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Keywords:

  • anal cancer;
  • combined chemoradiotherapy;
  • human papillomavirus;
  • prognostic factor;
  • p16

Abstract

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

The prognostic relevance of tumor human papillomavirus (HPV) status in anal squamous cell carcinoma (SCC) had not been previously investigated, although its relevance to cervical, head and neck SCC is known. We retrospectively evaluated outcomes in 47 patients with anal SCC treated with combined chemoradiotherapy (CCRT) and determined tumor HPV status by HPV DNA chip method and p16 expression by immunohistochemistry (IHC) from paraffin-embedded tumor tissues. The median age was 65 years (range, 44–90 years). Sixteen (34%) patients were diagnosed with T stage 3 to 4, and 18 (38%) patients had regional nodal disease (N-positive). Thirty-five (75%) patients were HPV positive, and 31 (66%) patients were genotype 16 (HPV16-positive). Thirty-nine (83.0%) patients were positive for p16. After median follow-up of 51.7 months (range, 5.1–136.0 months), HPV16-positive group had significantly better 4-year progression-free survival (PFS, 63.1% vs. 15.6%, p < 0.001) and overall survival (84.6% vs. 39.8%, p = 0.008) than HPV genotype 16 negative (HPV16-negative) group. Patients with p16-positive tumor also had a better 4-year PFS (52.5% vs. 25.0%, p = 0.014) than those with p16-negative tumor. In multivariate analysis for PFS, N-positive and HPV16-negative were independent prognostic factors for shorter PFS. Comparing patterns of failure, time to loco-regional failure was statistically superior in HPV16-positive over HPV16-negative groups (p = 0.006), but time to systemic failure was not different (p = 0.098). Tumor HPV genotype 16 status is a prognostic and predictive factor in anal SCC treated with CCRT, and p16 expression determined by IHC might be advocated as a surrogate biomarker of HPV integration in anal SCC. Further studies are warranted.

Anal squamous cell carcinoma (SCC) is an uncommon malignancy of the anal canal and perianal skin area. The clinical biology of anal SCC is distinct from other gastrointestinal tract cancers. It is mostly a loco-regional disease at diagnosis, with metastasis in only 15% of patients.1 Therefore, in managing anal cancer, the concerns of treatment strategies include improving loco-regional control and preserving sphincter function. Combined chemoradiotherapy (CCRT) represents the standard of care for patients with anal SCC, because in previous randomized phase III trials, CCRT was found to be associated with improved loco-regional control and reduced the need for colostomy without increasing late complications, when compared to radiation therapy alone.2–4 Several studies seeking to determine the prognostic factors for outcome after CCRT in patients with anal SCC have consistently reported that the T and N stages are important prognostic factors.1–3, 5–7 In addition to the T and N stages, other clinical variables such as gender and age have been suggested to have a prognostic role,2, 5, 6 but their role has not been confirmed. Additionally, some studies have shown that molecular markers including p53,8 p219, 10 and cyclin A9 expression might have a prognostic role, but their role still needs to be more defined.11

Human papillomavirus (HPV) is a group of small, double-stranded deoxyribonucleic acid (DNA) viruses of which approximately 200 genotypes have now been identified.12 HPV, particularly HPV genotype 16, is recognized as an important etiologic factor for anal SCC13–15 and is also implicated in the development of cervical, head and neck SCC.16, 17 In head and neck SCC, particularly oropharyngeal cancer, the role of tumor HPV status is under active investigation. Patients with a HPV-positive tumor have a more favorable prognosis than those whose tumors are HPV-negative,18–20 which might be associated with chemo- or radio-sensitivity of HPV-positive tumors.21, 22 Recently, several studies demonstrated that the p16 expression status determined by immunohistochemical (IHC) staining is a useful surrogate biomarker for HPV integration and predicts the treatment outcome of conventional CCRT in patients with HPV-associated oropharyngeal cancer.19, 20, 23 Moreover, HPV viral load is also a prognostic factor in cervical cancer,24 with high-risk HPV genotypes being detected in greater than 90% of patients.16 However, the prognostic relevance of tumor HPV status in anal SCC had not been investigated yet. Considering the same etiologic factors and similar treatment strategies between these HPV-associated SCCs, we were interested in the prognostic and predictive role of tumor HPV status in anal SCC treated with conventional CCRT.

Thus, in our study, we aimed to investigate the impact of tumor HPV status on progression-free survival (PFS), overall survival (OS) and patterns of treatment failure in patients with anal SCC treated with conventional CCRT.

