Incidence trends for papillary thyroid carcinoma and their correlation with thyroid surgery and thyroid fine-needle aspirate cytology

An update on papillary microcarcinoma

PURPOSE OF REVIEW

There is a worldwide increasing incidence of thyroid cancer, mostly due to the increased diagnosis of papillary microcarcinoma (PMC). This review examines its clinical significance and optimal treatment.

RECENT FINDINGS

It is unclear whether or not the increase in PMC is real, or is simply due to the increased detection and diagnosis. The increase has been attributed to the widespread availability of thyroid ultrasound, with increasing numbers of clinically insignificant thyroid nodules subject to fine needle aspiration biopsy and surgical excision. An additional explanation is simply an increase in the number of routine histologic sections taken from the thyroidectomy specimens over the years. There have been two recent large clinical series with long-term follow-up highlighting the excellent prognosis of PMC. Novel research into immunohistochemical markers and advanced imaging with fluorodeoxyglucose positron emission tomography aims to identify the markers of more aggressive PMC. Management of PMC remains controversial, from observation alone to total thyroidectomy/radioiodine ablation.

SUMMARY

PMC has been increasing rapidly over recent decades due to increased cervical ultrasound and increased detection in pathological specimens. There is no compelling evidence base for the management of PMC, with retrospective series highlighting the excellent prognosis.

Rising thyroid cancer incidence in the United States by demographic and tumor characteristics, 1980-2005

Thyroid cancer incidence has been rising in the United States, and this trend has often been attributed to heightened medical surveillance and the use of improved diagnostics. Thyroid cancer incidence varies by sex and race/ethnicity, and these factors also influence access to and utilization of healthcare. We therefore examined thyroid cancer incidence rates by demographic and tumor characteristics based on 48,403 thyroid cancer patients diagnosed during 1980-2005 from the Surveillance, Epidemiology and End Results program of the National Cancer Institute. The rates varied by histologic type, sex, and race/ethnicity. Papillary carcinoma was the only histologic type for which incidence rates increased consistently among all racial/ethnic groups. Subsequent analyses focused on the 39,706 papillary thyroid cancers diagnosed during this period. Papillary carcinoma rates increased most rapidly among females. Between 1992-1995 and 2003-2005, they increased nearly 100% among White non-Hispanics and Black females but only 20% to 50% among White Hispanics, Asian/Pacific Islanders, and Black males. The increases were most rapid for localized stage and small tumors; however, rates also increased for large tumors and tumors of regional and distant stage. Since 1992-1995, half the overall increase in papillary carcinoma rates was due to increasing rates of very small (<or=1.0 cm) cancers, 30% to cancers 1.1 to 2 cm, and 20% to cancers>2 cm. Among White females, the rate of increase for cancers>5 cm almost equaled that for the smallest cancers. Medical surveillance and more sensitive diagnostic procedures cannot completely explain the observed increases in papillary thyroid cancer rates. Thus, other possible explanations should be explored.

Annual report to the nation on the status of cancer, 1975-2005, featuring trends in lung cancer, tobacco use, and tobacco control

BACKGROUND

The American Cancer Society, the Centers for Disease Control and Prevention (CDC), the National Cancer Institute (NCI), and the North American Association of Central Cancer Registries (NAACCR) collaborate annually to provide updated information on cancer occurrence and trends in the United States. This year's report includes trends in lung cancer incidence and death rates, tobacco use, and tobacco control by state of residence.

METHODS

Information on invasive cancers was obtained from the NCI, CDC, and NAACCR and information on mortality from the CDC's National Center for Health Statistics. Annual percentage changes in the age-standardized incidence and death rates (2000 US population standard) for all cancers combined and for the top 15 cancers were estimated by joinpoint analysis of long-term (1975-2005) trends and by least squares linear regression of short-term (1996-2005) trends. All statistical tests were two-sided.

RESULTS

Both incidence and death rates from all cancers combined decreased statistically significantly (P < .05) in men and women overall and in most racial and ethnic populations. These decreases were driven largely by declines in both incidence and death rates for the three most common cancers in men (lung, colorectum, and prostate) and for two of the three leading cancers in women (breast and colorectum), combined with a leveling off of lung cancer death rates in women. Although the national trend in female lung cancer death rates has stabilized since 2003, after increasing for several decades, there is prominent state and regional variation. Lung cancer incidence and/or death rates among women increased in 18 states, 16 of them in the South or Midwest, where, on average, the prevalence of smoking was higher and the annual percentage decrease in current smoking among adult women was lower than in the West and Northeast. California was the only state with decreasing lung cancer incidence and death rates in women.

