Sentinel node biopsy after neoadjuvant therapy: Relevance of sentinel node micrometastases, isolated tumor cells, and value of immunohistochemistry

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Background: Sentinel node biopsy (SNB) is used in breast cancer patients that present with clinically negative nodes. In this setting, most guidelines do not support the use of immunohistochemistry (IHC) and recommend against completion node dissection (CND) when only isolated tumor cells (pN0(i+)) or micrometasases (pN1mi) are identified. When SNB is used after neoadjuvant therapy (NAT), the relevance of ypN0(i+) and ypN1mi sentinel nodes (SNs) and the value of IHC are not well established. The goals of this study are to determine if CND should be recommended in the presence of ypN0(i+) or ypN1mi SNs and if IHC should be used to evaluate SNs after NAT. Methods: From March 2009 to December 2012, 152 women with biopsy proven node positive breast cancer were accrued to the multicentric prospective SN FNAC trial. After NAT, SNB was followed by a CND in all participants. SNs were cut in serial slices no thicker than 2 mm. Hematoxylin and eosin stains (H and E) were done on all slices, and if negative, IHC was used. The size of the largest SN metastasis and the primary method of identification (H and E or IHC) were recorded. ypN0(i+), ypN1mi and ypN1 SNs were considered as positive. Pathology was centrally reviewed. Results: 145 women were eligible for the trial. Axillary pathologic complete response rate = 34% (49/145). SNB success rate = 88% (127/145). False negative rate = 8.4% (7/83). If ypN0(i+) SNs are classified as node negative, the false negative rate is increased to 13.3% (11/83). For patients with ypN0(i+) (n=7), ypN1mi (n=8) and ypN1 (n=61) SNs, the rates of non-SN involvement are 57%, 38% and 56% respectively (p=NS). 40% (27/68) of positive SNBs are primarily detected by IHC. This is increased to 64% (9/14) for the identification of SN metastases ≤ 2mm. Conclusions: After NAT, particularly when presenting with biopsy proven node positive breast cancer, patients with ypN0(i+) and ypN1mi SNs have a significant rate of non-SN involvement. In the absence of evidence to show that a CND can be safely avoided, efforts should be made to identify even minimal amounts of disease when SNBs are done following NAT. IHC is useful to increase the detection of small SN metastases in this setting. Clinical trial information: NCT00909441.

Sentinel node biopsy following neoadjuvant chemotherapy in biopsy proven node positive breast cancer: The SN FNAC study

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Background: A significant and increasing proportion of patients (>30%) with biopsy proven node positive breast cancer will obtain a pathological complete response (pCR) in the axilla after neoadjuvant chemotherapy (NAC). If sentinel node biopsy (SNB) can accurately identify these patients, they could potentially avoid the morbidity of an axillary node dissection. The primary aim of this study is to evaluate the identification rate (IR), false negative rate (FNR) and accuracy of SNB in this setting. The accuracy of post NAC axillary ultrasound and clinical examination are evaluated as secondary endpoints. Methods: Patients with biopsy proven node positive breast cancer (T0-3, N1-2, M0) treated with NAC were eligible to participate in this multi-centre prospective trial. Following NAC, axillary ultrasound and clinical examination results were obtained. At time of surgery, all participants underwent both a SNB and a completion node dissection. A SNB IR greater than 90% and a FNR of less than 10% were pre-determined as being optimal. Results: From September 2009 to December 2012, 153 patients were accrued to the study. 7 patients were not eligible and 5 patients had not yet undergone surgery at the time of analysis. Axillary pCR rate = 34.0% (48/141). SNB IR = 87.2% (123/141), 95% CI [81.7%-92.7%] and FNR = 9.9% (8/81), 95% CI [3.4%-16.4%]. If only one sentinel node was removed, FNR = 19.0%(4/21); if there were 2 or more sentinel nodes, FNR = 6.6% (4/61) (p < 0.0001). Accuracy of SNB, axillary ultrasound and clinical examination were 93.5%, 63.2%, and 45.5% respectively. Conclusions: SNB following NAC in biopsy proven node positive breast cancer is associated with a suboptimal IR. FNR (less than 10%) and accuracy of SNB in this study are comparable to that of patients that present with clinically negative nodes. The FNR decreases when more than one sentinel node is identified. However, in an era where regional nodal radiation is increasingly used, the relevance of leaving residual disease in the undissected axilla after NAC is unknown and remains to be investigated. Clinical trial information: NCT00909441.

