Skip to main content
Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

P53 Status as a Predictive Biomarker for Patients Receiving Neoadjuvant Radiation-Based Treatment: A Meta-Analysis in Rectal Cancer

  • Min-Bin Chen ,

    Contributed equally to this work with: Min-Bin Chen, Xiao-Yang Wu

    Affiliation Department of Medical Oncology, Kunshan First People’s Hospital Affiliated to Jiangsu University, Kunshan, Jiangsu Province, People’s Republic of China

  • Xiao-Yang Wu ,

    Contributed equally to this work with: Min-Bin Chen, Xiao-Yang Wu

    Affiliation Department of Surgical Oncology, Kunshan First People’s Hospital Affiliated to Jiangsu University, Kunshan, Jiangsu Province, People’s Republic of China

  • Rong Yu,

    Affiliation Department of Oncology, Suzhou Municipal Hospital, Affiliated Suzhou Hospital of Nanjing Medical University, Suzhou, Jiangsu Province, People’s Republic of China

  • Chen Li,

    Affiliation Department of Gastroenterology,Xuzhou Chinese Medical Hospital Affiliated to Nanjing University of Chinese Medicine, Xuzhou, Jiangsu Province, People’s Republic of China

  • Li-Qiang Wang,

    Affiliation Department of Medical Oncology, Kunshan First People’s Hospital Affiliated to Jiangsu University, Kunshan, Jiangsu Province, People’s Republic of China

  • Wei Shen,

    Affiliation Department of General Surgery, Wuxi People’s Hospital Affiliated to Nanjing Medical University, Wuxi City, Jiangsu Province, People’s Republic of China

  • Pei-Hua Lu

    lphty1_1@yahoo.com.cn

    Affiliation Department of General Surgery, Wuxi People’s Hospital Affiliated to Nanjing Medical University, Wuxi City, Jiangsu Province, People’s Republic of China

Abstract

Background

Numerous studies have yielded inconsistent results regarding the relationship between p53 status and the response to neoadjuvant radiation-based therapy in patients with rectal cancer. We conducted a meta-analysis to clarify the relationship between p53 status and response to radiation-based therapy in rectal cancer.

Methods/Findings

A total of 30 previously published eligible studies including 1,830 cases were identified and included in this meta-analysis. Wild-type form of p53 status (low expression of p53 protein and/or wild-type p53 gene) was associated with pathologic response in rectal cancer patients who received neoadjuvant radiation-based therapy (good response: risk ratio [RR] = 1.30; 95% confidence intervals [CI] = 1.14–1.49; p<0.001; complete response RR = 1.65; 95% CI = 1.19–2.30; p = 0.003; poor response RR = 0.85; 95% CI = 0.75–0.96; p = 0.007). In further stratified analyses, this association remained for sub-groups of good and poor response in neoadjuvant radiotherapy (RT) setting, good and complete response in chemoradiotherapy (CRT) setting. And the association between response and the presence of p53 gene mutations was stronger than that between response and protein positivity.

Conclusion

The results of the present meta-analysis indicate that P53 status is a predictive factor for response in rectal cancer patient undergoing neoadjuvant radiation-based therapy.

Introduction

In 2011, it is estimated that 39,870 new cases of rectal cancer will occur in the United states. In the same year, an estimated 49,380 people will die from rectal and colon cancer comined [1]. Today the increasing use of neoadjuvant radiation-based therapy(it is mostly RT and CRT) and improvements in the quality of rectal cancer surgery, particularly the standardisation of total mesorectal excision (TME), the combination of this strategies is recommended as a standard procedure for treatment of locally advanced rectal cancer[2][4]. However, despite generally high response rates, a small proportion of patients fail to respond to neoadjuvant radiation-basedtherapy, or even progress during therapy. There is now substantial evidence that biological markers may be useful for identifying those patients who would benefit from neoadjuvant therapy [5].

