001 respectively.


Introduction
Thyroid cancer (TCA) is a relatively rare disease accounting for approximately 1-2% of all cancers worldwide. However, it is the most common (95%) endocrine malignancy associated with more deaths annually than all other endocrine cancers combined [1,2].
The incidence of thyroid cancer has continuously and sharply increased globally due to advanced technology to detect/screen in early preclinical stage, increased gender differences and a possible consequence of increased population exposure to radiation and to other still unrecognized carcinogens [3][4][5].
TCA commonly affects women (about 3-4 times) than men, can occur at any age but most tumors are diagnosed during the third to the sixth decades of life. It is the second and the fth most common cancer in women in Italy and USA respectively. In USA only about 62, 000 new cases occurred in men and women in 2015 [6].
Despite, early diagnosis and better treatment of thyroid cancer, its mortality rate is increasing and in USA among patients diagnosed with thyroid cancer from 1974-2013, the overall incidence of thyroid cancer increased by 3.6% annually [7,8].
A cohort study conducted in Australia among 2,260 patients underwent thyroidectomy performed over 40 years, thyroid cancer was diagnosed among 3.6 to 7.5% (P < 0.05) and con rmed an increase in the incidence of thyroid cancer over 4 decades [9]. The study conducted in Turkey among patients underwent thyroidectomy reported 14% of thyroid cancer rate [10].
Most thyroid malignancies are well differentiated thyroid cancers (DTC) and have an excellent prognosis with survival rates of more than 95% at 20 years although the recurrence or persistent rate is still high [11][12][13][14][15]. However, a notable proportion of cases are undifferentiated carcinomas and exhibit aggressive characteristics associated with a signi cantly higher recurrence and mortality rates [16][17][18][19].
PTC is the most common type and it accounts for 85-90% of all thyroid cancer cases [27][28][29][30] followed by FTC which is the second common carcinoma constituting about 5-10% of all thyroid cancers [31][32][33]. Medullary thyroid tumors accounts about 5-10% of all thyroid carcinoma and are familial in approximately 25% of cases [34]. ATC which is an undifferentiated thyroid carcinoma accounts for less than 2% of thyroid cancers and typically diagnosed in the elderly patients and is associated with poor prognosis [35][36][37].
Thyroid cancer, particularly undifferentiated thyroid carcinoma, is a cause of signi cant mortality and morbidity. Death from differentiated thyroid carcinoma, although rare, can also occur; early diagnosis and treatment is the key for good prognosis.

Methods
The study was conducted at Jimma medical center (JMC) which is one of the known teaching referral hospitals of the country located at distance of 335 km from the capital of Ethiopia, Addis Ababa to southwest direction. It was established in 1930 and owned initially by Jimma health science (Jimma University currently). It provides health services for approximately 9000 in patient and 80,000 outpatient attendances per year with a very wide catchment population (about 15 million people) in southwest Ethiopia. The study was conducted from November December, 2019 by reviewing patient cards that underwent thyroid surgery from 2015 to 2019 by employing a cross-sectional study design among sampled 260 patients. But, the histo-pathologic results of 48 patients were not available (probably not done/missed) and nally only 212 patients were analysed for pattern of CA. A structured questionnaire was used to record patient information including previous laboratory results.
Data was checked for missed values and outliers, cleaned, entered into Epidata version 4.3.1 and nally exported to SPSS version 22 for analysis. Both descriptive and analytical statistics were applied and the nding of the study was reported by tables, graphs and narration. Cross tabulation and logistic regression were applied to assess the association of outcome variable (thyroid cancer) and associated factors. P-value < 0.05 was declared as statistically signi cant.
Ethical clearance was obtained from Jimma University ethical committee after the proposal was approved by Jimma University ethical review board and support letter was collected from the University and hospital. All the information obtained from the records was anonymous.

Socio-demographic and baseline characteristics of respondents
Among total sample of 260 patients underwent thyroid surgery, majority of them belongs to female 219(84.2%), at age interval of 31-40 years (34.6%), Oromia region (91.2%) and Jimma zone (83.8%) as detailed in Table 1. Clinical pro le of thyroid patients The clinical pro le of thyroid disease was recorded/ retrieved from patient cards including patient history, physical examination, laboratory results (T3, T4 and TSH) and pathologic results (FNAC and biopsy) as seen in Table 2.

Pattern of thyroid diseases by histopathology results
Colloid goiter was the most prevalent (74.6%) pattern of thyroid disease followed by follicular CA (4.2%), papillary CA (1.9%) and medullary CA (0.77%). But, biopsy results of 18.46% patients were not known. In general from total patients of 212 who had biopsy results, the burden of benign and malignancy accounted for 91.5% and 8.5% respectively (Fig. 1).

Association of thyroid diseases with other variables
Logistic regression was applied to evaluate the associated factors of thyroid malignancy based on histopathological biopsy result. Accordingly, about six variables (duration of the disease, marital status, family history of the disease, nodularity, surface and border of the thyroid mass) were the candidate variables in binary logistic regression (p-value < 0.25) and nally, three variables (duration of the disease (> 10 years), surface (rough) and border (irregular) of the thyroid mass) were identi ed as the predictors of thyroid malignancy with AOR 0.05(0.004-0.60, P-v = 0.016; 1.9(1.17-5.8), P-v = 0.012 and 2.5(1.13-16.16), P-v < 0.001 respectively as detailed in Table 4.

Conclusion
In general, about the 81.5% of the thyroid lesion was identi ed as benign type while malignancy accounted for 8.5% from a total of 212 biopsy result analyzed for CA pattern. Among malignancy, follicular CA was the commonest (4.2%) among thyroid lesion patients underwent thyroidectomy. Short duration of the disease, rough surface and irregular border of the thyroid mass were identi ed as the predictors of thyroid malignancy.

Declarations
Ethics approval and consent to participate Ethical clearance was obtained from Jimma University ethical committee after the proposal was approved by Jimma University ethical review board and support letter was collected from the University and hospital.
All the information obtained from the records was anonymous.

Consent to publish
Not applicable.

Availability of data and materials
Needed materials can be provided upon request of corresponding author.

Con ict of interests
The authors declared that there is not con ict of interests.

Funding
Jimma University provided funding as post graduate research in 2019 for data collection.