Pediatric Head and Neck Malignancies: US Incidence and Trends Over 2 Decades

Background  Recent reports have noted an increase in the overall incidence of pediatric cancer.

Objective  To determine whether this trend is applicable to malignancies of the head and neck in children.

Design  Using the National Cancer Institute's Surveillance, Epidemiology, and End Results tumor database, we determined the incidence of all cancers diagnosed from 1973 through 1996 in children younger than 19 years. This was compared with the incidence of head and neck malignancies within the same population. Rates were then determined for eight 3-year periods from 1973-1975 to 1994-1996 and adjusted by use of three 5-year age groups weighted by the 1970 US standard population.

Results  A total of 24 960 malignancies diagnosed in children younger than 19 years were identified for the study period. From this group, 3050 tumors (12%) were located in the head and neck. The average annual rate of all cancer (number of malignancies per 100 000 person-years) in children younger than 15 years rose 25% from 11.22 (95% confidence interval [CI], 10.70-11.74) for 1973-1975 to 14.03 (95% CI, 13.46-14.60) for 1994-1996. Among malignancies of the head and neck, the incidence rate increased 35% from 1.10 (95% CI, 0.94-1.26) to 1.49 (95% CI, 1.30-1.68) during the same period.

Conclusion  The incidence of head and neck malignancies among children younger than 15 years in the United States from 1973 through 1996 increased at a greater rate than childhood cancer in general.

CANCER REPRESENTS a significant cause of mortality among the pediatric population. The frequency with which children between the ages of 5 and 14 years die from cancer is second only to death from accidental trauma.¹ Despite improvements in managing many pediatric malignancies, the incidence of childhood cancer continues to rise. Over the past 2 decades, annual increases of 1% to 2% in the rate of pediatric malignancies have been reported in the United States.^2-5 Similar increases have been reported in Australia, Spain, and Britain.^6-8

Whether this rising trend applies to pediatric head and neck cancer remains unknown. Pediatric oncology reports often lack specific information regarding the incidence and trends of head and neck cancer. Past reviews of this population have been limited to single-institution studies, which has made meaningful interpretation of long-term trends difficult.^9-12 To determine if the rate of pediatric head and neck cancer has increased in the United States, we performed a search of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) tumor registry.

The SEER database is a large, population-based tumor registry maintained by the National Cancer Institute since 1973. The geographic areas included are diverse, encompassing the states of Connecticut, Hawaii, Iowa, New Mexico, and Utah as well as the metropolitan areas of Atlanta, Ga, Detroit, Mich, Los Angeles, Calif, San Francisco-Oakland, Calif, and Seattle-Puget Sound, Wash. The SEER database represents an estimated 10% of the US population. All malignant neoplasms, with the exception of squamous and basal cell skin cancers, are included within the database. Data are available through special public access.¹³

For our study, all cases of cancer newly diagnosed from 1973 through 1996 in children younger than 19 years were identified. Head and neck malignancies were selected using appropriate codes from the International Classification of Diseases for Oncology, 2nd Edition.¹⁴ Tumors of the central nervous system were excluded. Descriptive statistics were compiled for each patient's age at diagnosis, sex, and tumor histologic characteristics.

Incidence rates for those children aged 14 years or younger were determined for eight 3-year periods from 1973-1975 to 1994-1996. Three-year means reduced the potential for annual variation. The US Bureau of the Census supplied annual population estimates. All rates were then adjusted by use of 5-year age groups weighted by the 1970 US standard population. Incidence rates were expressed in malignancies per 100 000 person-years. Because the US Bureau of the Census provides adjustment data in 5-year age groupings, we were compelled to designate 14 years rather than 18 years as the top age limit for this analysis. Male and female incidence rates for each cohort were also determined. Standard errors and the resulting 95% confidence intervals (CIs) were calculated according to the method described by Keyfitz.¹⁵

A total of 24 960 malignancies diagnosed in children younger than 19 years were identified through the SEER database from 1973 through 1996. This group was made up of 12 369 boys (49.6%) and 12 591 girls (50.4%), with a mean age of 9.6 years.

