Disparities and guideline adherence for HPV testing among patients with oropharyngeal squamous cell carcinoma, NCDB, and SEER

BACKGROUND

Human papilloma virus testing for oropharyngeal squamous-cell carcinoma has been recommended by the National Comprehensive Cancer Network since 2012. We examine disparities, reported rates of human papillomavirus (HPV) testing, and the impact on these findings of limitations with the variable in database registries.

METHODS

The HPV variable was queried for patients with oropharyngeal squamous carcinoma (OPSCC) from 2013 to 2016 in National Cancer Data Base (NCDB) and Surveillance, Epidemiology, and End Results (SEER). Multivariable regression was used to identify disparities based on sociodemographic variables. Sensitivity analyses were used to investigate limitations of the variable.

RESULTS

Despite limitations in the HPV variable in the databases, there was less than 100% adherence to recommended testing, and there were significant disparities in multiple sociodemographic variables. For example, in NCDB 70% of white versus 60.4% of black patients were tested (odds ratio [OR] 0.75, confidence interval [CI] 0.66-0.85, p ≤ 0.0001); in SEER 59.8% of white and 47.6% of black patients were tested (OR 0.73, CI 0.67-0.81; p ≤ 0.0001).

CONCLUSIONS

Disparities exist among patients undergoing testing for HPV-associated OPSCC and adherence to guideline recommended HPV testing has been suboptimal. In addition, the HPV variable definition, especially as it relates to p16 positivity, and use in these two registries should be improved.

Any day, split halfway: Flexibility in scheduling high-dose cisplatin-A large retrospective review from a high-volume cancer center

High-dose (HD) cisplatin remains the standard of care with chemoradiation for locally advanced oropharyngeal cancer (OPC). Cooperative group trials mandate bolus-HD (100 mg/m²  × 1 day, every 3 weeks) cisplatin administration at the beginning of the week to optimize radiosensitization-a requirement which may be unnecessary. This analysis evaluates the impact of chemotherapy administration day of week (DOW) on outcomes. We also report our institutional experience with an alternate dosing schedule, split-HD (50 mg/m²  × 2 days, every 3 weeks). We retrospectively reviewed 435 definitive chemoradiation OPC patients from 10 December 2001 to 23 December 2014. Those receiving non-HD cisplatin regimens or induction chemotherapy were excluded. Data collected included DOW, dosing schedule (bolus-HD vs split-HD), smoking, total cumulative dose (TCD), stage, Karnofsky Performance Status, human papillomavirus status and creatinine (baseline, peak and posttreatment baseline). Local failure (LF), regional failure (RF), locoregional failure (LRF), distant metastasis (DM), any failure (AF, either LRF or DM) and overall survival (OS) were calculated from radiation therapy start. Median follow-up was 8.0 years (1.8 months-17.0 years). DOW, dosing schedule and TCD were not associated with any outcomes in univariable or multivariable regression models. There was no statistically significant difference in creatinine or association with TCD in split-HD vs bolus-HD. There was no statistically significant association between DOW and outcomes, suggesting that cisplatin could be administered any day. Split-HD had no observed differences in outcomes, renal toxicity or TCD compared to bolus-HD cisplatin. Our data suggest that there is some flexibility of when and how to give HD cisplatin compared to clinical trial mandates.

The head and neck cancer genome in the era of immunotherapy

The recent success of immunotherapy in head and neck squamous cell carcinoma (HNSCC) has necessitated a new perspective on the cancer genome. Here we review recent advances in the carcinogenesis and molecular genetics of HNSCC with an eye on their implications for cancer immunity. Newer sequencing technologies have recently facilitated dissection of the complex interaction between the HPV virus, tumor, host factors, and the tumor microenvironment (TME) that help shed light on how the immune system interacts with head and neck malignancies.

The 3 Bs of cancer care amid the COVID-19 pandemic crisis: "Be safe, be smart, be kind"-A multidisciplinary approach increasing the use of radiation and embracing telemedicine for head and neck cancer

Because of the national emergency triggered by the coronavirus disease 2019 (COVID-19) pandemic, government-mandated public health directives have drastically changed not only social norms but also the practice of oncologic medicine. Timely head and neck cancer (HNC) treatment must be prioritized, even during emergencies. Because severe acute respiratory syndrome coronavirus 2 predominantly resides in the sinonasal/oral/oropharyngeal tracts, nonessential mucosal procedures are restricted, and HNCs are being triaged toward nonsurgical treatments when cures are comparable. Consequently, radiation utilization will likely increase during this pandemic. Even in radiation oncology, standard in-person and endoscopic evaluations are being restrained to limit exposure risks and preserve personal protective equipment for other frontline workers. The authors have implemented telemedicine and multidisciplinary conferences to continue to offer standard-of-care HNC treatments during this uniquely challenging time. Because of the lack of feasibility data on telemedicine for HNC, they report their early experience at a high-volume cancer center at the domestic epicenter of the COVID-19 crisis.

Abstract PR05: APOBEC mutagenesis is tightly linked to the immune landscape and immunotherapy biomarkers in head and neck squamous cell carcinoma

Significant interest is focused on the immune microenvironment of head and neck squamous cell carcinoma (HNSCC) due in part to the recent success of immune modulating therapeutics. HNSCC is known to be an immunologically active tumor with immune cell infiltration levels among the highest of all cancers, high mutational burden, and a subset of patients who respond to immune checkpoint blockade. One of the primary sources of mutations in HNSCC is the cytidine deaminase APOBEC3, which is also a known factor in innate immunity. Why particular HNSCCs have higher rates of APOBEC mutations and how these mutations relate to the immune microenvironment and immune activation remain unknown. We utilized whole-exome and RNA-Seq datasets from 276 HNSCC patients from TCGA to annotate APOBEC mutations, immune cell populations, activating and end effectors of immunity and predict neoantigens. In combination with FFPE tissue sections from matched patients, patient demographic data and germline APOBEC polymorphism status, we interrogated the relationship between APOBEC mutations and the immune landscape. Immune cell populations and composite scores of immune activation and infiltration (IFNy score, CYT score, Estimate Immune score) are tightly associated with APOBEC mutational burden, both univariately and after controlling for HPV status (p = 0.013-0.014). HNSCC has the highest levels of IFNy across cancer types with high APOBEC mutational burden, with the highest IFNy scores in HPV mediated HNSCC (HPVmHNSCC) (p = 0.05). Similarly, PD-L1 expression is positively associated with APOBEC mutational burden (p = 0.04). Mutation-induced tumor-specific neoantigen burden is strongly associated with APOBEC mutational burden while other sources of neoantigens are not associated (p = 8e-12). The presence of a germline APOBEC gene polymorphism is more prevalent in non-white, non-black race patients and within this group, patients with the polymorphism have higher APOBEC mutational burden (p= 0.002). Taken together, these data suggest that multiple mechanisms may exist within HNSCC that lead to APOBEC mutations. Immune upregulation, potentially in response to mutation-induced neoantigens, appears to be the primary driver, with viral infection inducing additional IFNy production in the subset of tumors caused by HPV. These mechanisms may be additive and not mutually exclusive, which could explain the higher levels of APOBEC mutations in HPVmHNSCC. The tight interconnectedness of APOBEC mutations and the immune landscape in HNSCC, including numerous known markers of response to immunotherapy, highlights the importance of the immune microenvironment in mutation acquisition in HNSCC.

