Abstract
Objectives/hypothesis
To describe the incidence and determinants of survival of patients with nasopharyngeal adenocarcinoma between the years of 1973 to 2012 using the Surveillance, Epidemiology, and End Result (SEER) database.
Study design
Retrospective cohort study using a national database.
Methods
The SEER registry was utilized to calculate survival trends for patients with nasopharyngeal adenocarcinoma between 1973 and 2012. Patient data was then analyzed with respect to histopathology, age, sex, race, stage, grade, and treatment modalities (surgery and radiation therapy). Overall (OS) and disease-specific survival (DSS) were calculated.
Results
A total of 148 cases of nasopharyngeal adenocarcinoma were identified. The cohort was composed of 54.7% males. The mean age at diagnosis was 59.0 years. The median OS was 60.6 months. 59.4% of cases were treated with surgery, while 64.1% received radiation therapy. OS at 2, 5, and 10 years was 63%, 49%, and 36%, respectively. There was no significant difference in OS and DSS between adenocarcinoma of the nasopharynx versus the sinonasal tract ( p > 0.05). On univariate analysis, younger age, surgery, surgery and radiation, and lower tumor grade were associated with improved OS and DSS, while papillary subtype, lower stage, and no distant metastasis were associated with improved OS alone (all p < 0.05).
Conclusions
Nasopharyngeal adenocarcinoma is an extremely rare malignancy with poor prognosis, with the exception of the papillary subtype. Age, grade, and surgical therapy are predictors of survival.
1
Introduction
Nasopharyngeal adenocarcinoma (NPAC) is a rare malignancy, accounting for only 0.5% of neoplasms originating from the nasopharynx . All available clinical data on this rare disease are based on small case series, largely originating from Asia . It is a distinct clinicopathologic entity from the more common nasopharyngeal carcinoma (NPC), which is a tumor of epithelial origin accounting for approximately 95% to 98% of nasopharyngeal neoplasms, and is traditionally thought to have poorer or similar prognosis to NPC in retrospective reports . Recent evidence supports the classification of NPAC as originating from surface or mucosal origin, or arising from the submucosal minor salivary glands within the nasopharynx . Subtypes within mucosal and submucosal regions have been further described owing to the varying clinicopathologic characteristics and tumor behavior . Of note, patients with NPAC of mucosal origin are typically low grade, younger, display a female predominance, and have a relatively excellent prognosis with definitive surgical management . On the other hand, submucosal or NPAC arising from minor salivary glands are higher grade, more frequently affect older males, and display a poorer prognosis, often requiring multimodality therapy . To further distinguish NPAC from NPC, there appears to be no association, or at least an uncertain association, of NPAC with Epstein-Barr virus (EBV) infection . Additionally, there is limited data and no consensus on optimal treatment strategies .
Due to the paucity of data and only anecdotal evidence in smaller series, there is value in studying extremely rare tumors through analyzing large population databases. In this study, we use the Surveillance, Epidemiology, and End Result (SEER) database to describe the incidence and determine factors independently associated with survival in NPAC, and to compare NPAC tumor characteristics and survival with other primary adenocarcinomas of the sinonasal tract.
2
Methods
The SEER registry is an anonymous, large-sample, publically accessible, and validated database released and maintained by the National Cancer Institute. For this reason, Institutional Review Board approval was not required for this study. Our group, as well as many others, have previously utilized the SEER database to effectively draw insights on rare sinonasal malignancies .
Using the SEER database, appropriate cases were queried and selected in order to calculate descriptive statistics and survival data for patients with a diagnosis of adenocarcinoma, not otherwise specified (NOS, histologic code 8140/3); papillary adenocarcinoma of the nasopharynx, NOS (8260/3); clear cell adenocarcinoma, NOS (8310/3); and mucinous or mucin-producing adenocarcinoma (8480-1/3) between January 1, 1973 and January 1, 2012. Site-specific codes were checked to ensure that primary sites were limited to the nasopharynx. Patient demographic and clinical data, including age, sex, race, TNM stage as determined by the American Joint Commission on Cancer, grade, and treatments rendered (surgery and/or radiation) were collected.
Primary outcomes included overall survival (OS), or time from initial treatment to death from any cause, and disease-specific survival (DSS), or time from initial treatment to death from NPAC and malignancy-related causes. Kaplan-Meier curves based on OS and DSS were constructed, with differences evaluated by the log-rank test. Multivariate regression was performed using a Cox proportional hazards model using univariate variables significantly associated with OS and/or DSS. Statistical analysis was performed using SPSS 21 (IBM Corporation, Armonk, NY). A significance level of 0.05 was used for all tests.
