Pre-operative CT cephalometry and functional outcomes after open partial horizontal laryngectomy| ACTA Otorhinolaryngologica Italica

Abstract

Objectives. To identify pre-operative radiological parameters that are able to predict the functional outcomes of open partial horizontal laryngectomy (OPHL).
Methods. The present retrospective study concerned a cohort of 96 patients with laryngeal squamous cell carcinoma who underwent pre-operative radiological staging with contrastenhanced computerised tomography of the neck, and subsequent supracricoid or supratracheal laryngectomy. Univariate and multivariate analyses were run to assess the prognostic value of the main demographic and surgical variables, and the pre-operative cephalometric values, respectively, in terms of predicting patients’ functional outcomes.
Results. Multivariate analysis showed that a larger anteroposterior cross-sectional dimension of the aero-digestive tract in the mid-retroglossal area, and a greater distance between the genial tubercle and the hyoid bone in the mid-sagittal plane correlated significantly with better functional outcomes in terms of decannulation rate at discharge.
Conclusions. Our findings show that larger pre-operative upper aero-digestive tract diameters and volumes coincide with better post-operative functional outcomes after OPHL.

Introduction

In recent decades, open partial horizontal laryngectomy (OPHL) has come to be adopted largely as a conservative surgical option for treating selected cases of laryngeal squamous cell carcinoma (LSCC) ¹. The purpose of partial laryngectomy is to ensure oncological radicality by completely removing the tumour while preserving laryngeal functions. The functional success of reconstructive laryngectomies is judged mainly from the rate of decannulation, which can only be achieved after breathing and swallowing have fully recovered. The functional outcome after OPHL is good, with a reported 5-year laryngeal function preservation rate of 97.8% for early-to-intermediate disease, and 91.2% for intermediate-to-advanced disease ^2,3.

Current contraindications to partial laryngectomy include alcohol and drug abuse, and major general comorbidities (heart failure, lung diseases, diabetes mellitus, or severe neurocognitive decline). Predictors of a poor functional outcomes include: patient-related factors, such as very old age; and surgery-related factors, such as the type of procedure, i.e. supracricoid with/without suprahyoid epiglottis preservation (OPHL type IIA/B) or supratracheal laryngectomy with/without suprahyoid epiglottis preservation (OPHL type IIIA/B) ^4,5.

To the best of our knowledge, there are no pre-operative radiological parameters known to predict functional outcomes after OPHL. Identifying such prognostic indicators would help laryngologists to choose the best treatment option for each patient, and provide appropriate pre-operative counselling.

Conventional two-dimensional cephalometry has been used extensively in the fields of orthodontics and anthropology to record craniofacial dimensions. More recently, it has also been applied to the evaluation of skeletal and aero-digestive tract anatomy in patients with obstructive sleep apnoea syndrome (OSAS) ^6-9. It has been claimed, however, that two-dimensional images cannot accurately reflect three-dimensional (3D) aero-digestive tract anatomy ^10,11.

Contrast-enhanced computerised tomography (CT) scanning of the neck is currently part of the diagnostic work-up and staging of patients with LSCC. CT imaging enables linear measurements to be obtained, and volumes and cross-sectional areas of the aero-digestive tract can be calculated in three planes (coronal, sagittal, and axial). The axial plane, which is not visible on a lateral cephalogram, is the most relevant physiologically because it is perpendicular to the air flow ¹².

The primary endpoint of the present study was to investigate the value of pre-operative cephalometric CT scan parameters in predicting functional outcomes after OPHL, and decannulation rates at discharge in particular. Secondary endpoints were to analyse the value of other pre-operative demographic and surgical parameters for the purpose of predicting functional outcomes.

Materials and methods

Patients

The present study concerned a cohort of 96 patients with glottic LSCC who underwent pre-operative radiological staging with contrast-enhanced neck CT scans and subsequent supracricoid with/without suprahyoid epiglottis preservation (OPHL type IIA/B) or supratracheal laryngectomy with/without suprahyoid epiglottis preservation (OPHL type IIIA/B) ¹ at Vittorio Veneto Hospital - Otolaryngology Department from 2010 to 2016. According to the modular OPHL approach, the open partial laryngectomy could be intra-operatively converted from supracricoid to supratracheal, in relation to results of frozen sections on surgical margins ¹³. An attempt to occlude the tracheostomy with gauze was made as of the third post-operative day, depending on the patients’ respiratory condition. All patients started with the oral ingestion of water on the sixth post-operative day with a trained speech therapist. If swallowing was satisfactory, the patient continued with semisolid and solid foods, otherwise they continued rehabilitation with gel water up to a satisfactory improvement. The nasogastric feeding tube (NFT) was kept in place until oral intake was satisfactory (> 75%). Functional assessment of swallowing efficiency with flexible endoscopy was performed in all patients with persistent dysphagia (< 75% oral food intake) after 1 week of rehabilitation, or in case of complications, such as ab ingestis pneumonia. Our OPHL patients currently remove the tracheostomy tube during feeding and replace it after a meal. A percutaneous endoscopic gastrostomy (PEG) was considered in cases of persistent dysphagia at 3 weeks after surgery or in case of ab ingestis pneumoniae. Patients could be discharged without a tracheostomy tube only after breathing and swallowing had recovered adequately, with no significant aspiration. Failing this, they were discharged with a tracheostomy tube in place, and outpatient re-assessment was scheduled at one month. Patients’ clinical charts were retrospectively reviewed, considering the post-operative decannulation and complication rates, length of hospital stay, and need for a NFT.