Citation Format: Yan Lin, Shuyan Zhai, Fengshen Kuo, Timothy A. Chan, Luc G. Morris, Robert L. Ferris, Daniel L. Faden, Fei Ding. APOBEC mutagenesis is tightly linked to the immune landscape and immunotherapy biomarkers in head and neck squamous cell carcinoma [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr PR05.

APOBEC mutagenesis is tightly linked to the immune landscape and immunotherapy biomarkers in head and neck squamous cell carcinoma

HNSCC is an immunologically active tumor with high levels of immune cell infiltration, high mutational burden and a subset of patients who respond to immunotherapy. One of the primary sources of mutations in HNSCC is the cytidine deaminase APOBEC3, which is a known participant in innate immunity. Why particular HNSCCs have higher rates of APOBEC mutations and how these mutations relate to the immune microenvironment remains unknown. Utilizing whole exome and RNA-Seq datasets from TCGA HNSCCs we annotated APOBEC mutations, immune cell populations, activating and end effectors of immunity and neoantigens in order to interrogate the relationship between APOBEC mutations and the immune landscape. Immune cell populations and composite scores of immune activation were tightly associated with APOBEC mutational burden (p = 0.04-1.17e-5). HNSCC had the highest levels of IFNy across cancer types with high APOBEC mutational burden, with the highest IFNy scores in HPV mediated HNSCC. Tumor specific neoantigens were significantly correlated with APOBEC mutational burden while other sources of neoantigens were not (0.53 [0.24, 0.76] p = 8e-5). The presence of a germline APOBEC polymorphism was more prevalent in non-white, non-black patients and within this group, patients with the polymorphism had higher APOBEC mutational burden (p = 0.002). APOBEC mutations are tightly linked to immune activation and infiltration in HNSCC. Multiple mechanisms may exist within HNSCC leading to APOBEC mutations including immune upregulation in response to neoantigens and viral infection, via induction of IFNy. These mechanisms may be additive and not mutually exclusive, which could explain higher levels of APOBEC mutations in HPV mediated HNSCC.

Acoustic Rhinometry Predicts Tolerance of Nasal Continuous Positive Airway Pressure: A Pilot Study

Background

Nasal continuous positive airway pressure (nCPAP) is usually the first-line intervention for obstructive sleep apnea, but up to 50% of patients are unable to tolerate therapy because of discomfort–-usually nasal complaints. No factors have been definitively correlated with nCPAP tolerance, although nasal cross-sectional area has been correlated with the level of CPAP pressure, and nasal surgery improves nCPAP compliance. This study examined the relationship between nasal cross-sectional area and nCPAP tolerance.

Methods

We performed acoustic rhinometry on 34 obstructive sleep apnea patients at the time of the initial sleep study. Patients titrated to nCPAP were interviewed 18 months after starting therapy to determine CPAP tolerance. Demographic, polysomnographic, and nasal cross-sectional area data were compared between CPAP-tolerant and -intolerant patients.

Results

Between 13 tolerant and 12 intolerant patients, there were no significant differences in age, gender, body mass index, CPAP level, respiratory disturbance index, or subjective nasal obstruction. Cross-sectional area at the inferior turbinate differed significantly between the two groups (p = 0.03). This remained significant after multivariate analysis for possibly confounding variables. A cross-sectional area cutoff of 0.6 cm2 at the head of the inferior turbinate carried a sensitivity of 75% and specificity of 77% for CPAP intolerance in this patient group.

Conclusion

Nasal airway obstruction correlated with CPAP tolerance, supporting an important role for the nose in CPAP, and providing a physiological basis for improved CPAP compliance after nasal surgery. Objective nasal evaluation, but not the subjective report of nasal obstruction, may be helpful in the management of these patients.

Nasal Obstruction and Sleep-Disordered Breathing: A Study Using Acoustic Rhinometry

Background

The relationship between nasal airway function and sleep-disordered breathing (SDB) remains unclear. Although correction of nasal obstruction can significantly improve nighttime breathing in some patients, nasal obstruction may not play a role in all cases of SDB. An effective method of stratifying these patients is needed. Acoustic rhinometry (AR) is a reliable, noninvasive method of measuring the dimensions of the nasal airway.

Methods

In 44 patients, we performed acoustic rhinometric measurements of nasal airway cross-sectional area, followed by hospital-based polysomnography and nasal continuous positive airway pressure (nCPAP) level titration. We compared anatomic nasal obstruction to perceived nasal obstruction, as well as respiratory distress index and nCPAP titration level, using the Pearson correlation and multiple linear regression analysis within body mass index groups.

Results

Perceived nasal obstruction correlated significantly with objective anatomic obstruction as measured by AR (r = 0.45, p < 0.01). For certain subgroup analyses inpatients with a body mass index below 25, AR measurements correlated significantly with both nCPAP titration pressure (r = 0.85, p < 0.01) and respiratory distress index (r = 0.67, p = 0.03).

Conclusion

Nasal airway function may be a significant component of SDB in some patients, perhaps playing a larger role in patients who are not overweight. The best responders to nasal surgery for SDB may be nonoverweight patients with nasal obstruction. AR along with nasal examination may be helpful in the evaluation and treatment of the SDB patient.

The thyroid cancer epidemic, 2017 perspective

PURPOSE OF REVIEW

Thyroid cancer incidence and mortality trends have been identified as being consistent with overdiagnosis, and several recent efforts have been made to mitigate this problem.

RECENT FINDINGS

Major guidelines for thyroid nodule management recommend against general biopsy of nodules less than 1 cm in size. Data supporting the safety of active surveillance of low-risk thyroid cancers is now recognized. Tumors previously labeled as encapsulated follicular variant papillary thyroid cancers are now recommended to be called noninvasive follicular thyroid neoplasm with papillary-like nuclear features.

SUMMARY

Workup, diagnostic, and management of papillary thyroid cancer are changing rapidly to accommodate the recognition that many thyroid cancers are low risk and do not require aggressive, immediate intervention.