To date, p53 is the most studied response predictor in rectal cancer [6]. It is a master gene in the stress response that plays an important role in cancer development. The p53 tumour suppressor gene is the most widely mutated gene in human tumorigenesis, with mutations occurring in at least 50% of human cancers [7]. p53 encodes a transcriptional activator whose targets may include genes that regulate genomic stability, the cellular response to DNA damage, and cell-cycle progression [8]. Preclinical studies have shown that wild-type p53 was required for radiation-induced cell death in mouse thymocytes [9]. Thymocytes carried p53-homozygous mutants could resistant to 5.0 Gy, and p53 heterozygous thymocytes were relatively resistant to the same dose of radiation; while wild-type p53 cells were highly sensitive to the same dose of radiation [9]. These results have been confirmed in models of colorectal cancer in vitro and in vivo [10], [11].

The use of p53 status as a biological marker to predict the response of rectal cancer to neoadjuvant therapy, however, is disappointing, and the findings to date have shown conflicting results [6], [12][15]. Several studies found that patients with wild-type form of p53 often had better responses to therapy than those with mutation p53 [16][19]. Other studies, however, evaluated p53 status in rectal cancer patients and drew different conclusions [12][15]. These conflicting results may be attributable to the limited detection power inherent in studies that test small subsets of patients. We therefore performed a meta-analysis of the value of p53 status for predicting response to neoadjuvant radiation-based therapy in rectal cancer.

Materials and Methods

Publication Search

PubMed, Embase, and Web of Science databases were searched (up to May 8, 2012) using the search terms: ‘TP53’, ‘p53’, ‘p53 protein’, ‘p53 mutation’, ‘17p13 gene’, and ‘rectal cancer’. All potentially eligible studies were retrieved and their bibliographies were carefully scanned to identify other eligible studies. Additional studies were identified by a hand search of the references cited in the original studies. When multiple studies of the same patient population were identified, we included the published report with the largest sample size. Only studies published in English were included in this meta-analysis.

thumbnail
Figure 1. Improving the quality of reports of meta-analyses of randomized controlled trials; the Quality of Reporting of Meta-Analyses (QUOROM) statement flow diagram.

https://doi.org/10.1371/journal.pone.0045388.g001

thumbnail
Table 2. Characteristics of studies included in the meta-analysis.

https://doi.org/10.1371/journal.pone.0045388.t002

Inclusion and Exclusion Criteria

Studies included in this meta-analysis had to meet all of the following criteria: (a) evaluation of p53 status for predicting the response to neoadjuvant radiation-based therapy in early-stage rectal cancer, locally-advanced rectal cancer, (b) described therapeutic pathological response, (c) retrospective or prospective cohort study, (d) inclusion of adequate data to allow the estimation of a risk ratio (RR) with 95% confidence intervals (95% CI), and (e) studies published in English. Reviews, letters to the editor, and articles published in books were excluded.

thumbnail
Figure 2. Forest plots of RR were assessed for association between p53 and good response among rectal cancer patients treated with neoadjuvant radiation-based therapy.

https://doi.org/10.1371/journal.pone.0045388.g002

thumbnail
Figure 3. Forest plots of RR were assessed for association between p53 and complete response among rectal cancer patients treated with neoadjuvant radiation-based therapy.

https://doi.org/10.1371/journal.pone.0045388.g003

thumbnail
Figure 4. Forest plots of RR were assessed for association between p53 and poor response among rectal cancer patients treated with neoadjuvant radiation-based therapy.

https://doi.org/10.1371/journal.pone.0045388.g004

Data Extraction and Definitions

According to the inclusion criteria listed above, the following data were extracted for each study: the first author’s surname, publication year, country of origin, number of patients analyzed, treatment, types of measurement and over expression of TP53 protein and/or TP53 gene mutation frequency. Data on the main outcomes were entered in tables showing the pathological responses to radiation-based therapy with respect to p53 status. Information was carefully and independently extracted from all eligible publications by two of the authors (Chen and Wu). Any disagreement between the researchers was resolved by discussions until a consensus was reached. If they failed to reach a consensus, a third investigator (Lu) was consulted to resolve the dispute.

