Latin American Consensus on the Treatment of Head and Neck Cancer.

Head and neck squamous cell carcinoma (HNSCC) is well known as a serious health problem worldwide, especially in low-income countries or those with limited resources, such as most countries in Latin America. International guidelines cannot always be applied to a population from a large region with specific conditions. This study established a Latin American guideline for care of patients with head and neck cancer and presented evidence of HNSCC management considering availability and oncologic benefit. A panel composed of 41 head and neck cancer experts systematically worked according to a modified Delphi process on (1) document compilation of evidence-based answers to different questions contextualized by resource availability and oncologic benefit regarding Latin America (region of limited resources and/or without access to all necessary health care system infrastructure), (2) revision of the answers and the classification of levels of evidence and degrees of recommendations of all recommendations, (3) validation of the consensus through two rounds of online surveys, and (4) manuscript composition. The consensus consists of 12 sections: Head and neck cancer staging, Histopathologic evaluation of head and neck cancer, Head and neck surgery-oral cavity, Clinical oncology-oral cavity, Head and neck surgery-oropharynx, Clinical oncology-oropharynx, Head and neck surgery-larynx, Head and neck surgery-larynx/hypopharynx, Clinical oncology-larynx/hypopharynx, Clinical oncology-recurrent and metastatic head and neck cancer, Head and neck surgery-reconstruction and rehabilitation, and Radiation therapy. The present consensus established 48 recommendations on HNSCC patient care considering the availability of resources and focusing on oncologic benefit. These recommendations could also be used to formulate strategies in other regions like Latin America countries.

Survival inequalities in head and neck cancers: A hospital-based cohort study.

BACKGROUND: We investigated whether the socioeconomic status (SES) influenced survival rates in oropharynx cancers (OPC), oral cavity cancers (OCC), and larynx cancers (LC) in Brazilian patients. METHODS: This hospital-based cohort study assessed the age-standardized 5-year relative survival (RS) using the Pohar Perme estimator. RESULTS: Overall, we identified 37 191 cases, and 5-year RS were 24.4%, 34.1%, and 44.9% in OPC, OCC, and LC, respectively. In multiple Cox regression, the highest risk of death occurred in the most vulnerable social strata for all subsites-that is, illiterates or patients relying on publicly funded healthcare services. Disparities increased over time by 34.9% in OPC due to the rising of survival rates in the highest SES, whereas they reduced by 10.2% and 29.6% in OCC and LC. CONCLUSIONS: The potential inequities were more significant for OPC than for OCC and LC. It is urgent to tackle social disparities to improve prognoses in highly unequal countries.

Time to Recurrence as a Prognostic Factor in Parathyroid Carcinoma.

Background: Parathyroid carcinoma (PC) is a rare and challenging disease without clearly understood prognostic factors. Adequate management can improve outcomes. Characteristics of patients treated for PC over time and factors affecting prognosis were analyzed. Methods: Retrospective cohort study including surgically treated patients for PC between 2000 and 2021. If malignancy was suspected, free-margin resection was performed. Demographic, clinical, laboratory, surgical, pathological, and follow-up characteristics were assessed. Results: Seventeen patients were included. Mean tumor size was 32.5 mm, with 64.7% staged as pT1/pT2. None had lymph node involvement at admission, and 2 had distant metastases. Parathyroidectomy with ipsilateral thyroidectomy was performed in 82.2%. Mean postoperative calcium levels were different between patients who developed recurrence vs those who did not (P = .03). Six patients (40%) had no recurrence during follow-up, 2 (13.3%) only regional, 3 (20%) only distant, and 4 (26.6%) both regional and distant. At 5 and 10 years, 79% and 56% of patients were alive, respectively. Median disease-free survival was 70 months. Neither Tumor, Nodule, Metastasis system nor largest tumor dimension (P = .29 and P = .74, respectively) were predictive of death. En bloc resection was not superior to other surgical modalities (P = .97). Time between initial treatment and development of recurrence negatively impacted overall survival rate at 36 months (P = .01). Conclusion: Patients with PC can survive for decades and have indolent disease course. Free margins seem to be the most important factor in initial surgery. Recurrence was common (60%), but patients with disease recurrence within 36 months of initial surgery had a lower survival rate.