PD-1 Expression in Head and Neck Squamous Cell Carcinomas Derives Primarily from Functionally Anergic CD4+ TILs in the Presence of PD-L1+ TAMs

Oral tongue squamous cell carcinoma (OTSCC) is the most common oral cavity tumor. In this study, we examined the basis for the activity of programmed cell death protein (PD-1)-based immune checkpoint therapy that is being explored widely in head and neck cancers. Using multispectral imaging, we systematically investigated the OTSCC tumor microenvironment (TME) by evaluating the frequency of PD-1 expression in CD8⁺, CD4⁺, and FoxP3⁺ tumor-infiltrating lymphocytes (TIL). We also defined the cellular sources of PD-1 ligand (PD-L1) to evaluate the utility of PD-1:PD-L1 blocking antibody therapy in this patient population. PD-L1 was expressed in 79% of the OTSCC specimens examined within the TME. Expression of PD-L1 was associated with moderate to high levels of CD4⁺ and CD8⁺ TILs. We found that CD4⁺ TILs were present in equal or greater frequencies than CD8⁺ TILs in 94% of OTSCC and that CD4⁺FOXP3neg TILs were colocalized with PD-1/PD-L1/CD68 more frequently than CD8⁺ TILs. Both CD4⁺PD1⁺ and CD8⁺PD1⁺ TILs were anergic in the setting of PD-L1 expression. Overall, our results highlight the importance of CD4⁺ TILs as pivotal regulators of PD-L1 levels and in determining the responsiveness of OTSCC to PD1-based immune checkpoint therapy. Cancer Res; 77(22); 6365-74. ©2017 AACR.

Variation in use of postoperative chemoradiation following surgery for T1 and T2 oropharyngeal squamous cell carcinoma; National Cancer Database

BACKGROUND AND OBJECTIVES

Primary surgical treatment of patients with early T-classification (T1-T2) oropharyngeal squamous cell carcinoma (OPSCC) has increased. We sought to determine how often these patients receive postoperative chemoradiation (CRT).

METHODS

Patients with T1-T2 OPSCC in the National Cancer Database who underwent primary surgery were evaluated for receipt of postoperative CRT. Postoperative CRT use was examined among patients with high risk factors (positive margins and/or extracapsular spread [ECS]), intermediate risk factors (negative margins, no ECS, and either pT3-4 and/or N2-N3), and no apparent risk factors.

RESULTS

Of 4833 patients with T1-T2 OPSCC who underwent primary surgery, 43% had high risk pathologic factors, of whom only 63% received postoperative CRT. Another 31% had no apparent risk factors, of whom 16% nonetheless received postoperative CRT. On multivariable analysis, in addition to tumor and demographic factors, patients treated at community hospitals were more likely to receive postoperative CRT (O.R. 1.41 C.I. 1.18-1.87, P = 0.001).

CONCLUSIONS

Variation in postoperative CRT use indicates a lack of consensus and/or knowledge about its benefits and indications. Usage of postoperative CRT regardless of pathologic risk factors suggests an area where future efforts at implementation of best practices may be targeted.

A personalized approach using hypoxia resolution to guide curative-intent radiation dose-reduction to 30 Gy: A novel de-escalation paradigm for HPV-associated oropharynx cancers (OPC)

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Background: We conducted a pilot study using functional imaging to guide reduction in radiation (RT) to 30Gy with concurrent chemotherapy in patients with HPV+ OPC. Methods: 19 patients were enrolled prospectively from 7/2015-10/2016. Primary tumors were excised and analyzed for DNA repair foci ex-vivo. A pre-RT dynamic 18F-FMISO (fluoromisonidazole) PET was then used to assess tumor hypoxia (defined as > 1.2 tumor to muscle SUV ratio) in cervical lymph nodes. Patients without hypoxia on baseline or repeat scan done 5-10 days after initiation of chemoRT received 30Gy (57% reduction) over 3 weeks to the tumor bed and neck with 2 cycles of concurrent chemotherapy (high-dose cisplatin or carboplatin/5-FU). Patients with persistent hypoxia received the standard dose of 70Gy over 7 weeks with chemo. Neck dissection (ND) was done 4-months post chemoRT. Weekly DWI MRI, ctDNA, whole exome & RNA sequencing were performed. Results: 19 patients (11 tonsil, 5 BoT, 3 unknown primaries) were enrolled. Staging: 11 T1, 5 T2, 3 Tx; 5 N1, 3 N2a, 11 N2b; all M0. On pre-RT 18F-FMISO scans, 13 were positive and 6 were negative for hypoxia. Of the 12 intra-treatment 18F-FMISO scans (1 not done due to intermittent illness, this patient received 70Gy), 3 were positive and these patients received 70Gy chemoRT. 15 patients were de-escalated to 30Gy. To date, analysis showed complete pathologic response in 8 of 9 patients (all 15 expected to have ND by April 2017. The one positive case received only 1 cycle of cisplatin. To date, 18 of 19 patients (95%-6 pending ND) remain disease free. Correlative analysis with sequencing, DNA repair foci, ctDNA, and results from pathologic and intra-treatment imaging response will be presented. Conclusions: This is the first report of apersonalized approach to a major decrease in RT dosing for definitive treatment of HPV+ oropharyngeal carcinoma guided by patient-specific imaging-based treatment response. De-escalation to 30Gy informed by intra-treatment imaging for hypoxia appears feasible, safe and efficacious. A multi-center trial to validate these pilot results is planned. Clinical trial information: NCT00606294.

White adipose tissue inflammation and cancer-specific survival in patients with squamous cell carcinoma of the oral tongue

BACKGROUND

Obesity is associated with increased adipose tissue in the tongue. Chronic white adipose tissue (WAT) inflammation commonly occurs in the obese. We investigated whether WAT inflammation in the tongue impacts survival in patients with squamous cell carcinoma (SCC) of the oral tongue.

METHODS

In a retrospective cohort study, patients with T1 and T2 SCC of the oral tongue who underwent curative-intent resection were included. Tongue WAT inflammation was defined by the presence of dead or dying adipocytes surrounded by macrophages forming crown-like structures. The primary and secondary endpoints were disease-specific survival (DSS) and overall survival (OS), respectively. Subgroup analyses were carried out in patients without lymph node involvement for whom adjuvant therapies were not indicated.

RESULTS

Archived tissue was available from 125 patients. The median follow-up was 55 months (range, 3-156 months). Overall, 49 of 125 patients (39%) had tongue WAT inflammation, which was associated with higher body mass index, increased tumor thickness, and vascular invasion (P < .05). The 3-year DSS rate for patients with tongue WAT inflammation was 59% (95% confidence interval [CI], 46%-76%) versus 82% (95% CI, 73%-92%) for those without inflammation. For patients without lymph node involvement for whom adjuvant therapy was not indicated (N = 70), tongue WAT inflammation was associated with shortened DSS and OS (P < .05). When adjusted for body mass index and potential prognostic covariates, the hazard ratio for DSS and OS was 5.40 (95% CI, 1.20-24.26) and 2.97 (95% CI, 1.02-8.65), respectively.