thumbnail
Table 3. Risk ratio for the association between wild-type form of TP53 and the response to neoadjuvant radiation-based radiotherapy.

https://doi.org/10.1371/journal.pone.0045388.t003

thumbnail
Figure 5. The funnel plot shows that there was no obvious indication of publication bias for the outcome of good response setting.

https://doi.org/10.1371/journal.pone.0045388.g005

We used the definitions and standardizations for ‘p53’ and ‘response to radiation-based therapy’. For consistency, we used ‘p53 status’ to refer to both the gene and protein markers. Wild-type form of p53 status means patients with low expression of p53 protein and/or wild-type p53 gene. Pathologic response after neoadjuvant radiation-based therapy in different studies were according to different tumor regression grade (TRG) systems, most of the studies used TRG system described by Dworak et al. [20] and Rodel et al. [21], which categorize tumour regression in four grades, and TRG 2 and 3 determination is semiquantitatively defined as more/less than 50% tumour regression, respectively. Other grading systems have been proposed to categorize tumour regression in three grades where intermediate responders are grouped [22]. For consistency, we defined the pathologic response classification in the table 1. Briefly, poor response (residual tumor rate ≥75%); good response (residual tumor rate <50%); complete response (residual tumor rate = 0%).

Statistical Analysis

RR with 95% CIs was used to estimate the association between p53 status and response to neoadjuvant radiation-based therapy in rectal cancer patients. Subgroup analyses were performed to evaluate the effects of different treatment regimens (CRT and RT) and different methods of p53 gene determination (protein and gene). The presence of statistical heterogeneity was assessed with Cochran’s Q test (considered significant for Ph<0.10). The pooled RR was calculated using a fixed-effects model (the Mantel–Haenszel method) or a random-effects model (the DerSimonian and Laird method), according to the heterogeneity. Funnel plots and the Egger’s test were employed to estimate the possible publication bias. We also performed sensitivity analysis by omitting each study or specific studies to find potential outliers. Statistical analyses were conducted using Stata (version SE/10; StataCorp, College Station, TX). p values for all comparisons were two-tailed and statistical significance was defined as p<0.05 for all tests, except those for heterogeneity.

Results

Eligible Studies

A total of 467 articles were retrieved by a literature search of the PubMed, Embase, and Web of Science databases, using different combinations of key terms. As indicated in the search flow diagram (Figure 1), 30 studies [12][15], [17][19], [26], [27], [30][49] reported at least one of the outcomes of interest and were finally included in the meta-analysis. The characteristics of the eligible studies are summarized in Table 2. Eighteen used neoadjuvant CRT and six used neoadjuvant RT, while five include both CRT and RT (Table 2), Twenty-five of the studies employed protein detection (including immunohistochemistry), seven employed gene detection (including genomic sequencing, Polymerase Chain Reaction-Single Strand Conformation Polymorphism[PCR-SSCP] etc.), two employed both methods (Table 2). The sample sizes in all the eligible studies ranged from 22–111 patients (median = 58 patients, mean = 61 patients, standard deviation [SD] = 4.73). Overall, the eligible studies included 1,830 patients. Eighteen of the studies were conducted in European or North American populations with mixed but mostly white participants (1,127 patients), whereas ten were conducted in East Asian populations (703 patients).

Evidence Synthesis

Among the studies of rectal cancer patients who received neoadjuvant radiation-based therapy, 28 studies involving 1,769 patients contributed data on good response setting. Wild-type form of p53 status was significantly associated with improved good response among patients treated with neoadjuvant radiation-based therapy (RR = 1.30; 95% CI = 1.14–1.49; p<0.001, Figure 2). Ten studies involving 646 patients contributed data on complete response setting. Wild-type form of p53 status was significantly associated with improved complete response (RR = 1.65; 95% CI = 1.19–2.30; p = 0.003, Figure 3). Finally, 24 studies involving 1,478 patients provided information on poor response setting. Wild-type form of p53 status was significantly associated with decreases in poor response setting (RR = 0.85; 95% CI = 0.75–0.96; p = 0.007, Figure 4).