Oral squamous cell carcinoma cancer stem cells have different drug sensitive to pharmacological NFκB and histone deacetylation inhibition.

Despite many progresses in the development of new systemic therapies for oral squamous cell carcinoma (OSCC), the five-year survival rate of OSCC is low. The traditional chemotherapies approach (cisplatin - CDDP) shows some limitations like drug toxicity, limited efficacy, and drug resistance. Promising studies suggested OSCC cancer stem cells (CSC) presented resistance to CDDP. We have previously studied many targets, and we extensively showed the efficacy of the NFκB signaling and the role of histones acetylation, on different malignant tumors, including adenoid cystic carcinoma and mucoepidermoid carcinoma, but until then the effects of the NFkB inhibitor and histone deacetylase (HDAC) inhibitor on the biology of OSCC were not evaluated. Here we assessed the pharmacological inhibitor of NFκB emetine and HDAC inhibitor SAHA on the behavior of CSC derived from OSCC. Our data suggested that CDDP administration resulted in reduced viability of bulk OSCC cells and increased CSC. A single and isolated shot of emetine and SAHA were able to disrupt CSC by inhibiting the NFκB pathway and increasing the histone acetylation levels, respectively. Further, the combined administration of emetine and SAHA presented the same CSC disruption as seen in emetine alone.

Tumor glycolytic profiling through 18F-FDG PET/CT predicts immune checkpoint inhibitor efficacy in advanced NSCLC.

Background: A significant proportion of patients with non-small-cell lung cancer (NSCLC) do not respond to immune checkpoint inhibitors (ICIs). Since metabolic reprogramming with increased glycolysis is a hallmark of cancer and is involved in immune evasion, we used 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) to evaluate the baseline glycolytic parameters of patients with advanced NSCLC submitted to ICIs, and assessed their predictive value. Methods: 18F-FDG PET/CT results in the 3 months before ICIs treatment were included. Maximum standardized uptake values, whole metabolic tumor volume (wMTV), and whole-body total lesion glycolysis (wTLG) were evaluated. Cutoff values for high or low glycolytic categories were determined using receiver-operating characteristic curves. Progression-free survival (PFS) and overall survival (OS) were evaluated. Patients with a complete response and a matching group with resistance to ICIs underwent immunohistochemistry analysis. An unsupervised k-means clustering model integrating programmed cell death ligand 1 (PD-L1) expression, glycolytic parameters, and ICIs therapy was performed. Results: In all, 98 patients were included. Lower baseline 18F-FDG PET/CT parameters were associated with responses to ICIs. Patients with low wMTV or wTLG had improved PFS and OS. High wTLG, strong tumor expression of glucose transporter-1, and lack of responses were significantly associated. Patients with low glycolytic parameters benefited from ICIs, regardless of chemotherapy. Conversely, those with high parameters benefited from the addition of chemotherapy. Patients with higher wTLG and lower PD-L1 were associated with progression and worse survival to ICIs monotherapy. Conclusions: Glycolytic metabolic profiles established through baseline 18F-FDG PET/CT are useful biomarkers for evaluating ICI therapy in advanced NSCLC.

Brief Report: Exploratory Analysis of Maintenance Therapy in Patients With Extensive-Stage SCLC Treated First Line With Atezolizumab Plus Carboplatin and Etoposide.