CONCLUSIONS

Tongue WAT inflammation is associated with worse DSS and OS in patients who have early stage SCC of the oral tongue. Cancer 2016;122:3794-3802. © 2016 American Cancer Society.

Increase in primary surgical treatment of T1 and T2 oropharyngeal squamous cell carcinoma and rates of adverse pathologic features: National Cancer Data Base

BACKGROUND

There has been increasing interest in the primary surgical treatment of patients with early T classification (T1-T2) oropharyngeal squamous cell carcinoma (OPSCC), with the stated goal of de-escalating or avoiding adjuvant treatment. Herein, the authors sought to determine the degree to which this interest has translated into changes in practice patterns, and the rates of adverse postoperative pathologic features.

METHODS

Patients with T1 to T2 OPSCC in the National Cancer Data Base who were treated from 2004 through 2013 were categorized as receiving primary surgical or primary radiation-based treatment. Trends in treatment selection and factors related to the selection of primary surgery were examined. The rates of adverse pathologic features including positive surgical margins, extracapsular spread (ECS), and advanced T and N classifications after surgery were analyzed.

RESULTS

Of 8768 patients with T1 to T2 OPSCC, 68% underwent primary surgical treatment, increasing from 56% in 2004 to 82% in 2013 (P<.0001). The highest versus lowest volume hospitals treated 78% versus 59% of patients with primary surgery (odds ratio, 2.23; 95% confidence interval, 1.55-3.22 [P<.0001]). Higher lymph node classification was found to be predictive of lower rates of primary surgery, but the majority of patients with clinical N2/N3 disease underwent primary surgery. Among patients treated with surgery, positive surgical margins were present in 24% and ECS in 25% of patients. The rate of positive surgical margins decreased over time (P<.0001) and was observed less often at high-volume centers (P<.0001). Among candidates for single-modality therapy (those with clinical T1-T2/N0-N1 disease), 33% had positive surgical margins and/or ECS and 47% had at least 1 adverse feature (T3-T4 disease, N2-N3 disease, positive surgical margins, and/or ECS).

CONCLUSIONS

Primary surgical treatment among patients with early T classification OPSCC has become more widespread. Cancer 2016;122:1523-32. © 2016 American Cancer Society.

Outcomes for patients with papillary thyroid cancer who do not undergo prophylactic central neck dissection

BACKGROUND

The role of prophylactic central neck dissection (CND) in the management of papillary thyroid cancer (PTC) is controversial. This report describes outcomes of an observational approach in patients without clinical evidence of nodal disease in PTC.

METHODS

All patients who had surgery between 1986 and 2010 without CND for PTC were identified. All patients had careful clinical assessment of the central neck during preoperative and perioperative evaluation, with any suspicious nodal tissue excised for analysis. The cohort included patients in whom lymph nodes had been removed, but no patient had undergone a formal neck dissection. Recurrence-free survival (RFS), central neck RFS and disease-specific survival (DSS) were calculated using the Kaplan-Meier method.

RESULTS

Of 1798 patients, 397 (22.1 per cent) were men, 1088 (60.5 per cent) were aged 45 years or more, and 539 (30.0 per cent) had pT3 or pT4 disease. Some 742 patients (41.3 per cent) received adjuvant treatment with radioactive iodine. At a median follow-up of 46 months the 5-year DSS rate was 100 per cent. Five-year RFS and central neck RFS rates were 96.6 and 99.1 per cent respectively.

CONCLUSION

Observation of the central neck is safe and should be recommended for all patients with PTC considered before and during surgery to be free of central neck metastasis.

Postoperative PET/CT and target delineation before adjuvant radiotherapy in patients with oral cavity squamous cell carcinoma

BACKGROUND

The purpose of this study was for us to present our evaluation of the effectiveness of positron emission tomography (PET)/CT imaging in postoperative patients with oral cavity squamous cell carcinoma (SCC) before initiating adjuvant radiation therapy.

METHODS

Treatment planning PET/CT scans were obtained in 44 patients with oral cavity SCC receiving adjuvant radiation. We identified target areas harboring macroscopic disease requiring higher radiation doses or additional surgery.

RESULTS

Fourteen PET/CT scans were abnormal. Thirteen patients underwent surgery and/or biopsy, increased radiation dose, and/or addition of chemotherapy. Eleven patients received higher radiation doses. Patients undergoing imaging >8 weeks were more likely to have abnormal results (p = .01). One-year distant metastases-free survival was significantly worse in patients with positive PET/CT scans (61.5% vs 92.7%; p = .01). The estimated positive predictive value (PPV) was 38% for postoperative PET/CT scanning.

CONCLUSION

We demonstrated that 32% of patients have abnormal PET/CT scans resulting in management changes. Patients may benefit from postoperative PET/CT imaging to optimize adjuvant radiation treatment planning. © 2015 Wiley Periodicals, Inc. Head Neck 38: E1285-E1293, 2016.

Unraveling the molecular genetics of head and neck cancer through genome-wide approaches

The past decade has seen an unprecedented increase in our understanding of the biology and etiology of head and neck squamous cell carcinomas (HNSCC). Genome-wide sequencing projects have identified a number of recurrently mutated genes, including unexpected alterations in the NOTCH pathway and chromatin related genes. Gene-expression profiling has identified 4 distinct genetic subtypes which show some parallels to lung squamous cell carcinoma biology. The identification of the human papilloma virus as one causative agent in a subset of oropharyngeal cancers and their association with a favorable prognosis has opened up avenues for new therapeutic strategies. The expanding knowledge of the underlying molecular abnormalities in this once very poorly understood cancer should allow for increasingly rational clinical trial design and improved patient outcomes.

Irradiation for locoregionally recurrent, never-irradiated oral cavity cancers

BACKGROUND

The purpose of this study was to report the clinical outcomes and related prognostic factors of patients who underwent radiotherapy (RT) for the treatment of recurrent, never-irradiated oral cavity cancer (recurrent OCC).

METHODS

The records of consecutive patients with nonmetastatic recurrent OCC who presented to and were treated with RT at our institution between 1989 and 2011 were reviewed. The Kaplan-Meier method was used to calculate overall survival (OS). The cumulative incidences of disease-specific death, local failure, regional failure, and distant metastasis were calculated with death as a competing risk.

RESULTS

One hundred twenty-three patients were identified. Median follow-up for living patients was 54 months and 16 months for all patients. Ninety-one patients had salvage surgery followed by adjuvant RT. Definitive RT was utilized in the remaining 32 patients. The 5-year OS was 40%. The 5-year cumulative incidence of disease-specific death, local failure, regional failure, and distant metastasis was 55%, 34%, 22%, and 20%, respectively. Recurrent T classification and lack of salvage surgery were independently associated with worse disease-specific death and decreased OS, respectively. Subset analysis of patients who underwent salvage surgery demonstrated that age, recurrent T classification, and perineural invasion (PNI) were independently associated with decreased OS; recurrent T classification and thicker tumors were independently associated with worse disease-specific death; and positive/close margins and primary T classification were independently associated with increased local failure.

