Anal carcinoma: a clinical approach to p53 and RB gene proteins

HPV positive, wild type TP53, and p16 overexpression correlate with the absence of residual tumors after chemoradiotherapy in anal squamous cell carcinoma

Background

Anal residual tumors are consensually identified within six months of chemoradiotherapy and represent a persistent lesion that may have prognostic value for overall survival. The aim of this study was to evaluate the association of HPV and HIV status, p16 expression level and TP53 mutations with the absence of residual tumors (local response) in Squamous Cell Carcinoma (SCC) of the anal canal after chemoradiotherapy.

Methods

We performed a study on 78 patients with SCC of the anal canal who submitted to chemoradiotherapy and were followed for a six-month period to identify the absence or presence of residual tumors. HPV DNA was identified by polymerase chain reaction and direct sequencing, HIV RNA was detected by TaqMan amplification, p16 expression was detected by western blotting, and the mutational analysis of TP53 was performed by direct sequencing; additionally, samples carrying mutations underwent fluorescent in sit hybridization. The evaluation of the tumor response to treatment was conducted six months after the conclusion of chemoradiotherapy. The following classifications were used to evaluate the outcomes: a) no response (presence of residual tumor) and b) complete response (absence of residual tumor).

Results

The significant variables associated with the absence of residual tumors were HPV positive, p16 overexpressed, wild-type TP53, female gender, and stages I and II. Only the presence of HPV was independently correlated with the clinical response; this variable increased the chances of a response within six months by 31-fold.

Conclusions

The presence of HPV in tumor cells was correlated with the absence of a residual tumor. This correlation is valuable and can direct future therapeutic approaches in the anal canal.

Background and Current Treatment of Squamous Cell Carcinoma of the Anus

In this review, a summary of our current understanding of squamous cell carcinoma of the anus (SCCA) and the advances in our knowledge of SCCA regarding screening, prevention, the role of the immune system, current treatment and the potential for novel targets are discussed. The present standard of care in terms of treatment is 5-fluorouracil (5-FU) and mitomycin C (MMC) concurrently with radiation, which results in a high level of disease control for small early cancers. Preservation of the anal sphincter is achieved in the majority, although anorectal function is often impaired. Although evidence from prospective studies to support a change in the treatment strategy is lacking, patients with HPV-negative SCCA appear to be less responsive to chemoradiation (CRT) and relapse more frequently. In contrast, HPV-positive tumours usually fare better, but oncological outcomes are modified by smoking and immune incompetence. There is current interest in escalating the radiotherapy dose for larger, more advanced tumours, and de-escalating treatment for HPV-positive tumours. The use of novel immunological treatments to target the underlying different molecular pathways of HPV-positive cancers is exciting.

Prospective phase II study of tomotherapy based chemoradiation treatment for locally advanced anal cancer

BACKGROUND AND PURPOSE

To evaluate toxicity, local control, and survival of anal cancer patients treated with helical tomotherapy (HT) and concurrent 5-fluorouracil and mitomycin-C (5FU/MMC).

MATERIALS AND METHODS

Fifty-seven patients were treated with HT and concurrent 5FU/MMC. The planning objectives were to deliver 54 Gy to the tumor (PTV54) and 45 Gy to the nodes at risk (PTV45) in 30 fractions. Patients were reviewed for toxicity weekly during HT, every 6 weeks for 3 months, and then every 3-4 months for 5 years.

RESULTS

The median follow-up was 40 months. The median age was 58 years (range: 37-83). Stage distribution: stage II-48%, IIIA-18%, IIIB-34%. The majority of patients developed ⩽ grade 2 acute toxicity scores. The most common ⩾ grade 3 acute toxicity was neutropenia (40%). Common late toxicities were grade 2 anal incontinence (16%) and telangiectasia (12%). The 3 year colostomy-free survival rate was 77% (95% CI: 61-87%), 3 year disease-free survival rate was 80% (CI: 66-89%), and 3 year overall survival was 91% (CI: 77-96%).

CONCLUSIONS

Incorporation of HT with concurrent 5FU/MMC had low treatment-related acute and late morbidity with few treatment breaks. However, the expected dosimetric benefit for hematological toxicity was not experienced clinically.

Prognostic biomarkers in squamous cell carcinoma of the anus: a systematic review

BACKGROUND

recent decades have seen combination chemoradiotherapy become the standard treatment for anal squamous cell carcinoma (SCC). However, the burden of this disease continues to rise, with only 10% of patients with metastatic disease surviving >2 years. Further insight into tumour characteristics and molecular biology may identify novel therapeutic targets. This systematic review examines current prognostic markers in SCC of the anus.

METHODS

an extensive literature search was performed to identify studies reporting on biomarkers in anal cancer in the context of clinical outcome following treatment primarily with chemoradiotherapy.

RESULTS

in all, 21 studies were included. A total of 29 biomarkers were studied belonging to 9 different functional classes. Of these biomarkers, 13 were found to have an association with outcome in at least one study. The tumour-suppressor genes p53 and p21 were the only markers shown to be of prognostic value in more than one study.

CONCLUSIONS

an array of biomarkers have been identified that correlate with survival following chemoradiotherapy in anal cancer. However, investigators are yet to identify a biomarker that has the ability to consistently predict outcome in this disease. Further studies are needed to elucidate whether these candidate biomarkers demonstrate their optimum value when they serve as targets for new therapeutic strategies.

