Evaluation of different time schedules in training with the Da Vinci simulator.

BACKGROUND: This prospective study analyzed the effect of different time schedules in training on the main performance outcomes: overall score, time to complete, and economy of motion. METHODS: The study was performed on the da Vinci Skills Simulator from December 2014 to April 2016. Forty robotic novices were randomized into two groups of 20 participants, which trained in the same three exercises but with different intervals between their training sessions. Each group performed training in Peg Board 1 in their first week, Match Board 2 in their second week, and Ring and Rail 2 in their third week. On their last day, Needle Targeting and Energy Dissection 2, for which no previous training had been received, were performed. Regarding the different training intervals, group 1 trained each exercise six times in a row once a week. Group 2 performed their training once a day for 5 days. Technical performance parameters were recorded by the Mimics simulator software for further analysis. In addition, the participants were asked to fill out a questionnaire concerning the robotics training. RESULTS: Group 2 performed significantly better compared to group 1 in the main metrics in the more advanced exercises. For the easier exercises, the training frequency did not lead to significant differences in performance outcome. A significant skills gain was seen between the first and last training sessions for all exercises in both groups. CONCLUSIONS: Performance in the final exercise NT was significantly better in group 2 than group 1. Regarding ED 2, no difference was found between the two groups. As the training of group 2 led to significantly better outcomes, we suggest that, especially for advanced exercises, it seems to be more favorable to perform training every day for a short period than to train once a week six times in a row.

The effect of different training exercises on the performance outcome on the da Vinci Skills Simulator.

BACKGROUND: Increasing usage of robotic surgery presents surgeons with the question of how to acquire the special skills required. This study aimed to analyze the effect of different exercises on their performance outcomes. METHODS: This prospective study was conducted on the da Vinci Skills Simulator from December 2014 till August 2015. Sixty robotic novices were included and randomized to three groups of 20 participants each. Each group performed three different exercises with comparable difficulty levels. The exercises were performed three times in a row within two training sessions, with an interval of 1 week in between. On the final training day, two new exercises were added and a questionnaire was completed. Technical metrics of performance (overall score, time to complete, economy of motion, instrument collisions, excessive instrument force, instruments out of view, master work space range, drops, missed targets, misapplied energy time, blood loss and broken vessels) were recorded by the simulator software for further analysis. RESULTS: Training with different exercises led to comparable results in performance metrics for the final exercises among the three groups. A significant skills gain was recorded between the first and last exercises, with improved performance in overall score, time to complete and economy of motion for all exercises in all three groups. CONCLUSIONS: As training with different exercises led to comparable results in robotic training, the type of exercise seems to play a minor role in the outcome. For a robotic training curriculum, it might be important to choose exercises with comparable difficulty levels. In addition, it seems to be advantageous to limit the duration of the training to maintain the concentration throughout the entire session.

Structured training on the da Vinci Skills Simulator leads to improvement in technical performance of robotic novices.

BACKGROUND: The increasing use of minimally invasive techniques such as robotic-assisted devices raises the question of how to acquire robotic surgery skills. The da Vinci Skills Simulator has been demonstrated to be an effective training tool in previous reports. To date, little data are available on how to acquire proficiency through simulator training. We investigated the outcome of a structured training programme for robotic surgical skills by robotic novices. METHODS: This prospective study was conducted from January to December 2013 using the da Vinci Skills Simulator. Twenty participants, all robotic novices, were enrolled in a 4-week training curriculum. After a brief introduction to the simulator system, three consecutive repetitions of five selected exercises (Match Board 1, 2, 3 and Ring and Rail 1, 2) were performed in a defined order on days 1, 8, 15 and 22. On day 22, one repetition of a previously unpractised more advanced module (Needle Targeting) was also performed. After completion of each study day, the overall performance, time to completion, economy in motion, instrument collisions, excessive instrument force, instruments out of view, master workspace range and number of drops were analysed. RESULTS: Comparing the first and final repetition, overall score and time needed to complete all exercises, economy of motion and instrument collisions were significantly improved in nearly all exercises. Regarding the new exercise, a positive training effect could be demonstrated. While its overall entry score was significantly higher, the time to completion and economy of motion were significantly lower than the scores on the first repetition of the previous 5 exercises. CONCLUSIONS: It could be shown that training on the da Vinci Skills Simulator led to an improvement in technical performance of robotic novices. With regard to a new exercise, the training had a positive effect on the technical performance.