CONCLUSION

In this group of patients with recurrent OCC, clinical outcomes were similar or improved when compared with other recurrent OCC-specific reports. In the salvage surgery subset, tumor thickness and PNI are recurrent pathologic features associated with outcomes that were only previously demonstrated in studies of primary disease. Because of the relatively worse outcomes in patients receiving definitive or adjuvant RT for recurrent OCC, we advocate for the appropriate use of postoperative RT in the initial management of oral cavity cancers.

Impact of obesity on the survival of patients with early-stage squamous cell carcinoma of the oral tongue

BACKGROUND

Although obesity increases risk and negatively affects survival for many malignancies, the prognostic implications in squamous cell carcinoma (SCC) of the oral tongue, a disease often associated with prediagnosis weight loss, are unknown.

METHODS

Patients with T1-T2 oral tongue SCC underwent curative-intent resection in this single-institution study. All patients underwent nutritional assessment prior to surgery. Body mass index (BMI) was calculated from measured height and weight and categorized as obese (≥ 30 kg/m(2) ), overweight (25-29.9 kg/m(2) ), or normal (18.5-24.9 kg/m(2) ). Clinical outcomes, including disease-specific survival, recurrence-free survival, and overall survival, were compared by BMI group using Cox regression.

RESULTS

From 2000 to 2009, 155 patients (90 men, 65 women) of median age 57 years (range, 18-86 years) were included. Baseline characteristics were similar by BMI group. Obesity was significantly associated with adverse disease-specific survival compared with normal weight in univariable (hazard ratio [HR] = 2.65, 95% confidence interval [CI] = 1.07-6.59; P = .04) and multivariable analyses (HR = 5.01; 95% CI = 1.69-14.81; P = .004). A consistent association was seen between obesity and worse recurrence-free survival (HR = 1.87; 95% CI = 0.90-3.88) and between obesity and worse overall survival (HR = 2.03; 95% CI = 0.88-4.65) though without reaching statistical significance (P = .09 and P = .10, respectively) in multivariable analyses.

CONCLUSIONS

In this retrospective study, obesity was an adverse independent prognostic variable. This association may not have been previously appreciated due to confounding by multiple factors including prediagnosis weight loss.

Impact of obesity on survival in patients (pts) with early-stage squamous cell carcinoma (SCC) of the oral tongue

6048

Background: Obesity is a risk factor for several malignancies and an independent predictor of worse outcomes. In contrast, low body mass index (BMI) has been associated with increased risk of oropharyngeal cancers and poorer prognosis. In tongue SCC, impaired nutrition, smoking, and alcohol use impact BMI, and pre-diagnosis weight (wgt) loss negatively affects survival. The prognostic effect of obesity in tongue cancer is unknown. Methods: We conducted a single-institution, retrospective study of pts who underwent resection of T1/T2 SCC of the oral tongue. All pts underwent nutritional assessment prior to surgery. BMI was calculated from measured height and wgt at surgery and categorized as obese (≥30), overwgt (25-29.9), or normal (18.5-24.9). The association between BMI and the primary endpoint, disease specific survival (DSS), was evaluated by Cox regression. The effect of BMI on the secondary endpoints, recurrence free survival (RFS) and overall survival (OS), was also assessed. Results: From 2000 to 2005, 155 pts (90 men, 65 women) of median age 57 (range 18-86) were included. Clinicopathologic characteristics were similar by BMI group. Obesity was significantly associated with adverse DSS compared with normal wgt in univariable (Table) and multivariable analyses (HR 2.87; 95% CI, 1.08-7.67; p=0.04). Obesity was also significantly associated with adverse RFS (HR 2.53; 95% CI, 1.12-5.74; p=0.03). Overwgt subjects may also have worse RFS (HR 1.74; 95% CI, 0.85-3.55; p=0.13). In pts without pre-diagnosis wgt loss (n=94), obesity was significantly associated with adverse OS (HR 2.70; 95% CI, 1.12-6.54; p=0.03). Conclusions: These data suggest that obesity is associated with a worse prognosis in tongue cancer, which may not have previously been appreciated due to confounding by pre-diagnosis wgt loss. [Table: see text]

Outcomes of temporal bone resection for locally advanced parotid cancer

This study was conducted to report outcomes and identify factors predictive of survival and recurrence in patients undergoing lateral temporal bone resection (LTBR) as part of an extended radical parotidectomy for parotid cancer. This is a retrospective cohort study which includes all patients undergoing LTBR for parotid cancer between 1994 and 2010 at two affiliated academic centers. Survival and recurrence rates were analyzed using the Kaplan-Meier method and Cox multivariate regression. A total of 12 patients with median follow-up duration of 30.6 months were included: 6 de novo cases and 6 patients referred after local recurrence. Actuarial locoregional control at 2 years was 73%. Most patients (11; 92%) developed disease recurrence with distant metastases the most common site of first failure (83%). Overall and disease-specific survival rates were 80% at 2 years and 22.5% at 5 years. Recurrence-free survival (RFS) was 67% at 2 years and 8.3% at 5 years. On multivariate analysis, surgical margin status was an independent predictor of RFS (hazard ratio = 3.85, p = 0.045). In advanced parotid cancer, LTBR with a goal of gross total resection offers good locoregional control with an acceptable complication rate. The benefits of this surgery must be balanced with the morbidity and low likelihood of long-term survival, with most patients ultimately experiencing disease recurrence and death.

Abstract 3911: Functional copy number alterations (CNAS) in oral cancer

Background: Alterations in DNA copy number can functionally affect genes and produce a transformed cancer phenotype. Discoevery of novel cancer genes can be facilitated by identifying genomic regions undergoing frequent, significant alteration. Array comparative genomic hybridization techniques have generated vast amounts of raw copy number data requiring computational analysis to identify aberrations likely to be functional. In this analysis, we present data from a comprehensive computational approach designed to robustly map chromosomal aberrations in oral cavity squamous cell carcinoma (OCSCC).

Methods: DNA was extracted from 31 microdissected OCSCC frozen tumors and hybridized with reference DNA on the Agilent 1M copy number array, containing nearly 1 million probes across the genome at high resolution. The RAE computational framework was used to identify CNAs. In this analysis, segmentation of probe data is first performed using paired reference HapMap data and individual-tumor thresholds to account for stromal admixture and tumor heterogeneity. Scores (single-copy gain, amplification, hemizygous loss, homozygous deletion) are then assigned, followed by soft discrimination thresholding and significance testing with false discovery rate correction. Regions of interest (ROIs) are then agnostically identified as regions of significant (FDR&lt;0.01) alteration, expanded to adjacent loci to account for spatial and amplitude uncertainty. Finally, described copy number polymorphisms were excluded.