Subgroup Analysis

Among the 30 studies in the neoadjuvant subgroup, 18 used neoadjuvant CRT and six used neoadjuvant RT, while five include both CRT and RT (Table 3). The results of the neoadjuvant CRT and RT were therefore calculated separately. Wild-type form of p53 status was associated with improved response in rectal cancer patients who received neoadjuvant CRT (good response: RR = 1.20, 95% CI = 1.01–1.43, p = 0.043, complete response: RR = 1.92, 95% CI = 1.26–2.91, p = 0.002), but not with poor response (RR = 0.91, 95% CI = 0.68–1.12, p = 0.284). Wild-type form of p53 status was associated with good response in neoadjuvant RT settings (RR = 1.90, 95% CI = 1.44–2.51, p<0.001), and with decreased poor response (RR = 0.81; 95% CI = 0.69–0.94; p = 0.007), but not with complete response(RR = 2.80, 95% CI = 0.88–8.86, p = 0.081).

Different measurements of p53 status (either by protein or gene detection) have been used to evaluate associations with favorable responses to neoadjuvant radiation-based therapy. We therefore calculated the associations using both protein and gene statuses of p53. The results of subgroup analysis are presented in Table 3. For gene detection, wild-type p53 gene was significantly associated with increased response (good response: RR = 1.48, 95% CI = 1.15–1.91, p = 0.002, complete response: RR = 2.78, 95% CI = 1.40–5.50, p = 0.003), and with decreased Poor response (RR = 0.79; 95% CI = 0.64–0.98; p = 0.033) among patients treated with neoadjuvant therapy. For protein-based detection, low expression of p53 protein was significantly associated with increased good response (RR = 1.18, 95% CI = 1.02–1.36, p = 0.025) among patients treated with neoadjuvant therapy, but not with complete response (RR = 1.35; 95% CI = 0.92–1.98; p = 0.124) and poor response (RR = 0.91; 95% CI = 0.79–1.05; p = 0.191).

Publication Bias

Begg’s funnel plot and Egger’s test were used to estimate the publication bias of the included literature. The shapes of the funnel plots showed no evidence of obvious asymmetry (Figure 5), and Egger’s test indicated the absence of publication bias (p>0.05). Moreover, sensitivity analysis was carried out to assess the influence of individual studies on the summary effect. No individual study dominated this meta-analysis, and the removal of any single study had no significant effect on the overall results (data not shown).

Discussion

The p53 status had been shown to play a pivotal role in the response to radiation-based therapy [6], [50]. Previous studies suggested that rectal cancers with p53 mutations might be either resistant or sensitive to neoadjuvant radiation-based therapy. However, the issue could not be resolved, because most of the available clinical reports involved small sample sizes, and the results were therefore unable to determine the value of p53 status for predicting the response to neoadjuvant radiation-based therapy. We therefore concluded that a meta-analysis was the best way of evaluating the association between p53 status and response to neoadjuvant radiation-based therapy in a large population.

The current meta-analysis of 30 studies systematically evaluated the association between p53 status and response to neoadjuvant radiation-based therapy in a large population. The results indicate that wild-type form of p53 status may predict good response rates to neoadjuvant therapy in patients with rectal cancer. Wild-type form of p53 status was associated with improved good and complete response, decreased poor response. Stratification according to different treatments showed that this association remained for sub-groups of good and poor response in RT, good and complete response in CRT, except for poor response in CRT and complete response in RT. Further stratification by gene detection revealed imprecise results, but amplification of the wild-type p53 gene was also associated with relevant increases in good and complete response, decreased poor response; however, although low expression of p53 was associated with relevant increases in good resonse, it was not associated with complete response and poor response. Gene detection was associated with advantages regarding response rates to neoadjuvant radiation-based therapy in patients with rectal cancer. The current meta-analysis suggests that p53 status as an independent predictive factor for neoadjuvant radiation-based therapy outcome in patients with rectal cancer, and gene detection may be a better assay to use in the evaluation of p53 status and sensitivity to neoadjuvant radiation-based therapy. Radiosensitive tumors could be identified by the detection of p53 status, a selective and individualized form of chemoradiation might be instituted. Novel molecular treatment strategies specifically designed to reactivate p53 within resistant tumors can be used as combined modality protocols to improve local response rate [5].

