|Year : 2011 | Volume
| Issue : 1 | Page : 6-11
Voice outcomes after laser cordectomy
Faustino Nunez-Batalla, Juan Pablo Díaz-Molina, Andres Coca-Pelaz, Carlos Suarez-Nieto
Department of Otolaryngology, Hospital Universitario Central de Asturias, University of Oviedo, Oviedo, Spain
|Date of Web Publication||7-Feb-2011|
c/Las Mazas #40-6, 33191, Oviedo
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Early glottic carcinoma can be treated using endoscopic surgery, radiotherapy, or partial open surgery. Lesions limited to the vocal fold are normally treated with endoscopic surgery or partial open surgery, with local control results between 80% and 90%. The choice of one treatment over another should contemplate the cure rate, larynx preservation rate, post-treatment voice quality, morbidity, and treatment cost. Although both external beam radiotherapy and endoscopic carbon dioxide laser excision of early glottic cancer will affect voice quality, it is difficult to compare them. A complete voice assessment including perceptual, objective, and subjective evaluation is mandatory whenever a meaningful analysis of the pathological voice is to be accomplished. Meta-analyses of the results of voice treatments are generally limited and may even be impossible owing to the major diversity in the ways functional outcomes are assessed. The postsurgical voice outcome depends upon having a straight postoperative vocal fold for glottic closure and intact vibration from the contralateral vocal fold. Subepithelial and subligamental cordectomies are oncologically safe resections and have a quality of voice comparable to that of controls. By contrast, with wider resections (types III-V cordectomies), a concave neocord may form resulting in an aerodynamic glottic incompetence. In order to select the most appropriate treatment modality according to the patient's age, gender, compliance, and professional activity, a detailed preoperative counseling concerning vocal outcome is recommended. After phonosurgical resection, patients who have lost paraglottic musculature may benefit from medialization and augmentation procedures to re-establish glottic competence.
Keywords: CO2 laser surgery, glottic cancer, phonosurgery, radiotherapy, voice, voice outcome
|How to cite this article:|
Nunez-Batalla F, Díaz-Molina JP, Coca-Pelaz A, Suarez-Nieto C. Voice outcomes after laser cordectomy. J Laryngol Voice 2011;1:6-11
| Introduction|| |
Surgery and radiotherapy offer the same results in the treatment of early glottic carcinoma, with a cure rate of approximately 90%.  The introduction of endoscopic CO 2 laser surgery in early glottic carcinoma (i.e., epidermoid carcinoma confined to the true vocal cords with normal mobility) has added controversy to the standard treatment choice. Laser surgery is quicker, and therefore reduces costs considerably. However, many institutions prefer to use radiotherapy in the belief that the voice will be better preserved after treatment.  Although the principal objective of oncology treatment is the complete eradication of the illness, normal voice preservation is another important factor to take into consideration in the treatment choice for early glottic carcinoma. For this reason, post-treatment voice quality is a relevant factor to take into account when evaluating the results.
| Review of Literature|| |
Early glottic carcinoma can be treated using endoscopic surgery, radiotherapy, or partial open surgery. Lesions limited to the vocal fold are normally treated with endoscopic surgery or partial open surgery, with local control results between 80% and 90%. , The choice of one treatment over another should contemplate the cure rate, larynx preservation rate, post-treatment voice quality, morbidity, and treatment cost. 
In recent years, endoscopic CO 2 laser surgery has made headway compared to radiotherapy based on its good oncologic results and reduced morbidity. CO 2 laser treatment in early glottic carcinoma has greatly improved voice quality if compared to that obtained following cordectomy via laryngofissure as documented by some authors.  However, in other published studies  this improvement is not as evident. One of the advantages of laser surgery is its low cost when compared to radiotherapy as well as the additional benefit of being able to opt for radiotherapy at a later stage to treat a relapse or a second primary malignancy. In many institutions, these tumors are treated with external radiotherapy as to obtain supposed better functional and quality life results, if compared to patients treated with surgery. 
Various studies have been published comparing voice quality after both treatments. ,, In some studies, voice quality is similar, while other authors maintain that the voice is better after radiotherapy than after laser surgery. ,, However, there are fewer published works that include patients' opinions with regard to the impact that the illness and the treatment have had on their quality of life. ,,,
Because of problems associated with study design and data collection, studies exploring voice outcomes after laser or radiotherapy treatment vary. There are reports demonstrating favorable VHI (voice handicap index) scores in laser-treated patients, , which include carcinoma in situ patients. Since these patients would require less invasive surgery, their voice results may be better, biasing the results in favor of laser management. To test the hypothesis that endoscopic resection produces comparable levels of voice handicap as radiotherapy, studies should only include T1 patients excluding carcinoma in situ. 
