Management of the parotid for high-risk cutaneous squamous cell carcinoma: A review from the salivary section of the American Head and Neck Society.

BACKGROUND: Metastases to the parotid nodal basin in patients with high-risk cutaneous squamous cell carcinoma (HRcSCC) impact disease specific survival (DSS) and overall survival (OS). METHODS: A writing group convened by the Salivary Section of the American Head and Neck Society (AHNS) developed contemporary, evidence-based recommendations regarding management of the parotid nodal basin in HRcSCC based on available literature, expert consultation, and collective experience. The statements and recommendations were then submitted and approved by the AHNS Salivary Committee. RESULTS: These recommendations were developed given the wide variation of practitioners who treat HRcSCC in order to streamline management of the parotid nodal basin including indications for imaging, surgery, radiation, and systemic treatment options as well. CONCLUSIONS: This clinical update represents contemporary optimal management of the parotid nodal basin in HRcSCC and is endorsed by the Salivary Section of the AHNS.

Moving to a more restrictive transfusion protocol: Outcomes in head and neck free flap surgery.

PURPOSE: To determine if a more restrictive transfusion protocol results in increased rates of adverse flap outcomes in patients undergoing free tissue transfer. MATERIALS AND METHODS: Mixed retrospective and prospective cohort study. Patients who underwent surgery before the protocol change were collected retrospectively. Patients who underwent surgery after the protocol change were collected prospectively. RESULTS: Of the 460 patients who underwent free tissue transfer, 116 patients in the pre-change cohort (N = 211) underwent transfusion (54.98%) and 78 in the post-change cohort(N = 249) (31.33%) (p < 0.001). The mean number of units transfused was 1.55 + 2.00 in the pre-change cohort, and 0.78 + 1.51 in the post-change cohort (p < 0.001). When separated temporally, the pre-change cohort received significantly more blood transfusions than the post-change cohort in the operating room (33.65% vs 18.07%) (p < 0.01), within 72 h of surgery (35.55% vs 15.66%) (p < 0.001), and after 72 h after surgery to discharge (16.59% vs 8.03%) (p = 0.018017). The rate of flap failure was 6.70% in the pre-change cohort, and 5.31% in the post-change cohort (p = 0.67). In a logistic regression model controlling for potential confounders, transfusion protocol was not significantly associated with flap failure (OR = 1.1080, 95% CI: 0.48-2.54). There were no significant differences between cohorts for medical morbidity, ICU transfer, or death. CONCLUSION: Our data support the conclusion that patients undergoing free tissue transfer to the head and neck can be transfused following the same protocols as other patients, without increasing the rate of flap failure or other morbidities. LEVEL OF EVIDENCE: 3 (mixed retrospective, prospective cohort study).

Lipid microsphere bound oxycodone for pain management in patients receiving radiotherapy for head and neck cancer.

BACKGROUND: Wax microsphere bound oxycodone was developed as an abuse-deterrent opioid and maintains a similar pharmacokinetic profile whether administered with or without an intact capsule. We hypothesized that microsphere oxycodone could be utilized for extended release analgesia in patients undergoing radiation (RT) for head-and-neck cancer (HNC) and would not need to be discontinued due to dysphagia or gastrostomy tube dependence. METHODS AND MATERIALS: We performed a prospective trial that enrolled participants > 18 years with histologically confirmed HNC who were scheduled to receive RT. Analgesia was prescribed in accordance with the WHO pain ladder. Microsphere oxycodone was initiated when total daily opioid dose exceeded 30 mg of morphine sulfate equivalent and was titrated weekly during RT. Pain level and effect on quality of life were assessed using the Brief Pain Inventory. The primary feasibility endpoint was frequency of microsphere oxycodone discontinuation within 3 months of RT for reasons other than pain resolution. RESULTS: Twenty-six eligible patients were enrolled. Microsphere oxycodone was initiated in 16 (61.5%) patients. Six (23.1%) patients utilized a gastrostomy tube to administer microsphere oxycodone during all or part of RT. Microsphere oxycodone was discontinued in 1 (7.6%) patient due to perceived inefficacy. No patients were discontinued due to toxicity or difficulty with administration. Ratings for average pain was 3.1 (± 3.4) at enrollment, 4.0 (± 2.4) at week 6 of RT, and 1.8 (± 2.2) at 3-month follow-up. CONCLUSIONS: These results support the feasibility and safety of microsphere oxycodone for extended release analgesia among patients with HNC undergoing RT.