Treatment in elderly patients with head and neck cancer : A challenging dilemma.

Despite the increasing number of elderly patients requiring treatment for head and neck cancer, there is insufficient available evidence about the oncological results of treatment and its tolerability in such patients. Owing to comorbidities, elderly patients often need complex evaluation and pretreatment management, which often results in their exclusion from clinical trials. The question of which patients constitute the highest-risk groups regarding treatment-related morbidity and mortality, and who can tolerate and benefit from aggressive treatment, has not been adequately studied. Biologic rather than chronologic age should be a more important factor in treatment protocols. Age-specific prospective clinical studies are needed on the treatment of head and neck cancer in elderly patients.

[Clinical aspects of transoral laser surgery and neck dissection for oro- and hypopharyngeal cancer in elderly patients]. / Klinische Aspekte der transoralen Laserchirurgie und Neck-Dissection bei Oro- und Hypopharynxkarzinomen im fortgeschrittenen Lebensalter.

BACKGROUND: The number of elderly patients with head and neck cancer is increasing. However, there are few valid data on postoperative course after head and neck cancer surgery in elderly patients. The aim of this study was to evaluate the oncological outcome of elderly patients after surgical treatment for oro- and hypopharyngeal cancer. MATERIAL AND METHODS: The clinical data of 81 patients, separated into two age groups (62 < 65 years vs. 19 ≥ 65 years), were retrospectively analysed. The cohort comprised T1 and T2 oro- and hypopharyngeal cancer patients, who had undergone primary treatment with transoral laser surgery and neck dissection. Overall and disease-free survival times of the patients were analysed. Additionally, comorbidities and perioperative complications were compared between the two age groups. Median follow-up time was 5.9 years. RESULTS: Comparison of different clinical and histopathological data revealed no significant differences between the age groups. The Kaplan-Meier method revealed no significant difference in disease-free survival between the age groups (p = 0.52). Age had no effect on disease-free survival in uni- or multivariate analysis (p = 0.53 vs. 0.94). Surgery-related complications were observed in 13 patients (16 %), 11 cases of which concerned the younger group of patients. CONCLUSION: Transoral laser surgery and neck dissection can lead to satisfactory oncological and surgical outcomes in elderly patients with oro- and hypopharyngeal cancer.

[The new S2k AWMF guideline for the treatment of obstructive sialadenitis in commented short form]. / Die neue S2k AWMF Leitlinie zur Behandlung der obstruktiven Sialadenitis in kommentierter Kurzform.

A new and interdisciplinary S2k AWMF guideline for the treatment of obstructive sialadenitis has been published. There have been several technical achievements, for instance in the field of ultrasonography, via sialendoscopy, or by MR-sialography, that have increased the possibilities for diagnosis and treatment of patients with obstructive sialadenitis. In the past, the treatment of choice in case of unsuccessful medical treatment was a complete extirpation of the affected salivary gland. Nowadays, using a variety of modern treatment options (like sialendoscopy, or extracorporeal shock-waves lithotripsy sometimes combined with salivary duct incision), it is possible in most patients, especially in cases of sialolithiasis, to preserve the affected gland. A functional recovery after gland-sparing surgery is described but more data is needed to finally evaluate the long-time results. The new guideline describes all relevant steps to diagnose an obstructive sialadenitis and values all diagnostic tools critically. Finally, all recommendable therapy options are described and valued, too.

Prospective evaluation of reliability of cone-beam computed tomography in detecting different position of vibroplasty middle ear implants.