Material and Methods

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Patients

Between January 1998 and July 2009, patients with histologically proven localized or locally advanced anal SCC who were treated with CCRT and whose paraffin-embedded tumor tissue from the time of diagnosis was available were enrolled at four Korean institutions. The tumor stages ranged from I to IIIB according to the American Joint Committee on Cancer staging. Patients were excluded if they had recurrent/metastatic anal SCC, a positive serology test for human immunodeficiency virus, anal carcinoma in situ or anal intraepithelial neoplasm. Data regarding patient demographics, disease-related characteristics, treatment and treatment outcomes were collected using study-specific case record forms. Our study protocol was approved by the Institutional Review Board (IRB) from each participating institution.

HPV detection and genotyping

DNA extraction.

Genomic DNA was prepared from the formalin-fixed paraffin-embedded tissue using a LaboPass Tissue Mini DNA Purification Kit (Cosmo Genetech, Seoul, Korea). Briefly, the specimen, fixed by paraffin, was cut to 20 μm by a microcutter, and the three consequent sections were transferred to microcentrifuge tubes. Then, two extractions with 1.2 mL of xylenes were performed, and excess xylene was removed by two washes with 1.2 mL of 100% ethanol. Dried tissue samples were then incubated with lysis buffer and proteinase K, provided by the manufacturer, for 30 min at 56°C. Subsequently, the mixture was applied to the spin column and centrifuged into a collection tube according to the method recommended by the manufacturer. The purified DNA was used directly for PCR.

DNA amplification and genotyping of HPV.

DNA amplification and genotyping of HPV were performed using the GG HPV DNA Genotyping Chip Kit (Goodgene, Seoul, Korea). This method contains 22 type-specific probes: 15 probes are high-risk types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68 and 69) and 7 probes are low-risk types (6, 11, 34, 40, 42, 43 and 44). Briefly, DNA amplification was performed in a 2720 Thermal Cycler (Applied Biosystems, Foster City, CA) by PCR with primer sets of target L1 and L2 regions of HPV DNA. A fragment of the human beta-globin gene was also amplified as a control gene. These primer sets and the reaction premixture were provided by the manufacturer. The PCR conditions were, first, initial denaturation for 5 min at 94°C, then 40 cycles that each consisted of 30 sec denaturation at 94°C, primer annealing for 30 sec at 50°C and extension for 30 sec at 72°C. The final step was extension for 30 sec at 72°C. The PCR products were detected by electrophoresis with a 2% agarose gel, and the products were mixed with a reaction buffer, provided by manufacturer, for the hybridization reaction, which was performed in the chamber at 48°C for 30 min. The hybridized signal on the HPV DNA chip was visualized by using a DNA chip scanner (GeneScan; Goodgene, Seoul, Korea).

IHC staining for p16

Five-micrometer sections from paraffin-embedded tissues were analyzed for p16 expression using the CINtec Cytology Kit (MTM laboratory, Heidelberg, Germany). Each paraffin section was deparaffinized, and an antigen retrieval was carried out using 10 mM citrate buffer and microwaved for 10 min. Tissue sections were then incubated with a mouse monoclonal antibody against p16. The antibody use and subsequent steps were performed according to the manufacturer's instruction. Cervical cancer sections known to be HPV positive were used as a positive control, and omission of primary antibody was used as a negative control. Staining was defined as positive if it was strong and diffuse nuclear and cytoplasmic staining in 80% or more of the tumor cells.25

Statistical analysis

The primary endpoints of our study were PFS and OS. The PFS was calculated from the first day of treatment to the date of the first documentation of disease progression or death from any cause or until the date of last follow-up for patients who were still alive and had not progressed. The OS was measured from the first day of treatment to the date of death or the last follow-up. The time to loco-regional failure (TTLF) was defined as the time from the first day of treatment to the date of the first documentation of disease progression within the radiotherapy field or the last follow-up day. The time to systemic failure (TTSF) was defined as the time from the first day of treatment to the date of documented distant metastasis, progression beyond the radiotherapy field, or the last follow-up day. The PFS, OS, TTLF and TTSF were estimated by the Kaplan-Meier method, and comparisons between groups were made using log-rank test.

