Prognostic value of p53 in muscle-invasive bladder cancer treated with preoperative radiotherapy

Harnessing citizen science through mobile phone technology to screen for immunohistochemical biomarkers in bladder cancer

BACKGROUND

Immunohistochemistry (IHC) is often used in personalisation of cancer treatments. Analysis of large data sets to uncover predictive biomarkers by specialists can be enormously time-consuming. Here we investigated crowdsourcing as a means of reliably analysing immunostained cancer samples to discover biomarkers predictive of cancer survival.

METHODS

We crowdsourced the analysis of bladder cancer TMA core samples through the smartphone app 'Reverse the Odds'. Scores from members of the public were pooled and compared to a gold standard set scored by appropriate specialists. We also used crowdsourced scores to assess associations with disease-specific survival.

RESULTS

Data were collected over 721 days, with 4,744,339 classifications performed. The average time per classification was approximately 15 s, with approximately 20,000 h total non-gaming time contributed. The correlation between crowdsourced and expert H-scores (staining intensity × proportion) varied from 0.65 to 0.92 across the markers tested, with six of 10 correlation coefficients at least 0.80. At least two markers (MRE11 and CK20) were significantly associated with survival in patients with bladder cancer, and a further three markers showed results warranting expert follow-up.

CONCLUSIONS

Crowdsourcing through a smartphone app has the potential to accurately screen IHC data and greatly increase the speed of biomarker discovery.

Recent Aspects in the Diagnosis and Prognosis of Bladder Cancer

Epidemiologic studies have stated the progressive increase of bladder tumors during the last decades. The aim of our review is to refer to factors implicated in bladder carcinogenesis (such as activated oncogenes, growth factors and chromosomal aberrations) and to resistance to drug uptake (i.e., multidrug resistance gene and P-glycoprotein). The review also provides information of diagnostic and prognostic significance, based on DNA analysis of transitional cancer cells. In addition to cytometric data, alternative counterings for estimation of the S-phase fraction, useful in indicating the biologic behavior of bladder cancer, are presented. Knowledge of such mechanisms results in a better approach to the diagnosis, prognosis and prevention of bladder carcinomas, especially those that do not respond to systemic intravesical chemotherapy. We have tried to mention all significant factors related to the development of bladder cancer. We conclude that the progress made in understanding the pathogenesis of bladder cancer has been significant. However, more studies are needed in order to introduce and adopt reliable criteria to accurately predict the clinical behavior.

MRE11 expression is predictive of cause-specific survival following radical radiotherapy for muscle-invasive bladder cancer

Radical radiotherapy and surgery achieve similar cure rates in muscle-invasive bladder cancer, but the choice of which treatment would be most beneficial cannot currently be predicted for individual patients. The primary aim of this study was to assess whether expression of any of a panel of DNA damage signaling proteins in tumor samples taken before irradiation could be used as a predictive marker of radiotherapy response, or rather was prognostic. Protein expression of MRE11, RAD50, NBS1, ATM, and H2AX was studied by immunohistochemistry in pretreatment tumor specimens from two cohorts of bladder cancer patients (validation cohort prospectively acquired) treated with radical radiotherapy and one cohort of cystectomy patients. In the radiotherapy test cohort (n = 86), low tumor MRE11 expression was associated with worse cancer-specific survival compared with high expression [43.1% versus 68.7% 3-year cause-specific survival (CSS), P = 0.012] by Kaplan-Meier analysis. This was confirmed in the radiotherapy validation cohort (n = 93; 43.0% versus 71.2%, P = 0.020). However, in the cystectomy cohort (n = 88), MRE11 expression was not associated with cancer-specific survival, commensurate with MRE11 being a predictive marker. High MRE11 expression in the combined radiotherapy cohort had a significantly better cancer-specific survival compared with the high-expression cystectomy cohort (69.9% versus 53.8% 3-year CSS, P = 0.021). In this validated immunohistochemistry study, MRE11 protein expression was shown and confirmed as a predictive factor associated with survival following bladder cancer radiotherapy, justifying its inclusion in subsequent trial designs. MRE11 expression may ultimately allow patient selection for radiotherapy or cystectomy, thus improving overall cure rates.