Prospective cohort study of chemotherapy-induced alopecia with or without scalp cooling

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Background: Scalp cooling can prevent chemotherapy-induced alopecia. Success varies according to the type of chemotherapy. A controversy exists regarding the use of scalp cooling because of the lack of efficacy data with modern chemotherapy regimen and safety data. We present a prospective cohort study design to measure alopecia. Methods: The prospective study was conducted at the Centre des Maladies du Sein Deschênes-Fabia (CMS) in Quebec City (where scalp cooling is offered routinely and 85% of women use it) and at the Centre Hospitalier Universitaire de Montreal (CHUM), in Montreal (where scalp cooling is not available). Women were eligible if they were going to receive neoadjuvant or adjuvant chemotherapy for breast cancer. The study involved completion of questionnaires (on degree of alopecia, hair type, hair care, use of head accessories, tolerance to scalp cooling and questions related to sick leave from work) and having pictures taken at baseline, cycle 3 and at the last cycle of chemotherapy. For the last 43 patients, the EORTC QLQ-C30/BR23 and an adaptation for Hairdex were added. Results: A total of 136 patients were recruited (110 at CMS over 2 years and 26 at the CHUM over a 9-month period). Preliminary efficacy results are shown in the Table (data on quality of life have not yet been analyzed). Hair preservation was defined as a SUCCESS for hair loss (since the beginning of chemotherapy) characterized as “not at all”, “a little” or “moderate” and “FAILURE” when characterized as “a lot” or “all” or “hair shaved”. Overall, in the scalp cooling group, 34% were considered a “success” using hairdresser evaluation and 49% using patient evaluation; for the non scalp-cooling group, these rates were 9% and 4% respectively. Conclusions: Scalp cooling appears to be efficacious for preventing chemotherapy-induced alopecia in this exploratory cohort study. [Table: see text]

Pharmacokinetics of intraperitoneal irinotecan in a pig model

Complete surgical cytoreduction of peritoneal implants and immediate intraperitoneal (lP) chemotherapy offers the greatest survival in selected patients with peritoneal carcinomatosis. This study was undertaken to describe the metabolism and pharmacokinetics of normothermic intraperitoneal CPT-11, free and glucuronized SN-38, in a pig model. Thirteen pigs were used for experimentation. Animals were grouped for IV and IP CPT-1 1 administration. Eleven pigs underwent laparotomy through a midline incision and instillation of 100, 200, and 400mg IP CPT-11. Systemic venous blood, portal blood and peritoneal fluid samples were taken at 5, 10, 20, 30, and 45 min, then every hour up to 8 hr for the 100 mg. For the three groups, peritoneal CPT-11 exposition was on average 4.9 times greater in the peritoneum than in the systemic venous or portal circulations and the systemic CPT-11 fraction absorbed from the peritoneum linearly increased with time. Free SN-38 was measurable in the earliest peritoneal samples taken. The initial instillation dose of CPT-11 did not impact on the SN-38 converted fraction, which remained stable at approximately 0.04% during the first 4 hour. Mean peritoneal SN-38: CPT-11 AUC ratio was 0.043. OPT-11 peritoneal conversion into SN-38 appeared slightly Inferior to the systemic conversion ratio. This norrnothermic IP OPT-11 pharmacokinetic study performed in a pig model confirms the possibility to achieve at least a 30 times higher peritoneal than systemic exposure. Peritoneal exposure to active SN-38 begins at the moment of CPT-11 peritoneal instillation. A fixed and small traction of less than 0.1% of CPT-11 is converted into SN-38, underlying the importance of a sufficient initial IP dose of CPT-11.

Merkel cell carcinoma of the hand: case report and literature review

We are reporting on a 72-year-old male who was diagnosed with Merkel cell carcinoma on the dorsal aspect of his left index finger. This rare highly aggressive malignancy of the skin has only exceptionally been described on the finger or hand. This case report helps review important findings associated with this rare malignancy and reviews the pertinent literature.