Head and neck cancer survivors' preferences for and evaluations of a post-treatment dietary intervention.

BACKGROUND: Dietary preferences vary depending on cancer type. The purpose of this study was to report dietary intervention preferences and a study program evaluation from post-treatment head and neck cancer survivors participating in a dietary intervention. METHODS: Between January 2015 and August 2016, 24 head and neck cancer survivors participated in a 12-week randomized clinical dietary intervention trial that promoted weekly consumption of 2.5 cups of cruciferous vegetables and 3.5 cups of green leafy vegetables. At study completion, survivors completed a preferences survey and a study program evaluation to probe interests and improvement aspects for planning future dietary intervention trials. Descriptive statistics (means and frequencies) were generated for multiple choice question responses. Responses to open-ended questions were recorded and grouped based on themes, and verified by quality assurance checks by a second study team member. RESULTS: Twenty-three survivors completed the preferences and evaluation surveys (response rate 96%). Overall, most participants reported a preference for one-on-one telephone counseling from a registered dietitian nutritionist before beginning treatment. Ninety-six percent of participants ranked the overall study program as "very good" to "excellent," and all agreed the objectives of the study were clear, the study staff was helpful and easy to contact, and the registered dietitian nutritionist was knowledgeable. CONCLUSIONS: Future research and dietary intervention planning for head and neck cancer survivors should focus on strategies to promote one-on-one telephone or other distance-based counseling combined with face-to-face visits, according to survivor preference.

Higher carbohydrate intake is associated with increased risk of all-cause and disease-specific mortality in head and neck cancer patients: results from a prospective cohort study.

No studies have evaluated associations between carbohydrate intake and head and neck squamous cell carcinoma (HNSCC) prognosis. We prospectively examined associations between pre- and post-treatment carbohydrate intake and recurrence, all-cause mortality, and HNSCC-specific mortality in a cohort of 414 newly diagnosed HNSCC patients. All participants completed pre- and post-treatment Food Frequency Questionnaires (FFQs) and epidemiologic surveys. Recurrence and mortality events were collected annually. Multivariable Cox Proportional Hazards models tested associations between carbohydrate intake (categorized into low, medium and high intake) and time to recurrence and mortality, adjusting for relevant covariates. During the study period, there were 70 deaths and 72 recurrences. In pretreatment analyses, high intakes of total carbohydrate (HR: 2.29; 95% CI: 1.23-4.25), total sugar (HR: 3.03; 95% CI: 1.12-3.68), glycemic load (HR: 2.10; 95% CI: 1.15-3.83) and simple carbohydrates (HR 2.26; 95% CI 1.19-4.32) were associated with significantly increased risk of all-cause mortality compared to low intake. High intakes of carbohydrate (HR 2.45; 95% CI: 1.23-4.25) and total sugar (HR 3.03; 95% CI 1.12-3.68) were associated with increased risk of HNSCC-specific mortality. In post-treatment analyses, medium fat intake was significantly associated with reduced risk of recurrence (HR 0.08; 95% CI 0.01-0.69) and all-cause mortality (HR 0.27; 95% CI 0.07-0.96). Stratification by tumor site and cancer stage in pretreatment analyses suggested effect modification by these factors. Our data suggest high pretreatment carbohydrate intake may be associated with adverse prognosis in HNSCC patients. Clinical intervention trials to further examine this hypothesis are warranted.