Trimodality Treatment and Selective Organ Preservation for Bladder Cancer

Standard treatment for muscle-invasive bladder cancer is cystectomy. Trimodality treatment, including transurethral resection of the bladder tumor (TURBT), radiation therapy and chemotherapy, has been shown to produce survival rates comparable to those of cystectomy. With these programs, cystectomy has been reserved for patients with incomplete response or local relapse. During the past 15 years, organ preservation by trimodality treatment has been investigated in prospective series from single centers and cooperative groups, with more than 1,000 patients included. Five-year overall survival rates in the range of 50% to 60% have been reported, and approximately three quarters of the surviving patients maintained their bladder. Clinical criteria helpful in determining ideal patients for bladder preservation include early tumor stage (including high-risk T1 disease), a visibly complete TURBT, and absence of ureteral obstruction. Close coordination among all disciplines is required to achieve optimal results. Future investigations will focus on (1) optimizing radiation techniques and incorporating more effective systemic chemotherapy, and (2) the proper selection of patients based on molecular makers.

Apoptosis and chemotherapy for bladder cancer

PURPOSE

We discuss the role of apoptosis, that is gene directed self-destruction of a cell, in the response of bladder transitional cell carcinoma cells to chemotherapy.

MATERIALS AND METHODS

A directed MEDLINE literature search of apoptosis, bladder cancer and chemotherapy was performed to extract relevant information for review. The characteristics of apoptotic cells were defined and the methods in common use to detect these traits is described. The role of the key mediators of the apoptotic process in bladder cancer is discussed in the context of chemosensitivity and disease stage. The importance of the apoptosis induction after chemotherapy is highlighted.

RESULTS

On stimulus by appropriate external or internal signals a cell may alter the expression of genes encoding for proteins associated with the apoptotic process. The development of apoptosis depends on the balance between pro-apoptotic and anti-apoptotic proteins. Key alterations in genes and proteins related to apoptosis within bladder cancer result in a shift away from the default state of apoptosis toward a cell with increased survival properties that is chemoresistant.

CONCLUSIONS

Much current research in bladder cancer is aimed at restoring chemosensitivity by shifting the cell toward a pro-apoptotic phenotype. Successful translation of this work into clinical practice may improve survival in patients in whom prognosis is currently poor.

Correlation between p53 mutations and HPV in bilharzial bladder cancer

Alterations of the p53 tumor suppressor gene are the most common genetic changes detected in human cancers as well as in papillary and invasive bladder cancer. Several studies have demonstrated an association between HPV infection and urological malignancies. In the present work, the p53 gene status was studied together with the frequency of HPV in 99 cases of Bilharzial bladder cancer [BBC] in Egypt and both were correlated to the clinicopathological features of the patients. SSCP and sequencing were used to screen the p53 gene for mutations at exons 4-10 and IHC was performed to detect protein overexpression. PCR was used for detection and typing of HPV-DNA in tumor samples. p53 mutations were detected in 33.3% of the studied cases whereas protein overexpression was detected in 35.6% of the cases. The highest concordance rate was observed in cases harboring mutations at exon 4 [87.5%]. Bilharzial infestation was obvious in 72.2% of the cases that showed mutations. Exon 8 showed the highest rate of mutation [32%] followed by exons 4 and 5 [22% each]. The commonest mutational event was G:C transversion [15/50] especially at CpG dinucleotides. A mutational hot spot was detected at exon 4, codons 72-73. HPV-DNA was detected in 48.97% of the cases the majority of which [64.6%] were of type 16. Significant correlation was found between p53 mutation and the pathological stage as well as p53 overexpression and tumor grade. Our results demonstrate that the mutational spectrum in BBC is different from that of bladder cancer in Western countries in many aspects and suggest an etiological role of HPV in this type of neoplasm. However, both HPV infection and p53 gene abnormalities may contribute to Bilharzial bladder carcinogenesis in an independent way.

Current understanding of the biology of advanced bladder cancer

Transitional cell carcinoma (TCC) is reported to be the fifth most common solid malignancy in the U.S. Although radical cystectomy will cure a substantial number of patients with minimally invasive TCC, many patients with deeply muscle-invasive or extravesical disease who are treated with radical cystectomy alone die of metastatic TCC, as do patients with metastatic disease. The differing clinical course and the limited value of established prognosticators make analysis of new molecular parameters of interest in predicting the prognosis of patients with bladder cancer, particularly those in high-risk groups who are at risk of disease progression and recurrence. In the current review, a comprehensive MEDLINE/PubMed search of articles pertaining to the biology of TCC from 1965 to the present was performed, as well as a bibliographic review of cross references. TCC follow the general concept of multistep carcinogenesis and proceed through two distinct genetic pathways responsible for generating different TCC morphologies, namely the inactivation of cyclin-dependent kinase inhibitors in low-grade TCC and early p53-mediated abnormalities in high-grade TCC. TCC progression correlates with genetic instability and the accumulation of collaborative genetic lesions mainly involving p53, retinoblastoma, and growth factors. The bulk of these data are derived from cases of localized/locally advanced disease and none are ready yet for routine clinical application; however, the current knowledge has led to the clinical testing of novel biologic observations in several important trials. Understanding of the molecular biology of advanced bladder cancer continues to improve. It is likely that in the new millennium, real breakthroughs in the identification and therapy of high-risk, poor-prognosis patients will come from an integration of molecular modalities in the clinical application.