In interpreting our results of the current meta-analysis, some limitations need to be addressed. First, the meta-analysis may have been influenced by publication bias; although we tried to identify all relevant data and retrieve additional unpublished information, some missing data were unavoidable. Second, the studies used different measurements of p53 status (either protein or gene detection), and different tumor regression grade systems. Standardization is therefore of great importance for obtaining an accurate assessment of the clinical significance of p53 status. Although we made considerable efforts to standardize definitions, some variability in definitions of methods, measurements, and outcomes among studies was inevitable, which may lead to a misclassification bias. Third, Different measurements of p53 status (either byIHC or by DNA sequencing techniques) have been employed to evaluate association with favorable response to neoadjuvant radiation-based therapy. Cut-off values of p53 for both overexpression by IHC and gene amplification by PCR were not the same in each study, which might lead to inconsistent results between these studies. Therefore, standardization is particularly important when assessing p53 status (gene and protein), which will help to obtain accurate data with clinical significance. Fourth, our analysis was observational in nature, and we therefore cannot exclude confounding as a potential explanation of the observed results. Despite these limitations, this meta-analysis had several advantages. First, a large number of cases were pooled from different studies, and 1,830 subjects represent a sizeable number, significantly increasing the statistical power of the analysis. Secondly, no publication biases were detected, indicating that the pooled results may be unbiased.

This study is the first meta-analysis to assess the usefulness of p53 status for predicting the response of rectal cancer patients to neoadjuvant radiation-based therapy. Our data support p53 status as a useful predictive factor for assessing treatment response to neoadjuvant radiation-based therapy in rectal cancer patients. However, future studies with larger sample sizes, more advanced and accurate detection methods and more comprehensive study designs are required to confirm our finding.

Author Contributions

Conceived and designed the experiments: MBC XYW PHL. Performed the experiments: MBC XYW LQW RY. Analyzed the data: MBC XYW PHL. Contributed reagents/materials/analysis tools: XYW RY LQW. Wrote the paper: MBC XYW. Helped edit the manuscript: CL WS.