Studies that suggest that radiotherapy resulted in an equivalent or superior voice quality did not include the most recent developments in phonosurgical management of early glottic cancer (i.e., ultranarrow margins and reconstruction). Some of those patients probably underwent more extensive resections than necessary, while others did not undergo phonosurgical reconstruction. A key goal of the endoscopic management of T1 glottic cancer is to narrow the cancer-free margin to minimize patient morbidity while not altering the cure rate. The disease must be eradicated with maximal preservation of the vocal folds' normal layered structure. Modern phonosurgical management of early glottic cancer comprises employing ultranarrow margins during the resection; 1-2 mm surface margins at the perimeter of the lesion resulted in an acceptable 3% rate of local recurrence. 
A minimum 6-month period of recovery after treatment should be observed before proceeding with assessment. This time period is chosen to allow adequate healing, to verify the absence of early recurrence, and to evaluate the voice rehabilitation that can be achieved by voice therapy if indicated. 
| Methodology for Measurement of Outcome|| |
There are several limitations to any conclusions that can be obtained from these studies mainly owing to differing voice-measuring methods [Table 1]. Furthermore, voice analysis instruments used lack uniformity, reliability, and validity. In most studies, only 1 or 2 aspects of voice function are evaluated, whereas the European Laryngological Society (ELS) concluded that the assessment of voice pathological conditions needs to be multidimensional. A minimal set of basic requirements for presenting and publishing results of voice treatments is necessary in order to make comparisons and meta-analyses possible. In the basic set for the assessment of voice outcomes, the following components need to be considered, since all of them provide quantitative data: (a) perception; (b) videostroboscopy; (c) acoustics; (d) aerodynamics/efficiency; (e) subjective rating by patients. 
|Table 1: Summary of current literature about voice out come in T1 glottic carcinoma laser surgery vs. radiotherapy|
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- Perceptual analysis of dysphonia (GRBAS). Perceptual analysis of the dysphonia should be performed using the GRBAS scale.  Each sample can be classified from 0 to 3 (0 = normal, 1 = mild, 2 = moderate, 3 = severe). The severity of hoarseness is quantified under the parameter G (grade), which refers to the overall voice quality. B (breathiness): audible impression of turbulent air leakage through an insufficient glottic closure may include short aphonic moments (i.e., unvoiced segments). R (roughness or harshness): audible impression of irregular glottic pulses, abnormal fluctuations in fundamental frequency and separately perceived acoustic impulses (as in vocal fry); it also includes diplophonia and register breaks. A (asthenicity): impression of weakness in the spontaneous phonation, hypokinetic, or hypofunctional voice. S (strain, vocal tension): auditive impression of excessive force or tension associated with the spontaneous phonation.
- Videolaryngostroboscopy is the main clinical tool for the etiological diagnosis of voice disorders. It can also be used for assessing the quality of vocal fold vibration, and thus the effectiveness of treatments, medical or surgical. Basic parameters are glottal closure and mucosal wave, accounting for the physiology of the layered structure of the vocal folds.
- Acoustic and spectrographic analysis. The acoustic analysis should be performed using a voice analysis software. Once the signal is digitized, the computer calculates the following acoustic parameters: fundamental frequency (F0), jitter or frequency variation (%), shimmer or amplitude variation (%), and normalized noise energy (NNE), which measures the degree of noise produced by turbulent air escaping through the glottis during vocal emission. Using the same digitized voice sample a narrowband spectrogram can be generated. The spectrograms obtained are grouped in four types according to the Yanagihara criteria  [Figure 1]. Also included in the basic acoustic measures are three critical points of the phonetogram (VRP: voice range profile). The highest frequency and the softest intensity (dB A at 30 cm) seem to be the most sensitive for changes in voice quality, the latter being related to phonation threshold pressure. The measurement of the lowest frequency makes it possible to compute the fundamental frequency range. 
|Figure 1: a: Narrow-band sonogram showing a normal voice. Vocal /ae/ at a comfortable pitch and intensity level|
b: Narrow-band sonogram showing a Yanagihara type IV dysphonia. Left type III cordectomy. Vocal /ae/.
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- Aerodynamic efficiency analysis. This consists in measuring the maximum phonation time (MPT) for the /a/ vocal after instructing the patient to sustain this vocal for the longest time possible in a comfortable pitch and intensity. Averaged phonation air flow or phonation quotient (PQ) = vital capacity (ml)/MPT (s). Vital capacity (VC) is defined as "the volume change at the mouth between the position of full inspiration and complete expiration." It can be measured in a reliable way by using a hand-held spirometer. 