INTRODUCTION: In the phase 1/3 IMpower133 study, atezolizumab plus carboplatin and etoposide (CP/ET) followed by maintenance atezolizumab for first-line treatment of extensive-stage SCLC (ES-SCLC) led to improvement in both overall survival (OS) and progression-free survival (PFS) versus placebo plus CP/ET followed by maintenance placebo. We explored the benefit of atezolizumab versus placebo in the subset of patients who reached the IMpower133 maintenance phase and the safety profile of maintenance therapy. METHODS: Patients with untreated ES-SCLC were randomized 1:1 to four 21-day cycles of CP/ET with atezolizumab or placebo, followed by maintenance atezolizumab or placebo. The primary end points were OS and investigator-assessed PFS. A multivariate Cox model from the start of maintenance treatment was used to evaluate the treatment effect and account for lead-time bias; a generalized linear model was used to identify prognostic or predictive characteristics for reaching the maintenance phase. RESULTS: A similar proportion of patients in each arm received at least the first dose of maintenance therapy (atezolizumab: 77%, n = 154 of 201; placebo: 81%, n = 164 of 202) and were included in the maintenance analysis population. An Eastern Cooperative Oncology Group performance status of 0 and absence of liver metastases at baseline were identified as prognostic factors for reaching the maintenance phase. The positive treatment effect with atezolizumab remained after adjusting for baseline characteristics. Median OS and PFS from the start of maintenance therapy in the atezolizumab versus placebo arm were 12.5 versus 8.4 months (hazard ratio = 0.59, 95% confidence interval: 0.43-0.80) and 2.6 versus 1.8 months (hazard ratio = 0.63 [95% confidence interval: 0.49-0.80]), respectively. Treatment-related adverse events from the start of maintenance therapy occurred in 41% (n = 64 of 155) and 25% (n = 41 of 163) of safety-evaluable patients in the atezolizumab and placebo arms, respectively, and were grade 3 or 4 in 28% (n = 43 of 155) and 23% (n = 37 of 163) of the respective populations; no patient in the atezolizumab arm and one patient in the placebo arm had a grade 5 treatment-related adverse event. CONCLUSIONS: These data in the context of other immunotherapy trials in ES-SCLC suggest that induction with atezolizumab plus CP/ET and maintenance treatment with atezolizumab are important components that contributed to the OS benefit observed in IMpower133. Safety results from randomization and from the start of maintenance therapy were similar between the treatment arms despite the continuation of atezolizumab in the maintenance phase.

Cephaeline is an inductor of histone H3 acetylation and inhibitor of mucoepidermoid carcinoma cancer stem cells.

AIM: To evaluate the potential use of Cephaeline as a therapeutic strategy to manage mucoepidermoid carcinomas (MEC) of the salivary glands. MATERIAL AND METHODS: UM-HMC-1, UM-HMC-2, and UM-HMC-3A MEC cell lines were used to establish the effects of Cephaeline over tumor viability determined by MTT assay. In vitro wound healing scratch assays were performed to address cellular migration while immunofluorescence staining for histone H3 lysine 9 (H3k9ac) was used to identify the acetylation status of tumor cells upon Cephaeline administration. The presence of cancer stem cells was evaluated by the identification of ALDH enzymatic activity by flow cytometry and through functional assays using in vitro tumorsphere formation. RESULTS: A single administration of Cephaeline resulted in reduced viability of MEC cells along with the halt on tumor growth and cellular migration potential. Administration of Cephaeline resulted in chromatin histone acetylation as judged by the increased levels of H3K9ac and disruption of tumorspheres formation. Interestingly, ALDH levels were increased in UM-HMC-1 and UM-HMC-3A cell lines, while UM-HMC-2 showed a reduced enzymatic activity. CONCLUSION: Cephaeline has shown anti-cancer properties in all MEC cell lines tested by regulating tumor cells' viability, migration, proliferation, and disrupting the ability of cancer cells to generate tumorspheres.

Induction Chemotherapy for Advanced Oral Cavity Cancer.