Radiological assessment

CT allows for precise measurements of cross-sectional areas on different levels, as well as three-dimensional reconstructions and volumetric assessments ¹⁴. All LSCC patients at Vittorio Veneto Radiology Department underwent pre-operative contrast-enhanced neck CT. A volumetric axial CT scan was performed with a 64-slice CT scanner (Revolution Evo, GE, Milwaukee, WI) using a slide thickness of 1.25 mm (120 KV, automatic modulating mA). Scout images (anterior and lateral views) were obtained to ascertain the scanning area covered, from the skull base to the mediastinum. Patients were placed supine, with their head in a neutral position, and instructed to remain still and avoid swallowing or coughing. Multiplanar reformatted sagittal and coronal images were then generated with a slice thickness of 0.6 mm, and the axial plane was reconstructed with an orientation parallel to the true vocal cords to better visualise the glottis. All scans were reworked and analysed by the same experienced radiologist (C.C.). Once the 3D digital models had been constructed, the following cephalometric parameters ¹¹ were obtained (Fig. 1):

1. volume (mL) of the aero-digestive tract from the base of the epiglottis to the hard palate (Vol);
2. length (mm) from the base of the epiglottis to the hard palate (L);
3. minimum cross-sectional area (mm²) of the retroglossal aero-digestive tract from the base of the epiglottis to the inferior aspect of the soft palate (RG);
4. minimum lateral dimension (mm) of cross section of the aero-digestive tract in the mid-retroglossal area (between the base of the epiglottis and the inferior aspect of the soft palate) (LAT);
5. minimum antero-posterior dimension (mm) of cross section of the aero-digestive tract in the mid-retroglossal area (between the base of the epiglottis and the inferior aspect of the soft palate) (AP);
6. distance (mm) between the genial tubercle and the hyoid bone in the mid-sagittal plane (GH).

Statistical analysis

Correlations between demographic, surgical and cephalometric parameters and their functional outcomes were assessed using univariate (Fisher’s exact test) and multivariate (logistic regression) analyses. As functional outcomes we considered: i) decannulation at discharge (0/1); ii) time to removal of the NFT (cut-off = 10 days); iii) post-operative complication rate (0/1); and iv) length of hospital stay (cut-off = 2 weeks).

The median values of NFT removal time and length of hospital stay (10 and 14 days, respectively), were considered as cut off points for statistical analysis. A p-value < 0.05 was considered significant. The STATA™ statistical package (Stata Corp, College Station, TX, USA) was used for all analyses.

Results

Among the cohort of 96 LSCC patients (88 males and 8 females; age range 28-80 years, median 62 years), 72 (75%) had a supracricoid laryngectomy (OPHL type II), and 24 (25%) had supratracheal laryngectomy (OPHL type III). Twenty-four patients (25%) were discharged with a tracheostomy cannula due to persistent dyspnoea or dysphagia, while 72 were decannulated after 7.2 ± 3.6 days (median 7 days). The time to NFT removal was in the range of 6-35 days (9.9 ± 4.0, median 9 days). A PEG was performed in 1 patient who had undergone OPHL type III due to persistent dysphagia. Thirty-three patients (34%) experienced at least 1 post-operative complication. The length of hospital stay ranged from 9 to 41 days (14.5 ± 4.8, median 13 days). Table I shows the results of the univariate analysis on the distribution of functional outcomes by demographic and surgical parameters. The functional outcomes of patients who had OPHL type II as opposed to type III are explained in detail below.

OPHL II patients

Seventy-two patients (age 28-71 years, median 63 years) underwent supracricoid laryngectomy, with conservation of the suprahyoid epiglottis (OPHL type IIA) in 66 cases, while in 6 cases the epiglottis was completely removed (OPHL type IIB). One arytenoid cartilage was sacrificed in 58 cases, while both cartilages were spared in 14 cases. Sixty-one patients were decannulated after 7.2 ± 3.6 days (84%), while 11 were discharged with the tracheostomy cannula still in place. Seven of these patients were successfully decannulated at 6 months after transoral laser microsurgery to treat post-operative laryngeal obstruction. Definitive decannulation was not possible in 4 cases because of persistent dyspnoea. The NFT was removed after 3.5 ± 3.2 days. Thirteen patients experienced at least 1 post-operative complication (18%), involving: persistent dyspnoea in 12 cases; persistent dysphagia in 3; ab ingestis pneumonia in 2; and a cervical abscess in one. The hospital stays for this group ranged from 9 to 25 days (mean 14.0 ± 4.1, median 13 days).