CONCLUSIONS

Although the decrease in overall cancer incidence and death rates is encouraging, large state and regional differences in lung cancer trends among women underscore the need to maintain and strengthen many state tobacco control programs.

Differentiation of thyroid nodules with macrocalcifications: role of suspicious sonographic findings

OBJECTIVE

The purpose of this study was to determine which types of macrocalcifications are associated with thyroid carcinoma and to assess the role of other suspicious sonographic findings in thyroid nodules with macrocalcifications.

METHODS

Our Institutional Review Board approved this retrospective study, and informed consent was not required. We reviewed sonographic findings of thyroid nodules in 722 patients that underwent thyroid surgery in our institution between March 2006 and August 2006. Sonographic results were grouped into 3 types of macrocalcifications. Each lesion was evaluated on the basis of other suspicious sonographic criteria, including marked hypoechogenicity, irregular or microlobulated margins, and a taller-than-wide shape. Sensitivity and specificity based on sonographic criteria were calculated and compared among the subtypes of macrocalcifications.

RESULTS

One hundred seventy-four nodules showed macrocalcifications; 116 were malignant, and 58 were benign. Among the macrocalcification categories, solitary calcifications were more common in benign thyroid lesions, whereas coarse calcifications not otherwise specified were more common in malignant lesions (P < .05). Although the risk of malignancy was 17.2% in cases with no suspicious sonographic findings, the risk of malignancy was up to 82.8% in cases with at least 1 of the sonographic criteria (P < .05). On the basis of the suspicious sonographic criteria, the overall sensitivity was 82.8%. There was no statistically significant difference in sensitivity among the macrocalcification subtypes (P > .05).

CONCLUSIONS

Suspicious sonographic features such as marked hypoechogenicity, irregular or microlobulated margins, and a taller-than-wide shape can play important roles in differentiating benign and malignant thyroid nodules with macrocalcifications.

Thyroid cancer in the Middle Eastern population of California

OBJECTIVE

To describe and compare the epidemiology of thyroid cancer in the rapidly growing Middle Eastern (ME) population and the non-Hispanic, non-Middle Eastern White (NHNMW) residents of California. Population with ME heritage that is officially not recognized as a distinct ethnicity has rarely been studied in the past.

METHODS

ME cases in the California cancer registry files for 1988-2004 were identified by surname recognition. ME population was estimated by ancestry from census data.

RESULTS

Thyroid cancer in ME group, 869 cases and 56 deaths were compared with 19,182 cases and 1,327 deaths in the NHNMW population. Age-adjusted rate ratio (RR) for incidence was 1.5 (95% CI 1.3-1.7) in men and 1.5 (95% CI 1.4-1.7) in women. RR for mortality was 1.4 (95% CI 0.9-2.4) in men and 2.3 (95% CI 1.4-3.9) in women. Papillary tumors comprised over 80% of all cases and their pattern correlated with the rapid increase in thyroid cancer in recent years. Five-year observed survival in ME men was significantly higher than in NHNMW men, but similar in women.

CONCLUSIONS

Eighty-five percent of ME cases identified in this study were born in the Middle East. The higher incidence of thyroid cancer in this immigrant population may largely reflect a combination of sequels of radiation treatment for fungal diseases of the scalp that was common in the area in early 1950s, benign proliferative thyroid disease that is common in the area due to dietary iodine imbalance, and possibly genetic predisposition.

Thyroid cancer incidence and socioeconomic indicators of health care access

OBJECTIVE

It has been hypothesized that changes in diagnostic practices have driven the dramatic rise in thyroid cancer incidence over the past two decades. This study investigated the relation between the incidence of thyroid cancer and socioeconomic indicators of health care access.

METHODS

We examined thyroid cancer incidence trends in Wisconsin, USA, between 1980 and 2004, according to patient and tumor characteristics. Ecologic analyses were conducted by county to examine the relation between thyroid cancer incidence and education, income, and health insurance coverage.