PURPOSE OF REVIEW: Head and neck cancer is a heterogeneous disease, comprising multiple subsites with diverse etiologic factors, pathology and molecular features, response to treatment, and prognosis. Systemic treatment is usually incorporated in the management of locally advanced head and neck squamous cell carcinoma, and the use of induction chemotherapy has theoretical benefits on reducing the risk of distant metastasis, provide an in vivo testing of response and tumor biology and the potential to allow a more personalized and less toxic local treatment after downstaging. The aim of this review is to access the role of induction chemotherapy in patients with locally advanced oral cavity cancer. RECENT FINDINGS: Clinical trials analyzing this treatment strategy in patients with resectable disease, followed by surgery, and in unresectable disease, followed by (chemo)radiotherapy or surgery are discussed, pointing out strengths and limitations of this data and highlighting the standard treatment in each clinical scenario. Future perspectives, including the incorporation of checkpoint inhibitors and biomarkers for patient selection are discussed. Surgery followed by (chemo)radiation is the standard of care for resectable oral cavity cancer patients, and chemoradiation is the standard for those considered as unresectable. Future trials with the incorporation of immunotherapy and better patient selection based on clinical and molecular biomarkers can bring new hopes for better therapeutic results in these patients.

Letter to the editor: radiomics analysis for predicting pembrolizumab response in patients with advanced rare cancers.

A commentary on the original research article: 'Radiomics analysis for predicting pembrolizumab response in patients with advanced rare cancers'. Of note, the predictor selection process, the cross-validation method, along with the lack of final testing of the developed model with a separated data set may mask overfitting, overestimating performance metrics.

Blood First Assay Screening Trial (BFAST) in Treatment-Naive Advanced or Metastatic NSCLC: Initial Results of the Phase 2 ALK-Positive Cohort.

INTRODUCTION: The Blood First Assay Screening Trial is an ongoing open-label, multicohort study, prospectively evaluating the relationship between blood-based next-generation sequencing (NGS) detection of actionable genetic alterations and activity of targeted therapies or immunotherapy in treatment-naive advanced or metastatic NSCLC. We present data from the ALK-positive cohort. METHODS: Patients aged more than or equal to 18 years with stage IIIB or IV NSCLC and ALK rearrangements detected by blood-based NGS using hybrid capture technology (FoundationACT) received alectinib 600 mg twice daily. Asymptomatic or treated central nervous system (CNS) metastases were permitted. Primary end point was investigator-assessed objective response rate (ORR; Response Evaluation Criteria in Solid Tumors version 1.1). Secondary end points were independent review facility-assessed ORR, duration of response, progression-free survival (PFS), overall survival, and safety. Exploratory end points were investigator-assessed ORR in patients with baseline CNS metastases and relationship between circulating biomarkers and response. RESULTS: In total, 2219 patients were screened and blood-based NGS yielded results in 98.6% of the cases. Of these, 119 patients (5.4%) had ALK-positive disease; 87 were enrolled and received alectinib. Median follow-up was 12.6 months (range: 2.6-18.7). Confirmed ORR was 87.4% (95% confidence interval [CI]: 78.5-93.5) by investigator and 92.0% (95% CI: 84.1-96.7) by independent review facility. Investigator-confirmed 12-month duration of response was 75.9% (95% CI: 63.6-88.2). In 35 patients (40%) with baseline CNS disease, investigator-assessed ORR was 91.4% (95% CI: 76.9-98.2). Median PFS was not reached; 12-month investigator-assessed PFS was 78.4% (95% CI: 69.1-87.7). Safety data were consistent with the known tolerability profile of alectinib. CONCLUSIONS: These results reveal the clinical application of blood-based NGS as a method to inform clinical decision-making in ALK-positive NSCLC.

SARS-CoV-2 testing for asymptomatic adult cancer patients before initiating systemic treatments: a systematic review.

