Abstract
Purpose
To examine the prognostic significance of expression of glutathione s-transferase π (GST-π) and p53 in patients treated with radiation alone for locally advanced head and neck cancer (RTOG trial 9003) or radiation +/− concomitant chemotherapy as post operative adjuvant therapy (RTOG trial 9501).
Patients and Methods
Immunohistochemical staining for p53 and GST-π was performed on tissue samples from 393 patients in RTOG 9003 and 142 patients in RTOG 9501. Kaplan-Meier survival analyses were performed.
Results
Patients who had low expression of both markers had longer survival than patients who had high expression of both markers. In trial 9003 median survival was 2.4 years for patients with low expression of both markers versus 1.4 years for patients who had elevated expression of both markers. (p=0.07) These differences were highly significant in trial 9501 and were accounted for by the chemotherapy treated arm. In this group, patients with low expression of both markers had a median survival of 7.0 years compared to 1.4 years for patients with elevated expression of both markers. (p=0.006).
In both trials, black patients had lower survival rates than did white patients and there was a trend toward higher expression of both markers in blacks compared to whites.
Conclusion
Given the poor outcome of chemoradiotherapy treatment patients with elevated expression of both p53 and GST-π, these patients may not be appropriate candidates for chemoradiotherapy based on standard protocols.
Some of the adverse outcome for black patients in both studies may be attributed to elevated expression of p53 and GST-π.
Introduction
Squamous cell cancer of the head and neck remains a major public health problem in the United States and world wide. More than 44,000 cases will be reported in the US in 2007 with more than 11,000 deaths.1 Concomitant chemoradiotherapy has emerged as the standard of care for many patients with locally advanced head and neck cancer both for organ preservation and as adjuvant therapy for patients with resectable high risk disease.2 Platinum drugs, particularly cisplatin, are the base of most concomitant chemotherapy regimens and have the widest experience in the literature.
Despite the adoption of concomitant chemoradiotherapy in the primary and adjuvant management of locally advanced head and neck cancer, cure rates remain suboptimal.
Numerous studies have evaluated biochemical and molecular markers as predictive and/or prognostic indicators in head and neck cancer.3,4,5,6,7,8 Most of these analyses have been performed retrospectively on small data sets, and very few investigators have validated their initial retrospective findings in independent data sets. As a result, no consensus has emerged about clinically practical markers which may be used to stratify risk or guide therapy.
Numerous studies have evaluated the prognostic significance of p53 in head and neck cancer and other malignancies.9,10,11 Immunohistochemical detection of mutated p53 in most but not all of these studies has been associated with poor prognosis.
Our own laboratory has developed several lines of evidence that phase II enzymes in the glutathione pathway may have an important role in mediating resistance to cisplatin based chemotherapy regimens.12 Elevation of intracellular glutathione levels or increased expression of the conjugating enzyme glutathione s-transferase π (GST-π) is associated with an increased ability of the cell to resist reactive oxygen species damage induced following cisplatin treatment.13 Our previous preliminary studies on retrospective data collected from 68 patients in two institutions suggested that over expression of GST-π had strong negative prognostic value in patients receiving neoadjuvant cisplatin based chemotherapy for locally advanced head and neck cancer. Overall survival at three years was 82% for patients with low GST-π expression compared with 46% for patients with elevated GST-π (p=0.0018). p53 expression measured by immunohistochemistry was also a strong negative prognostic indicator and was independent of GST-π expression. Overall survival at three years was 81% in the p53 low patients but only 30% in the p53 high group (p<0.0001).14 While these studies focused on the role of GST-π and p53 in patients treated with cisplatin based chemotherapy regimens, the broader function of GST-π in the cellular response to reactive oxygen species and the function of mutated p53 in regulation of apoptosis suggests that these markers may have a lesser but meaningful prognostic significance in patients treated with radiation as well.15
In this study, we analyzed expression of p53 and GST-π in samples from two Radiation Therapy Oncology Group randomized clinical trials in head and neck cancer. Trial 9003 was a four arm trial looking at differing fractionation schedules for radiotherapy as primary treatment in locally advanced head and neck cancers.16 This study of radiation alone in locally advanced tumors showed accelerated fractionation with concomitant boost and hyperfractionation schedules were associated with improved local regional control, but not a significant improvement in survival compared with standard fractionation. RTOG trial 9501 was a randomized trial of conventional fraction radiotherapy versus radiotherapy given with concomitant cisplatin (100 mg/m2 on days 1,22,43) as post operative adjuvant therapy for resectable high risk head and neck cancer patients.17 In that trial, concurrent chemotherapy and radiotherapy significantly improved local control and disease free survival compared with radiation alone.