Among this population, 3050 tumors (12%) were located in the head and neck. Primary tumors represented 3026 (99.2%) of the total number while an additional 24 (0.8%) were cases of second malignant neoplasms. Head and neck tumors were found in 1432 boys (47%) and 1618 girls (53%), with a slightly higher mean age of 10.4 years. The higher proportion of girls seen among the head and neck group was statistically significant (P<.05) when compared with the overall cancer population. Reported cases of head and neck cancer were most frequent among teenagers 15 to 18 years old (39%), followed by children 4 years or younger (27%), 10 to 14 years (21%), and 5 to 9 years (13%). Figure 1 illustrates the age distribution of pediatric head and neck malignancies.

There was a diverse range of tumor pathologic characteristics in the pediatric head and neck cancer population (Table 1). Taken as a whole, lymphoma involving the head and neck was the most common cancer type (27%), followed by neural tumors (23%), thyroid malignancies (21%), and soft tissue sarcomas (12%). Papillary thyroid carcinoma (18%) was the leading pathologic diagnosis. Other frequent malignancies included Hodgkin lymphoma (17%), retinoblastoma (16%), non-Hodgkin lymphoma (10%), and rhabdomyosarcoma (8%). Unlike adult head and neck cancer, pediatric cases of squamous cell carcinoma were rare, occurring in fewer than 2% of all cases.

Age differences were noted. Neural tumors and soft tissue sarcomas remained more prevalent among infants and toddlers (Table 2). Retinoblastoma, which is rarely diagnosed in patients older than 5 years, affected the youngest children in this study (mean age, 1.4 years); lymphoma and thyroid malignancies were most common among children in the middle age group; and papillary thyroid carcinoma was found among the oldest (mean age, 15.5 years).

The neck was the leading site of initial tumor involvement, particularly the thyroid gland (Table 3). Other sites included the orbit, skin (face and scalp), nasopharynx, and salivary glands. Of note, no cases of pediatric cervical esophageal or parathyroid malignancies were found in the SEER database.

The incidence of all cancers diagnosed in children younger than 15 years increased from 1973 to 1996 (Figure 2). The average annual rate for cancers in this population (number of malignancies per 100 000 person-years) rose 25% from 11.22 (95% CI, 10.70-11.74) for 1973-1975 to 14.03 (95% CI, 13.46-14.60) for 1994-1996 (Table 4). This rising trend also applied to those children younger than 15 years with head and neck malignancies. Among malignancies of the head and neck, the incidence rate increased 35% from 1.10 (95% CI, 0.94-1.26) to 1.49 (95% CI, 1.30-1.68) during the same period.

To determine whether these changes were also occurring in other regional head and neck tumors with a known heritable component, we analyzed the 497 cases of retinoblastoma within the series. Retinoblastoma, which was the first form of cancer directly linked to a gene, is caused by a deletion or mutation of the q14 band of chromosome 13.¹⁶ After performing an analysis identical to that performed in the other cohorts, we found that the incidence of retinoblastoma had remained static from the 1973-1975 rate of 0.36 (95% CI, 0.26-0.46) to the 1994-1996 rate of 0.36 (95% CI, 0.27-0.45) despite significant rate increases at other head and neck sites (Table 4).

Rates for cancers demonstrated sex differences. The average annual rate of malignancies among boys younger than 15 years rose significantly from 10.05 cases per 100 000 person-years for 1973-1975 to 15.11 cases for 1994-1996 (Table 4). During this same period, the incidence of cancers among girls remained statistically unchanged. In contrast, boys had slightly higher annual rates of head and neck malignancies than girls in this age group; however, there was no statistically significant difference over time. Overall, individual head and neck tumors that demonstrated strong sex predilection were thyroid carcinoma (1:4 boy-girl ratio) and lymphoma (5:3 boy-girl ratio) (Table 1).

This study represents the most extensive series of pediatric head and neck malignancies to date and incorporates data from a very large, demographically balanced tumor registry over an extended period. Malignancies of the head and neck account for a significant proportion of all pediatric cancers. Leukemia excluded, neural tumors and lymphoma have consistently been the leading types of childhood cancer.^2,5,7,17-19 Overall, we were able to demonstrate incidence rates among all cases of pediatric cancer that were consistent with those of other authors spanning similar periods.^2,17,20 We acknowledge that the observed increases among incidence rates may represent an artifact of improved reporting over time—a potential variable inherent to any review of a large population database. However, the reliability of the SEER database is reflected in its role as the benchmark registry for cancer statistics in the United States, and it remains the best available data source at this time.