RESULTS

The incidence of thyroid cancer nearly doubled in Wisconsin between 1980 and 2004, with almost all of the increase occurring between 1990 and 2004, during which an annual change of 4.0% (95% CI: 3.3-4.6) was observed. The bulk of the increase consisted of small, localized cancers of papillary histology. Ecologic analyses indicated moderate correlations by county between thyroid cancer incidence and median household income (r = 0.25), percent of residents with a college degree (r = 0.24), and percent of residents with health insurance (r = 0.41).

CONCLUSIONS

The association between thyroid cancer incidence and socioeconomic indicators of health care access is consistent with the hypothesis that the rising incidence trend is attributable to utilization of new diagnostic practices.

The thyroid dose burden in medical imaging A re-examination

Radiation is the best defined causative factor in thyroid cancer. The thyroid is especially susceptible to injury from radiation to which it may be exposed in a variety of circumstances in addition to natural background: radiotherapy, including, historically, therapy of such benign conditions as ring worm and haemangiomata, radiation exposure in nuclear accidents and fallout from nuclear bomb tests, and diagnostic exposures, particularly in the relatively high dose CT examination of head and neck. Both use of CT and the incidence of thyroid cancer appear to be increasing worldwide and it has been suggested that there may be a causative relationship between the two. It has been further posited that the iodine content of the thyroid might play a role in increasing the radiation dose absorption. Indeed, on the same basis, iodine administered in the form of an X-ray contrast-enhancing agent might also be expected to play some role in increasing thyroid radiation absorption resulting in a yet higher dose burden in any give circumstances than is generally assumed. In view of the importance of these ideas we have performed some calculations to estimate the magnitude of the iodine effects. We conclude that they are not great enough to cause concern.

[Thyroid incidentaloma. Overdiagnosis and overtreatment of healthy persons with thyroid illness?]

Thyroid incidentalomas have been found in about 20% of cases screened by neck ultrasound, and asymptomatic thyroid cancer is detected in about 10% of autopsies. The incidence of clinically treated thyroid cancer in Germany is increasing without an increase in cancer-specific mortality. Presently the incidence is about 4500 cases per year (7.3/100,000, 3000 females). For early detection and treatment of clinical thyroid cancer ultrasonography-guided fine needle aspiration cytology of suspicious nodules therefore is crucial. Thyroid lobectomy is the treatment of choice for suspicious nodules to lower the risk of morbidity in case of reoperation due to a postoperative diagnosis of cancer. However, subtotal lobectomy may also be justified, especially with nodules in anterior position, because the risk of malignancy is only 3-5%. Frozen selection and/or early final histopathology should be available to avoid two-stage thyroid cancer operations.

Staging systems for papillary thyroid carcinoma: a study of 2 tertiary referral centers

OBJECTIVE

To find out the most applicable and consistent staging system for papillary thyroid carcinoma (PTC) available in the literature.

BACKGROUND

The commonly used staging systems for PTC have predicted cancer-specific survival (CSS) well. However, their applicability and generalizability have not yet been evaluated in different clinical settings.

METHODS

A MEDLINE search from 1965 to 2005 was carried out to identify different staging systems available in the literature and 9 systems were applicable to 1634 PTC patients within 2 tertiary-referral centers. The CSS of each staging system within individual centers were calculated using Kaplan-Meier method and the CSS of each tumor stage in one individual center was compared with that of the other by log-rank test. In addition, within each center, the predictability of each staging system relative to the others was ranked based on the proportion of variation explained (PVE) value.

RESULTS

Clinicopathologic features, treatment received, and tumor stages were significantly different between the 2 centers. There were also significant differences in CSS within at least one tumor stage between the 2 centers in 8 of the 9 staging systems. The TNM was a highly predictive and consistent staging system within the 2 centers. Although the absolute PVE values differed between the 2 centers, the relative ranking of the 9 staging systems within each center correlated significantly to each other (P < 0.05).

CONCLUSIONS

Despite referral, treatment, and data collection biases inherent within each center, the TNM system remained to be the most applicable and consistent staging system for PTC in 2 centers managing the same population group.

Increasing incidence of thyroid cancer in Basilicata: an Italian study

OBJECTIVE

In recent years many authors have reported an increase in thyroid cancer (TC) incidence in several countries. The cause of such phenomenon remains unclear.

DESIGN

This study was designed to estimate the incidence of TC in Basilicata, the smallest region of Southern Italy with a population of 596,546 people, between 2001 and 2004.