Based on our previous work showing that elevated expression of p53 and GST-π were associated with poor outcome in patients treated with cisplatin based chemotherapy for locally advanced disease, we hypothesized that patients with low expression of GST-π and p53 would have a favorable prognosis in these studies while patients with high expression of both factors would have a poor prognosis and that this effect would be more pronounced in patients receiving chemotherapy compared with those receiving radiation alone. This study was undertaken to validate our previous preliminary findings in a totally independent data set.
As a secondary and exploratory analysis, we examined survival as well as expression of p53 and GST-π by race in the two studies. This was an effort to determine whether outcomes differ for black and white patients in these trials and whether these differences may be accounted for in part by differences in expression of p53 or GST-π.
Patients and Methods
Study Populations
RTOG studies 9003 and 9501 were selected for analysis because pretreatment biopsy specimens for many of the patients on those trials were available through the RTOG tissue bank. An application for access to applicable tissues was made to the RTOG translational research program and approved by that group.
RTOG 9003 randomized 1113 patients with locally advanced head and neck cancer to four radiotherapy fractionation schedules. 1073 patients were evaluable for outcome. Of these, 393 had staining results for both markers and complete clinical data available through the RTOG tissue bank.
RTOG 9501 randomized 459 resected patients with locally advanced head and neck cancer to receive adjuvant radiotherapy or adjuvant radiotherapy with concomitant cisplatin. Of these, 142 patients had tissue available through the RTOG tumor bank. For each trial, tissue microarrays were assembled by the RTOG tissue bank which included multiple punches (triplicate or quadruplicate) of each pretreatment biopsy for the majority of cases.
Immunohistochemistry
Immunohistochemistry for p53 and GST-π was performed as previously described 11 except monoclonal antibody clone 353-10 (Dako North America, Carpinteria, CA) was used for GST-π.
Sample Scoring
Samples were scored by a pathologist (N.N.) who had no knowledge of, or access to, clinical outcome data. Samples were scored for the percentage of tumor cells which showed positive staining as well as the intensity of staining per the published protocol of Allred.18 For subsequent
statistical analysis, intensity scores below the median were considered low and scores above the median were considered high.
Statistical Analysis
This is a prospectively designed study utilizing stored specimens of patients from two RTOG clinical trials in Stage III and IV H&N cancer involving radiotherapy only (RTOG 9003) or a randomization between radiation therapy only versus radiation therapy plus chemotherapy (RTOG 9501). Included in the analysis are 535 patients who had adequate specimen for the biomarker assays from a total 1572 patients in these two trials. The medians of the two biomarkers (GST-π and p53) in these patients are used as the cut points to group patients as the low (L) and high (H) expression groups. Hence, there were 4 categories of patients, i.e., LL, LH, HL, and HH. Overall survival (OS) was defined as the length of time from the date of randomization to death from any cause. The overall survival was estimated using the Kaplan-Meier method, and the log rank test was used to compare survival distribution among/ between different patient groups. The Cox regression model was utilized to assess significance of multiple factors such as biomarkers, patient clinical and demographic characteristics and protocols. Associations between categorical variables were assessed using a Fisher’s exact or Fisher-Freeman-Halton test. All statistical tests were done at the 2-sided 0.05 level of significance.
Results
Baseline pretreatment patient characteristics in this report (those with tumor specimens) are similar to those of the entire patient population in each of the two trials. (Table 1.) The Cox model suggests that there is no interaction between the four biomarker groups and protocols (p = 0.09). The survival distribution is significantly different among the four biomarker groups (p=0.004, stratified by the two RTOG protocols). The survival benefit in RTOG 9501 is significantly greater than that in RTOG 9003 (p= 0.02). The analysis for each specific protocol was then performed and is summarized in Tables 1-3 and Figures 1-3.