The p53 tumor suppressor gene and nuclear protein: basic science review and relevance in the management of bladder cancer

PURPOSE

An extensive body of literature regarding p53 has accumulated during the last 2 decades. The cellular mechanisms of p53 are complex yet well-defined, whereas its clinical usefulness in the management of bladder cancer remains controversial. We outline the basic constitutive functions of p53 and summarize its current role in the management of transitional cell carcinoma of the bladder.

MATERIALS AND METHODS

We conducted a MEDLINE based literature review concerning the fundamental mechanisms of p53 and its role in the management of bladder cancer.

RESULTS

The p53 gene is a tumor suppressor gene that acts as "guardian of the genome." Many diverse cellular events, including DNA damage and hypoxia, activate the p53 gene. The p53 protein functions as a transcription factor, regulating downstream genes involved in cell cycle arrest, DNA repair and programmed cell death. Loss of p53 function confers genomic instability, impaired apoptosis and diminished cell cycle restraint. Therefore, p53 mutations select for certain critical features of malignancy. Alteration of P53 is the most common mutation in human cancer. Roughly half of all human malignancies, including many urological cancers, exhibit p53 mutations. In bladder cancer p53 mutations have been associated with higher tumor grade and advanced stage, as well as progression of superficial disease to muscle invasion. Moreover, p53 nuclear over expression appears to be an independent predictor of disease progression and decreased survival after cystectomy.

CONCLUSIONS

The importance of p53 mutation in tumor cell biology is irrefutable. Wild-type p53 mediates imperative functions such as regulation of the cell cycle and programmed cell death. Deficiency of p53 function by mutation or inactivation abrogates normal cell cycle checkpoints and apoptosis, generating a favorable milieu for genomic instability and carcinogenesis. However, despite the manifest importance of p53 in human malignancy, its current role in the management of bladder cancer appears somewhat limited. A multitude of retrospective studies have associated p53 mutations with adverse outcomes in superficial and muscle invasive disease. Nonetheless, randomized prospective studies are needed to determine the potential clinical implications of p53 in bladder cancer.

Prognostic value of p53 overexpression in T1G3 bladder tumors treated with bacillus Calmette-Guérin therapy

OBJECTIVES

To evaluate the correlation between the overexpression of mutant protein p53 and disease recurrence and progression in patients treated with bacillus Calmette-Guérin (BCG) intravesical therapy for T1G3 bladder cancer.

METHODS

We analyzed the outcome of 29 consecutive patients treated for T1G3 bladder tumor with transurethral resection. Patients previously treated for a bladder tumor, those who underwent incomplete resection, and those in whom no assessment of the muscle cell layer was possible were excluded from the study. p53 overexpression was determined using monoclonal p53-DO7 antibody, with a 20% cutoff for definition of positivity. After the initial transurethral resection, all patients were treated with Pasteur BCG (75 mg in 50 mL saline), weekly for 6 weeks. The correlation between p53 overexpression and disease recurrence and progression was assessed by the Fisher exact test.

RESULTS

The median follow-up was 36.7 months (range 1 to 108). Of the 29 patients, 18 (62.1%) were p53 positive and 11 (37.9%) were p53 negative. Both groups were similar according to age, tumoral substage (T1a/T1b), association with carcinoma in situ, multifocality, and length of follow-up. The recurrence rate was 54.4% in the p53-negative group versus 38.9% in the p53-positive group (P = 0.47). The progression rate was 18.2% in the p53-negative group versus 33.3% in the p53-positive group (P = 0.67).

CONCLUSIONS

These findings suggest that overexpression of p53, as determined immunohistochemically, has no predictive value for recurrence and progression in T1G3 bladder cancers treated with intravesical BCG.