MAIN OUTCOME

A total of 302 cases of TC were identified. The annual incidence of TC changed over the years, from 10.0 per 100,000 people in 2001 to 15.7 per 100,000 people in 2004. The number of new TC cases per 100,000 people increased an average of 16% per yr. Median age at diagnosis was 49 yr. The most frequent histotype was papillary TC (PTC) (73.2%). In 20 (6.6%) patients with PTC, we identified at least one first-degree relative affected by differentiated TC.

CONCLUSIONS

The present study shows a high incidence of sporadic and familial non-medullary TC in Basilicata. The reason for this finding may be related to several factors discussed in the paper. Further studies evaluating the trends in the incidence of TC in Basilicata in the future could provide some answers for the potential pathogenetic hypothesis.

Staging systems for papillary thyroid carcinoma: a review and comparison

OBJECTIVE

To find out the most predictive staging system for papillary thyroid carcinoma (PTC) currently available in the literature.

BACKGROUND

Various staging systems or risk group stratifications have been used extensively in the clinical management of patients with PTC, but the most predictive system for cancer-specific survival (CSS) based on distinct histologic types remains unclear.

METHODS

Through a comprehensive MEDLINE search from 1965 to 2005, a total of 17 staging systems were found in the literature and 14 systems were applied to the 589 PTC patients managed at our institution from 1961 to 2001. CSS were calculated by Kaplan-Meier method and were compared by log-rank test. Using Cox proportional hazards analysis, the relative importance of each staging system in determining CSS was calculated by the proportion of variation (PVE).

RESULTS

All 14 staging systems significantly predicted CSS (P < 0.001). The 3 highest ranked staging systems by PVE were the Metastases, Age, Completeness of Resection, Invasion, Size (MACIS) (18.7) followed by the new AJCC/UICC 6th edition tumor, node, metastases (TNM) (17.9), and the European Organization for Research and Treatment of Cancer (EORTC) (16.6).

CONCLUSIONS

All of the currently available staging systems predicted CSS well in patients with PTC regardless of which histologic type from which they were derived. When predictability was measured by PVE, the MACIS system was the most predictive staging system and so should be the staging system of choice for PTC in the future.

Changing patterns in the incidence and survival of thyroid cancer with follicular phenotype--papillary, follicular, and anaplastic: a morphological and epidemiological study

Thyroid carcinomas with follicular phenotype have demonstrated changing patterns over 30 years (1973-2003) according to data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute. Papillary carcinomas have significantly increased. They accounted for 74% of all cases of thyroid cancers in 1973 and 87% in 2003. During this period, the incidence rate of papillary carcinoma (including the follicular variant) increased by 189%, the rate of follicular carcinoma remained stable, and the rate of anaplastic carcinoma decreased by 22%. The rate of the follicular variant of papillary carcinoma alone increased by 173%. Thyroid cancer was more common in whites than in blacks and in females more than in males. Papillary carcinomas rapidly increased during adolescence and reached a peak around age 52-56, then declined. Follicular carcinomas increased steadily, but at a lower rate until age 80. After 1988, both papillary and follicular carcinomas, less than 2 cm, increased at the same rate as carcinomas larger than 2 cm. However, papillary carcinomas less than 2 cm were more common. Overall, the 10-year relative survival rate was greater than 90% for blacks and whites with the exception of follicular carcinoma in blacks. The 10-year relative survival rate for anaplastic carcinoma in patients over 40 years of age was 4.7%. The decrease in incidence rate of anaplastic carcinoma may be the result of the successful treatment of papillary and follicular carcinomas.

Prognostic Factors in Papillary and Follicular Thyroid Carcinoma: Their Implications for Cancer Staging

BACKGROUND

Papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC) are two distinct histological types of thyroid carcinoma but have often been studied and staged as a collective group, known as differentiated thyroid carcinoma (DTC). However, this may not be an optimal approach to cancer staging.

METHODS

A total of 760 patients with DTC, comprising 589 (77.5%) with PTC and 171 with (22.5%) FTC, being managed at our institution from 1961 to 2001 were retrospectively reviewed. Their clinicopathological features, treatment modalities received, and postoperative outcome were analyzed. Both univariate and multivariate analyses were performed to identify prognostic factors related to cancer-specific survival (CSS) for PTC and FTC.