The contribution of founder mutations to early-onset breast cancer in French-Canadian women

In an ethnically-homogeneous population, it is valuable to identify founder mutations in cancer-predisposing genes. Founder mutations have been found in four breast-cancer-predisposing genes in French-Canadian breast cancer families. The frequencies of the mutant alleles have been measured neither in a large series of unselected breast cancer patients from Quebec, nor in healthy controls. These estimates are necessary to measure their contribution to the hereditary burden of breast cancer in Quebec and to help develop genetic screening policies which are appropriate for the province. We studied 564 French-Canadian women with early-onset invasive breast cancer who were treated at a single Montreal hospital. Patients had been diagnosed at age 50 or less, and were ascertained between 2004 and 2008. We screened all 564 patients for nine founder mutations: four in BRCA1, three in BRCA2 and one each in PALB2 and CHEK2. We also studied 6433 DNA samples from newborn infants from the Quebec City area to estimate the frequency of the nine variant alleles in the French-Canadian population. We identified a mutation in 36 of the 564 breast cancer cases (6.4%) and in 35 of 6443 controls (0.5%). In the breast cancer patients, the majority of mutations were in BRCA2 (54%). However, in the general population (newborn infants), the majority of mutations were in CHEK2 (54%). The odds ratio for breast cancer to age 50, given a BRCA1 mutation, was 10.1 (95% CI: 3.7-28) and given a BRCA2 mutation was 29.5 (95% CI: 12.9-67). The odds ratio for breast cancer to age 50, given a CHEK2 mutation, was 3.6 (95% CI: 1.4-9.1). One-half of the women with a mutation had a first- or second-degree relative diagnosed with breast or ovarian cancer. Thus, it can be concluded that a predisposing mutation in BRCA1, BRCA2, CHEK2 or PALB2 is present in approximately 6% of French-Canadian women with early-onset breast cancer. It is reasonable to offer screening for founder mutations to all French-Canadian women with breast cancer before age 50. The frequency of these mutations in the general population (0.5%) is too low to advocate population-based screening.

The Contribution of Founder Mutations to Early-Onset Breast Cancer in French-Canadian Women

Background: In an ethnically-homogeneous population, it is valuable to identify founder mutations in cancer-predisposing genes. Founder mutations have been found in four breast cancer predisposing genes in French-Canadian breast cancer families. The frequencies of the mutant alleles have not been measured in a large series of unselected breast cancer patients from Quebec, nor in healthy controls. These estimates are necessary to measure their contribution to the hereditary burden of breast cancer in Quebec and to help develop genetic screening policies which are appropriate for the province.Methods: We studied 564 French-Canadian women with early-onset invasive breast cancer who were treated at a single Montreal hospital. Patients had been diagnosed at age 50 or less, and were ascertained between 2004 and 2008. We screened all 564 patients for nine founder mutations; four in BRCA1, three in BRCA2 and one each in PALB2 and CHEK2. We also studied 6433 DNA samples from newborn infants from the Quebec City area to estimate the frequency of the nine variant alleles in the French-Canadian population.Results: We identified a mutation in 36 of the 564 breast cancer cases (6.4%) and in 35 of 6443 controls (0.5%). In the breast cancer patients, the majority of mutations were in BRCA2 (54%). However, in the general population (newborn infants), the majority of mutations were in CHEK2 (54%). The odds ratio for breast cancer to age 50, given a BRCA1 mutation was 10.1 (95% CI: 3.7 to 28) and given a BRCA2 mutation was 29.5 (95% CI: 12.9 – 67). The odds ratio for breast cancer to age 50, given a CHEK2 mutation was 3.6 (95% CI: 1.4 – 9.1). One-half of the women with a mutation had a first or second-degree relative diagnosed with breast or ovarian cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 902.

Drugs, carrier solutions and temperature in hyperthermic intraperitoneal chemotherapy

At the Fifth International Workshop on Peritoneal Surface Malignancy, in Milan, the consensus on technical aspects of cytoreductive surgery (CRS) for peritoneal surface malignancy was obtained through the Delphi process. Conflicting points concerning drugs, carrier solution and optimal temperature for hyperthermic intraperitoneal chemotherapy (HIPEC) were discussed.