OBJECTIVES: This study had the following objectives: (i) to determine the accuracy of determination of Vibrant Soundbridge position in the spectrum of typically implanted sites in the middle ear, (ii) to assess interobserver agreement between three observers with different levels of radiology experience and (iii) to determine the suitability of cone-beam computed tomography (CT) to be used as the baseline radiological assessment post implantation, confirm ferromagnetic transducer (FMT) position. DESIGN: Prospective research study. Using four fresh human cadaveric heads, different types of vibroplasty were performed. After each step, cone-beam CT was performed for each of the four cadaveric heads. SETTING: University hospital (ENT and Neuroradiology). PARTICIPANTS: Four fresh cadaveric heads of human donors were operated and analysed by radiological imaging. MAIN OUTCOME MEASURES: There are different ways of coupling an ferromagnetic transducer to the anatomical structures of the middle and inner ear. Possibilities of differentiation between these coupling variants should be presented. RESULTS: The individual reconstruction view was significantly different from a standardised view for each observer (observer 1: P = 0.003; observer 2: P = 0.001; observer 3: P = 0.002) for all coupling variants combined as well as for each individual coupling variant (overall correct diagnosis: 100% versus 60%). Regarding the frequency of correct diagnosis, no significant differences were found between the three observers (P > 0.500) for each individual coupling variant as well as for all coupling variants combined. The worst rates of correct diagnosis were found in the standardised view for incus (42%), stapes (0%) and TORP (17%) vibroplasty. CONCLUSION: Cone-beam CT as a radiological control for Vibrant Soundbridge is safe and adequately sensitive and reliable and is therefore suitable for clinical investigation. The position of the ferromagnetic transducer in the middle ear and the presence or absence of an additional coupler could be determined in this study. Therefore, cone-beam-CT is useful for the assessment of device failure when there has been gross displacement of the ferromagnetic transducer (or smaller displacements in case of a baseline postoperative cone-beam CT). Regarding the quality of imaging, cone-beam CT produced accurate results with different observers with widely varying radiological experience.

[Selective neck dissection in head and neck cancer]. / Selektive Neck dissection bei Karzinomen der oberen Luft- und Speisewege.

While (modified) radical neck dissection was seen formerly as an essential measure for securing local tumor control and improvement of the prognosis for head and neck cancer patients, this procedure is nowadays often replaced by selective neck dissection. Selective neck dissection is associated with a comparably low morbidity and acceptable functional results without having a negative impact on the prognosis of the patients. As staging procedure, neck dissection is currently the gold standard, so that selective neck dissection is an approved part of the therapy of the clinical N0 neck and is recommended as salvage therapy of the neck after radiochemotherapy. There are also aspects supporting the performance of selective neck dis-section in selected patients with N + neck.

[Imaging quality and dosage in ENT--what do we really need?]. / Dosisreduktion unter Betrachtung der erforderlichen Bildqualität--Wie viel Dosis braucht ein Bild?

BACKGROUND: Today, imaging of nose, paranasal sinuses and temporal bone by CT is standard in preoperative diagnostics. The need of reduction of applied dosage leads to the necessity of research in necessary imaging quality. Therefore this paper deals with new developed anatomical checklists and the analysis of imaging quality on anterior and lateral skull base. MATERIAL AND METHODS: With 3 human complete heads over 400 examinations were performed on one cone beam CT device under varying x-ray-tube adjustments. 31 anatomic parameters were evaluated (Excellent, well, poor, not evaluable) for every data set. A summation score was built for every examination. RESULTS: As well for paranasal sinuses as for temporal bone a constant excellent imaging quality could be seen in high dosages. Certainly, in low dosages a reduction of imaging quality was detected. The optimal range (all parameters visualized well as average) could be evaluated for paranasal sinuses between 2,0 and 3,0 mGy and between 3,0 and 4,0 mGy for temporal bone. So, a reduction of 70-80% in comparison to highest adjustments of today is possible and realistic. In comparison to standard protocols, a reduction of about 50% can be reached. CONCLUSION: The possibility of dose reduction by discussion of the necessary imaging quality from clinical point of view could be shown.

The value of spreader grafts in rhinoplasty: a critical review.

The value of spreader grafts in rhinoplasty cannot be underestimated. Various studies have demonstrated that they play a valuable role in the restoration of nasal dorsum aesthetics, provide support for the nasal valve and maintain the straightened position of the corrected deviated cartilaginous septal dorsum. However, there is still controversy on the extent of its value in nasal patency. This study reviews the literature and describes the values and limitations of spreader grafts in rhinoplasty and the alternatives to classic spreader grafts.

Artifacts of the electrode in cochlea implantation and limits in analysis of deep insertion in cone beam tomography (CBT).