Results: 49 ROIs were identified, 27 amplification regions (chromosomes 3,4,5,7,8,9,11,16,18,20,21) and 22 deletion regions (chromosomes 2,3,4,5,7,8,9,10,13,15,16,18,19). ROIs ranged in prevalence from 6.5-77.4% of samples, and encompassed 0-483 genes (total=2799, median=4), and 0-13 microRNAs (total=77, median=0). Eleven ROIs were focal intragenic CNAs. Four ROIs contained no named genes or microRNAs. Hierarchical clustering identified 3 clusters, based on escalating levels of CNA. Complete gene details of the 49 ROIs will be presented.

Conclusions: We report significant regions of CNA in oral cancer, by applying a robust computational framework to identify recurrent chromosomal aberrations in OCSCC, which represent highly significant candidate functional events.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3911. doi:10.1158/1538-7445.AM2011-3911

Phase Response Curve to Melatonin in a Putatively Diurnal Rodent,Octodon degus

The degu (Octodon degus) is a diurnal rodent, although phase inversions to nocturnal behavior have been reported under specific laboratory conditions. The reliability of this animal as a diurnal model of sleep therefore requires further characterization of intrinsic circadian pacemaker properties. A phase response curve to light has been reported in the degu, and is consistent with other diurnal animals. This study reports a phase response curve to melatonin in the degu, which is distinct in orientation from the light curve.

PNL2 melanocytic marker in immunohistochemical evaluation of primary mucosal melanoma of the head and neck

BACKGROUND

Histologic diagnosis of mucosal melanoma of the head and neck is difficult, requiring immunohistochemical stains which are less reliable than in cutaneous lesions. PNL-2 is a novel marker that has not been examined in mucosal melanoma.

METHODS

Nine formalin-fixed tissue sections of mucosal melanoma were stained with PNL-2, human melanoma black (HMB)-45, Melan-A, S-100, and microphthalmia transcription factor (MITF).

RESULTS

Disease in all 9 patients arose from the sinonasal mucosa. Rates of diffuse positive staining with the 4 stains were PNL-2 (77.8%), HMB-45 (77.8%), Melan-A (50%), S-100 (87.5%), and MITF (40%). In 3 patients, PNL2 staining was superior to Melan-A or MITF.

CONCLUSION

We report the first characterization of PNL-2 staining in head and neck mucosal melanoma. PNL-2 demonstrates high sensitivity for mucosal melanoma, likely superior to Melan-A and MITF, and comparable to HMB-45, with specificity superior to S-100. We advocate inclusion of PNL2 as an important adjunctive marker in the evaluation of these lesions.

SCCRO (DCUN1D1) is an essential component of the E3 complex for neddylation

Covalent modification of cullins by the ubiquitin-like protein NEDD8 (neddylation) regulates protein ubiquitination by promoting the assembly of cullin-RING ligase E3 complexes. Like ubiquitination, neddylation results from an enzymatic cascade involving the sequential activity of a dedicated E1 (APPBP1/Uba3), E2 (Ubc12), and an ill-defined E3. We show that SCCRO (also known as DCUN1D1) binds to the components of the neddylation pathway (Cullin-ROC1, Ubc12, and CAND1) and augments but is not required for cullin neddylation in reactions using purified recombinant proteins. We also show that SCCRO recruits Ubc12 approximately NEDD8 to the CAND1-Cul1-ROC1 complex but that this is not sufficient to dissociate or overcome the inhibitory effects of CAND1 on cullin neddylation in purified protein assays. In contrast to findings in cellular systems where no binding is seen, we show that SCCRO and CAND1 can bind to the neddylated Cul1-ROC1 complex in assays using purified recombinant proteins. Although neddylated (not unneddylated) Cul1-ROC1 is released from CAND1 upon incubation with testis lysate from SCCRO+/+ mice, the addition of recombinant SCCRO is required to achieve the same results in lysate from SCCRO(-/-) mice. Combined, these results suggest that SCCRO is an important component of the neddylation E3 complex that functions to recruit charged E2 and is involved in the release of inhibitory effects of CAND1 on cullin-RING ligase E3 complex assembly and activity.

Emergency parotidectomy for penetrating zone III neck trauma

Penetrating trauma to the face and upper zone III of the neck may present unique challenges when the parotid gland and associated neurovascular structures are involved. We report a case of massive hemorrhage from penetrating neck trauma that necessitated emergency parotidectomy for vascular exposure. Facial nerve repair was also necessary, underscoring the importance of this approach not only for successful vascular control but also for preservation of nearby vital structures. The management of penetrating trauma to the parotid region,and relevant anatomy, are discussed.

Monitoring tracheal tube cuff pressures in the intensive care unit: a comparison of digital palpation and manometry

OBJECTIVES

Tracheal tube cuff overinflation is a recognized risk factor for tracheal injury and stenosis. International studies report a 55% to 62% incidence of cuff overinflation among intensive care unit (ICU) patients. However, there are no data on tracheotomy tubes, and no recent data from ICUs in the United States. It is unknown whether routine cuff pressure measurement is beneficial. We sought to determine the incidence of cuff overinflation in the contemporary American ICU.

METHODS

We performed an Institutional Review Board-approved, prospective, observational study of endotracheal and tracheotomy tubes at 2 tertiary-care academic hospitals that monitor cuff pressure differently. At hospital A, cuff pressures are assessed by palpation; at hospital B, cuff pressures are measured via manometry. We audited cuff pressures in an unannounced fashion at these hospitals, using a handheld aneroid manometer. Cuffs were considered overinflated above 25 cm H2O.

RESULTS

We enrolled 115 patients: 63 at hospital A and 52 at hospital B. Overall, 44 patients (38%) were found to have overinflated cuffs. The incidence of overinflation was identical at the 2 hospitals (38%; p = .99). Of the endotracheal tubes, 43% were overinflated, as were 32% of the tracheotomy tubes (p = .24).

CONCLUSIONS

Despite increasing awareness among intensivists and respiratory therapists, the incidence of tracheal tube overinflation remains high, with both endotracheal and tracheotomy tubes. Our finding that the use of manometry to assess cuff pressures did not reduce the incidence of overinflation suggests that a more vigilant management protocol may be necessary.

Esthesioneuroblastoma: a population-based analysis of survival and prognostic factors

OBJECTIVES

To investigate the characteristics associated with survival in esthesioneuroblastoma and to determine whether the modified Kadish staging system can predict outcome.

DESIGN

Retrospective population-based cohort study.

SUBJECTS

All patients in the Surveillance, Epidemiology, and End Results tumor registry diagnosed as having esthesioneuroblastoma (1973-2002).

MAIN OUTCOME MEASURES

The modified Kadish stage and the overall and disease-specific survival rates were determined.