The Delphi approach to Attain consensus in methodology of local regional therapy for peritoneal surface malignancy

At the Fifth International Workshop on Peritoneal Surface Malignancy (PSM), held in Milan, December 2006, the consensus on technical aspects of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) was obtained through the Delphi process. The following topics were discussed: pre-operative workup; eligibility to CRS + HIPEC; intra-operative staging system; technical aspects of surgery; residual disease classification systems; HIPEC: nomenclature and modalities; drugs, carrier solution and optimal temperature; morbidity grading systems. Conflicting points regarding above-mentioned topics were elaborated and voted in two rounds by a panel of international experts in local-regional therapy. The purpose of this manuscript is to describe the organization and the methodology of the consensus statements and to interpret and discuss the implications of the most striking results.

Incidence of Postoperative Pancreatic Fistula and Hyperamylasemia after Cytoreductive surgery and Hyperthermic Intraperitoneal Chemotherapy

INTRODUCTION

The purpose of this study was to analyze the postoperative pancreatic morbidity of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) in the treatment of peritoneal surface malignancies (PSM).

PATIENTS AND METHODS

Two hundred and sixty five patients (87M/178F) with PSM underwent 270 consecutive procedures. The mean age was 52 years (range: 22-79 years). CRS was performed using peritonectomy procedures. HIPEC through the closed abdomen technique was conducted using cisplatin (CDDP 25 mg/m2/L of perfusate)+mitomycin C (MMC 3.3 mg/m2/L of perfusate) or CDDP (43 mg/L of perfusate)+doxorubicin (Dx 15.25 mg/L of perfusate), at 42.5 degrees C. Diagnosis and classification of postoperative pancreatic fistula (POPF) were performed according to the international study group on pancreatic fistula criteria. Serum amylase alterations were graded according to the National Cancer Institute (NCI) common terminology criteria for adverse events (CTCAE) v3.

RESULTS

POPF was observed in 13 (4.8%) cases. Three cases were classified as major (grade C). Two cases presented postoperative pancreatitis. G3-4 alteration of amylase was observed in 12.3% of the cases. Performing splenectomy and CDDP dosage for HIPEC >240 mg were proven to be independent risk factors for both G3-4 hyperamylasemia and POPF.

CONCLUSIONS

CRS+HIPEC presented an acceptable rate of pancreatic morbidity which did not contribute to the mortality related to the procedure. Most of the POPF were mild and/or easily controlled by conservative measures. Although not specific a normal amylasemia could be a useful marker of pancreatic integrity after CRS+HIPEC.

Impact of Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy on Systemic Toxicity

INTRODUCTION

The purpose of this study was to analyze the postoperative systemic toxicity and procedure-related mortality (PRM) of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) in the treatment of peritoneal surface malignancies (PSMs).

PATIENTS AND METHODS

A total of 242 (84 males/158 females) patients with PSM underwent 247 consecutive procedures. The mean age was 52 years (range 22-79). CRS was performed using peritonectomy procedures. The HIPEC technique through the closed abdomen was conducted with cisplatin (CDDP 25 mg/m(2)/l of perfusate)+mitomycin C (MMC 3.3 mg/m(2)/l perfusate) or CDDP (43 mg/l perfusate)+doxorubicin (Dx 15.25 mg/l perfusate) at 42.5 degrees C. These dosages were reduced by 30% when the patient had received systemic chemotherapy before the CRS+HIPEC. Systemic toxicities were graded according to the NCI CTCAE v3 criteria.

RESULTS

G3-5 systemic toxicity rate was 11.7 % and adverse events were bone marrow suppression, 13; nephrotoxicity, 14; neutropenic infection, 2 and pulmonary toxicity, 1. Independent risk factors for G3-5 systemic toxicity after multivariate analysis were a dose of CDDP for HIPEC of 240 mg or more (OR 2.78, CI 95% 1.20-6.45) and CDDP+Dx schedule for HIPEC (OR 2.36, CI 95% 1.02-5.45). PRM was 1.2%.

CONCLUSIONS

CRS+HIPEC presented acceptable systemic toxicity and PRM rates. Independent risk factors for systemic toxicity were the CDDP+Dx schedule and CDDP dose for HIPEC.