Until now more than 250,000 cochlea implantations have been performed worldwide. The surgical procedure is well standardized. A discussion about the kind of postoperative radiological control has started since cone beam tomography (CBT) has been established in ENT and hearing preservation operations have come more into the focus. Further research has been concentrated on the role of CBT and the insertion of the basal turn. The aim of this study was to look for the possibilities of CBT and deep insertion. The second aim was to analyze the artifacts of cochlea implants in CBT. Three human cadaver ears were implanted with a flex soft electrode of MedEl© in a standard operation procedure with round window insertion and a full insertion. Afterwards 72 CBT sets per ear were performed with different X-ray-tube currents (2-10 mA), voltages (72-90 kV), and exposure times (9 and 17 s). On each data set, the radiological diameter of the electrode 9 (basal), electrode 2 (apical), the diameter of the cable next to the electrodes 9 and 2, and the associated diameter of the cochlea next to the electrodes 9 and 2 were evaluated. Additionally, a comparison to the real diameter was done. The mean radiological diameters of the measure point at electrode 9 were: electrode = 1.19 mm; cable = 0.65 mm; cochlea = 1.77 mm. Results for measure point at electrode 2 were: electrode = 0.98 mm; cable = 0.48 mm; cochlea = 1.21 mm. The real diameters were at electrode 9 in lateral view 0.58 mm and in top view 0.63 mm and at electrode 2 in lateral view 0.36 mm and in top view 0.50 mm. Differences between the diameters of the electrode 9 and 2 were highly significant. Interestingly, the real diameter of the electrode is half in comparison to the radiological one. Also in comparison to the diameter of the cable and the associated electrode is nearly half. Nearly 50% artifact exists on radiologic evaluation of the diameter of the electrode. Varying the X-ray adjustments did not lead to optimized results. The difficulties in evaluating a cochlea electrode with CBT could be shown. The high rate of artifacts (50%) makes it extremely difficult to predict the inserted scale, especially when evaluating the intracochlear position in the medial and apical turn of the cochlea. In conclusion, until now CBT allows a relatively safe evaluation of the electrode in the basal turn, whereas in deep insertion it is not really a useful tool to answer the question of insertion trauma, implanted scale, or scale displacements.

[Current advances in diagnosis and surgical treatment of lymph node metastasis in head and neck cancer]. / Aktuelle Fortschritte in der Diagnostik und chirurgischen Therapie der Halslymphknotenmetastasen bei Kopf-Hals-Karzinomen.

Still today, the status of the cervical lymph nodes is the most important prognostic factor for head and neck cancer. So the individual treatment concept of the lymphatic drainage depends on the treatment of the primary tumor as well as on the presence or absence of suspect lymph nodes in the imaging diagnosis. Neck dissection may have either a therapeutic objective or a diagnostic one. The selective neck dissection is currently the method of choice for the treatment of patients with advanced head and neck cancers and clinical N0 neck. For oncologic reasons, this procedure is generally recommended with acceptable functional and aesthetic results, especially under the aspect of the mentioned staging procedure. In this review article, current aspects on pre- and posttherapeutic staging of the cervical lymph nodes are described and the indication and the necessary extent of neck dissection for head and neck cancer is discussed. Additionally the critical question is discussed if the lymph node metastasis bears an intrinsic risk of metastatic development and thus its removal in a most possible early stage plays an important role.

Radiological examinations of the anatomy of the inferior turbinate using digital volume tomography (DVT).

BACKGROUND: Since the last 120 years there were only few descriptions of the anatomical sizes of the inferior turbinate in the literature. On this background the current study should evaluate the radiological dimensions of the inferior turbinate and the septum using DVT. METHODS: The latest generation of the Accu-I-tomo was used. The data of 100 adult patients have been evaluated. RESULTS: The bony length was found to be 38.9 mm, the mucosal length 51.0 mm. The findings of the total mucosal thickness at different measuring points were between 8.1 mm and 10.9 mm, those of the bony thickness were between 0.9 mm and 2.3 mm and those of the bony height were between 3.9 mm and 20.8 mm. CONCLUSION: The results of this radiological study are able to point out the importance of preoperative anatomical evaluation of radiological images. The preoperative focus on the individual anatomy is very important because of the choice of an adequate surgical treatment. Today new radiological techniques can help to find out whether the reason for hypertrophied turbinates is caused by bone, mucosa or both. This knowledge enables a concerted treatment concept.

Wyburn-Mason syndrome: a case report.