INTRODUCTION: Cancer patients may have a higher risk of severe events and unfavourable outcomes in the setting of COVID-19. This review addresses the question of whether to test asymptomatic cancer patients before initiating systemic cancer treatments. METHODS: This systematic review was conducted based on the PRISMA framework. Pubmed, Embase, Web of Science and Cochrane Central Register of Controlled Trials were systematically searched, as well as guidelines from international institutions involved in cancer care and COVID-19 research. Studies published in English, from 1 December 2019 to 27 May 2020 were considered eligible. We included studies which mentioned testing strategies for SARS-CoV-2 of asymptomatic cancer patients before starting immunosuppressive treatments. RESULTS: We identified 1,163 studies and 4 guidelines through the literature search. A total of 18 articles were considered eligible and were included in the final analysis. Two articles were cohort studies, and the remaining were expert consensuses and published guidelines. The most common recommendation among the studies in this systematic review was to test asymptomatic patients for SARS-CoV-2 prior to treatment. CONCLUSION: There is a lack of studies which directly address COVID-19 testing of asymptomatic patients before treatment. Our systematic review showed that most of the published data favours routine test for SARS-CoV-2 before initiating systemic treatment but failed to identify a good level of evidence to support these recommendations. Based upon this review, we proposed local recommendations at our centre. Each institution should consider the pros and cons of testing asymptomatic patients, evaluating accessibility to testing resources and local epidemiology.

Influence of time between surgery and postoperative radiation therapy and total treatment time in locoregional control of patients with head and neck cancer: a single center experience.

OBJECTIVE: This study aimed to evaluate the effect of the delay to initiate postoperative radiation therapy (RT) on locoregional control to head and neck squamous cell carcinoma patients. METHODS: Retrospective cohort study that included patients submitted to surgery followed by adjuvant RT (with/without chemotherapy). The time interval between surgery and RT was dichotomized by the receiver operating characteristics curve method at 92 days. Other possible sources of heterogeneity with potential impact on locoregional control were explored by regressive analysis. RESULTS: A total of 168 patients were evaluated. The median time for locoregional recurrence (LRR) was 29.7 months. The relapse-free survival rates were 66.4% and 75.4% for patients who initiated RT more than and within 92 postoperative days (p=0.377), respectively. Doses lower than 60Gy were associated with worse rates of locoregional control (HR=6.523; 95%CI:2.266-18.777, p=0.001). Patients whose total treatment time (TTT) was longer than 150 days had LRR rate of 41.8%; no patient with TTT inferior to 150 days had relapses (p=0.001). CONCLUSIONS: The interval between surgery and RT did not show influence on locoregional control rates. However, doses <60Gy and the total treatment time >150 days were associated with lower locoregional control rates.

Young head and neck cancer patients are at increased risk of developing oral mucositis and trismus.

OBJECTIVES: To evaluate cancer treatment-related toxicities in young head and neck cancer (HNC) patients. MATERIAL AND METHODS: A total of 44 patients were included in the present retrospective cohort study, which was designed to access oral toxicities of cancer treatment in young (< 45 years of age, Group I, n = 22) and old (> 58 years of age, Group II, n = 22) HNC patients with similar tumor stage and treatment protocols. Oral mucositis (OM), xerostomia, dysphagia, dysgeusia, trismus, and radiodermatitis were assessed during days 7th, 21st, and 35th of head and neck radiotherapy (HNRT) according to previously validated scales (World Health Organization criteria and the National Cancer Institute and Common Terminology Criteria for Adverse Events version 4.0). RESULTS: Patients from both groups showed high incidence and severity of oral toxicities by the end of the HNRT with OM (81.9% (Group I); 63.6% (Group II)) and xerostomia (72.6% (Group I); 77.2% (Group II)) being the most prevalent toxicities. No differences regarding xerostomia, dysphagia, dysgeusia, and radiodermatitis incidences or severity could be observed between groups. However, higher incidences and severity of OM at 21st and 35th fractions (odds ratio = 2.22 and 5.71, respectively) and trismus at 21st and 35th fractions (odds ratio = 6.17 and 14.5, respectively) were observed throughout the treatment in young patients when compared to older patients (p < 0.01 and p < 0.05, respectively). CONCLUSION: Young HNC patients are more affected by cancer treatment-related OM and trismus despite the similarities in clinical staging and treatment protocols with elderly patients.