CDX-2 expression in pseudomyxoma peritonei: a clinicopathological study of 42 cases

AIMS

CDX-2 is a highly sensitive and specific marker of intestinal epithelial cells and their neoplastic counterparts. CDX-2 status in pseudomyxoma peritonei (PMP) has been barely reported. The aim of this study was to investigate the clinicopathological features of 42 cases of PMP with a special emphasis on CDX-2.

METHODS AND RESULTS

All patients were treated by cytoreduction. Immunohistochemistry was performed for CDX-2, MUC-2, MUC-5AC, cytokeratin (CK) 7 and CK20. Statistical correlation was evaluated for age, sex, completeness of cytoreduction and histological subtype with overall and progression-free survival (OS and PFS). PMP consisted of 32 cases of disseminated peritoneal adenomucinosis and 10 cases of peritoneal mucinous carcinomatosis. The appendix evaluated in 25 cases showed two mucinous adenocarcinomas and 21 low-grade appendiceal mucinous neoplasms. CDX-2 was diffusely positive in 40 cases, with the remaining two cases being focally positive. All cases demonstrated diffuse reactions to CK20 and MUC-2, and variable reactions to MUC-5AC, while CK7 was variably positive in 38 cases. Five-year OS was 97%. Histological type was significantly correlated with PFS (P=0.02).

CONCLUSIONS

CDX-2 is diffusely and strongly positive in PMP. This is a useful marker to confirm an appendiceal origin of PMP, particularly when used in conjunction with CK7, CK20, MUC-2 and MUC-5AC.

Cytoreduction combined with intraperitoneal hyperthermic perfusion chemotherapy in advanced/recurrent ovarian cancer patients: The experience of National Cancer Institute of Milan

AIMS

We report the effects of cytoreductive surgery (CRS) and intraperitoneal hyperthermic perfusion (IPHP) in the treatment of advanced/recurrent epithelial ovarian cancer (EOC) on survival, morbidity and mortality.

PATIENTS

Forty EOC patients were studied. Median age was 52.5 years (range: 30-68) and median follow-up 26.1 months (range: 0.3-117.6). Most patients presented advanced disease (stage III/IV). Previous systemic chemotherapy included cisplatin-based, taxol-based or taxol/platinum containing regimens.

RESULTS

After the CRS, 33 patients presented no macroscopic residual disease. Five-year overall survival was 15%; the mean overall and progression-free survivals were 41.4 and 23.9 months, respectively. The morbidity, toxicity and mortality rates were 5%, 15% and 0%, respectively.

CONCLUSION

Our results suggest that CRS + IPHP merits further evaluation by a formal prospective trial.

Cytoreductive surgery followed by intraperitoneal hyperthermic perfusion: analysis of morbidity and mortality in 209 peritoneal surface malignancies treated with closed abdomen technique

BACKGROUND

The purpose of this prospective Phase II study was to analyze morbidity and mortality of cytoreductive surgery (CRS) and intraperitoneal hyperthermic perfusion (IPHP) in the treatment of peritoneal surface malignancies.

METHODS

A total of 205 patients (50 with peritoneal mesothelioma, 49 with pseudomyxoma peritonei, 41 with ovarian cancer, 32 with abdominal sarcomatosis, 13 with colon cancer, 12 with gastric cancer, and 8 with carcinomatosis from other origins) underwent 209 consecutive procedures. Four patients underwent the intervention twice because of disease relapse. There were 70 men and 135 women. Mean age was 52 years (range, 22-76 yrs). CRS was performed by using peritonectomy procedures. IPHP through the closed abdomen technique was conducted with a preheated (42.5 degrees C) perfusate containing cisplatin + mitomycin C or cisplatin + doxorubicin.

RESULTS

Major morbidity rate was 12%. The most significant complications were 23 anastomotic leaks or bowel perforations, 4 abdominal bleeds, and 4 sepses. Operative mortality rate was 0.9%. On logistic regression model multivariate analysis, extent of cytoreduction (odds ratio [OR], 2.88; 95% confidence interval [CI], 1.29-6.40) and dose of cisplatin for IPHP > or = 240 mg (OR, 3.13; 95% CI, 1.24-7.90) were independent risk factors for major morbidity. Ten patients presented with Grade 3 to 4 toxicity.

CONCLUSIONS

CRS + IPHP presented acceptable morbidity, toxicity, and mortality rates, all of which support prospective Phase III clinical trials.