OBJECTIVE: Wyburn-Mason syndrome is a rare disease associated with multiple arteriovenous malformations of the brain, orbit, and face resulting from an insult occurring during embryonic development. CASE REPORT: We present the clinical and radiological features of a 47-year-old-man with Wyburn-Mason syndrome who suffered from recurrent bleeding episodes primarily at the nasal corner of the left orbit. After radiotherapy and several angioembolisations, surgical reduction with exenteration of the left orbit was performed and resulted in reduced bleeding. Two years later the patient presented with maxillary sinus empyema. Due to massive endonasal bleeding, endoscopy could not be performed and the maxillary empyema was treated via a transorbital approach. CONCLUSION: Although close observation represents the standard of care in Wyburn-Mason syndrome, patient-specific management decisions are required in the presence of symptoms or complications. In the presented case, surgical intervention proved to be successful.

[Function and dysfunction of the superior laryngeal nerve]. / Funktion und Dysfunktion des N. laryngeus superior.

BACKGROUND: Diseases of the superior laryngeal nerve occur more often than thought. Paresis of the superior laryngeal nerve is one of the most frequent causes of dysfunction of this nerve, mainly occurring in the context of thyroid surgery. RESULTS AND CONCLUSION: To avoid iatrogenic damage of the superior laryngeal nerve, knowledge of the exact topography of the course of this nerve is necessary. A lesion of the superior laryngeal nerve may be associated with changes in the voice as well as with swallowing disorders with aspiration. Diagnosis of this disease is clinically challenging because the clinical symptoms are frequently not pronounced. Besides laryngoscopy, stroboscopy and electromyography are required for exact diagnosis.

Health-related quality of life in oropharyngeal cancer survivors - a population-based study.

OBJECTIVE: The aim of this study was to compare QoL of oropharyngeal cancer survivors who had received different treatments. SUBJECTS AND METHODS: We contacted 954 survivors. Each survivor received the QoL questionnaires EORTC QLQ-C30 and EORTC QLQ-H&N35. RESULTS: A total of 263 survivors completed the questionnaires (28% responses). Forty-five of them had undergone surgery, 20 had received definitive radiotherapy or chemo-radiotherapy, 85 surgery plus adjuvant radiotherapy, and 111 surgery plus adjuvant chemo-radiotherapy. Survivors who had received adjuvant radiotherapy and surgery reported significantly more problems with swallowing (B=13.43 [95% Confidence Interval (CI) 1.83-25.03]), senses (B=24,91 [CI 11.86-37.97]), eating (B=16.91 [CI 3.46-30.36]), dry mouth (B=26.42 [CI 12.17-40.67]), sticky saliva (B=22.37 [CI 6.23-38.50]) and nutritional supplements (B=18.59 [CI 0.62-36.56]) than those who had received surgery only. Survivors who had received adjuvant chemo-radiotherapy and surgery reported significantly many more problems with dry mouth (B=34.15 [CI 18.91-49.39]) and sticky saliva (B=22.90 [CI 5.65-40.16]), and fewer problems with physical functioning (B=-12.07 [CI 0.49-23-64]). CONCLUSION: Survivors who participated in this survey and who had undergone surgery alone reported in some head- and neck-specific domains a better health-related quality of life than patients who had undergone multi-modal treatment or adjuvant radiotherapy.

Intraglandular application of botulinum toxin leads to structural and functional changes in rat acinar cells.

BACKGROUND AND PURPOSE: Intraglandular injection of botulinum toxin (BoNT) leads to a transient denervation of the submandibular gland and this is associated with reduced salivary secretion. The purpose of the present study was to verify whether temporary acinar atrophy occurs simultaneously with chemical denervation of the glands. EXPERIMENTAL APPROACH: Tissue specimens of the right submandibular gland taken from 18 Wistar rats after intraglandular injection of BoNT A, BoNT B, or a combination of both were examined. As a sham control, an equivalent volume of saline was injected into the left submandibular gland. Morphometric measurements, immunohistochemistry, electron microscopy and western blot analysis were used to analyse the morphological and functional changes of the denervated glands. KEY RESULTS: Morphological and ultrastructural analyses of the cell organelles and secretory granula showed a clear atrophy of the acini, which was more prominent in glands injected with the combination of BoNT/A and B. Morphometric measurements of the glandular acini revealed a significant reduction of the area of the acinar cells after injection of BoNT (P=0.031). The expression of amylase was significantly reduced in BoNT treated glands. CONCLUSIONS AND IMPLICATIONS: Intraglandular application of BoNT induces structural and functional changes of the salivary glands indicated by glandular atrophy. These effects may be due to glandular denervation induced by the inhibition of the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors (SNAREs) involved in acetylcholine release at the neuroglandular junction and also specially inhibition of those involved in exocytosis of the granula of the acinar cells.

