Oropharyngeal Cancer

The database maintained by the Department of Radiation Oncology at The University of Texas M.D. Anderson Cancer Center (MDACC) was searched to identify patients irradiated for oropharyngeal carcinoma (squamous cell, poorly differentiated or undifferentiated, or not otherwise specified) between the years 2000–2007. Our institutional review board granted permission to conduct this retrospective study.
The search identified 1162 medical records. Patients were excluded for the following reasons: distant metastases or concurrent malignancies (exclusive of a second malignancy of the oropharynx) at the time of diagnosis (16 patients), a previously treated malignancy of the head and neck or previous radiation to the head or neck (8), a history of any malignancy (excluding non-melanomatous skin cancer) within two years of diagnosis (7), or treatment with chemotherapy prior to staging at MDACC (8). In addition 69 patients who did not meet the staging criteria of interest (Stage 3- 4B), and 8 patients with poor performance statuses, staged 4B, and treated with palliative intent were excluded. One thousand forty-six patients formed the cohort for analysis.
Medical records were reviewed to assess patients’ demographic, clinical, radiologic and pathologic data. Based upon the medical history at presentation and as described previously [18 (link)] patients were classified as current smokers, former smokers, or never-smokers. Smokers were further evaluated to assess if they quit smoking, or continued to smoke during or subsequent to treatment.
Patients’ disease was staged according to the AJCC 2002 staging system [19 ]. Charts were reviewed to verify tumor size and sites of invasion. Staging variables of interest included T-category, N-category, and overall AJCC group stage. Patients staged Tx were typically those seen post-tonsillectomy and if the tumor size could not be determined after record review, these patients were staged T1 for the purpose of AJCC stage grouping in this analysis. Those staged Nx were patients in whom a solitary node was excised for diagnosis, and size could not be determined. These patients were coded as N1 for the purpose of this analysis.
Chi-squared tests were used to compare proportions between subsets. The t-test was used for comparison of means. The Kaplan-Meier method was used to calculate actuarial curves. Time of diagnosis was used as time zero. Comparisons between survival curves were made using the log-rank test. Multivariate analysis was performed using the Cox proportional model.
Our approach has been to perform neck dissection only in patients with suspected residual disease following radiation. During the years of this study reassessment principally consisted of physical examination and CT scan 6 to 8 weeks after radiation. Those patients with an obvious residual mass were operated. Patients with questionable residual disease had sonograms with aspiration performed to try to resolve whether there was viable disease. Routine use of positron-emission tomography had not become a routine practice during the years of this study. Details of our experience with regards to management of the neck in an overlapping cohort has been recently described [20 (link)]. Patients who had neck dissections performed within 6 months of radiation for suspected residual disease were not scored as having disease recurrence.

Head and neck cancer cases between 1980 and 2019 were obtained from the national Taiwan Cancer Registration (TCR) database (https://twcr.tw/). The Taiwan Cancer Registration (TCR) database has collected newly diagnosed cancer cases from hospitals with 50 or more beds in Taiwan since 1979 [9 (link), 10 (link)]. In addition, the completeness of the TCR, the percentage of cases with death certificates, and the percentage of morphological verification in 2016 were respectively 98.4, 0.9, and 93%, while the completeness was measured by all registered cancer cases divided by all potential cancer cases from profiles of death certificate, NHI catastrophic illnesses, and four major cancer screening programs [9 (link)]. All cases in this analysis were classified based on the International Classification of Diseases for Oncology, third edition (ICD-O-03) [11 ]. Head and neck cancer cases were categorized into oral cancer (C00, C02, C03, C04, C050, C058, C059, and C06, excluding C024), oropharyngeal cancer (C01, C024, C051, C052, C09, C10, C142, and C148), hypopharyngeal cancer (C12, C13, and C140), and laryngeal cancer (C32).
Based on the 2000 World Health Organization standard population, the age-adjusted incidence rate in men from 1980 to 2019 was only analyzed due to the low incidence in women in Taiwan. For the analysis of long-term trends, the age-specific incidence rate from 1980 to 2019 was calculated for specific age groups, time periods, and birth cohorts. The age-specific incidence rate was classified into eighteen 5-year age groups (0–4, 5–9, 10–14, 15–19, 20–24, 25–29, 30–34, 35–39, 40–44, 45–49, 50–54, 55–59, 60–64, 65–69, 70–74, 75–79, 80–84, and 85+) and eight 5-year time periods (1980–1984, 1985–1989, 1990–1994, 1995–1999, 2000–2004, 2005–2009, 2010–2014, and 2015–2019). In addition, the birth cohort was divided into eleven birth groups (1930–1934, 1935–1939, 1940–1944, 1945–1949, 1950–1954, 1955–1959, 1960–1964, 1965–1969, 1970–1974, 1975–1979, and 1980–1984) and twelve 5-year age groups (30–34, 35–39, 40–44, 45–49, 50–54, 55–59, 60–64, 65–69, 70–74, 75–79, 80–84, and 85+). Moreover, to describe the linear change in the age-adjusted incidence rate from 1980 to 2019, a join point regression model was utilized to detect the change point and calculate the average annual percent change (AAPC) and annual percent change (APC) [10 (link)]. In addition, the 95% confidence intervals of the average annual percent change (AAPC) and annual percent change (APC) were analyzed. 95% confidence interval indicated 95% would fall between the upper limit and the lower limit, while 95% confidence interval including 0 showed statistically nonsignificant. The research protocol was approved by the Institutional Review Board of Fu-Jen Catholic University (No. C104014).

Two distinct methods to characterize HPV status were used in this study. To determine the clinical HPV status, in situ hybridization (ISH) for HPV on tumor tissue was utilized whenever available. For oropharyngeal tumors that did not have HPV ISH status, p16 positivity was used a surrogate marker for HPV. The p16 threshold for positivity was a 70% nuclear and cytoplasmic staining cutoff, a commonly used threshold recommended by the 2018 practice guideline from the College of American Pathologists [20 (link)]. All tumors outside the oropharynx that did not have ISH data available were assumed to be HPV- because of the limited utility of p16 as a marker for HPV-driven cancers in non-oropharyngeal tumors. The HPV status via sequencing was determined based on RNA-Seq coverage of E6/E7 within the HPV16/18 viral genome alignment for each PDX, with a count greater than 50 considered to be HPV+. This alignment cutoff was determined empirically based on the distribution of counts and to facilitate concordance with clinically-based HPV status (as described above). Only reads classified as non-human by Xenome were aligned in the viral pipeline, using bwa-sw against GenBank’s HPV16 (K02718.1) and HPV18 (AY262282.1) genomes. All E6/E7 expression in PDXs from this study mapped only to the HPV16 genome, with no E6 or E7 expression found in the HPV18 alignment. Two PDXs were positive for HPV by sequencing but negative clinically (PDXs 27 and 41), and HPV ISH was not available for either. One patient had a base of tongue SCC that was p16-negative, while the other had SCC of the oral tongue (which stained positive for p16 but was assumed to be “clinically negative” due to positioning outside of the oropharynx). For the ultimate designation of HPV status in our PDXs for further analysis, the sequencing classification was chosen over clinical status to best identify tumors with objective evidence of HPV-mediated carcinogenesis.