References

  1. 1. Siegel R, Ward E, Brawley O, Jemal A (2011) Cancer statistics, 2011: the impact of eliminating socioeconomic and racial disparities on premature cancer deaths. CA Cancer J Clin 61: 212–236.
  2. 2. Kapiteijn E, Marijnen CA, Nagtegaal ID, Putter H, Steup WH, et al. (2001) Preoperative radiotherapy combined with total mesorectal excision for resectable rectal cancer. N Engl J Med 345: 638–646.
  3. 3. Sauer R, Becker H, Hohenberger W, Rodel C, Wittekind C, et al. (2004) Preoperative versus postoperative chemoradiotherapy for rectal cancer. N Engl J Med 351: 1731–1740.
  4. 4. Wong RK, Tandan V, De Silva S, Figueredo A (2007) Pre-operative radiotherapy and curative surgery for the management of localized rectal carcinoma. Cochrane Database Syst Rev: CD002102.
  5. 5. Cuddihy AR, Bristow RG (2004) The p53 protein family and radiation sensitivity: Yes or no? Cancer Metastasis Rev 23: 237–257.
  6. 6. Huerta S, Gao X, Saha D (2009) Mechanisms of resistance to ionizing radiation in rectal cancer. Expert Rev Mol Diagn 9: 469–480.
  7. 7. Tewari M, Krishnamurthy A, Shukla HS (2008) Predictive markers of response to neoadjuvant chemotherapy in breast cancer. Surg Oncol 17: 301–311.
  8. 8. Vousden KH, Prives C (2009) Blinded by the Light: The Growing Complexity of p53. Cell 137: 413–431.
  9. 9. Lowe SW, Schmitt EM, Smith SW, Osborne BA, Jacks T (1993) p53 is required for radiation-induced apoptosis in mouse thymocytes. Nature 362: 847–849.
  10. 10. Merritt AJ, Potten CS, Kemp CJ, Hickman JA, Balmain A, et al. (1994) The role of p53 in spontaneous and radiation-induced apoptosis in the gastrointestinal tract of normal and p53-deficient mice. Cancer Res 54: 614–617.
  11. 11. Spitz FR, Nguyen D, Skibber JM, Meyn RE, Cristiano RJ, et al. (1996) Adenoviral-mediated wild-type p53 gene expression sensitizes colorectal cancer cells to ionizing radiation. Clin Cancer Res 2: 1665–1671.
  12. 12. Shinto E, Hashiguchi Y, Ueno H, Kobayashi H, Ishiguro M, et al. (2011) Pretreatment CD133 and cyclooxygenase-2 expression as the predictive markers of the pathological effect of chemoradiotherapy in rectal cancer patients. Dis Colon Rectum 54: 1098–1106.
  13. 13. Chen Z, Duldulao MP, Li W, Lee W, Kim J, et al.. (2011) Molecular diagnosis of response to neoadjuvant chemoradiation therapy in patients with locally advanced rectal cancer. J Am Coll Surg 212: 1008–1017 e1001.
  14. 14. Garcia VM, Batlle JF, Casado E, Burgos E, de Castro J, et al. (2011) Immunohistochemical analysis of tumour regression grade for rectal cancer after neoadjuvant chemoradiotherapy. Colorectal Dis 13: 989–998.
  15. 15. Brophy S, Sheehan KM, McNamara DA, Deasy J, Bouchier-Hayes DJ, et al. (2009) GLUT-1 expression and response to chemoradiotherapy in rectal cancer. Int J Cancer 125: 2778–2782.
  16. 16. Chen MF, Lee KD, Yeh CH, Chen WC, Huang WS, et al. (2010) Role of peroxiredoxin I in rectal cancer and related to p53 status. Int J Radiat Oncol Biol Phys 78: 868–878.
  17. 17. Kandioler D, Zwrtek R, Ludwig C, Janschek E, Ploner M, et al. (2002) TP53 genotype but not p53 immunohistochemical result predicts response to preoperative short-term radiotherapy in rectal cancer. Ann Surg 235: 493–498.
  18. 18. Luna-Perez P, Arriola EL, Cuadra Y, Alvarado I, Quintero A (1998) p53 protein overexpression and response to induction chemoradiation therapy in patients with locally advanced rectal adenocarcinoma. Ann Surg Oncol 5: 203–208.
  19. 19. Fu CG, Tominaga O, Nagawa H, Nita ME, Masaki T, et al. (1998) Role of p53 and p21/WAF1 detection in patient selection for preoperative radiotherapy in rectal cancer patients. Dis Colon Rectum 41: 68–74.