Descriptive statistics were summarized as frequencies and percentages for categorical variables and as median and range for continuous variables. The comparisons for clinical variables between the HPV genotype 16 positive (HPV16-pos) and HPV genotype 16 negative (HPV16-neg) groups were made using Pearson's χ2 test or Fisher's exact test for categorical variables, and the Mann-Whitney test for continuous variables. Multivariate analysis was carried out using the Cox proportional hazards models. Variables with p < 0.10 in univariate analyses were included in the multivariate model, a forward conditional method was used, and the results were reported with a hazard ratio (HR) and 95% confidence interval (CI). A two-tailed p value of <0.05 was considered statistically significant. All statistical analyses were done using SPSS for Windows, version 12.0 (SPSS, Chicago, IL).

Results

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Patient cohort

We identified 56 patients at four Korean institutions from January 1998 to July 2009 who were diagnosed with invasive anal SCC from stage I to IIIB. Of the 56 patients identified, 50 patients who had been treated with front-line CCRT for anal SCC were screened. Then, three patients were excluded because their paraffin-embedded tumor tissues were not available from the time of diagnosis. Finally, 47 patients, who had been diagnosed with stage I to IIIB invasive anal SCC, treated with CCRT, and had paraffin-embedded tumor tissue available were included in our study.

Patient characteristics

The demographic and clinical characteristics of the patients are summarized in Table 1. Our study included 22 men and 25 women with a median age of 65 years (range, 44–90 years). Eighteen (38.3%) patients had a regional nodal disease, and 16 (34.0%) patients were diagnosed with T stage 3 to 4. Forty (85.1%) patients received combination chemotherapy of mitomycin and fluorouracil for CCRT, and others received the regimen of cisplatin and fluorouracil. The median radiation dose in CCRT was 54.0 Gy (range, 40.0–70.2 Gy), and ten (21.3%) patients were administered less than 50 Gy of radiation. Any induction or consolidation chemotherapy was not given to this cohort (Table 1). During a follow-up period with a median of 51.7 months, 13 patients died and 19 patients had disease progression. Nine patients had a loco-regional failure as an initial progression, six patients had a systemic failure, and four patients had concomitant loco-regional and systemic failure. Nine patients were treated with salvage surgery because of persistent or recurrent anal cancer. Eight patients underwent abdominoperineal resection (APR), and one patient had a colostomy alone. Fifteen patients received salvage systemic chemotherapy after disease progression.

Table 1. Demographics and characteristics of patients and tumors
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HPV detection, genotyping and p16 IHC staining

The HPV status was evaluable in all the 47 patients. The three different HPV genotypes were detected in 35 (74.5%) patients. Thirty-one (66.0%) patients were positive for genotype 16, three (6.4%) patients for genotype 58, and one (2.1%) patient for genotype 35, respectively (Table 2). According to HPV genotype 16 status, our cohort could be divided into HPV16-positive (31 patients, 66.0%) and HPV16-negative (16 patients, 44.0%) groups. The gender, median age, radiation dose, chemotherapy regimen and Eastern Cooperative Oncology Group (ECOG) performance status were not significantly different between the two groups. The T and N stage of the tumor was also not significantly different between groups, but there was a trend of lower T and N stage in the HPV-positive group (Table 1).

Table 2. Human papillomavirus in tumors from 47 patients with anal squamous cell carcinoma as determined by the DNA chip analysis
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The expression of p16 was evaluable in all the 47 patients. Thirty-nine (83.0%) patients had the diffuse and strong staining throughout the nucleus and the cytoplasm and were considered positive for p16 expression (Fig. 1). Twenty-nine (93.5%) of the 31 HPV16-positive patients exhibited the positive p16 IHC staining, indicating a high concordance between the HPV DNA chip results and p16 IHC staining in patients with anal SCC associated with HPV genotype 16. However, the results of IHC staining for p16 were slightly discordant in HPV16-negative patients. Ten of the 16 HPV16-negative patients demonstrated the positive IHC staining for p16. Interestingly, all the four patients with non-16 genotypes (genotype 58 and 35) in our series were positive for p16 expression.

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Figure 1. Representative examples of p16 IHC staining in anal squamous cell carcinoma (×400). (a) p16 expression was strong and diffuse throughout the nucleus and the cytoplasm, which is regarded as positive. (b) p16 staining was negative in both nucleus and cytoplasm, which is considered as negative. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

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Treatment outcomes according to the HPV genotype 16 and p16 expression

With a median follow-up duration of 51.7 months (range, 5.1–136.0 months), the 4-year PFS rate was 47.0% (95% CI, 38.7–55.2), and the 4-year OS rate was 69.2% (95% CI, 61.2–77.2). In the HPV16-positive group, the 4-year PFS and OS rates were 63.1% (95% CI, 53.1–73.1) and 84.6% (95% CI, 76.2–93.0), and the 4-year PFS and OS rates in the HPV16-negative group were 15.6% (95% CI, 5.6–25.7) and 39.8% (95% CI, 26.1–53.4), respectively. HPV16-positive group had significantly better PFS and OS than HPV16-negative group (PFS, p < 0.001; OS, p = 0.008; Figs. 2a and 2b).