Influence of time between surgery and postoperative radiation therapy and total treatment time in locoregional control of patients with head and neck cancer: a single center experience

OBJECTIVE: This study aimed to evaluate the effect of the delay to initiate postoperative radiation therapy (RT) on locoregional control to head and neck squamous cell carcinoma patients. METHODS: Retrospective cohort study that included patients submitted to surgery followed by adjuvant RT (with/without chemotherapy). The time interval between surgery and RT was dichotomized by the receiver operating characteristics curve method at 92 days. Other possible sources of heterogeneity with potential impact on locoregional control were explored by regressive analysis. RESULTS: A total of 168 patients were evaluated. The median time for locoregional recurrence (LRR) was 29.7 months. The relapse-free survival rates were 66.4% and 75.4% for patients who initiated RT more than and within 92 postoperative days (p=0.377), respectively. Doses lower than 60Gy were associated with worse rates of locoregional control (HR=6.523; 95%CI:2.266-18.777, p=0.001). Patients whose total treatment time (TTT) was longer than 150 days had LRR rate of 41.8%; no patient with TTT inferior to 150 days had relapses (p=0.001). CONCLUSIONS: The interval between surgery and RT did not show influence on locoregional control rates. However, doses <60Gy and the total treatment time >150 days were associated with lower locoregional control rates.

Molecular basis of oral squamous cell carcinoma in young patients: Is it any different from older patients?

Oral squamous cell carcinoma (OSCC) is the commonest subtype of oral cancer, mainly affecting older patients. It used to be a rare disease among individuals younger than 40 years, but recently increased incidences in this age group are being reported worldwide. The pathogenesis of OSCC affecting young patients remains controversial, and the well-known etiological factors for oral cancer, tobacco, and alcohol use are believed to play a minor role in the carcinogenesis of the neoplasm, suggesting that the etiology and the molecular basis of OSCC may differ between younger and older patients. Although several molecular markers and chromosomal abnormalities have been demonstrated to differ between both groups, most of the studies have failed to find significant differences. Moreover, divergent results have also been obtained regarding the presence of high-risk human papillomavirus infection in OSCC of young patients. Given these contradictory results and the limited methodological approaches of the majority of the studies, the exact difference between both age groups remains to be fully established. In this review, we evaluate the available data to establish the current evidence that might support the hypothesis that the molecular basis of OSCC in young patients (especially those under 40 years) differ from the older patients.

A randomised phase II study of chemoradiotherapy with or without nimotuzumab in locally advanced oesophageal cancer: NICE trial.

PURPOSE: Chemoradiotherapy is the standard treatment for patients with inoperable locally advanced oesophageal cancer. We sought to assess the safety and efficacy of chemoradiation combined with nimotuzumab, a humanised antibody directed against epidermal growth factor receptor (EGFR). PATIENTS AND METHODS: Untreated patients with inoperable locally advanced oesophageal cancer and no distant metastases were randomised to chemoradiotherapy (cisplatin and fluorouracil combined with external beam radiation) alone or in combination with nimotuzumab. The primary end-point was the endoscopic complete response (eCR) rate, and secondary end-points comprised quality of life (QoL) and safety. The combined eCR and pathologic complete response (cEPCR) and overall survival (OS) were also evaluated. RESULTS: We enrolled 107 patients with a mean age of 59 years, and 93% had squamous cell carcinoma. Toxicity was manageable in both arms with no important differences in adverse events (AEs). We performed post-treatment endoscopies in 67 patients, including 60 who had a biopsy. In the intent-to-treat population, the eCR rates with and without nimotuzumab were 47.2% and 33.3% (P = 0.17), respectively, and the cEPCR rates were 62.3% and 37.0% (P = 0.02), respectively. With a median follow-up of 14.7 months, the hazard ratio (HR) for OS was 0.68 (95% confidence interval (CI): 0.44-1.07; P = 0.09) with a median OS of 15.9 months for the nimotuzumab arm and 11.5 months for the control arm. Regarding QoL, a significant difference was observed for the physical subscale score (P = 0.03) with lower values for the control arm. CONCLUSION: Combined chemoradiotherapy plus nimotuzumab is safe for patients with locally advanced oesophageal cancer, it appears to increase the cEPCR rate, and without compromising QoL. CLINICAL TRIALS: Identification number: EF024-201; Trial registry: NCT01249352.