Prognostic analysis of clinicopathologic factors in 49 patients with diffuse malignant peritoneal mesothelioma treated with cytoreductive surgery and intraperitoneal hyperthermic perfusion

BACKGROUND

Diffuse malignant peritoneal mesothelioma (DMPM) is a subset of peritoneal mesothelioma with a poor clinical outcome. We performed a prognostic analysis in a cohort of DMPM patients treated homogeneously by cytoreductive surgery and intraperitoneal hyperthermic perfusion (IPHP).

METHODS

Forty-nine DMPM patients who underwent 52 consecutive procedures were enrolled onto the study. Cytoreductive surgery was performed according to the peritonectomy technique, and the IPHP was performed with cisplatin plus doxorubicin or cisplatin plus mitomycin C. We assessed the correlation of the clinicopathologic variables (previous surgical score, age, sex, performance status, previous systemic chemotherapy, carcinomatosis extension, completeness of cytoreduction, IPHP drug schedule, mitotic count [MC], nuclear grade, and biological markers [epidermal growth factor receptor, p16, matrix metalloproteinase 2 and matrix metalloproteinase 9]) with overall and progression-free survival.

RESULTS

The mean age was 52 years (range, 22-74 years). The mean follow-up was 20.3 months (range, 1-89 months). Regarding the biological markers, the rates of immunoreactivity of epidermal growth factor receptor, p16, matrix metalloproteinase 2, and matrix metalloproteinase 9 were 94%, 60%, 100%, and 85%, respectively. The strongest factors influencing overall survival were completeness of cytoreduction and MC, whereas those for progression-free survival were performance status and MC. No biological markers were shown to be of prognostic value.

CONCLUSIONS

Completeness of cytoreduction, performance status, and MC seem to be the best determinants of outcome. These data warrant confirmation by a further prospective formal trial. No biological markers presented a significant correlation with the outcome. The overexpression of epidermal growth factor receptor, matrix metalloproteinase 2, and matrix metalloproteinase 9 and absent or reduced expression of p16 might be related to the underlining tumor kinetics of DMPM and warrant further investigation with other methods.

Diffuse malignant mesothelioma of the peritoneum: a clinicopathological study of 35 patients treated locoregionally at a single institution

BACKGROUND

In the current study, the authors report the clinicopathologic features of patients with peritoneal diffuse malignant mesothelioma (DMM) who were treated in a uniform fashion at a single institution to assess prognostic factors.

METHODS

Thirty-five patients were treated with cytoreductive surgery (CRS) and intraperitoneal hyperthermic perfusion (IPHP). The tumors were classified into epithelial, sarcomatoid, and biphasic types. Immunohistochemistry stains were performed for calretinin, WT-1, pCEA, Ber-EP4, epidermal growth factor receptor (EGFR), p16, matrix metalloprotease-2 (MMP-2), and MMP-9. Statistical correlation was evaluated for age, gender, completeness of cytoreduction (CC), tumor histotype, mitotic count (MC), necrosis, nuclear grade (NG), and biologic markers with regard to overall survival (OS) and progression-free survival (PFS).

RESULTS

The patient group was comprised of 15 men and 20 women with a median age of 52 years (range, 24-73 yrs). Twenty-five patients underwent optimal cytoreduction. There were 32 epithelial tumors and 3 biphasic tumors, and 3 patients had an NG of 1, 19 had an NG of 2, and 13 had an NG of 3. The mean MC was 14.1 (range, 0-160 per 50 high-power fields). Necrosis was present in 11 cases. All the tumors were found to be positive for calretinin and WT-1 and were negative for pCEA and Ber-EP4. The NG and MC were found to be significantly associated with OS (P = 0.02 and P = 0.01, respectively) whereas CC was found to be associated with both OS (P = 0.05) and PFS (P = 0.03). No biologic markers were found to be of prognostic significance.

CONCLUSIONS

The results of the current study indicate that NG, MC, and CC may be useful prognostic factors in patients treated with CRS and IPHP. The expression of EGFR, MMP-2, and MMP-9 and absent and/or reduced expression of p16 in DMMs confirms the results of previous studies suggesting their role in tumor pathogenesis and kinetics.