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Figure 2. Kaplan-Meier survival curves of (a) PFS, (b) OS, (c) TTLF of patients according to tumor HPV genotype 16 status and (d) PFS of patients based on p16 expression. (a, b) Patients who were HPV16-positive (green line) had significantly better PFS and OS than those who were HPV16-negative (orange line) (PFS, p < 0.001; OS, p = 0.008). (c) TTLF was significantly better for patients who were HPV16-positive (green line) compared to those who were HPV16-negative (orange line) (p = 0.006). (d) Patients with p16-positive tumor (green line) had a better PFS than those with p16-negative tumor (orange line) (p = 0.014). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

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In univariate analysis for PFS, the presence of regional nodal disease (p < 0.001) and HPV16-negativity (<0.001) were related to poor PFS (Table 3). Based on the multivariate analysis, the presence of regional nodal disease (HR, 2.97; 95% CI, 1.19–7.43) and HPV16-negativity (HR, 3.36; 95% CI, 1.35–8.36) were independent prognostic factors for shorter PFS (Table 4). The other risk factor of ECOG performance status for earlier disease progression in the univariate analysis was included in multivariate analysis, but this variable was not a predictive factor for PFS.

Table 3. Univariate analysis for PFS and OS
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Table 4. Multivariate analysis of prognostic factors for PFS and OS
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In univariate analysis for OS, the presence of regional nodal disease (p = 0.006) and HPV16-negativity (p = 0.008) were associated with increased early death (Table 3). However, the presence of regional nodal disease (HR, 4.58; 95% CI, 1.40–14.98) was only an independent prognostic factor for reduced OS (Table 4). The other variables of ECOG performance status and T stage were included in multivariate analysis, but they were not predictive of earlier death.

Comparing patterns of treatment failure, TTLF was statistically superior for patients who were HPV16-positive relative to those who were HPV16-negative [4-year TTLF rate, 76.3% (95% CI, 66.9-85.7) vs. 36.8% (21.3-52.3), respectively; p = 0.006; Fig. 2c]. In contrast, TTSF was not significantly different between the HPV16-positive and the HPV16-negative groups, even though there was a trend toward a higher 4-year TTSF rate in favor of the HPV16-positive group [4-year TTSF rate, 75.6% (95% CI, 65.4–85.8) vs. 55.7% (40.7–70.7), respectively; p = 0.098].

Of the nine patients treated with salvage surgery after loco-regional failure, four patients ultimately died. In this subgroup, the 2-year OS rate after progression was 63.5% (95% CI, 46.6–80.4), and OS after progression was not significantly different between the HPV16-positive and HPV16-negative groups (p = 0.709).

Using p16 expression as a stratification biomarker, which was a well-known biomarker of HPV-oncoprotein, we also found that difference in PFS was consistent with that based on HPV genotype 16 status. Four-year PFS rates of the p16-positive and p16-negative patients were 52.5% (95% CI, 43.3–61.7) and 25.0% (95% CI, 9.7–40.3), respectively (p = 0.014; Fig. 2d). However, OS was not statistically different between p16-positive and p16-negative groups [4-year OS rate, 72.6% (95% CI, 64.0–81.2) vs. 52.5% (95% CI, 31.2–72.9); p = −0.591]. Comparing the patterns of failure based on p16 expression, TTLF was still superior in the p16-positive patients compared to that in the p16-negative patients [4-year TTLF rate, 69.3% (95% CI, 60.0–78.6) vs. 42.9% (95% CI, 24.2–61.6), respectively; p = 0.018], whereas TTSF was not statistically different [4-year TTSF rate, 71.1% (95% CI, 61.8–80.4) vs. 66.7% (47.4–86.0), respectively; p = 0.715].