  20. 20. Dworak O, Keilholz L, Hoffmann A (1997) Pathological features of rectal cancer after preoperative radiochemotherapy. Int J Colorectal Dis 12: 19–23.
  21. 21. Rodel C, Martus P, Papadoupolos T, Fuzesi L, Klimpfinger M, et al. (2005) Prognostic significance of tumor regression after preoperative chemoradiotherapy for rectal cancer. J Clin Oncol 23: 8688–8696.
  22. 22. Therasse P, Arbuck SG, Eisenhauer EA, Wanders J, Kaplan RS, et al. (2000) New guidelines to evaluate the response to treatment in solid tumors. European Organization for Research and Treatment of Cancer, National Cancer Institute of the United States, National Cancer Institute of Canada. J Natl Cancer Inst 92: 205–216.
  23. 23. Mandard AM, Dalibard F, Mandard JC, Marnay J, Henry-Amar M, et al. (1994) Pathologic assessment of tumor regression after preoperative chemoradiotherapy of esophageal carcinoma. Clinicopathologic correlations. Cancer 73: 2680–2686.
  24. 24. Edge SB, Compton CC (2010) The American Joint Committee on Cancer: the 7th edition of the AJCC cancer staging manual and the future of TNM. Ann Surg Oncol 17: 1471–1474.
  25. 25. JapaneseSocietyforCanceroftheColonandRectum (1994) Criteria for histopathological evaluation of radiotherapy effect. In: General roles for clinical and pathological studies on cancer of the colon, rectum and anus 5th ed Tokyo: Kanehara & Co,: 42.
  26. 26. Elsaleh H, Robbins P, Joseph D, Powell B, Grieu F, et al. (2000) Can p53 alterations be used to predict tumour response to pre-operative chemo-radiotherapy in locally advanced rectal cancer? Radiother Oncol 56: 239–244.
  27. 27. Kelley ST, Coppola D, Yeatman T, Marcet J (2005) Tumor response to neoadjuvant chemoradiation therapy for rectal adenocarcinoma is mediated by p53-dependent and caspase 8-dependent apoptotic pathways. Clin Colorectal Cancer 5: 114–118.
  28. 28. Scott N, Hale A, Deakin M, Hand P, Adab FA, et al. (1998) A histopathological assessment of the response of rectal adenocarcinoma to combination chemo-radiotherapy: relationship to apoptotic activity, p53 and bcl-2 expression. Eur J Surg Oncol 24: 169–173.
  29. 29. Wheeler JM, Warren BF, Mortensen NJ, Ekanyaka N, Kulacoglu H, et al. (2002) Quantification of histologic regression of rectal cancer after irradiation: a proposal for a modified staging system. Dis Colon Rectum 45: 1051–1056.
  30. 30. Moral M, Fdez-Acenero MA, Cuberes R, Suarez A (2009) Factors influencing histological response after neoadjuvant chemoradiation therapy for rectal carcinoma. Pathol Res Pract 205: 695–699.
  31. 31. Jakob C, Liersch T, Meyer W, Becker H, Baretton GB, et al. (2008) Predictive value of Ki67 and p53 in locally advanced rectal cancer: correlation with thymidylate synthase and histopathological tumor regression after neoadjuvant 5-FU-based chemoradiotherapy. World J Gastroenterol 14: 1060–1066.
  32. 32. Zlobec I, Vuong T, Compton CC, Lugli A, Michel RP, et al. (2008) Combined analysis of VEGF and EGFR predicts complete tumour response in rectal cancer treated with preoperative radiotherapy. Br J Cancer 98: 450–456.
  33. 33. Negri FV, Campanini N, Camisa R, Pucci F, Bui S, et al. (2008) Biological predictive factors in rectal cancer treated with preoperative radiotherapy or radiochemotherapy. Br J Cancer 98: 143–147.
  34. 34. Terzi C, Canda AE, Sagol O, Atila K, Sonmez D, et al. (2008) Survivin, p53, and Ki-67 as predictors of histopathologic response in locally advanced rectal cancer treated with preoperative chemoradiotherapy. Int J Colorectal Dis 23: 37–45.
  35. 35. Kobayashi H, Hashiguchi Y, Ueno H, Shinto E, Kajiwara Y, et al. (2007) Absence of cyclooxygenase-2 protein expression is a predictor of tumor regression in rectal cancer treated with preoperative short-term chemoradiotherapy. Dis Colon Rectum 50: 1354–1362.