Expression of p16, Rb, and p53 proteins in squamous cell carcinomas of the anorectal region harboring human papillomavirus DNA

Human papillomavirus (HPV) has been implicated as an etiologic agent for the development of squamous cell carcinoma of the anorectal region. It has been shown that the HPV E6 and E7 oncoproteins are able to inactivate the tumor suppressor functions of p53 and Rb. In cervical and head and neck cancers, HPV infection is also associated with an overexpression of p16, a cyclin-dependent kinase inhibitor. The expression of these cell cycle regulators in squamous cell carcinomas of the anorectal region has not been well studied. In the current study, 29 cases of squamous cell carcinoma of the anorectal region were immunohistochemically examined for the expression of p16, Rb, and p53 proteins. Tumor cell DNA was also extracted from paraffin blocks and subjected to broad-spectrum HPV DNA testing and typing. The results show that the tumor cells exhibited a strong and diffuse nuclear stain (with some cytoplasmic positivity) for p16 in all 29 cases (100%). The adjacent nonneoplastic squamous epithelium or colonic mucosa, in contrast, was completely negative. Loss of Rb nuclear staining in tumor cells was observed in 20 cases (69%). The p53 protein was essentially undetectable, with only 6 cases containing <10% positive cells. HPV DNA was detected in every case (100%), with 25 cases (86%) harboring Type 16. In addition, almost identical results were obtained in 12 HPV-positive squamous cell carcinomas of the upper aerodigestive tract. This was in marked contrast to those of HPV-negative tumors, where positive p16 staining and loss of Rb expression were seen in only 2/21 (10%) and 1/21 (5%) cases, respectively. These observations indicate that overexpression of p16 and loss of Rb nuclear staining are commonly associated with high-risk HPV infection, which may serve as useful surrogate biomarkers for identifying squamous cell carcinomas harboring HPV DNA.

Prognostic factors in anal carcinoma

The pathologist's role in the evaluation of patients with anal squamous carcinoma is now largely restricted to establishing the diagnosis on small biopsies. Staging is performed by imaging techniques and grading is uncertain as the biopsy may not be representative of the whole tumour. Histological subtyping is unreliable and has not been proven to be of prognostic significance. A considerable effort resulting in nearly 50 reports on cytogenetic, flow cytometric, immunohistochemical and other investigations has given new insight into pathogenesis but little guidance with regard to the individual prognosis or choice of treatment. It is concluded that future research should concentrate on larger, probably multicentre series using standardised methods and criteria for evaluation.

Reduced expression of p21WAF1 is an indicator of malignant behaviour in anal carcinomas

AIMS

p21 and p27 protein expression were examined in a comparatively large series of patients with squamous cell carcinoma of the anal canal and compared with clinical and histopathological data (tumour stage, nodal status and differentiation).

METHODS AND RESULTS

We analysed the expression of p21 and p27 protein in 94 anal carcinomas by immunohistochemistry. Nuclear p21 and p27 staining were detected in 71% (67/94) and 75% (71/94) of the cases, respectively. There was no significant association between p27 staining and tumour stage, nodal status or overall survival. We observed that negative p21 immunoreactivity was significantly associated with poorly differentiated anal carcinomas. Furthermore, a shorter overall survival for patients with no p21 protein expression was seen.

CONCLUSIONS

Our data indicate that p21 levels, but not p27 expression, may be a useful predictor of survival in patients with anal carcinomas.

Prognostic role of p53 protein expression in epidermoid carcinoma of the anal canal

PURPOSE

To assess the prognostic significance of p53 protein expression in patients with primary epidermoid carcinoma of the anal canal managed by radiation therapy (XRT), 5-fluorouracil (5-FU), and mitomycin C (MMC).

METHODS AND MATERIALS

From January 1991 to December 1993, 58 consecutive patients with primary epidermoid carcinoma of the anal canal were treated in a prospectively designed protocol of XRT (24 Gy/12--3(1/2) wk split--28 Gy/14) and concurrent 5-FU (1000 mg/m2/day 1-4) and MMC (10 mg/m2 day 1) of each cycle of XRT. Paraffin-embedded tumor samples were unavailable in 9 patients, leaving 49 patients in the study. Expression of p53 protein was studied using immunohistochemistry and quantified as percent tumor nuclei showing positive staining. Actuarial survival and disease-free survival (DFS) rates were estimated by the Kaplan-Meier method, and compared using the log-rank test. A Cox proportional hazard model was used for the multivariable analysis.

RESULTS

There were 6 T1, 26 T2, 7 T3, and 10 T4 lesions. Primary tumor sizes ranged from 1-15 cm with a median of 4 cm. There were 6 patients with nodal metastases. Median follow-up was 4.5 years. Positive nuclear immunostaining for p53 was observed in 40 of 49 patients. The median percent positive staining was 5%, with 13, 9, and 18 patients showing staining in <5%, 5 to <10%, and 10-50% of tumor nuclei respectively. There was no correlation of percent p53 staining with gender, age, tumor stage, size, or histology. Local, regional, and distant failures were observed in 12, 2, and 2 patients respectively. The 5-yr survival and DFS were 84% and 64% respectively. In univariate analysis, the only prognostic variable for survival was gender. For DFS, advanced T category and large tumor size were predictive of poor DFS. In multivariate analysis, poor DFS was associated with high T category (p = 0.0008), basaloid histology (p = 0.001), male gender (p = 0.002), and increasing percent of p53 protein expression (p = 0.01).

CONCLUSIONS

It is concluded that expression for p53 protein is present in a high percentage of patients with epidermoid carcinoma of the anal canal. For patients managed with combined XRT, 5-FU, and MMC, percent p53 protein expression is of prognostic value for DFS independent of other clinical factors such as T category, gender, and histology.