RESULTS

The cohort included 311 patients with a mean age of 53 years and a unimodal age distribution. The overall 5- and 10-year survival rates were 62.1% and 45.6%, respectively. The modified Kadish staging system was applied to 261 patients. Kaplan-Meier analysis showed the overall and disease-specific survival rates at 10 years to be 83.4% and 90%, respectively, for patients with stage A disease; 49% and 68.3% for patients with stage B disease; 38.6% and 66.7% for patients with stage C disease; and 13.3% and 35.6% for patients with stage D disease. Log-rank test comparisons found Kadish stage (P<.01), treatment modality (P<.002), lymph node status (P<.01), and age at diagnosis (P<.001) to be significant predictors of survival. Cox regression analysis confirmed that Kadish stage remained a significant predictor of disease-specific survival.

CONCLUSION

The modified Kadish staging system, lymph node status, treatment modality, and age are useful predictors of survival in patients who present with esthesioneuroblastoma.

Implication of Central Asymmetry in Speech Processing on Selecting the Ear for Cochlear Implantation

OBJECTIVE

Emerging evidence in auditory neuroscience suggests that central auditory pathways process speech asymmetrically. In concert with left cortical specialization for speech, a "right-ear advantage" in speech perception has been identified. The purpose of this study is to determine if this central asymmetry in speech processing has implications for selecting the ear for cochlear implantation.

STUDY DESIGN

Retrospective cohort study.

SETTING

Academic university medical center

PATIENTS

One hundred one adults with bilateral severe-to-profound sensorineural hearing loss

INTERVENTION

Cochlear implantation with the Nucleus 24 Contour device.

MAIN OUTCOME MEASUREMENTS

Patients were divided into two groups according to the ear implanted. Results were compared between left-ear- and right-ear-implanted patients. Further subgroup analysis was undertaken, limited to right-handed patients. Postoperative improvement on audiograms and scores on speech perception tests (Hearing in Noise test, City University of New York in quiet and in noise test, Consonant-Vowel Nucleus- Consonant words, and phonemes) at 1 year was compared between groups. Analysis of covariance was used to control for any intergroup differences in preoperative characteristics.

RESULTS

The groups were matched in age, duration of hearing loss, duration of hearing aid use, percentage implanted in the better hearing ear, and preoperative audiologic testing. Postoperatively, there were no differences between left-ear- and right-ear-implanted patients in improvement on speech recognition tests.

CONCLUSION

Despite central asymmetry in speech processing, our data do not support a right-ear advantage in speech perception outcomes with cochlear implantation. Therefore, among the many factors in choosing the ear for cochlear implantation, central asymmetry in speech processing does not seem to be a contributor to postoperative speech recognition outcomes.

Acoustic rhinometry predicts tolerance of nasal continuous positive airway pressure: a pilot study

BACKGROUND

Nasal continuous positive airway pressure (nCPAP) is usually the first-line intervention for obstructive sleep apnea, but up to 50% of patients are unable to tolerate therapy because of discomfort-usually nasal complaints. No factors have been definitively correlated with nCPAP tolerance, although nasal cross-sectional area has been correlated with the level of CPAP pressure, and nasal surgery improves nCPAP compliance. This study examined the relationship between nasal cross-sectional area and nCPAP tolerance.

METHODS

We performed acoustic rhinometry on 34 obstructive sleep apnea patients at the time of the initial sleep study. Patients titrated to nCPAP were interviewed 18 months after starting therapy to determine CPAP tolerance. Demographic, polysomnographic, and nasal cross-sectional area data were compared between CPAP-tolerant and -intolerant patients.

RESULTS

Between 13 tolerant and 12 intolerant patients, there were no significant differences in age, gender, body mass index, CPAP level, respiratory disturbance index, or subjective nasal obstruction. Cross-sectional area at the inferior turbinate differed significantly between the two groups (p = 0.03). This remained significant after multivariate analysis for possibly confounding variables. A cross-sectional area cutoff of 0.6 cm2 at the head of the inferior turbinate carried a sensitivity of 75% and specificity of 77% for CPAP intolerance in this patient group.

CONCLUSION

Nasal airway obstruction correlated with CPAP tolerance, supporting an important role for the nose in CPAP, and providing a physiological basis for improved CPAP compliance after nasal surgery. Objective nasal evaluation, but not the subjective report of nasal obstruction, may be helpful in the management of these patients.

Superficial Dorsal Artery of the Forearm

Although abnormalities of vascular anatomy in the forearm are common, variations of the radial and ulnar arteries are rare. Nevertheless, arterial variants in the forearm may present clinically with neurovascular signs or symptoms. Even when anomalous arteries are not apparent, they may complicate surgery of the forearm and hand, as well as reconstructive surgery that involves the harvest of radial or ulnar artery-based forearm free flaps. For example, the superficial ulnar artery has an incidence of 2.7% and has been well described as a "hidden trap" in the harvest of radial forearm flaps. We present a case report of a variant of the radial artery-the superficial dorsal artery of the forearm. This artery has an estimated incidence of 0.75% and is associated with either an absent or small-caliber radial artery. We believe this is the first report of such an artery presenting to clinical attention, as well as the first imaging of this structure with magnetic resonance angiography. The embryology of this structure and its clinical implications to the hand surgeon, peripheral vascular surgeon, and reconstructive microsurgeon, are also discussed.

Nasal obstruction and sleep-disordered breathing: a study using acoustic rhinometry

BACKGROUND

The relationship between nasal airway function and sleep-disordered breathing (SDB) remains unclear. Although correction of nasal obstruction can significantly improve nighttime breathing in some patients, nasal obstruction may not play a role in all cases of SDB. An effective method of stratifying these patients is needed. Acoustic rhinometry (AR) is a reliable, noninvasive method of measuring the dimensions of the nasal airway.

METHODS

In 44 patients, we performed acoustic rhinometric measurements of nasal airway cross-sectional area, followed by hospital-based polysomnography and nasal continuous positive airway pressure (nCPAP) level titration. We compared anatomic nasal obstruction to perceived nasal obstruction, as well as respiratory distress index and nCPAP titration level, using the Pearson correlation and multiple linear regression analysis within body mass index groups.

RESULTS

Perceived nasal obstruction correlated significantly with objective anatomic obstruction as measured by AR (r = 0.45, p < 0.01). For certain subgroup analyses in patients with a body mass index below 25, AR measurements correlated significantly with both nCPAP titration pressure (r = 0.85, p < 0.01) and respiratory distress index (r = 0.67, p = 0,03).

CONCLUSION

Nasal airway function may be a significant component of SDB in some patients, perhaps playing a larger role in patients who are not overweight. The best responders to nasal surgery for SDB may be nonoverweight patients with nasal obstruction. AR along with nasal examination may be helpful in the evaluation and treatment of the SDB patient.