First-Line Treatment of Widely Metastatic BRAF-Mutated Salivary Duct Carcinoma With Combined BRAF and MEK Inhibition.

Salivary duct carcinoma (SDC) is a rare and aggressive malignancy for which limited data exist to guide treatment decisions. With the advent of advanced molecular testing and tumor genomic profiling, clinicians now have the ability to identify potential therapeutic targets in difficult-to-treat cancers such as SDC. This report presents a male patient with widely metastatic SDC found on targeted next-generation sequencing to have a BRAF p.V600E mutation. He experienced a prolonged and robust response to first-line systemic chemotherapy with dabrafenib and trametinib. During his response interval, new data emerged to justify subsequent treatment with both an immune checkpoint inhibitor and androgen blockade after his disease progressed. To our knowledge, this is the first report of frontline BRAF-directed therapy eliciting a response in metastatic SDC.

Oncologic Procedures Amenable to Fluorescence-guided Surgery.

OBJECTIVE: Although fluorescence imaging is being applied to a wide range of cancers, it remains unclear which disease populations will benefit greatest. Therefore, we review the potential of this technology to improve outcomes in surgical oncology with attention to the various surgical procedures while exploring trial endpoints that may be optimal for each tumor type. BACKGROUND: For many tumors, primary treatment is surgical resection with negative margins, which corresponds to improved survival and a reduction in subsequent adjuvant therapies. Despite unfavorable effect on patient outcomes, margin positivity rate has not changed significantly over the years. Thus, patients often experience high rates of re-excision, radical resections, and overtreatment. However, fluorescence-guided surgery (FGS) has brought forth new light by allowing detection of subclinical disease not readily visible with the naked eye. METHODS: We performed a systematic review of clinicatrials.gov using search terms "fluorescence," "image-guided surgery," and "near-infrared imaging" to identify trials utilizing FGS for those received on or before May 2016. INCLUSION CRITERIA: fluorescence surgery for tumor debulking, wide local excision, whole-organ resection, and peritoneal metastases. EXCLUSION CRITERIA: fluorescence in situ hybridization, fluorescence imaging for lymph node mapping, nonmalignant lesions, nonsurgical purposes, or image guidance without fluorescence. RESULTS: Initial search produced 844 entries, which was narrowed down to 68 trials. Review of literature and clinical trials identified 3 primary resection methods for utilizing FGS: (1) debulking, (2) wide local excision, and (3) whole organ excision. CONCLUSIONS: The use of FGS as a surgical guide enhancement has the potential to improve survival and quality of life outcomes for patients. And, as the number of clinical trials rise each year, it is apparent that FGS has great potential for a broad range of clinical applications.

Reconstruction of midface defects with the osteocutaneous radial forearm flap: Evaluation of long term outcomes including patient reported quality of life.

BACKGROUND: Maxillectomy defects significantly impair quality of life. Prosthetics can overcome some of these issues, but has limitations. The role of the osteocutaneous radial forearm free flap (OC-RFFF) has been established for reconstruction of smaller maxillectomy defects, but its role in larger defects is not well defined. We aim to evaluate outcomes after midface reconstruction utilizing the OC-RFFF. METHODS: Retrospective review of prospective database collected between 2005 and 2014 of midface reconstruction using OC-RFFF in a tertiary care centre. Donor site complications and acute and long-term recipient site complications were measured. Health related quality of life was assessed using the University of Washington Quality of Life (UW-QOL) Questionnaire. RESULTS: A total of 68 midface defects were reconstructed using the OC-RFFF. Acute recipient site complications included three flap failures (4%), and two additional microvascular revision cases for vascular compromise. Late recipient complications included fistula (n = 10, 14%), ectropion (n = 7, 10%), diplopia (n = 6, 9%) and exposed hardware (n = 5, 7%). Resection of cheek skin or orbital rim correlated with orbital complications. The incidence of fistula was not affected by defect size or prior radiation. There were two donor site infections and no instances of forearm fracture. Patients undergoing OC-RFFF repair had mean scores for UW-QOL outcomes higher than published rates of obturator quality of life. CONCLUSION: The OC-RFFF is suited to a variety of midface defects and can be combined with hardware to reconstruct the orbital floor. Recipient site complications are common, but donor site morbidity is low and outcomes, including HR-QOL, are acceptable.

