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Authors' Affiliations: 1 University of Maryland Marlene and Stewart Greenebaum Cancer Center, Baltimore, Maryland; 2 Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts; and 3 sanofi-aventis, Bridgewater, New Jersey
Requests for reprints: Kevin J. Cullen, University of Maryland Marlene and Stewart Greenebaum Cancer Center, Room N9E17, 22 South Greene Street, Baltimore, MD 21201. Phone: 410-328-5506; Fax: 410-328-8455; E-mail: kcullen{at}umm.edu.
| Abstract |
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Several studies recently analyzed national data from the U.S. Surveillance, Epidemiology, and End Results database. The oral and pharyngeal cancer analyses within these studies consistently showed that blacks present with more advanced disease and have twice the age-adjusted mortality rate compared with whites (5, 6). A recent analysis of the same Surveillance, Epidemiology, and End Results data suggested that even after correcting for stage at diagnosis, blacks had a significantly worse survival than did whites (7). A recent analysis of racial disparities in 35 trials from the Southwest Oncology Group found worse survival for black patients with sex-specific cancers (breast, ovarian, and prostate), but not for black patients with lung cancer, colon cancer, lymphoma, myeloma, or leukemia (8). No head and neck cancer trials were included in this analysis.
A single-institution retrospective study confirmed that disease-specific mortality was significantly higher for black than for white head and neck cancer patients after adjusting for other factors including tumor-node-metastasis stage (9). Intensity of treatment was similar for the two groups and did not account for the differences in survival. In a previously reported retrospective analysis (10), we showed that disease-free survival was significantly greater in white than in black SCCHN patients who were treated with chemoradiation; the greatest black-white difference occurred in the oropharyngeal subgroup. We also recently analyzed race-related outcomes in two Radiation Therapy Oncology Group studies in head and neck cancer, finding in both studies that blacks had a significantly poorer outcome compared with whites, despite receiving identical treatment (11).
Significant data of the last few years show that human papillomavirus (HPV; primarily HPV-16) infection is associated with a significant percentage of oropharyngeal cancers, primarily of the base of the tongue and tonsil (12, 13). Furthermore, the incidence of oropharyngeal cancer is increasing, as is the prevalence of HPV infection in oropharyngeal cancer patients (14, 15). Very recent data indicate that HPV-positive cancers have a significantly better prognosis than do the HPV-negative diseases (16). The striking effect of HPV on cervical screening (17) and neoplasia risk and the U.S. Food and Drug Administration approval of HPV vaccines to reduce this risk (18) highlight the growing focus on HPV in research of head and neck cancer etiology, therapy, and prevention.
These collective data on overall and oropharyngeal SCCHN outcome disparities and on the growing association of HPV with SCCHN development and outcome led us to test the hypothesis in the present study that HPV may play an important role in racial disparity within SCCHN. We first examined overall survival (OS) differences by oropharyngeal and non-oropharyngeal sites in a retrospective group of black and white patients with stage III and IV SCCHN treated at the University of Maryland Marlene and Stewart Greenebaum Cancer Center. We then analyzed patients from the multicenter randomized phase 3 TAX 324 trial for the presence of HPV-16 in pretreatment biopsy specimens. In TAX 324, stage III or IV SCCHN patients with no distant metastases received induction cisplatin and fluorouracil alone (PF) or induction PF plus docetaxel (TPF), followed by radiotherapy with concomitant carboplatin (19). We evaluated the overall effect of HPV positivity, compared the rate of HPV positivity between black and white patients, and evaluated the effect of HPV positivity on survival differences between the two racial groups in TAX 324.
| Patients and Methods |
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Prospective patients
TAX 324 was a phase 3 clinical trial in which patients with stage III or IV SCCHN and no distant metastases were randomly assigned to induction PF or TPF. After this induction chemotherapy, patients received radiotherapy with concomitant carboplatin. As previously reported, after a minimum of 2 years of follow-up for each patient, mortality was 30% lower in the TPF than in the PF arm (death hazard ratio of 0.70; P = 0.006; ref. 19). For the present study, we selected TAX 324 patients for whom pretreatment paraffin-embedded biopsy specimens were available.