RESULTS

There were statistically significant differences between PTC and FTC in terms of age >/=50 years at diagnosis (P = .040), tumor size (P < .001), lymph node metastases (P < .001), distant metastases (P < .001), extrathyroidal extension (P < .001), multifocality (P = .002), capsular invasion (P < .001), extent of thyroid resection (P < .001), radioiodine ablation (P < .001), and external-beam irradiation (P = .003). Although PTC and FTC had similar 10-year and 15-year CSS (P = .846), each possessed its own set of independent prognostic factors for CSS. Age at diagnosis and completeness of resection were independent prognostic factors in both PTC and FTC.

CONCLUSIONS

There were marked differences in clinicopathologic features, treatment, and prognostic factors between the two histologic types of DTC. Different staging systems should be evaluated and validated for PTC and FTC individually in the future.

Trend in thyroid carcinoma size, age at diagnosis, and histology in a retrospective study of 500 cases diagnosed over 20 years

Recently, the Italian Network of Cancer Registries analyzed 5101 cases of thyroid carcinoma showing a reduction of mortality rate of 4%/year. This prompts us to evaluate the temporal trend in tumor size, age at diagnosis, and histology in a retrospective analysis of 500 thyroid cancers diagnosed over 20 years. Thyroid cancers were divided in two groups. The first included 193 cases diagnosed from 1985 to 1994, and the second 307 from 1995 to 2004. The size of all tumors was significantly reduced from 30 +/- 1.4mm in the first group to 15 +/- 0.8mm in the second group. In particular, papillary thyroid carcinoma (PTC) size decreased from 28 +/- 1.2mm to 14 +/- 0.8mm and follicular carcinoma from 40 +/- 6.3mm to 17 +/- 4.5 mm. Age at diagnosis of all carcinomas increased significantly from 40 +/- 1.3 years in the first group to 48 +/- 0.9 years in the second group. Analysis of the histological types revealed a significant increase of PTC rate in the second decade from 82% to 92% and a concomitant reduction of anaplastic thyroid carcinoma (ATC) from 3.7% to 1.0%. Moreover, a significant increase of micro-PTC rate, from 7.3% to 36.4%, was observed. In conclusion, it may be speculated that the above mentioned decreased mortality rate for thyroid carcinoma could be related to the significant reduction with time of cancer size, to the progressive increase of PTC rate and to the reduction of ATC rate. These data, if confirmed in other series, underscore the importance of evaluating thyroid nodules smaller than 10mm and corroborate recent findings suggesting that age be reconsidered as an independent prognostic factor for differentiated thyroid cancers.

Annual report to the nation on the status of cancer, 1975–2003, featuring cancer among U.S. Hispanic/Latino populations

BACKGROUND

The American Cancer Society, Centers for Disease Control and Prevention, National Cancer Institute, and North American Association of Central Cancer Registries collaborate annually to provide U.S. cancer information, this year featuring the first comprehensive compilation of cancer information for U.S. Latinos.

METHODS

Cancer incidence was obtained from 90% of the Hispanic/Latino and 82% of the U.S. populations. Cancer deaths were obtained for the entire U.S. population. Cancer screening, risk factor, incidence, and mortality data were compiled for Latino and non-Latino adults and children (incidence only). Long-term (1975-2003) and fixed-interval (1995-2003) trends and comparative analyses by disease stage, urbanicity, and area poverty were evaluated.

RESULTS

The long-term trend in overall cancer death rates, declining since the early 1990s, continued through 2003 for all races and both sexes combined. However, female lung cancer incidence rates increased from 1975 to 2003, decelerating since 1991 and breast cancer incidence rates stabilized from 2001 to 2003. Latinos had lower incidence rates in 1999-2003 for most cancers, but higher rates for stomach, liver, cervix, and myeloma (females) than did non-Latino white populations. Latino children have higher incidence of leukemia, retinoblastoma, osteosarcoma, and germ-cell tumors than do non-Latino white children. For several common cancers, Latinos were less likely than non-Latinos to be diagnosed at localized stages.

CONCLUSIONS

The lower cancer rates observed in Latino immigrants could be sustained by maintenance of healthy behaviors. Some infection-related cancers in Latinos could be controlled by evidence-based interventions. Affordable, culturally sensitive, linguistically appropriate, and timely access to cancer information, prevention, screening, and treatment are important in Latino outreach and community networks.