Discussion

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

The role of high-risk HPV in the etiology of anal SCC has been well established in several population-based epidemiologic studies.13–15 However, the prognostic relevance of tumor HPV status in patients with anal SCC had not been elucidated. In head and neck SCC, particularly oropharyngeal cancer, tumor HPV status is considered as an important predictor of overall and disease-specific survival.18, 26 Recent analysis of the cohort in large randomized clinical trials revealed that oropharyngeal cancer patients with HPV have markedly superior survival after conventional CCRT compared to those who are HPV-negative.19, 20 Additionally, analyses of the patterns of failure reported that they were mainly related to the lower rate of loco-regional failure in patients with HPV-associated oropharyngeal cancer.19, 20 Furthermore, Kim et al.24 reported that the tumor HPV viral load in cervical cancer, in which more than 90% of patients had HPV infection, was a strong independent prognostic factor for disease-free survival. In this sense, we are interested in the impact of tumor HPV status on treatment outcomes in terms of PFS and OS in anal SCC treated with conventional CCRT.

In our present study, 66% of the cohort with anal SCC had the HPV genotype 16, which was associated with better PFS and OS than not having the HPV genotype 16. Interestingly, TTLF was significantly better for HPV16-positive group than for HPV16-negative group, but HPV genotype 16 status did not affect TTSF. This finding suggests that improved PFS and OS in the HPV16-positive group are related to the reduction of loco-regional failure irrespective of systemic failure. This is very similar to recent reports on HPV-associated oropharyngeal cancer,19, 20 which may have a carcinogenic process similar to HPV-associated anal cancer. It has not been well known why HPV positive tumors have better responsiveness to radiotherapy, chemotherapy or both, although the functional integrity of the p53 tumor suppressor pathway among HPV-positive tumors has been suggested as an explanation.27, 28 The wild-type p53 protein product is bound and degraded by HPV oncoprotein E6, but significant amounts of functional p53 are still expressed. Consequently, HPV positive tumors maintain some function of the p53-mediated apoptotic pathway under the stress of chemotherapy or radiotherapy, which might contribute to responsiveness to these treatments.27, 29–31 Tumor HPV status in anal cancer was found to be inversely associated with the presence of a p53 mutation, and thus HPV-associated anal SCC subsequently preserved the function of the p53 pathway.32 Thus, the improved loco-regional control of the HPV16-positive group in our series is likely to be related to these biologic findings. However, despite the molecular background knowledge, conclusions about the impact of HPV genotype 16 status in anal cancer on clinical treatment outcomes could not be drawn from our study because of small sample size, retrospective design and consequent some differences in the distribution of the T and N stage between HPV16-positive and HPV16-negative groups. Therefore, further prospective studies with a large population are warranted.

p16 is an inhibitor of the cyclin-dependent kinase, which is induced as a consequence of pRb inactivation by the HPV E7 gene product.23 The recent understanding of HPV infection as a causative factor of oropharyngeal cancer led to an active investigation on the role of p16 overexpression as a predictive biomarker. Several studies revealed that p16 expression determined by IHC staining was a useful surrogate biomarker for predicting the treatment outcome of conventional CCRT in patients with HPV-associated oropharyngeal cancer.19, 20, 23

In our present study, patients with p16-positive anal SCC had a better PFS and loco-regional control compared to those with p16-negative cancer. Besides, we found that 93.5% of HPV16-positive tumors were positive for p16 IHC staining. Considering these results and relatively similar treatment strategies between oropharyngeal cancer and anal SCC, p16 status in anal cancer might also give important information on treatment outcomes. However, some discrepancy was noted in HPV16-negative patients. Sixty-three percent of HPV16-negative tumors were positive for p16 by IHC staining. This discrepancy was also seen in other HPV-associated oropharyngeal cancer studies,19, 20, 33 which suggested that the discrepancy could be related with the presence of non-16 genotype of HPV and a false negativity of HPV DNA detection method. Actually, all the four patients with non-16 genotypes (genotype 58 and 35) of HPV in our series were positive for p16, representing that a subset of discordant patients (i.e., HPV16-negative by HPV DNA chip method, but p16-positive by IHC staining) might be related with the presence of non-16 genotypes of HPV. The sensitivity of HPV DNA detecting method might also affect this discordance. When we consider the recently raised issue of the low sensitivity in HPV in-situ hybridization method,20 technical problems of the HPV DNA chip method might contribute to this discordance. Nonetheless, our study showed promise of p16 expression status as a surrogate biomarker of HPV integration in patients with anal SCC.