Table 1.
Patient Characteristics
| Characteristic | RTOG 9003 | RTOG9501 | All patients |
|---|---|---|---|
| Number of patients, N | 393 | 142 | 535 |
| Assigned treatment, N (%) | |||
| SFX | 94 (23.9) | ||
| HFX | 116(29.5) | ||
| AFX-S | 96(24.4) | ||
| AFX-C | 87(22.1) | ||
| RT | 75 (52.8) | ||
| RT+CT | 67 (47.2) | ||
| Age on the study (yrs) | |||
| Median | 60 | 55 | 59 |
| Range | 30-90 | 31-79 | 30-90 |
| Gender, N (%) | |||
| M | 301(76.6) | 125 (88.0) | 426(79.6) |
| F | 92(23.4) | 17 (12.0) | 109(20.4) |
| Karnofsky performance status, N (%) | |||
| 60 | 18(4.6) | 1 (0.7) | 19(3.5) |
| 70 | 47(12.0) | 23 (16.2) | 70(13.1) |
| 80 | 91(23.1) | 35 (24.6) | 126(23.5) |
| 90 | 181(46.1) | 63 (44.4) | 244(45.6) |
| 100 | 56(14.2) | 20 (14.1) | 76(14.2) |
| Primary tumor site, N (%) | |||
| Oral cavity | 36(9.2) | 32 (22.5) | 68(12.7) |
| Oropharynx | 227(57.8) | 63 (44.4) | 290(54.2) |
| Hypopharynx | 53(13.5) | 19 (13.4) | 72(13.4) |
| Supraglottic larynx | 77(19.6) | 21 (14.8) | 98(18.3) |
| Glottic larynx | 0 | 5 (3.5) | 5 (0.9) |
| Subglottic larynx | 0 | 2 (1.4) | 2 (0.4) |
Table 3.
T and N stage distribution of black and white patients with available biopsy tissue in RTOG trial 9501. There is no statistical difference in T stage (p=0.34) or N stage (p=0.56) between black and white patients in this trial (Fisher-Freeman- Halton test, 2 sided exact value).
| T1 | T2 | T3 | T4 | Total | |
|---|---|---|---|---|---|
| White | 14 (14%) | 28 (28%) | 29 (29%) | 30 (30%) | 101 |
| Black | 1 (3%) | 9 (27%) | 10 (30%) | 13 (39%) | 33 |
| N0 | N1 | N2 | N3 | Total | |
| White | 2 (2%) | 2 (2%) | 96 (95%) | 1 (1%) | 101 |
| Black | 0 | 2 (6%) | 31 (94%) | 0 | 33 |
Figure 1.
RTOG 9003: Survival curves estimated by the Kaplan-Meier method. Patients with low expression of p53 and GST-π trend toward better survival when compared with patients with elevated expression of one or both markers (p=0.07).
Figure 3.
Survival curves for black and white patients. Panel 3A - RTOG 9003. Panel 3B - RTOG 9501. For patients with available biopsy specimens for analysis, black patients had a significantly worse survival rate than did whites. In trial 9003, median survival was 2.2 years for white versus 1.5 years for blacks. Five year survival was 34% for whites and 22% for blacks. (p=0.011) In trial 9501, black patients had a strong trend for worse survival compared with whites. Median survival was 3.8 years for white versus 2.2 years for blacks. Five year survival was 46% for whites and 22% for blacks. (p=0.053).
RTOG 9003
Figure 1 shows the survival curves for the 393 patients with available tumor biopsies based on expression of GST-π and p53. The four subgroups (p53 and GST-π low, p53 high and GST-π low, p53 low and GST-π high, p53 high and GST-π high) had different survival experiences (marginal statistical significance, p=0.07, the log rank test). As expected, patients who had low expression of both markers had better survival than patients who had elevated expression of both markers while patients with a single marker had an intermediate result. Median survival was 2.4 years (95% CI : 1.4-3.0 years) for patients with both markers elevated versus 1.3 years (95% CI: 1.0-1.9 years) for patients with both markers low. Five year survival was 35% for patients for patients with low expression of both markers compared with 22% for patients with high expression of both markers.