Mammary analog secretory carcinoma, low-grade salivary duct carcinoma, and mimickers: a comparative study.

Mammary analog secretory carcinoma (MASC) is a recently recognized low-grade salivary carcinoma characterized by a specific ETV6 rearrangement. We describe 14 new MASCs and examine their immunophenotypic and genetic profiles in the context of look-alikes, namely, low-and high-grade salivary duct carcinoma and acinic cell carcinoma. ETV6 rearrangement, and robust expression of mammaglobin and S100, were demonstrated in 11/11, 14/14, and 12/14 MASCs, respectively. All low-grade salivary duct carcinomas coexpressed S100/mammaglobin (6/6); none harbored ETV6 rearrangements (0/5). Given that S100/mammaglobin coexpression and absence of zymogen granules are features of both MASC and low-grade salivary duct carcinoma, these two are best distinguished histologically. The former is predominantly an extraductal neoplasm with bubbly pink cytoplasm, whereas the latter is a distinct intraductal micropapillary and cribriform process. Querying ETV6 gene status may be necessary for difficult cases. No acinic cell carcinoma expressed mammaglobin (0/13) or harbored an ETV6 rearrangement (0/7); only 1/13 acinic cell carcinomas weakly expressed S100. DOG1 expression was limited or absent among all tumor types, except acinic cell carcinoma which expressed DOG1 diffusely in a canalicular pattern. Therefore, histology and immunohistochemistry (mammaglobin, S100, DOG1) suffices in distinguishing acinic cell carcinoma from both MASC and low-grade salivary duct carcinoma. HER2 (ERBB2) amplification was detected in only 1/10 acinic cell carcinomas, but none of the MASCs or low-grade salivary duct carcinomas tested. High-grade salivary duct carcinomas frequently expressed mammaglobin (11/18) and harbored HER2 amplifications (13/15); none harbored ETV6 rearrangements (0/12). High-grade salivary duct carcinomas can easily be distinguished from these other entities by histology and HER2 amplification.

[(99m)Tc]Tilmanocept Accurately Detects Sentinel Lymph Nodes and Predicts Node Pathology Status in Patients with Oral Squamous Cell Carcinoma of the Head and Neck: Results of a Phase III Multi-institutional Trial.

BACKGROUND: [(99m)Tc]Tilmanocept, a novel CD206 receptor-targeted radiopharmaceutical, was evaluated in an open-label, phase III trial to determine the false negative rate (FNR) of sentinel lymph node biopsy (SLNB) relative to the pathologic nodal status in patients with intraoral or cutaneous head and neck squamous cell carcinoma (HNSCC) undergoing tumor resection, SLNB, and planned elective neck dissection (END). Negative predictive value (NPV), overall accuracy of SLNB, and the impact of radiopharmaceutical injection timing relative to surgery were assessed. METHODS AND FINDINGS: This multicenter, non-randomized, single-arm trial (ClinicalTrials.gov identifier NCT00911326) enrolled 101 patients with T1-T4, N0, and M0 HNSCC. Patients received 50 µg [(99m)Tc]tilmanocept radiolabeled with either 0.5 mCi (same day) or 2.0 mCi (next day), followed by lymphoscintigraphy, SLNB, and END. All excised tissues were evaluated for tissue type and tumor presence. [(99m)Tc]Tilmanocept identified one or more SLNs in 81 of 83 patients (97.6 %). Of 39 patients identified with any tumor-positive nodes (SLN or non-SLN), one patient had a single tumor-positive non-SLN in whom all SLNs were tumor-negative, yielding an FNR of 2.56 %; NPV was 97.8 % and overall accuracy was 98.8 %. No significant differences were observed between same-day and next-day procedures. CONCLUSIONS: Use of receptor-targeted [(99m)Tc]tilmanocept for lymphatic mapping allows for a high rate of SLN identification in patients with intraoral and cutaneous HNSCC. SLNB employing [(99m)Tc]tilmanocept accurately predicts the pathologic nodal status of intraoral HNSCC patients with low FNR, high NPV, and high overall accuracy. The use of [(99m)Tc]tilmanocept for SLNB in select patients may be appropriate and may obviate the need to perform more extensive procedures such as END.