Precision oncology: as much expectations as limitations.

It is encouraging to witness the recent price reduction and expanded access to next generation sequencing platforms, the increasing number of investments and publications on new targets and respective targeted drugs, as well as the worldwide excitement with anti-cancer personalised therapies. This editorial aims to highlight the limitations regarding the small proportion of solid cancers potentially eligible for the use of molecular-based targeted drugs until now. It also covers the expected clinical benefits in refractory patients treated by matched therapies, and detailed cost-effectiveness analysis of the use of DNA sequencing analysis oncology practice in an academic and large-scale community.

Head and neck radiotherapy does not increase gelatinase (metalloproteinase-2 and -9) expression or activity in teeth irradiated in vivo.

OBJECTIVE: Recent studies suggested that head and neck radiotherapy increases active forms of matrix metalloproteinases (MMPs) in the dentin-enamel junction (DEJ), leading to enamel delamination and radiation-related caries. This study aimed to assess the expression and activity of the gelatinases MMP-2 and MMP-9 in the DEJ and dentin-pulp complex tissues of teeth irradiated in vivo. STUDY DESIGN: Thirty-six teeth were studied, including 19 irradiated and 17 non-irradiated controls. In situ zymography was used to investigate the gelatinolytic activity in the micromorphologic components of enamel, DEJ, dentin-pulp complex, and caries. Immunohistochemical analysis was conducted on the demineralized samples to assess MMP-2 and MMP-9 expression levels in the DEJ, dentin-pulp complex components, and caries. RESULTS: No statistically significant differences were detected between groups in gelatinolytic activity or in MMP-2 expression levels (P > .05). Odontoblast MMP-9 expression was reduced in the irradiated group (P = .02). CONCLUSIONS: The study rejected the hypothesis that MMP-2 and MMP-9 would be overexpressed or more activated in the DEJ and dentin-pulp complex of irradiated teeth. Direct effects of radiation should not be regarded as an independent factor for explaining radiation-related caries onset and progression.

Postradiation Matrix Metalloproteinase-20 Expression and Its Impact on Dental Micromorphology and Radiation-Related Caries.

Recent evidence suggests that head-and-neck radiotherapy (HNRT) increases active forms of matrix metalloproteinase-20 (MMP-20) in human tooth crowns, degrading the dentin-enamel junction (DEJ) and leading to enamel delamination, which is a pivotal step in the formation of radiation-related caries (RRC). Additional participation of enzymatic degradation of organic matrix components in caries progression was attributed to MMP-20 in dentin. Therefore, the current study tested the hypothesis that MMP-20 is overexpressed in the DEJ, dentin-pulp complex components, and carious dentin of post-HNRT patients, leading to detectable micromorphological changes to the enamel and dentin. Thirty-six teeth were studied, including 19 post-HNRT specimens and 17 nonirradiated controls. Optical light microscopy was used to investigate the micromorphological components of the DEJ, dentin-pulp complex components, and carious dentin. The samples were divided into 2 subgroups: nondemineralized ground sections (n = 20) and demineralized histological sections (n = 16). In addition, immunohistochemical analysis using the immunoperoxidase technique was conducted to semiquantitatively assess MMP-20 expression in the DEJ, dentin-pulp complex components, and carious dentin. No apparent damage to the DEJ microstructure or other dentin-pulp complex components was observed and no statistically significant differences were detected in MMP-20 expression (p > 0.05) between the irradiated and control groups. This study rejected the hypothesis that MMP-20 is overexpressed in the DEJ, dentin-pulp complex components, and carious dentin of post-HNRT patients, leading to detectable micromorphological changes. Hence, direct effects of radiation may not be regarded as an independent factor to explain aggressive clinical patterns of RRC.