RTOG 9501
Figure 2A shows the survival curves for patients on trial 9501 (n=142) based on expression of GST-π and p53. In this trial, expression of the markers was highly significant with regression analysis showing a highly significant adverse survival difference based on marker expression (p=0.02). Patients with low expression of both markers had a median survival of 6.8 years (the lower bound of the 95% CI is 1.9 years, the upper has not been reached yet) compared to 1.5 years (95% CI: 1.1-2.9 years) for patients with high expression of both markers. Five year survival was 54% for patients with low expression of both markers compared with 24% for patients with elevated expression of both markers.
Figure 2.
RTOG 9501: Survival curves estimated by the Kaplan-Meier method. In this trial of adjuvant radiotherapy randomized with concomitant chemo-radiotherapy, patients with low expression of both markers had significantly improved survival compared with patients with elevated expression of one or both markers. (Panel 2A - All 142 patients p=0.02). In the combined chemotherapy arm (Panel 2B) expression of one or both markers correlated negatively with survival (p=0.06). Patients with high expression of both markers had a median survival of 1.5 years while for patients with low expression of both markers, median survival had not been reached. (p=0.006) . Analysis of the radiation alone cohort showed no significant difference in survival based on marker expression. (Panel 2C, p=0.54)
Further analysis of trial 9501 demonstrated that the survival difference predicted by the markers was accounted for almost exclusively by the patients in the combined chemotherapy/radiation arm. Figure 2B shows the survival analysis for patients who received chemotherapy and radiation. In this group, median survival time for patients with low expression of both markers has not been reached yet (the lower boundary of the 95% CI is 2.5 years) , and was 1.4 years (95% CI: 1.0-2.9 years) for patients high for both markers. This difference in overall survival was highly statistically significant, p=0.006 (the log rank test). Five year survival was 60% for patients with low expression of both markers versus 16% for patients with elevated expression of both markers.
Multivariate Cox regression model adjusted for patients’ demographic and clinical characteristics including age, gender, race, primary tumor site, T stage, and N stage revealed that these two bio markers continued to have statistically significant effect on overall survival (p<0.02).
In contrast, the markers were not predictive in the radiation alone arm of trial 9501. Figure 2C shows survival curves for the radiation arm in that study. Marker expression was not associated with differences in survival (p=0.54).
Racial Disparities Analysis
Of the 393 complete samples available for analysis from RTOG 9003, 78 (20%) were from blacks while 286 (73%) were from whites. In study RTOG 9501, of the 142 specimens available, 33 (23%) were from blacks and 101 (71%) were from whites. This significant percentage of participation by black patients prompted a preliminary analysis of survival and marker expression in the two racial groups. In trial 9003, for patients with available biopsy material, median survival was 2.1 years (95% CI: 1.7-2.7 years) for white patients versus 1.3 (95% CI: 1.1-1.9 years) years for blacks. Five year survival was 32% for whites versus 21% for blacks (p=0.011) (Figure 3A).
For patients with available biopsy tissue in trial 9501, blacks similarly fared less well than whites. Median survival was 4.3 years (95% CI: 2.2-4.7 years) for whites versus 2.2 years (95% CI: 1.3-3.2 years) for blacks. Five year survival was 47% for whites versus 23% for blacks. (Figure 3B). Because of the smaller sample size in trial 9501, the p-value for the log rank test comparing overall survival is of marginal significance (p=0.053), but the magnitude of racial difference is similar in both trials. Black patients in trial 9003 had significantly higher N stage at presentation than white patients with a trend toward higher T stage (Table 2). In trial 9501, there was no statistical difference in T stage or N stage between black and white patients (Table 3) likely reflecting the relatively small number (n=33) of blacks with available tumor biopsies in that trial.
Table 2.