Combined p21WAF1/CIP1 and p53 overexpression predict improved survival in muscle-invasive bladder cancer treated by radical radiotherapy

PURPOSE

The prognostic value of p21 and p53 expression was evaluated for patients with muscle-invasive bladder cancer treated by radical radiotherapy.

METHODS AND MATERIALS

Sixty-eight paraffin-embedded sections from surgically resected tumors taken prior to irradiation were immunostained for p21 and p53.

RESULTS

Nuclear staining for p21 and p53 was demonstrated in 32/68 (47%) and 46/68 (68%) tumors, respectively. There was no correlation between p21 and p53 immunopositivity in this group (r = 0.067, p = 0.56). Patients were stratified into four distinct groups depending on staining for p21 and p53: p21+p53+, p21+p53-, p21-p53+, and p21-p53-. Patients with p21+p53+ tumors had the best prognosis with a 3-year survival of 82% compared to 12% for p21-p53+ tumors (p = 0.0031), 29% for p21+p53- tumors (p = 0.0108); and 45% for p21-p53- tumors (p = 0.0375). The p21+p53+ group also demonstrated significantly improved survival when a combined analysis was performed of p21-p53+, p21-p53-, and p21+p53- tumors (3-year survival = 30%, p = 0.0062). In a multivariate model, p21+p53+ tumors (p = 0.0108, relative risk [RR] = 5.18) and complete/partial response (p = 0.0019, RR = 3.76) were the only independent predictors of improved survival.

CONCLUSIONS

With muscle-invasive bladder tumors treated by radical radiotherapy, stratification for p21 and p53 identifies distinct prognostic groups, with p21+p53+ tumors being associated with the best survival and p21-p53+ the worst.

p53, p21 and mdm2 expression vs the response to radiotherapy in transitional cell carcinoma of the bladder

OBJECTIVE

To identify, in a retrospective study, possible molecular markers predictive of radioresponsiveness in patients with transitional cell carcinoma (TCC) of the bladder.

PATIENTS AND METHODS

Patients with T2-T4a TCC treated with preoperative radiotherapy and cystectomy were included in the study if their cystectomy specimen was pT3b (in 42) or pT0 (in 17). Because treatment schedules changed over time, radiotherapy was given either as 2 Gy x 23 over 4-5 weeks with cystectomy 4-5 weeks later (in 23), or as 4 Gy x 5 during 1 week with cystectomy in the following week (in 36 patients). Protein expression of p53, mdm2 and p21 (CDKN1 A/WAF1/CIP1/SDI1) was assessed immunohistochemically in biopsies taken before radiotherapy.

RESULTS

There was no difference in protein expression when comparing all patients with pT0 and pT3b. However, for patients receiving 46 Gy, increased p53 expression (but not p21 or mdm2) predicted the absence of residual tumour (P = 0.005): six of seven patients with > 50% p53 expression had pT0 in the cystectomy specimen, whereas 10 of 12 patients with < or = 5% expression had pT3b. Over-expression of p53 correlated with longer overall (P = 0.045) and cancer-specific survival (P = 0.020).

CONCLUSION

The expression of mdm2 or p21 did not predict radioresponsiveness in patients with TCC of the bladder. The role of p53 remains unclear; the view that p53 over-expression confers radioresistance in bladder cancer is not supported.

p53 immunohistochemistry in bladder cancer. Combined analysis: a way to go?

Seven years after the initial reports of the potential prognostic value of p53 immunohistochemistry in bladder cancer, key questions remain unanswered. This is mainly due to conflicting results obtained through multiple retrospective trials mostly performed with small numbers of poorly defined patients. The aim of this article was to investigate the feasibility of a combined analysis of previously published data. Based on a MEDLINE search in 1997, papers reporting on the prognostic role of p53 alterations were identified and the respective groups were invited to participate. Twenty-six of 38 study centers approached contributed patient data sets according to the protocol requirements. Acceptance of the initiative was similar in Europe, North America, and Australasia. A total of 3,421 patients with bladder cancer from 25 centers are included in the further analysis. With regard to gender, age distribution, and tumor stage the patients contributed are comparable with a normal bladder cancer population. Considering tumor grade, G2 tumors appear to be over- represented while the amount of G1 tumors is smaller than expected. The reason for this is probably related to the low rate of p53 accumulation in G1 tumors. No significant differences between those groups initially approached and those that finally cooperated were noted. Therefore, it is concluded that a combined study is feasible, and the patient data collected are representative for the population presented in the published literature. The final analysis of the data is the subject of current investigation.