Evidence of lymphangiogenesis in Warthin's tumor of the parotid gland.

The details of the pathogenesis of cystadenolymphoma (Warthin's tumor) of the parotid gland are still unclear. Neovascularization is considered to be a pivotal factor for solid tumor progression and biological behavior of the tumor. Using double-labeling immunohistochemistry for LYVE-1 and CD34 (specific markers for lymphatic and vascular endothelial cells, respectively) this study analyzes lymphatic vessel density (LVD) and blood vessel density (BVD) in 10 Warthin's tumors and 10 pleomorphic adenomas of the parotid gland as well as in 5 normal parotid glands and 5 normal parotid lymph nodes. There was no significant difference in the intratumoral LVD and BVD among pleomorphic adenoma and normal parotid gland tissue. In contrast, the intratumoral LVD and BVD were significantly higher in Warthin's tumor than pleomorphic adenoma, normal parotid gland and parotid lymph node (P<0.0001 versus P<0.004). The increase in lymphatic vessels in Warthin's tumor suggests that epithelial tumor cells might promote lymphangiogenesis in this kind of lesions.

Indications of cone beam CT in head and neck imaging in children.

For imaging of bony structures, especially for the anterior and lateral skull base in ORL medicine, cone beam computed tomography (CBCT) is an increasingly used alternative to CT, with a lower exposition to plain radiography that makes its use for imaging, particularly in children, very interesting. The aim of this study was to analyse possible indications and settings for CBCT in children and compare them to those of adults. A total of 554 patients (age range 0-18 years, mean age 10.36 years), who underwent CBCT between 01/2004-06/2013 in the ENT department at the university clinic of Marburg were enrolled in this retrospective analysis to evaluate technical parameters and indications. Data on CBCT of all children were compared with previously published data collected from 1730 adults who were diagnosed with the help of CBCT in the ENT department at the university clinic of Marburg, during the years 2012-2013. The most frequent indications of CBCT in children vs. adults were in the anterior skull base region: mid-facial trauma (60.4%) vs. chronic rhinosinusitis (54.8%), disturbed nasal breathing (13.9% vs. 13.0%) and chronic rhinosinusitis (12%) vs. mid-facial trauma (10.8%). For the lateral skull base the main indications were cholesteatoma (20.3%) vs. position control of cochlear implant (CI) electrode (31.2%), chronic otorrhoea (17.5%) vs. cholesteatoma (20.9%), and position control of CI electrode (11.8%) vs. chronic otitis media mesotympanalis (6.8%). CBCT is a suitable imaging modality for bony structures in adults and children. Settings mainly depend on the region of interest. One aim should also be to reduce exposure to radiation in both adults and children.

Clinical features of cystadenolymphoma (Warthin's tumor) of the parotid gland: a retrospective comparative study of 96 cases.

The details of the etiopathogenesis of cystadenolymphoma (Warthin's tumor) are still unclear. To explore the possible risk factors for the development of this tumor, medical records of 81 patients with 96 Warthin's tumors of the parotid glands were compared retrospectively with those of 91 patients with pleomorphic adenoma. The medical history and clinical tumor characteristics of all patients were similar. There were no significant differences between these two patient groups with respect to concomitant diseases, regular medications, and preoperative laboratory findings. However, a significant male predominance of patients with Warthin's tumor could be noted (P<0.05). The male to female ratio was 3.3:1 in patients with Warthin's tumor. Multifocal Warthin's tumor were detected in five cases (6.2%), and 10 patients (12.3%) had bilateral lesions. The odds ratio for the incidence of Warthin's tumor among current smokers compared with never smokers was 8.3 (P<0.0001). Compared with never smokers, clearly higher odds of Warthin's tumor was observed in heavy smokers (more than 30 pack-years) (odds ratio=24.1, P<0.0001) than patients who smoked less than 30 pack-years (odds ratio=4.9, P<0.0001).