T and N stage distribution of black and white patients with available biopsy tissue in RTOG trial 9003. The T stage distribution shows a non significant trend toward increased stage in black patients (p=0.09 Fisher-Freeman- Halton test, 2 sided exact value), while N stage distribution is different between blacks and whites with black patients presenting with higher N stage. (p=0.0002).
| T1 | T2 | T3 | T4 | Total | |
|---|---|---|---|---|---|
| White | 16 (5%) | 73 (25%) | 127 (44%) | 71 (25%) | 287 |
| Black | 2 (2%) | 19 (24%) | 28 (35%) | 31 (39%) | 80 |
| N0 | N1 | N2 | N3 | Total | |
| White | 73 (25%) | 73 (25%) | 121 (42%) | 20 (7%) | 287 |
| Black | 14 (17%) | 11 (14%) | 36 (45%) | 19 (24%) | 80 |
An exploratory analysis of marker expression in black and white patients showed a trend toward elevated expression in blacks which approached but did not reach statistical significance. In trial 9003, the median score for both GST-π and p53 was higher in blacks versus whites. For GST-π median score was 2.0 among blacks versus 1.5 for whites (p=0.19). For p53, the median score was 2.0 for blacks versus 1.75 for whites (p=0.06). In trial 9003, of 286 white patients, 107 (37%) scored low for both markers while among black patients 22 out of 78 (28%) scored low for both markers (p=0.14). Eighteen percent of white patients expressed high levels of both markers while for blacks, 27% scored high for both (p=0.0).
In trial 9501, no significant differences in expression of GST-π or p53 were seen comparing blacks to whites, possibly because of the relatively small number of black patients (33) available for analysis from that trial. The 4 point semiquantitative immunohistochemistry scoring scheme used makes it difficult to discriminate close scoring differences in small groups.
Discussion
Cisplatin based chemo/radiatiotherapy has become the standard of care both for locally advanced unresectable head and neck cancer, to facilitate organ preservation and for adjuvant therapy of post operative patients at high risk for recurrence. However, a significant portion of patients recur with either local or distant disease which is generally fatal. Attempts to identify biomarkers of prognosis which would improve upon clinical parameters including TNM staging have been limited. To date, no biomarkers have been accepted for routine clinical use. Most of the available literature consists of retrospective single institution studies which have not been validated in independent sample sets, particularly in a clinical trial setting. The current study attempted to validate a previous retrospective analysis in two independent data sets, RTOG clinical trials 9003 and 9501. Our previous two institution retrospective study showed significant negative prognostic value for both p53 and GST-π in patients receiving chemotherapy for locally advanced head and neck cancer. That analysis consisted primarily of patients receiving neoadjuvant chemotherapy prior to radiation.
Based on that analysis, we predicted that elevated expression of these two markers would be a negative prognostic indicator in patients undergoing combined chemotherapy and concomitant chemotherapy and radiation. Because of the broad roles of p53 and GST-π in cellular damage response, we predicted that these markers would have a lesser significance in patients receiving radiation alone. The current study demonstrates that both of these hypotheses were correct. Analysis of available biopsy tissues from RTOG 9003 demonstrated that patients with expression of both p53 and GST-π did worse than patients who did not express either marker; this difference approached statistical significance. In contrast, results from trial 9501 demonstrated a significant difference in survival between patients who expressed both markers and patients who expressed neither marker. As expected, patients who expressed only one marker had an intermediate outcome. These differences were largely accounted for by patients who had been randomized to the chemotherapy/radiation arm as patients who received radiation alone showed no statistical differences based on biomarker expression. These findings support abundant in vitro data which suggests that glutathione and enzymes on the glutathione pathway, particularly GST-π, have an important role in the cellular defense against platinum agents.
The current findings suggest that a readily completed immunohistochemical marker analysis may have important prognostic significance for patients undergoing cisplatin based combined chemoradiotherapy for locally advanced head and neck cancer. The analysis used readily available reagents and a simple standardized scoring scheme. Given the poor outcome of chemoradiotherapy treatment patients with elevated expression of both p53 and GST-π, these patients may not be appropriate candidates for organ preservation based on standard protocols and may be better managed with primary surgery or considered for clinical trials with alternative radiation sensitizing regimens. Conversely, patients with low expression of both markers appear to be good candidates for combined chemoradiotherapy and can be treated with relative confidence of a favorable outcome.
It is important to note that the chemoradiotherapy arm of trial 9501 was in the postoperative adjuvant setting. While we hypothesize that similar outcomes would be seen in an examination of patients receiving cisplatin based chemoradiotherapy as primary treatment of advanced disease, the data presented here do not establish that with certainty. Unfortunately, the RTOG tissue bank does not contain such a clinical sample set. An analysis of biopsy samples from the recently published neoadjuvant trial of cisplatin/5-FU vs cisplatin/5-FU/docetaxel19 is underway and may provide further clarity in that area.