Apoptosis, p53, bcl-2, and Ki-67 in invasive bladder carcinoma: possible predictors for response to radiochemotherapy and successful bladder preservation

PURPOSE

Several groups have reported the value of bladder preservation by a combined treatment protocol, including transurethral resection (TUR-B) and radiochemotherapy (RCT). As more experience is acquired with organ-sparing treatment, patient selection should be optimized. The purpose of this study was to investigate the role of several biologic markers that may predict response to RCT in muscle-invasive bladder carcinoma.

METHODS AND MATERIALS

The apoptotic index (AI), Ki-67, p53, and bcl-2 were evaluated by immunohistochemistry on pretreatment biopsies from 70 patients treated for invasive bladder cancer by TUR-B and RCT. Expression of each marker was correlated with initial response, local control, and cancer-specific survival with preserved bladder. An exploratory multivariate analysis was also performed that included clinical and immunohistochemical variables.

RESULTS

A high AI (> median = 1.6%) and a high Ki-67 index (> median = 8.8%), but not the p53- and bcl-2 expression, were significantly related to initial complete response (CR) and local control with preserved bladder after 5 years. When the AI and Ki-67 expression were considered simultaneously, the association with initial CR (p < 0. 001), local control (p = 0.0002), and cancer-specific survival with preserved bladder (p = 0.008) was highly significant. In an exploratory multivariate analysis (final model), only AI, Ki-67, and the combined AI/Ki-67 variable retained significance for local control with preserved bladder at 5 years.

CONCLUSION

Patients with a high spontaneous AI and a high pretreatment Ki-67 index should be considered preferentially for treatment with RCT, whereas tumors with low proliferation and low levels of apoptosis are less likely to respond to RCT.

A critical analysis of the use of p53 as a marker for management of bladder cancer

Delineating the important molecular pathways in carcinogenesis has helped develop and advance the field of molecular diagnosis. Bladder cancer has served as an excellent model in translating some of the advances from the laboratory to clinical settings. Many investigators have examined the use of p53 to help manage patients with bladder cancer who are at high risk of tumor progression. This article reviews the clinical studies that have used p53 as a marker in bladder carcinoma and concludes by determining whether routine assessment of the p53 tumor suppressor gene/protein is indicated at this time.

Radiotherapy in bladder cancer

In the present review, we have evaluated the outcome of radiotherapy in patients with bladder cancer. The exact value of radical radiotherapy is difficult to establish because changes in treatment techniques and selection of patients have biased the results. The 5-year survival rates are reported to be 35-71% in T1 tumors, 27-59% in T2 tumors, 10-38% in T3 tumors and 0-16% in T4 tumors. Several other factors, like performance status and hemoglobin level, are important for the outcome. Morbidity of radical radiotherapy depends on several treatment and patient related factors, but 50-75% experience acute intestinal or urological symptoms and 10-20% may develop severe late toxicity, depending on the kind of registration. The importance of field size or overall treatment time cannot be established from available data. Hyperfractionation with dose escalation has proven effective in one study. Preoperative radiotherapy with cystectomy has not proven better than cystectomy alone or better than radiotherapy alone. The addition of systemic chemotherapy has increased disease-free survival, but has not significantly reduced the rate of distant metastases or improved overall survival. Presently, the standard radiation regimen is a conventional dose and fractionation schedule to a total dose of 60-66 Gy with a three- or four-field technique covering the bladder and tumor. The efficacy of additional irradiation of regional lymph nodes is questionable. New treatment possibilities with advanced techniques of radiotherapy, hyperfractionation and dose escalation and/or the addition of systemic chemotherapy may improve outcome. These options should be further explored in clinical trials.

Regulation of metastasis-related gene expression by p53: a potential clinical implication

Tumor metastasis is the main cause of mortality and treatment failure in cancer patients. It is a complex biological process regulated by alternations in expression of many genes. The p53 tumor suppressor gene has been shown to regulate expression of some metastasis-related genes. p53 transcriptionally activates expression of the genes encoding epidermal growth factor receptor, matrix metalloproteinase (MMP)-2, cathepsin D, and thrombospondin-1 but represses expression of the genes encoding basic fibroblast growth factor and multidrug resistance-1. Decreased expression of E-cadherin is associated with p53 alternations. Because these p53-regulatory genes either promote or inhibit tumor metastasis, the net effect of p53 expression on tumor metastasis depends upon the pattern of expression of these genes in a particular tumor. Because radiotherapy has been shown to increase tumor metastasis in both animal and human studies and because p53 is activated by radiation or DNA-damaging reagents, here we propose the working hypothesis that p53 may promote tumor metastasis upon induction by local radiotherapy or chemotherapy in some tumor types. For patients whose tumors contain wild-type p53, MMP inhibitors might be given with or before radiotherapy or chemotherapy to prevent an increase in tumor metastasis. Special caution should be taken with patients with cancers such as nasopharyngeal carcinoma in which p53 mutation is infrequent and radiotherapy is the main choice of treatment. To test our hypothesis, three studies are proposed and could serve as an initial step in understanding the complex biological process following radiation-induced p53 activation and its roles in regulation of tumor metastasis.