In our study, the HPV genotype 16, which was detected in 66% of tissue tested, was most commonly detected. Previous population-based studies consistently reported that HPV genotype 16 was most frequently associated with anal cancer and was detected in approximately 73–76% of cases.13–15 As above mentioned, the sensitivity of HPV DNA detection method might be related with the difference in detection rates of HPV genotype 16 between previous studies and our series. However, we also suggest possibility that the slightly lower proportion of HPV16-positive tissues in our series may be related to the different inclusion criteria between studies. Previous population-based studies included patients with cloacogenic or basaloid as well as squamous cell histology,13, 14 whereas our study included only squamous cell histology. Daling et al.14 reported that HPV genotype 16 DNA was found in approximately 95% of anal cancers with cloacogenic/basaloid histology. Moreover, even though epidemiologic data on the HPV genotypes of anal cancer in Asia are lacking, the difference in the distribution of HPV genotypes between Asian and non-Asian regions might be attributable to the lower proportion of patients with HPV genotype 16. In our cohort, HPV genotypes 58 and 35 were detected in 8.6% and 2.9%, respectively, while HPV genotype 18 was not found. This was considerably different from the epidemiologic data of anal cancer in Europe, where HPV genotype 18 was the second most commonly detected subtype, and HPV genotypes 58 and 35 were not observed.13 A recent Chinese survey of cervical HPV status in the general population, which could inform us of the prevailing HPV genotypes as causes of anogenital cancer, showed a similar result to our cohort.34 According to this survey, HPV genotypes 16, 58 and 33 were the most prevalent genotypes among approximately 5,500 sexually active women, whereas HPV genotype 18 was the less common subtype in this region. Because our sample size was very small, we could not conclusively predict the patterns of distribution of HPV genotypes in our region. Nevertheless, the differences in the distributions of HPV genotypes in our study might be associated with common HPV subtypes according to geographic location.

The research for prognostic factors in anal cancer treated with CCRT has shown that tumor size and nodal disease status are important prognostic factors.1–3, 6, 7 Recently, a secondary analysis of the US Gastrointestinal Intergroup Radiation Therapy Oncology Group (RTOG) 98-11 study, the largest prospective cohort of anal cancer treated with CCRT to date, reported that nodal disease and large tumor size were independent prognostic factors for disease-free survival and OS.5 In our present analysis, a positive regional nodal status was a consistently independent prognostic factor for PFS and OS, in agreement with the results of the RTOG 98-11. Additionally, our data also demonstrate that tumor HPV genotype 16 status is an independent prognostic factor for PFS. To our knowledge, no other studies have investigated the prognostic relevance of the tumor HPV status in anal SCC to date. However, our analysis found that tumor HPV status did not influence on OS. Although it remains unclear why the prognostic role of tumor HPV genotype 16 status was not evident for OS, the data on the treatment and the clinical outcome of the subgroups of patients who were treated with salvage surgery after loco-regional failure offer some explanations. The preferred treatment for patients with loco-regional failure after CCRT was surgical salvage, especially APR. Although the APR was associated with a relatively high rate of complication, it may result in long-term survival in some patients with the 5-year survival rate of 44–52%.35–37 Data in the current analysis demonstrated that the 2-year OS rate after progression was 63.5%, which is comparable to the previous series, and that the 2-year OS rate after progression was not different between the HPV16-positive and HPV16-negative groups. Absolutely, great caution is needed in interpreting these results because of the extremely small number of patients included in this subgroup analysis. However, considering observations on high rates of long-term survival after salvage APR in anal SCC with loco-regional failure in the previous series, our findings imply that surgical salvage may provide a similar benefit in selected patients regardless of tumor HPV genotype 16 status. Therefore, further analysis of a large number of patients is required to evaluate the true meaning of this finding.

Our study has several limitations. First, our present analysis is a retrospective study with a small number of patients, so unexpected bias may exist. Second, the effects of HPV genotypes other than genotype 16 on CCRT outcomes were not fully addressed because HPV genotypes 58 and 35 were detected in only a minority of patients. Nevertheless, our study is the first to investigate tumor HPV genotype 16 status as a relevant prognostic and predictive factor in patients with anal SCC treated with conventional CCRT.

In conclusion, tumor HPV status should be verified in anal SCC treated with CCRT. Tumor HPV genotype 16 status in anal SCC appears to be a prognostic and predictive factor for CCRT. p16 status might be advocated as a surrogate biomarker of HPV integration in patients with anal SCC. Further prospective studies in large population are required to identify the prognostic role of tumor HPV status.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

The authors thank Dr. Dong Sug Kim for his excellent support in the IHC staining for p16.

References

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  2. Abstract
  3. Material and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References
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