The current study findings also provide disquieting new data regarding the racial disparities in head and neck cancer and hint that biochemical differences in the tumors may explain some of the differences in outcome for the two groups. In both trials 9003 and 9501, black patients fared worse than did white patients. The poor survival for black patients approached significance in trial 9501 and was highly significant in trial 9003. Trial 9003 had a sufficient sample size to facilitate the preliminary analysis of marker expression by race. In that study, black patients had a trend for higher expression of both p53 and GST-π which approached statistical significance. The semiquantitative immunohistochemical scheme used in this analysis has the benefit of simplicity, but makes it difficult to quantify small differences in expression in small groups of patients. We have previously shown that overexpression of GST-π measured by immunohistochemistry is frequently associated with increased gene copy number measured by FISH.20 More precise quantitative assessment of GST-π may be possible with that methodology.
Of note, black patients in 9003 presented with higher N stage and a trend toward higher T stage than white patients in the same study. We cannot make firm conclusions about whether the adverse survival seen is due to delay in time to diagnosis or whether elevated expression of p53 or GST-π in and of themselves are associated with more aggressive tumor behavior resulting in more advanced stage at diagnosis.
The biologic bases of differences in outcome for blacks and whites remain largely undefined, especially in head and neck cancer. The NCI Black/White Cancer Survival Study examined colon, breast, uterine and bladder tumors and demonstrated poorer survival for black patients in all those diseases after adjustment for both clinical and socioeconomic characteristics.21,22 These findings gave credence to the concept that some cancers may be biologically more aggressive in blacks compared with whites. However, a more recent meta- analysis of survival from clinical studies reported for 14 tumor types including head and neck demonstrated decreased survival for blacks only for breast, uterine and bladder cancer. The authors conclude that disparities in survival for other tumors including head and neck are accounted for principally by differences in treatment, stage at presentation and mortality from other conditions.23 Several studies have recently analyzed national data from the Surveillance, Epidemiology and End Results (SEER) database. These analyses of oral and pharyngeal cancer consistently demonstrate that blacks present with more advanced disease than whites and that the age adjusted mortality rate for these cancers is nearly twice as high for blacks compared to whites.24,25 One recent analysis of the same SEER data suggests that even correcting for stage at diagnosis, blacks had significantly worse survival than whites.26 A single institution retrospective study confirmed that disease specific mortality was significantly higher for blacks than whites after adjusting for other factors including TNM stage. Intensity of treatment was similar for both groups and did not account for the differences in survival.27
The current study was not designed or powered to address these issues definitively, but does show a trend toward increased expression of these two adverse markers in black patients and suggests that further attention to this research issue is warranted.
Acknowledgements
This work was supported by NCI grant R01 CA 090328 and by grants from the Maryland Cigarette Restitution Fund and the Orokawa Foundation.
The authors appreciate the assistance of Dr. Elizabeth Hammond, Director of the RTOG tumor bank for her help with tissue acquisition as well as Dr. Thomas Pajak and Mr. Jonathan Harris of the RTOG for providing the clinical outcomes data from trials 9003 and 9501. In addition we appreciate the critical comments of Dr. Marshall Posner.
References
- 1.Cancer Facts and Figures 2007. www.acs.org.
- 2.NCCN clinical practice guidelins in oncology V.1.2007. www.nccn.org.