Recurrent acute pancreatitis in anorexia and bulimia

CONTEXT

Mild pancreatitis has been reported as a consequence of anorexia nervosa, bulimia nervosa, or what has been termed the "dietary chaos syndrome". Either chronic malnutrition, or refeeding after periods of malnutrition, may precipitate acute pancreatitis through several pathogenetic mechanisms.

CASE REPORT

A 26-year-old woman with a ten-year history of anorexia and bulimia presented with a third episode of acute pancreatitis in three months. The patient had been abstinent from alcohol for many years. Imaging studies during all three admissions failed to identify any biliary disease, including gallstones or biliary sludge. A cholecystectomy was performed, with a normal intraoperative cholangiogram, and no abnormalities on pathologic examination of the gallbladder and bile. The patient was discharged on hospital day 10 with no pain, and she has begun to return to regular eating habits. Pancreatitis has not recurred after 6 months of follow up. We have identified 14 cases in the literature of acute pancreatitis associated with anorexia or bulimia.

CONCLUSION

In the absence of evidence for gallstone, alcohol or metabolic etiologies, eating disorders may contribute to the pathophysiology of some idiopathic cases of pancreatitis.

Mechanisms underlying stabilization of temporally summated muscle contractions in the lobster (Panulirus) pyloric system

Muscles are the final effectors of behavior. The neural basis of behavior therefore cannot be completely understood without a description of the transfer function between neural output and muscle contraction. To this end, we have been studying muscle contraction in the well-investigated lobster pyloric system. We report here the mechanisms underlying stabilization of temporally summating contractions of the very slow dorsal dilator muscle in response to motor nerve stimulation with trains of rhythmic shock bursts at a physiological intraburst spike frequency (60 Hz), physiological cycle periods (0.5-2 s), and duty cycles from 0.1 to 0.8. For temporal summation to stabilize, the rise and relaxation amplitudes of the phasic contractions each burst induces must equalize as the rhythmic train continues. Stabilization could occur by changes in rise duration, rise slope, plateau duration, and/or relaxation slope. We demonstrate a generally applicable method for quantifying the relative contribution changes in these characteristics make to contraction stabilization. Our data show that all characteristics change as contractions stabilize, but their relative contribution differs depending on stimulation cycle period and duty cycle. The contribution of changes in rise duration did not depend on period or duty cycle for the 1-, 1.5-, and 2-s period regimes, contributing approximately 30% in all cases; but for the 0.5-s period regime, changes in rise duration increased from contributing 25% to contributing 50% as duty cycle increased from 0.1 to 0.8. At all cycle periods decreases in rise slope contributed little to stabilization at small duty cycles but increased to contributing approximately 80% at high duty cycles. The contribution of changes in plateau duration decreased in all cases as duty cycle increased; but this decrease was greater in long cycle period regimes. The contribution of changes in relaxation slope also decreased in all cases as duty cycle increased; but for this characteristic, the decrease was greatest in fast cycle period regimes, and in these regimes at high duty cycles these changes opposed contraction stabilization. Exponential fits to contraction relaxations showed that relaxation time constant increased with total contraction amplitude; this increase presumably underlies the decreased relaxation slope magnitude seen in high duty cycle, fast cycle period regimes. These data show that changes in no single contraction characteristic can account for contraction stabilization in this muscle and suggest that predicting muscle response in other systems in which slow muscles are driven by rapidly varying neuronal inputs may be similarly complex.

Muscles express motor patterns of non-innervating neural networks by filtering broad-band input

We describe three slow muscles that responded to low-frequency modulation of a high-frequency neuronal input and, consequently, could express the motor patterns of neural networks whose neurons did not directly innervate the muscles. Two of these muscles responded to different frequency components present in the same input, and as a result each muscle expressed the motor pattern of a different, non-innervating, neural network. In an analogous manner, the distinct dynamics of the multiple intracellular processes that most cells possess may allow each process to respond to, and hence differentiate among, specific frequency ranges present in broad-band input.

Muscle response to changing neuronal input in the lobster (Panulirus interruptus) stomatogastric system: slow muscle properties can transform rhythmic input into tonic output

Slow, non-twitch muscles are widespread in lower vertebrates and invertebrates and are often assumed to be primarily involved in posture or slow motor patterns. However, in several preparations, including some well known invertebrate "model" preparations, slow muscles are driven by rapid, rhythmic inputs. The response of slow muscles to such inputs is little understood. We are investigating this issue with a slow stomatogastric muscle (cpv1b) driven by a relatively rapid, rhythmic neural pattern. A simple model suggests that as cycle period decreases, slow muscle contractions show increasing intercontraction temporal summation and at steady state consist of phasic contractions overlying a tonic contracture. We identify five components of these contractions: total, average, tonic, and phasic amplitudes, and percent phasic (phasic amplitude divided by total amplitude). cpv1b muscle contractions induced by spontaneous rhythmic neural input in vitro consist of phasic and tonic components. Nerve stimulation at varying cycle periods and constant duty cycle shows that a tonic component is always present, and at short periods the muscle transforms rhythmic input into almost completely tonic output. Varying spike frequency, spike number, and cycle period show that frequency codes total, average, and tonic amplitudes, number codes phasic amplitude, and period codes percent phasic. These data suggest that tonic contraction may be a property of slow muscles driven by rapid, rhythmic input, and in these cases it is necessary to identify the various contraction components and their neural coding. Furthermore, the parameters that code these components are interdependent, and control of slow muscle contraction is thus likely complex.

Muscle response to changing neuronal input in the lobster (Panulirus interruptus) stomatogastric system: spike number- versus spike frequency-dependent domains

We aimed to determine the neuronal parameters controlling the contraction of slowly contracting, non-twitch ("tonic") muscles driven by rhythmic neuronal activity. These muscles are almost completely absent in mammals but are common in lower vertebrates and invertebrates. Slow muscles are often believed to function primarily in tonic motor patterns. However, previous research and data presented here indicate that slow muscles are also driven by rhythmic neuronal inputs. In rapidly contracting "twitch" muscles, motor unit force is believed to be primarily determined by motor neuron spike frequency. What determines slow muscle output is less well understood. We present a simple model that suggests that when motor neuron burst duration is brief compared with muscle summation time, spike number, not spike frequency, determines slow muscle contraction amplitude. We present analyses that distinguish between spike number and spike frequency dependence in two slow muscles in the lobster stomatogastric system. Our analysis shows that, functionally, one muscle is spike number dependent, whereas the other is primarily spike frequency dependent. Thus, both of these parameters can determine slow muscle output. To predict the movements elicited by neuronal activity in preparations in which slow muscles are common, it may be necessary to determine spike number versus spike frequency dependence for each muscle. Spike number dependence couples motor neuron burst duration and spike frequency in that changing either parameter alone alters spike number (and hence muscle contraction amplitude). Neural networks innervating spike number-dependent muscles may therefore have specific properties to compensate for the complexity intrinsic to spike number coding.