Radiotherapy for oesophagus carcinoma: the impact of p53 on treatment outcome

BACKGROUND AND PURPOSE

Wildtype p53 protein plays an important role in the cellular response to ionizing radiation and other DNA damaging agents and is mutated in many human tumours. We evaluated the relationship of the immunohistochemically determined p53 protein status and the disease control with radiotherapy alone for carcinoma of the oesophagus.

MATERIALS AND METHODS

Immunostaining for p53 protein was performed on paraffin-embedded specimens from 69 patients with adeno- and squamous cell carcinoma of the oesophagus. All patients were treated by radiotherapy exclusively, consisting of a combination of external irradiation and intraluminal brachytherapy, using two different dose levels.

RESULTS

Fifty-four percent (37/69) of the tumours showed overexpression of the p53 protein. No difference in pre-treatment parameters for p53-positive and p53-negative cases was detected. In multivariate analysis p53 was significantly associated with overall survival (OS) next to weight loss, tumour stage and N-stage. For metastatic-free survival (MFS) p53 status proved to be the sole independent prognostic factor. The influence of p53 on local recurrence-free survival (LRFS), however, was not as strong as on OS and MFS.

CONCLUSIONS

Immunohistochemically detected overexpression of mutated p53 protein in oesophagus carcinoma was an independent prognostic factor in a group of patients treated with radiotherapy alone.

Retinoblastoma protein expression and radiation response in muscle-invasive bladder cancer

PURPOSE

The retinoblastoma protein (pRB) is a key regulator of the G1 cell cycle checkpoint and has been implicated as having a role in G1 arrest and apoptosis induced by radiation damage. In this report we examine the association between pRB expression and radiation response in patients treated between 1960 and 1983 with preoperative radiotherapy (50 Gy in 25 fractions) followed 4-6 weeks later by radical cystectomy. The correlation of pRB to patient outcome and how this relationship is complimentary to that seen with p53 staining status is also described.

METHODS AND MATERIALS

Immunohistochemical staining of pRB and p53 in paraffin-embedded tumor sections using WL-1 anti-RB and DO1 anti-p53 antibodies was considered adequate in 98 and 97 pretreatment tumor samples, respectively. There were 46 patients with clinical Stage T2, 28 with Stage T3a, and 24 with Stage T3b disease. The median age was 62 years and follow-up for those living was 85 months.

RESULTS

Staining for pRB was negative in 30% of the cases. Correlations were observed between pRB negativity and high pretreatment apoptosis level (p = 0.06), locally advanced clinical stage (p = 0.01), increased clinical-to-pathologic downstaging (p = 0.014), and more pathologic complete responses (Path-CRs; p = 0.019). Several other factors were tested and were not associated with pRB status, including p53 expression. RB status was the only pretreatment prognostic factor in the univariate analyses that correlated with downstaging and was independently associated with Path-CR using multivariate logistic regression. Despite these significant relationships, no correlations with patient outcome were observed when the entire cohort was analyzed. Restriction of the analyses to Stage T3b patients, however, revealed that pRB negativity predicted for enhanced distant metastasis freedom (p = 0.006, log rank) and overall survival (p = 0.02). The overexpression of p53 also correlated with distant metastasis freedom and overall survival in Stage T3b patients. Patient outcome was best when RB negative and p53 negative staining were seen.

CONCLUSION

Our results indicate that loss of RB function as measured by immunohistochemical staining is the strongest correlate of radiation response thus far recognized. Loss of RB expression also predicted for poor outcome in Stage T3b patients, which appeared to compliment the finding of normal p53 expression. While normal RB protein expression is usually associated with better patient outcome, other series have not examined patients treated with radiotherapy. The absence of pRB may be a useful marker for selecting patients for bladder preservation with radiotherapy, particularly when wild-type p53 is present.