- 3.Laimer K, Spizzo G, Gastl G, Obrist P, Brunhuber T, Fong D, Barbieri V, Jank S, Doppler W, Rasse M and Norer B High EGFR expression predicts poor prognosis in patients with squamous cell carcinoma of the oral cavity and oropharynx: a TMA-based immunohistochemical analysis, Oral Oncol., 43: 193–198, 2007. [DOI] [PubMed] [Google Scholar]
- 4.Chin D, Boyle GM, Williams RM, Ferguson K, Pandeya N, Pedley J, Campbell CM, Theile DR, Parsons PG and Coman WB Novel markers for poor prognosis in head and neck cancer, Int.J.Cancer, 113: 789–797, 2005. [DOI] [PubMed] [Google Scholar]
- 5.Salesiotis A, Cullen KJ. Molecular markers predictive of response and prognosis in the patient with advanced squamous cell carcinoma of the head and neck: evolution of a model beyond TNM staging. Current Opinion in Oncology, 12:229–239, 2000. [DOI] [PubMed] [Google Scholar]
- 6.Laimer K, Spizzo G, Gastl G, Obrist P, Brunhuber T, Fong D, Barbieri V, Jank S, Doppler W, Rasse M and Norer B High EGFR expression predicts poor prognosis in patients with squamous cell carcinoma of the oral cavity and oropharynx: a TMA-based immunohistochemical analysis, Oral Oncol., 43: 193–198, 2007. [DOI] [PubMed] [Google Scholar]
- 7.Yu Z, Weinberger PM, Haffty BG, Sasaki C, Zerillo C, Joe J, Kowalski D, Dziura J, Camp RL, Rimm DL and Psyrri A Cyclin d1 is a valuable prognostic marker in oropharyngeal squamous cell carcinoma, Clin.Cancer Res, 11: 1160–1166, 2005. [PubMed] [Google Scholar]
- 8.Ruokolainen H, Paakko P and Turpeenniemi-Hujanen T Expression of matrix metalloproteinase-9 in head and neck squamous cell carcinoma: a potential marker for prognosis, Clin.Cancer Res, 10: 3110–3116, 2004. [DOI] [PubMed] [Google Scholar]
- 9.Sampaio-Goes FC, Oliveira DT, Dorta RG, Nonogaki S, Landman G, Nishimoto IN and Kowalski LP Expression of PCNA, p53, Bax, and Bcl-X in oral poorly differentiated and basaloid squamous cell carcinoma: relationships with prognosis, Head Neck, 27: 982–989, 2005. [DOI] [PubMed] [Google Scholar]
- 10.Lim SC, Zhang S, Ishii G, Endoh Y, Kodama K, Miyamoto S, Hayashi R, Ebihara S, Cho JS and Ochiai A Predictive markers for late cervical metastasis in stage I and II invasive squamous cell carcinoma of the oral tongue, Clin.Cancer Res, 10: 166–172, 2004. [DOI] [PubMed] [Google Scholar]
- 11.Geisler SA, Olshan AF, Weissler MC, Cai J, Funkhouser WK, Smith J and Vick K p16 and p53 Protein expression as prognostic indicators of survival and disease recurrence from head and neck cancer, Clin.Cancer Res, 8: 3445–3453, 2002. [PubMed] [Google Scholar]
- 12.Nishimura T, Newkirk K, Rasmussen A, Trock B, Montgomery EA, Sessions RB, Cullen KJ. Glutathione s-transferase expression predicts response to cisplatin-based chemotherapy in head and neck cancer. Clinical Cancer Research, 2:1859–1865, 1996. [PubMed] [Google Scholar]
- 13.Yang Z, Faustino PJ, Andrews PA, Monastra R, Rasmussen AA, Ellison CD, Cullen KJ. Decreased cisplatin/DNA adduct formation is associated with cisplatin resistance in human head and neck cancer cell lines. Cancer Chemotherapy and Pharmacology, 46:255–262, 2000. [DOI] [PubMed] [Google Scholar]
- 14.Shiga H, Heath EI, Rasmussen AA, Trock B, Johnston PG, Forastiere AA, Langmacher M, Baylor A, Lee M and Cullen KJ Prognostic value of p53, glutathione S- transferase pi, and thymidylate synthase for neoadjuvant cisplatin-based chemotherapy in head and neck cancer, Clin.Cancer Res, 5: 4097–4104, 1999. [PubMed] [Google Scholar]