A ratiometric threshold for determining presence of cancer during fluorescence-guided surgery.

BACKGROUND AND OBJECTIVE: Fluorescence-guided imaging to assist in identification of malignant margins has the potential to dramatically improve oncologic surgery. However, a standardized method for quantitative assessment of disease-specific fluorescence has not been investigated. Introduced here is a ratiometric threshold derived from mean fluorescent tissue intensity that can be used to semi-quantitatively delineate tumor from normal tissue. METHODS: Open-field and a closed-field imaging devices were used to quantify fluorescence in punch biopsy tissues sampled from primary tumors collected during a phase 1 trial evaluating the safety of cetuximab-IRDye800 in patients (n = 11) undergoing surgical intervention for head and neck cancer. Fluorescence ratios were calculated using mean fluorescence intensity (MFI) from punch biopsy normalized by MFI of patient-matched tissues. Ratios were compared to pathological assessment and a ratiometric threshold was established to predict presence of cancer. RESULTS: During open-field imaging using an intraoperative device, the threshold for muscle normalized tumor fluorescence was found to be 2.7, which produced a sensitivity of 90.5% and specificity of 78.6% for delineating disease tissue. The skin-normalized threshold generated greater sensitivity (92.9%) and specificity (81.0%). CONCLUSION: Successful implementation of a semi-quantitative threshold can provide a scientific methodology for delineating disease from normal tissue during fluorescence-guided resection of cancer.

Additivity of substituent effects in aromatic stacking interactions.

The goal of this study was to experimentally test the additivity of the electrostatic substituent effects (SEs) for the aromatic stacking interaction. The additivity of the SEs was assessed using a small molecule model system that could adopt an offset face-to-face aromatic stacking geometry. The intramolecular interactions of these molecular torsional balances were quantitatively measured via the changes in a folded/unfolded conformational equilibrium. Five different types of substituents were examined (CH3, OCH3, Cl, CN, and NO2) that ranged from electron-donating to electron-withdrawing. The strength of the intramolecular stacking interactions was measured for 21 substituted aromatic stacking balances and 21 control balances in chloroform solution. The observed stability trends were consistent with additive SEs. Specifically, additive SE models could predict SEs with an accuracy from ±0.01 to ±0.02 kcal/mol. The additive SEs were consistent with Wheeler and Houk's direct SE model. However, the indirect or polarization SE model cannot be ruled out as it shows similar levels of additivity for two to three substituent systems, which were the number of substituents in our model system. SE additivity also has practical utility as the SEs can be accurately predicted. This should aid in the rational design and optimization of systems that utilize aromatic stacking interactions.

Assessment of erlotinib as adjuvant chemoprevention in high-risk head and neck cancer patients.