HPV-16 analysis
DNA extraction from paraffin sections
Sections of pretreatment paraffin-embedded biopsy specimens were deparaffinized in xylene. The tissue was scraped with a sterile scalpel into a microcentrifuge tube, rehydrated with graded ethanol washes, and air-dried. DNA extraction was done using the QIAamp DNA Micro Kit (Qiagen) following the instruction manual protocol for laser-microdissected tissue. DNA was quantitated using the Quant-iT dsDNA Assay Kit (Invitrogen) and stored at –80°C. Working dilutions of 0.5 ng/µL were prepared from stored aliquots.
HPV-16 PCR
PCR was done for the E6 (forward, AAACTAAGGGCGTAACCGAAA; reverse, TAGTTGTTTGCAGCTCTGTGC) and E7 (forward, ACAAGCAGAACCGGACAGAG; reverse, GATGGGGCACACAATTCCTA) genes of HPV-16. These primers are type specific for HPV-16. Forty cycles of standard three-step PCR (annealing temperature, 55°C) were done on 0.5 ng of DNA. Multiple negative controls (no DNA) were included in every PCR run. Products were visualized on 1.7% agarose gels stained with GelStar nucleic acid stain (Cambrex). Only cases positive for both genes were scored HPV-16 positive. Cases positive for one but negative for the other gene were excluded. In the case of ambiguity in interpreting either gene, both genes were amplified again from a freshly diluted DNA aliquot using a different primer set (overlapping but not nested with the original primer set). Cases that remained ambiguous were excluded. HPV-16 status could be scored for 237 of the 265 cases with sufficient DNA. In a validation series of 49 repeat reactions, the error rate was 0% for the E6 gene and 1% for the E7 gene.
Statistical methods
The effects of HPV status and race on patient OS and the related hazard ratios were assessed using univariate Cox proportional hazards models. The Kaplan-Meier survival distribution functions were estimated for different groups of patients. Patients were grouped by race, site of SCCHN, and HPV status. The survival distributions were compared using the log-rank test at the 0.05 level of significance.
| Results |
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In the TAX 324 trial, pretreatment, paraffin-embedded biopsy specimens were available for 270 of 561 patients. Sufficient DNA for PCR analysis was recovered for 265 of these 270 patients. Of the 270 patients, 237 had specimens that could be scored for HPV infection. Ninety-five percent (224 of 237) of the patients self-identified as either white or black. The baseline characteristics of this TAX 324 cohort, including numbers and percentages of oropharyngeal and other head and neck cancer sites, are presented in Table 1.
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| Discussion |
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Results from the phase 3 TAX 324 trial—the first prospective, biopsy-confirmed comparison of HPV status in black and white SCCHN patients—help to interpret these retrospective and other SCCHN data. OS in TAX 324 was dramatically better for HPV-positive than for HPV-negative SCCHN patients as a result mainly of improved OS in the oropharyngeal subgroup. HPV positivity was nearly 9-fold higher in white (34% rate of positivity) than in black (4% rate) patients, explaining the greater part of the outcome disparity between black and white patients in the present study and, likely, in other studies over the years.
There was no difference in stage of disease between the HPV-positive and HPV-negative TAX 324 patients, and so the survival difference seems to be directly related to HPV status. HPV-positive patients do well on treatment with combined chemotherapy and radiation, such as that used in the TAX 324 trial. On the other hand, HPV-negative patients do less well with this approach. Because of this substantial positive effect on OS in the subgroup of HPV-positive patients, positive recent studies of combined chemotherapy and radiation in SCCHN should be interpreted with some caution. Biologically, HPV-positive and HPV-negative tumors have markedly different behavior, and our results indicate that the great majority of black patients have HPV-negative diseases that did not respond optimally to chemoradiotherapy.