- 15.Ogawa T, Shiga K, Tateda M, Saijo S, Suzuki T, Sasano H, Miyagi T and Kobayashi T Protein expression of p53 and Bcl-2 has a strong correlation with radiation resistance of laryngeal squamous cell carcinoma but does not predict the radiation failure before treatment, Oncol.Rep, 10: 1461–1466, 2003. [PubMed] [Google Scholar]
- 16.Fu KK, Pajak TF, Trotti A, Jones CU, Spencer SA, Phillips TL, Garden AS, Ridge JA, Cooper JS and Ang KK A Radiation Therapy Oncology Group (RTOG) phase III randomized study to compare hyperfractionation and two variants of accelerated fractionation to standard fractionation radiotherapy for head and neck squamous cell carcinomas: first report of RTOG 9003, Int.J.Radiat.Oncol.Biol.Phys, 48: 7–16, 2000. [DOI] [PubMed] [Google Scholar]
- 17.Cooper JS, Pajak TF, Forastiere AA, Jacobs J, Campbell BH, Saxman SB, Kish JA, Kim HE, Cmelak AJ, Rotman M, Machtay M, Ensley JF, Chao KS, Schultz CJ, Lee N and Fu KK Postoperative concurrent radiotherapy and chemotherapy for high-risk squamous-cell carcinoma of the head and neck, N.Engl.J.Med, 350: 1937–1944, 2004. [DOI] [PubMed] [Google Scholar]
- 18.Allred DC, Harvey JM, Berardo M and Clark GM Prognostic and predictive factors in breast cancer by immunohistochemical analysis, Mod.Pathol, 11: 155–168, 1998. [PubMed] [Google Scholar]
- 19.Posner MR, Hershock DM, Blajman CR, Mickiewicz E, Winquist E, Gorbounova V, Tjulandin S, Shin DM, Cullen K, Ervin TJ, Murphy BA, Raez LE, Cohen RB, Spaulding M, Tishler RB, Roth B, Viroglio RC, Venkatesan V, Romanov I, Agarwala S, Harter KW, Dugan M, Cmelak A, Markoe AM, Read PW, Steinbrenner L, Colevas AD, Norris CM Jr. and Haddad RI Cisplatin and fluorouracil alone or with docetaxel in head and neck cancer, N.Engl.J.Med, 357: 1705–1715, 2007. [DOI] [PubMed] [Google Scholar]
- 20.Cullen KJ, Newkirk KA, Schumaker LM, Aldosari N, Rone JD and Haddad BR Glutathione S-transferase pi amplification is associated with cisplatin resistance in head and neck squamous cell carcinoma cell lines and primary tumors, Cancer Res, 63: 8097–8102, 2003. [PubMed] [Google Scholar]
- 21.Hunter CP, Redmond CK, Chen VW, Austin DF, Greenberg RS, Correa P, Muss HB, Forman MR, Wesley MN, Blacklow RS and . Breast cancer: factors associated with stage at diagnosis in black and white women. Black/White Cancer Survival Study Group, J.Natl.Cancer Inst, 85: 1129–1137, 1993. [DOI] [PubMed] [Google Scholar]
- 22.Eley JW, Hill HA, Chen VW, Austin DF, Wesley MN, Muss HB, Greenberg RS, Coates RJ, Correa P, Redmond CK and . Racial differences in survival from breast cancer. Results of the National Cancer Institute Black/White Cancer Survival Study, JAMA, 272: 947–954, 1994. [DOI] [PubMed] [Google Scholar]
- 23.Bach PB, Schrag D, Brawley OW, Galaznik A, Yakren S and Begg CB Survival of blacks and whites after a cancer diagnosis, JAMA, 287: 2106–2113, 2002. [DOI] [PubMed] [Google Scholar]
- 24.Goodwin WJ, Thomas GR, Parker DF, Joseph D, Levis S, Franzmann E, Anello C and Hu JJ Unequal burden of head and neck cancer in the United States, Head Neck, 2007 [DOI] [PubMed] [Google Scholar]
- 25.Shiboski CH, Schmidt BL and Jordan RC Racial disparity in stage at diagnosis and survival among adults with oral cancer in the US, Community Dent.Oral Epidemiol., 35: 233–240, 2007. [DOI] [PubMed] [Google Scholar]
- 26.Morse DE and Kerr AR Disparities in oral and pharyngeal cancer incidence, mortality and survival among black and white Americans, J.Am.Dent.Assoc, 137: 203–212, 2006. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Murdock JM and Gluckman JL African-American and white head and neck carcinoma patients in a university medical center setting. Are treatments provided and are outcomes similar or disparate?, Cancer, 91: 279–283, 2001. [DOI] [PubMed] [Google Scholar]