OPHL III patients

Twenty-four patients (age 37-80 years, median 62 years) underwent supratracheal laryngectomy, with preservation of the suprahyoid epiglottis (OPHL type IIIA) in 23 cases, and its complete removal (OPHL type IIIB) in one case. One crico-arytenoid unit (CAU) was sacrificed in 23 cases, while both were spared in one case. Eleven of the 24 patients were decannulated (45%) after 7.1 ± 3.8 days, while 13 were discharged with the tracheostomy cannula still in place. Eight of these patients were successfully decannulated at 6 months after transoral laser microsurgery to treat post-operative laryngeal obstruction. Definitive decannulation was not possible in 5 cases because of persistent dyspnoea. The NFT was removed after 11.0 ± 5.7 days. Sixteen patients experienced at least 1 post-operative complication (66%), involving: persistent dyspnoea in 11 cases; persistent dysphagia in 5; ab ingestis pneumonia in 4; pharyngo-cutaneous fistula in 1; and post-operative haemorrhage in one case. The hospital stay ranged from 10 to 41 days (mean 15.9 ± 6.2, median 15 days).

Cephalometric parameters

Analysing the 3D digital models for the whole cohort of OPHL patients, the volume of the aero-digestive tract from the base of the epiglottis to the hard palate (Vol) was in the range of 8101 to 67698 mL (mean 29473.9 ± 12787.2, median 26589 mL). The length (mm) from the hard palate to the base of the epiglottis (L) ranged from 45 to 98 mm (mean 72.7 ± 9.1, median 72 mm). The minimum cross-sectional area of the retroglossal aero-digestive tract (RG) ranged from 94 to 898 mm² (mean 405.6 ± 167.5, median 367 mm²). The lateral dimension of the cross section of aero-digestive tract in the mid-retroglossal area (LAT) ranged from 12 to 48 mm (mean 31.5 ± 7.4, median 32 mm). The antero-posterior dimension of the cross section of aero-digestive tract in the mid-retroglossal area (AP) ranged from 6 to 26 mm (mean 16.1 ± 4.2, median 16 mm). The distance from the genial tubercle to the hyoid bone on the midsagittal plane (GH) ranged from 24 to 44 mm (mean 33.7 ± 4.9, median 34 mm). Table II shows detailed results of the multivariate analysis for the distribution of functional outcomes by cephalometric parameters. In particular, we found that a larger GH significantly correlated with higher decannulation rate at discharge and shorter hospital stay (p = 0.045 and p = 0.048, respectively), and a greater AP was related to better functional outcomes in terms of decannulation rate at discharge (p = 0.021) (Fig. 2).

Discussion

Compared with conventional 2D cephalometry, 3D digital models acquired with CT enable better assessment of the cross-sectional dimensions of the aero-digestive tract ¹⁵. Assessments of the upper aero-digestive tracts in 3D based on CT scans have already been extensively described in patients with OSAS ⁸. Ouyang et al. also used CT scans to analyse anatomical changes after partial laryngectomies such as vertical partial and supracricoid laryngectomies that promoted the onset of post-operative OSAS ¹⁶. To the best of our knowledge, the present study is the first to have investigated the value of pre-operative cephalometric parameters acquired from CT scans in predicting functional outcomes after OPHL.

After conventional supracricoid laryngectomy with resection of the thyroid cartilage, the epiglottis or hyoid bone are sutured directly to the cricoid cartilage, and the hyoid bone is moved down, driving the base of the tongue backwards. The antero-posterior diameter of the cross-section of aero-digestive tract in the mid-retroglossal area (AP) is the narrowest dimension of the retrolingual space. Rodenstein et al. found on CT scans that the tongue was displaced backwards and downwards after OPHL type II; and they reported that smaller AP dimensions correlated with more severe post-OPHL OSAS ¹⁷. A similar concept may explain the onset of persistent obstruction of the neoglottis as a post-operative complication.

In the present study, multivariate analysis showed that larger AP and GH significantly correlated with better functional outcomes in terms of decannulation rate at discharge (p = 0.021, and 0.045, respectively). Patients with larger Vol and RG also experienced better functional outcomes (Tab. II), although the corresponding p-values were not statistically significant. A larger GH also correlated significantly with a shorter hospital stay (p = 0.048). Patients with a larger AP experienced lower complication rates as well (Tab. II), although with no statistical significance. Taken together, our results show that patients whose upper aero-digestive tracts are larger in diameter and volume have better functional outcomes after OPHL. Since the most common post-operative complication of such surgery is persistent dyspnoea due to obstruction of the airway, a condition that would hinder decannulation, the pre-operative finding of low aero-digestive tract dimensions may reasonably predict the functional success of the OPHL.