The reason for the apparent racial difference in HPV prevalence between black and white oropharyngeal patients is not known, nor is the etiologic influence of this difference on oropharyngeal cancer development in the two racial subgroups. Although studies have provided evidence of an association between sexual risk behaviors and HPV-positive oral cancer (20, 21), differences in outcome based on race have not been examined extensively in these studies. Host immunity, viral integration, and oral carcinogenic potential of HPV infection may differ in the two groups. A study of HPV-16 infection in a black South African population showed a strong association between seropositivity for HPV-16 and incidence of cervical, anogenital, and esophageal tumors, but not of oropharyngeal or prostate cancers (22).
The other major neoplasia setting where HPV is an established factor is the cervix, where important differences (besides gender) from the oropharynx include the importance of HPV-16 and HPV-18 (versus just HPV-16 in the oropharynx) and the nearly 100% infection rate (versus
50% in oropharyngeal cancer; ref. 23). HPV screening in the cervix (which would involve women with and without cervical neoplasia) indicates that the rate of high-risk HPV-16 and HPV-18 may be higher in black than in white women, although the reason for this is not clear and could be confounded by socioeconomic status (24, 25). In high-grade cervical intraepithelial neoplasia, however, HPV infection may be more common in whites than in blacks (26), loosely paralleling our present finding of a greater prevalence of HPV in white than in black oropharyngeal cancer patients. The dual possibility that HPV prevalence is higher in blacks overall but lower in black neoplasia patients suggests that cervical (and oropharyngeal) neoplasia may develop or progress less frequently in HPV-infected blacks than in HPV-infected whites. Black women unquestionably have an increased incidence of and mortality from cervical cancer, but the biological, socioeconomic, or cultural reasons for this are unknown. Cervical cancer is very sensitive to concurrent chemoradiation (27), suggesting a parallel to the increased treatment sensitivity of HPV-related (versus nonrelated) oropharyngeal cancer. Oropharyngeal cancer has a 3:1 ratio of males to females overall and in HPV-related cases (14), suggesting the possibility that gender-related hormonal differences may confound any comparison of oropharyngeal to cervical neoplasia.
The great success of HPV vaccines in reducing cervical cancer risk is a model for chemoprevention studies in HPV-related oropharyngeal carcinogenesis (17). These studies would benefit from an understanding of oropharyngeal premalignancy, which has yet to be characterized in the literature. Nevertheless, infection clearly precedes cancer development—seropositivity to HPV-16 confers a 14-fold increase in subsequent risk of oropharyngeal cancer (28). Although HPV DNA has been detected in in situ, invasive, and metastatic disease (29), the histopathologic progression from infection to in situ disease is poorly documented. It likely involves HPV infection of the basal cell layer of tonsillar crypts, which seem to be uniquely prone to transformation by the virus (30).
Although the data presented here require confirmation in future analyses, they nevertheless may explain some, but not all, outcome disparities based on race for patients with locally advanced SCCHN. Adding to efforts to eliminate racial socioeconomic disparities, this evidence of a racial biological difference that affected SCCHN survival moves us a step closer, we believe, to realizing the hope expressed by Dr. Otis Brawley: "Perhaps advances in our understanding of biology will lead us away from concerns about race and we will better define high-risk populations using pathologic markers of disease" (31). This approach should allow more intelligent treatment choices for patients using biologically based prognostic information including, but not limited to, HPV status.
| Disclosure of Potential Conflicts of Interest |
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| Footnotes |
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Received for publication July 1, 2009.
Revision received July 9, 2009.
Accepted July 13, 2009
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Commentary
This article has been cited by other articles:
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O. W. Brawley Oropharyngeal Cancer, Race, and the Human Papillomavirus Cancer Prevention Research, September 1, 2009; 2(9): 769 - 772. [Abstract] [Full Text] [PDF] |
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