2
Methods
The SEER registry is an anonymous, large-sample, publically accessible, and validated database released and maintained by the National Cancer Institute. For this reason, Institutional Review Board approval was not required for this study. Our group, as well as many others, have previously utilized the SEER database to effectively draw insights on rare sinonasal malignancies .
Using the SEER database, appropriate cases were queried and selected in order to calculate descriptive statistics and survival data for patients with a diagnosis of adenocarcinoma, not otherwise specified (NOS, histologic code 8140/3); papillary adenocarcinoma of the nasopharynx, NOS (8260/3); clear cell adenocarcinoma, NOS (8310/3); and mucinous or mucin-producing adenocarcinoma (8480-1/3) between January 1, 1973 and January 1, 2012. Site-specific codes were checked to ensure that primary sites were limited to the nasopharynx. Patient demographic and clinical data, including age, sex, race, TNM stage as determined by the American Joint Commission on Cancer, grade, and treatments rendered (surgery and/or radiation) were collected.
Primary outcomes included overall survival (OS), or time from initial treatment to death from any cause, and disease-specific survival (DSS), or time from initial treatment to death from NPAC and malignancy-related causes. Kaplan-Meier curves based on OS and DSS were constructed, with differences evaluated by the log-rank test. Multivariate regression was performed using a Cox proportional hazards model using univariate variables significantly associated with OS and/or DSS. Statistical analysis was performed using SPSS 21 (IBM Corporation, Armonk, NY). A significance level of 0.05 was used for all tests.
3
Results
A total of 148 cases of NPAC were identified in the SEER database and met inclusion criteria. Table 1 summarizes the clinicopathologic and demographic data for the study population.
| Age | Years |
|---|---|
| Mean | 59.0 ± 16.8 |
| Range | 8-85 |
| Characteristic | Percentage ( n ) |
| Sex | |
| Female | 45.3% (67) |
| Male | 54.7% (81) |
| Race | |
| White | 73.0% (108) |
| Black | 10.1% (15) |
| Other | 16.9% (25) |
| Treatment | |
| Surgery | 59.4% (60) |
| Radiation therapy | 64.1% (93) |
| Surgery and radiation | 25.9% (29) |
| Histologic subtype | |
| Adenocarcinoma, NOS | 73.0% (108) |
| Papillary, NOS | 14.9% (22) |
| Clear cell, NOS | 6.8% (10) |
| Mucinous or mucin-producing | 5.4% (8) |
| Stage | |
| I | 22.2% (8) |
| II | 5.6% (2) |
| III | 30.6% (11) |
| IV | 41.7% (15) |
| T | |
| 1 | 36.6% (15) |
| 2 | 17.1% (7) |
| 3 | 24.4% (10) |
| 4 | 22.0% (9) |
| N | |
| 1 | 62.2% (23) |
| 2 | 24.3% (9) |
| 3 | 10.8% (4) |
| 4 | 2.7% (1) |
| M | |
| 0 | 87.5% (35) |
| 1 | 12.5% (5) |
| Grade | |
| Well differentiated | 17.1% (18) |
| Moderately differentiated | 32.4% (34) |
| Poorly differentiated | 43.8% (46) |
| Undifferentiated | 6.7% (7) |
Table 2 reports the median and 2-year, 5-year, and 10-year OS and DSS for NPAC. The median OS and DSS of NPAC were 60.6 and 123.2 months, respectively. The papillary subtype appears to have significantly improved OS as compared to the other histologic subtypes ( p = 0.018). In comparing NPAC survival statistics to that of adenocarcinoma of other sinonasal tract primary sites (nasal cavity and all paranasal sinuses), there was no significant difference in OS ( p = 0.396) and DSS ( p = 0.056). Kaplan-Meier curves displaying OS and DSS for all NPAC cases are presented in Fig. 1 .
| Median survival (months) | Overall (OS) | Disease-specific (DSS) |
|---|---|---|
| Overall | 60.6 | 123.2 |
| By histologic subtype | ||
| Adenocarcinoma, NOS | 33.3 | 81.4 |
| Papillary, NOS | 226.9 | 444.0 |
| Clear cell, NOS | 86.3 | 110.73 |
| Mucinous or mucin-producing | 36.0 | 82.0 |
| Percent survival (%) | ||
| at 2 years | 63% | 69% |
| at 5 years | 49% | 61% |
| at 10 years | 36% | 51% |
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