When we considered demographic parameters, age at surgery correlated with functional outcomes, as reported elsewhere ³. Our results confirmed that younger patients (< 65 years old) have better functional outcomes, particularly in terms of post-operative complications (p = 0.034) (Tab. I). It is generally agreed nowadays that functional recovery and response to post-operative rehabilitation are better in younger patients, in terms of both the timing and the percentage of this recovery.

There is now ample evidence in the available literature on the topic of the significant impact of the type of surgery on the functional outcome. In a previous study, we found that post-operative laryngeal obstruction (the most common complication after partial laryngectomy) occurred in 11% of patients who had supracricoid laryngectomy (OPHL type II) and 34% of those who had supratracheal laryngectomy (OPHL type III). OPHL type II coincided with a better functional outcome than OPHL type III, in terms of decannulation rate, time to tracheostomy closure and need for transoral laser microsurgery to manage post-operative laryngeal obstruction ⁴. In a detailed comparison of functional outcomes after OPHL, Schindler et al. found that patients experienced better vocal and swallowing results after OPHL type II than after OPHL type III ⁵. The results of the present study confirm as much: functional outcomes were worse after OPHL type III than after OPHL type II, in terms of decannulation rate at discharge, hospital stay and post-operative complications (p = 0.000, p = 0.045, p = 0.000, respectively). Intuitively, we can assume that sacrificing the epiglottis (OPHL type B) had a negative impact on the recovery of swallowing function and length of hospital stay (p = 0.011 and p = 0.011, respectively). Similarly, the functional outcome was worse, in terms of hospital stay (p = 0.049), after the removal of one of the arytenoid cartilages, compared with cases in which both arytenoids were spared.

Probably the main limitation of the present study lies in the relatively small cohort of OPHL patients (we only considered cases with pre-operative CT scans available). On the other hand, one of its strengths concerns the homogeneity of the data (all the patients were operated and rehabilitated by the same surgical team, and all CT scans were reworked and analysed by the same radiologist). Further studies on larger cohorts of OPHL patients are nonetheless needed to confirm our findings.

Conclusions

Larger diameters and volumes of the upper aero-digestive tracts correlated with better functional outcomes after OPHL. In particular, the decannulation rate at discharge was higher, the larger the antero-posterior diameter of the aero-digestive tract in the retroglossal area.

Acknowledgements

The authors thank Frances Coburn for correcting the English version of this paper. They also thank all the medical and paramedical staff at the Otolaryngology Unit - Vittorio Veneto Hospital, for collecting the follow-up data, and the Association “Amici della voce” (Friends of the Voice) for its support in preparing the manuscript.

Conflict of interest statement

The authors declare no conflict of interest.

Funding

This study was supported by a personal grant.

Author contributions

ML: study design, data collection and elaboration, manuscript writing and editing; CC, CV: data collection; LF: statistical analysis; SG, GP, PN, AB: paper review.

Ethical consideration

This study was approved by the Institutional Ethics Committee (Nucleo Ricerca Clinica – Servizio Farmaceutico Aziendale – approval protocol number 19881).

The research was conducted ethically, with all study procedures being performed in accordance with the requirements of the World Medical Association’s Declaration of Helsinki.

Written informed consent was obtained from each participant/patient for study participation and data publication.

Figures and tables

Figure 1.Cephalometric parameters on CT scans. (A) length from hard palate to base of epiglottis (L); (B) distance from genial tubercle to hyoid bone in mid-sagittal plane (GH); (C) lateral dimension of cross section of aero-digestive tract in the mid-retroglossal area (between base of epiglottis and inferior aspect of soft palate (LAT); antero-posterior dimension of cross section of aero-digestive tract in mid-retroglossal area (between base of epiglottis and inferior aspect of soft palate (AP); (D) volume of aero-digestive tract from base of epiglottis to hard palate (Vol); (E) cross-sectional area of retroglossal aero-digestive tract from base of epiglottis to inferior aspect of soft palate (RG); (F) RG plane.

Figure 2.Distributions of probabilities of decannulation at discharge by antero-posterior diameter of the cross-section of aero-digestive tract in the mid-retroglossal area (A), and distances from the genial tubercle to the hyoid bone in the mid-sagittal plane (B) (p = 0.021, and 0.045, respectively). Distribution of the probabilities of hospital stay > 14 days by distances from the genial tubercle to the hyoid bone in the mid-sagittal plane (C) (p = 0.048).

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