PURPOSE: To determine the tolerability and efficacy of long-term treatment with erlotinib for head and neck squamous cell carcinoma after salvage surgery. METHODS: An open-label study was conducted of 150 mg of daily erlotinib for 12 months in patients who completed definitive surgical therapy for recurrent head and neck squamous cell carcinoma. The primary outcome measures were tolerability of prolonged erlotinib therapy and disease-free survival and overall survival at 1 and 2 years. RESULTS: Thirty-one patients were enrolled onto this study. Mean duration of erlotinib therapy was 5 months (range 2-374 days), with 8 patients completing the full 12-month course of erlotinib. Of the remaining patients, 8 discontinued therapy as a result of recurrence, 10 for medical or surgical complications deemed unrelated to the study medication, and 3 for drug-related toxicities. There were 25 grade 3 adverse events; 4 were classified as possibly related to study medication. The most common adverse events included acneiform rash (n = 26 patients), fatigue (n = 22), and diarrhea (n = 22). Overall survival was 61 % at 1 year and 56 % at 2 years. Disease-free survival was 54 % at 1 year and 45 % at 2 years. Mean time to recurrence (n = 16) was 8.7 months. CONCLUSIONS: Long-term erlotinib is safe and demonstrates some potential survival benefit compared to historical controls. However, despite the absence of grade 3/4 adverse events attributable to the drug, tolerance of long-term erlotinib was a significant barrier to completion of a 12-month course of therapy.

Conformational preferences of N,N-dimethylsuccinamate as a function of alkali and alkaline earth metal salts: experimental studies in DMSO and water as determined by 1H NMR spectroscopy.

The fraction of gauche conformers of N,N-dimethylsuccinamic acid (1) and its Li(+), Na(+), K(+), Mg(2+), Ca(2+), and N(Bu)4(+) salts were estimated in DMSO and D2O solution by comparing the experimental vicinal proton-proton couplings determined by (1)H NMR spectroscopy with those calculated using the Haasnoot, de Leeuw, and Altona (HLA) equation. In DMSO, the gauche preferences were found to increase with decreasing Ahrens ionic radius of the metal counterion. The same trend was not seen in D2O, where the gauche fraction for all of the metallic salts were estimated to be approximately statistical or less. This highlights the importance of metal chelation on the conformation of organic molecules in polar aprotic media, which has implications for protein folding.

Conformational preferences of cis-1,3-cyclopentanedicarboxylic acid and its salts by 1H NMR spectroscopy: energetics of intramolecular hydrogen bonds in DMSO.

The conformational populations of cis-1,3-cyclopentanedicarboxylic acid (1) and its mono- and dianion were established in DMSO solution by comparing the vicinal proton­proton coupling constants (3J(HH)) obtained in solution to their theoretical counterparts. Geometries used for 3J(HH) theoretical estimation (using Karplus-type equations) were obtained from optimized structures at the B3LYP/6-31G(2d,2p) level. The diacid (1) adopted many conformations, whereas the ionized species (1A mono- and 1B dianion) assumed single conformations. A downfield chemical shift of 19.45 ppm (Δδ(H) = 7.43 ppm) observed at −60 °C was indicative of intramolecular hydrogen bonding in 1A, which was later corroborated by determining the ratio of the first (K1) to the second (K2) ionization constants. K1/K2 in DMSO (1.3 × 10(7)) was significantly larger than the value in water (2 × 10). In addition, K1/K(E) = 200 (where K(E) is the acidity constant of the monomethylester of 1) was greater than the intramolecular hydrogen bonding threshold value of 2. The calculated intramolecular hydrogen bond strength of 1A was ~3.1 kcal mol(­1), which is ~2.7 kcal mol(­1) more stable than the values for cis-1,3-cyclohexanedicarboxylic acid (2A). Thus, the relative energies of intramolecular hydrogen bonding in the monoanions 1A and 2A suggests that 1,3-diaxial conformers are more favored for cyclopentane than for cyclohexane rings.

Conformational analysis of N,N,N-Trimethyl-(3,3-dimethylbutyl)ammonium iodide by NMR spectroscopy: a sterically hindered trans-standard.