  36. 36. Takeuchi K, Nakajima M, Miyazaki T, Ide M, Asao T, et al. (2007) Is p53 and heat shock protein 70 expression a useful parameter for preoperative hyperthermoradiation therapy in advanced rectal carcinoma. Hepatogastroenterology 54: 367–372.
  37. 37. Sadahiro S, Suzuki T, Maeda Y, Tanaka Y, Nakamura T, et al. (2007) Predictors of tumor downsizing and regression with preoperative radiotherapy alone and with concomitant tegafur/uracil (UFT) for resectable advanced rectal adenocarcinoma. Hepatogastroenterology 54: 1107–1112.
  38. 38. Lopez-Crapez E, Bibeau F, Thezenas S, Ychou M, Simony-Lafontaine J, et al. (2005) p53 status and response to radiotherapy in rectal cancer: a prospective multilevel analysis. Br J Cancer 92: 2114–2121.
  39. 39. Komuro Y, Watanabe T, Tsurita G, Muto T, Nagawa H (2005) Evaluating the combination of molecular prognostic factors in tumor radiosensitivity in rectal cancer. Hepatogastroenterology 52: 666–671.
  40. 40. Suzuki T, Sadahiro S, Fukasawa M, Ishikawa K, Kamijo A, et al. (2004) Predictive factors of tumor shrinkage and histological regression in patients who received preoperative radiotherapy for rectal cancer. Jpn J Clin Oncol 34: 740–746.
  41. 41. Charara M, Edmonston TB, Burkholder S, Walters R, Anne P, et al. (2004) Microsatellite status and cell cycle associated markers in rectal cancer patients undergoing a combined regimen of 5-FU and CPT-11 chemotherapy and radiotherapy. Anticancer Res 24: 3161–3167.
  42. 42. Diez M, Ramos P, Medrano MJ, Muguerza JM, Villeta R, et al. (2003) Preoperatively irradiated rectal carcinoma: analysis of the histopathologic response and predictive value of proliferating cell nuclear antigen immunostaining. Oncology 64: 213–219.
  43. 43. Saw RP, Morgan M, Koorey D, Painter D, Findlay M, et al. (2003) p53, deleted in colorectal cancer gene, and thymidylate synthase as predictors of histopathologic response and survival in low, locally advanced rectal cancer treated with preoperative adjuvant therapy. Dis Colon Rectum 46: 192–202.
  44. 44. Komuro Y, Watanabe T, Hosoi Y, Matsumoto Y, Nakagawa K, et al. (2003) Prediction of tumor radiosensitivity in rectal carcinoma based on p53 and Ku70 expression. J Exp Clin Cancer Res 22: 223–228.
  45. 45. Rebischung C, Gerard JP, Gayet J, Thomas G, Hamelin R, et al. (2002) Prognostic value of P53 mutations in rectal carcinoma. Int J Cancer 100: 131–135.
  46. 46. Rodel C, Grabenbauer GG, Papadopoulos T, Bigalke M, Gunther K, et al. (2002) Apoptosis as a cellular predictor for histopathologic response to neoadjuvant radiochemotherapy in patients with rectal cancer. Int J Radiat Oncol Biol Phys 52: 294–303.
  47. 47. Nasierowska-Guttmejer A (2001) The comparison of immunohistochemical proliferation and apoptosis markers in rectal carcinoma treated surgically or by preoperative radio-chemotherapy. Pol J Pathol 52: 53–61.
  48. 48. Sakakura C, Koide K, Ichikawa D, Wakasa T, Shirasu M, et al. (1998) Analysis of histological therapeutic effect, apoptosis rate and p53 status after combined treatment with radiation, hyperthermia and 5-fluorouracil suppositories for advanced rectal cancers. Br J Cancer 77: 159–166.
  49. 49. Spitz FR, Giacco GG, Hess K, Larry L, Rich TA, et al. (1997) p53 immunohistochemical staining predicts residual disease after chemoradiation in patients with high-risk rectal cancer. Clin Cancer Res 3: 1685–1690.
  50. 50. Smith FM, Reynolds JV, Miller N, Stephens RB, Kennedy MJ (2006) Pathological and molecular predictors of the response of rectal cancer to neoadjuvant radiochemotherapy. Eur J Surg Oncol 32: 55–64.