The SEER data demonstrate that 12% of all children with cancer are affected by a malignancy of the head and neck. This is higher than noted by Healy (5%)¹¹ and lower than observed by Sutow (27%).⁹ Differences can be explained by varying tumor inclusion criteria. In keeping with the clinical focus of this study, we chose to include tumors such as retinoblastoma and lymphoma. While the treatment of these malignancies has traditionally fallen to other medical specialties, the head and neck surgeon is frequently involved with their initial evaluation and diagnosis. We believed that limiting our investigation to cancer of a specific anatomic region rather than certain tumor histologic characteristics was more clinically relevant for the practitioner.

The increase in head and neck cancer incidence among children younger than 15 years has outpaced the overall rise in malignancies for this age group. Epidemiologists reason that inheritable types of cancer form a small portion of childhood tumors.²¹ Our finding that the incidence of retinoblastoma has remained constant compared with other head and neck tumors is suggestive that nongenetic causes may explain this trend.

Well-established environmental carcinogens implicated in the development of pediatric head and neck tumors include ionizing radiation, excessive solar exposure, and certain chemotherapeutic agents.²² Other potential carcinogens are suspected but not proven. Environmental pollution, parental exposure to toxins, electromagnetic fields, and even infectious agents have been mentioned. Perinatal factors such as prematurity and low birth weight have also been associated with an increased risk of childhood cancer.²³ Unfortunately, the heterogeneous nature of pediatric head and neck malignancies makes the search for clear etiologic factors difficult.

The incidence of childhood cancer clearly varies by sex. The overall cancer rates among girls younger than 15 years have remained statistically unchanged from 1973 through 1996, while those among boys of a similar age have experienced a significant increase. Remarkably, rates among boys moved from lower to higher than those among girls during this period. This trend has been confirmed by several studies.^5,7,8,17

When older children are included, girls are more likely to have a head and neck tumor than boys. This change most likely reflects the high number of adolescent girls affected by thyroid carcinoma. Depending on patient age, head and neck cancer has either no sex bias or a female predilection. This is in contrast to the clear male predominance seen with pediatric malignancies in general. These sex differences for head and neck tumors were not observed in younger children (<15 years). Further research aimed at identifying causes of the growing rate of childhood cancer may profit by exploring this discrepancy.

Thyroid carcinoma represents a larger proportion of pediatric malignancies than previously reported. Our finding that 21% of head and neck tumors were thyroid carcinoma was higher than described by Jaffe and Jaffe (5%),¹⁰ Sutow (7%),⁹ and Cunningham et al (10%).¹² Indeed, papillary thyroid cancer was the leading pathologic diagnosis in this study, which reinforces the need for a thorough thyroid examination by the pediatrician when routinely evaluating adolescent girls.

This study builds on previous work by quantifying the changing incidence of pediatric head and neck cancer in a large population over time. The uncommon occurrence of head and neck cancer in children had previously been an obstacle to establishing the true incidence and ongoing trends of this disease. The SEER database includes a large number of patients with an extended period of follow-up. These features ameliorated the prior limitations of studying head and neck cancer in children.

In conclusion, the incidence of head and neck malignancies in the United States from 1973 through 1996 among children younger than 15 years increased at a greater rate than childhood cancer in general. Reasons for this discrepancy remain unclear, although research on a variety of potential carcinogens is ongoing. Continued surveillance is necessary.

Accepted for publication November 5, 2001.

This study was presented at the 16th Annual American Society of Pediatric Otolaryngology Meeting, Scottsdale, Ariz, May 11, 2001.

We would like to thank Dennis H. Kraus, MD, Division of Otolaryngology–Head and Neck Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY, for his critical review of the manuscript.

Corresponding author and reprints: James T. Albright, MD, Division of Pediatric Otolaryngology–Head and Neck Surgery, Children's Hospital and Health Center, 3030 Children's Way, Suite 402, San Diego, CA 92123 (e-mail: jtalbright@yahoo.com).