A predominantly trans-1,2-disubstituted ethane system - N,N,N-trimethyl-(3,3-dimethylbutyl)ammonium iodide - is of particular interest for conformational analysis, because it contains both an organic and a highly polar substituent, making it soluble and thus applicable to study in a large variety of solvents. The fraction of the trans conformer of this molecule in a wide range of protic and aprotic solvents was determined by the nuclear magnetic resonance proton couplings to be approximately 90%, in contrast to the previously assumed 100%. The consistently strong preference of the trans conformation should establish N,N,N-trimethyl-(3,3-dimethylbutyl)ammonium iodide as a possibly useful 'trans-standard' in conformational analysis, much more so than 1,2-ditert-butylethane, which has a poor solubility in many solvents.

Positive Deep Initial Incision Margin Affects Outcomes in TORS for HPV+ Oropharynx Cancer.

OBJECTIVE: Evaluate the effect of initial incision margins (IIM) on clinical outcomes after transoral robotic surgery (TORS) for human papillomavirus positive (HPV+) squamous cell cancers of the oropharynx (OPSCC). METHODS: Retrospective chart review of patients undergoing TORS for HPV+ OPSCC from 2007 to 2015 was performed. Overall survival (OS), disease-specific survival (DSS), recurrence, and metastases were evaluated in the context of pathology, IIM, final margins, adjuvant therapy, and patient characteristics. RESULTS: Ninety-five patients with HPV+ OPSCC undergoing primary surgery were identified. 88% of these patients had no evidence of disease at the conclusion of the study (average follow-up 45 months). Twenty were identified that had true positive IIM and 16 had very close IIM, with the remainder demonstrating widely negative margins. Tumor very close to or involving the deep margin but not a mucosal margin was associated with a higher risk of recurrence. Perineural invasion and lymphovascular invasion were associated with positive IIM. Positive or very close IIM on the deep margin was found to impact DSS and recurrence. CONCLUSION: Obtaining negative IIM while performing TORS for HPV+ OPSCC is a modifiable factor that affects recurrence and DSS. Larger surgical margins should be considered in patients with perineural invasion or whose tumor abuts the initial deep margin. LEVEL OF EVIDENCE: 4 Laryngoscope, 133:1132-1137, 2023.

Conformational preferences of trans-1,2- and cis-1,3-cyclohexanedicarboxylic acids in water and dimethyl sulfoxide as a function of the ionization state as determined from NMR spectroscopy and density functional theory quantum mechanical calculations.

The populations of diaxial (aa) and diequatorial (ee) conformers of trans-1,2- and cis-1,3-cyclohexanedicarboxylic acids (CDCAs; 1 and 2, respectively) and their salts were determined in water and dimethyl sulfoxide (DMSO) solutions from vicinal proton-proton NMR J couplings ((3)J(HH)). Optimized geometries and free energies for these compounds were obtained at the M06-2X/cc-pVTZ(-f)++ level. Although carboxylic acid groups in cyclohexane rings are generally believed to be far more stable (~2 kcal/mol) in equatorial than axial positions, this investigation demonstrated that an aa conformation (normally assumed to be completely insignificant for these compounds) can be favored depending on the medium and ionization state: strong ee preferences (>90%) were observed in water and DMSO for both diacids and their salts, except for the dianion of 1 in DMSO, which was found to be substantially aa (~57%). The possibility of intramolecular hydrogen bonding (H-bonding) was also investigated; the ratios of the ionization constants (K(1)/K(2)) indicated an absence of intramolecular H-bonding because K(1)/K(2) ≪ 10(4) (a standard criterion for non-H-bonding in dicarboxylic acids) for both 1 and 2 in water and also for 2 in DMSO. For 1, K(1)/K(2) increased drastically in DMSO (K(1)/K(2) = 4 × 10(6)), where (3)J(HH) and the ratio K(1)/K(E) = 10, K(E) being the acidity constant of the monomethyl ester of 1, indicated the formation of an intramolecular H-bond for the monoanion in this solvent. An explanation for the observation of compact dianions in solution in terms of the generalized Born equation is also provided.