- Patient self-perception analysis (voice handicap index). The patients complete the VHI via a self-evaluation form comprising 30 questions covering 3 domains:  functional, physical, and emotional. Each question has assigned a score of 0 to 4 (from least disability to most). In each domain, the maximum score is 40 points; less than 20, can be classified as mild disability, 21-30 as moderate, and more that 30 as severe. Adding the three scores together, the maximum possible is 120; the vocal disability can then be classified as mild (less than 30), moderate (31-60), severe (61-90), and very severe (91-120).
| Results|| |
1. Vocal outcome after endoscopic cordectomies
Vocal outcome is strictly related to glottic competence, which is modulated by the amount of vocal muscle resected. Zeitels  coded individual patients according to the depth of the initial surgical resection: (1) superficial lamina propria, (2) vocal ligament, and (3) vocalis muscle. Results of acoustic and aerodynamic assessment showed that lesions confined to the superficial lamina propria resected superficial to the vocal ligament had minimal vocal disturbance subsequent to healing and epithelialization. After a resection of the vocal fold epithelium and its underlying lamina propria (including vocal ligament), the healed neocord usually shows a concavity depending on the extent of ligament and muscle resection. Voice outcome in this vocal ligament group was comparable to those of the superficial lamina propria cohort. Increasing the magnitude of the resection to the paraglottic musculature leads to deteriorating vocal function associated with aerodynamic incompetence of the glottic closure and to an unavoidable loss of epithelial pliability. Peretti et al.  report similar results. They found that patients who underwent a type I or II excision have a quality of voice comparable to that of controls. By contrast, cordectomies including the entire vocal cord (type III/IV) and/or the anterior commisure (type V) showed significantly worse vocal scores.
2. Vocal outcomes comparison of laser excision versus radiotherapy
Perceptual analysis of dysphonia. Voice quality was examined by subjective voice analysis and by the GRBAS score. Both showed no significant difference between treatment groups,  but the results did trend toward favoring the XRT group. ,,,,,,
Videolaryngostroboscopy. Videostroboscopy showed abnormal patterns in almost all patients. It is not unusual for T1 glottic cancer patients to have abnormal contralateral mucosal waves as a result of a long-term phonotrauma related to their vocal behavior or vocation, long-term negative effects of smoking, and other environmental abuses on the vocal cords.  More than a half of the patients in each group had incomplete closure of the vocal cords.  There was no significant difference between treatment groups with respect to the stroboscopic analysis of mucosal wave. ,, Nevertheless, the result showed a trend toward a better outcome for the radiotherapy group. ,,,
Acoustic analysis. Findings have differed from one study to another. The results of a meta-analysis  showed an overall slight trend toward superiority for radiotherapy with respect to fundamental frequency and phonation intensity range, whereas the perturbation measures of jitter and shimmer favored the laser surgery group.  By contrast, Tamura  reported that all phonetic parameters (maximum phonation time, fundamental frequency, intensity, jitter, shimmer, harmonic-to-noise ratio, etc.) were similar in the laser therapy and the radiotherapy groups, whereas Rydell  reported voice quality, both at 3 months and at 2 years after radiotherapy, to be significantly better than after laser treatment. Comparing the narrow-band spectrograms obtained in both groups, there were no statistically significant differences. 
Aerodynamic efficiency analysis. Studies report contradictory findings. According to Higgings,  there are significant differences in the maximum phonation time favoring the radiotherapy group in the meta-analysis, while Núñez-Batalla  favors the laser group. However, Sjögren  and Tamura  state that there is no significant difference between a normal group and both treatment groups.
Patient self-perception analysis (VHI). Six studies in which the VHI was assessed at least 3 months after treatments for T1 glottic cancer were identified and analyzed by meta-analysis techniques by Cohen et al. The post-treatment VHI scores were similar for the radiotherapy and laser groups. In another study, Peeters  found a significant difference between treatment modalities for the total VHI score with a lower score for the patients treated with endoscopic laser surgery as compared to the radiated patients. Nevertheless, regarding the statement on overall voice quality, no differences between treatment modalities was found, which reports on 70% of the patients overall good voice quality. Sjögren  reported that the VHI for most patients is minimal, with few severely affected patients in both groups. There was no significant difference in the total score or in any of the subclass scores on the VHI between irradiated and laser surgery treated patients. By contrast, Nuñez-Batalla  reports, upon completing the comparison of VHI scores between the two groups, that the statistical difference is significant in favor of the radiotherapy patients in the functional and emotional ratings as well as on the global scores. No significant differences were found in the physical scales.
3. Benefit and risk issue with each modality of treatment for equitable voice outcome
Radiotherapy and laser surgery are established treatment modalities for T1 glottic carcinoma, although their comparative benefits are debated. The two main concerns are disease control and post-treatment voice quality. Both modalities offer a high probability of local control; therefore, voice quality may have an important role in decisions about treatment strategies.  Introduction of endoscopic cordectomy and, particularly in the past decade, of partial resection prompts a detailed comparison among different types of cordectomy in relation to tumor extension and volume, expectations of the patient, and vocal results. 
A normal vocal outcome is usually obtained after types I and II cordectomies. Both perceptual and subjective evaluations show a clear trend toward postoperative reduction of the grade of dysphonia and of the severity of handicap in daily social and professional life. Therefore, other advantages of endoscopic excision must be discussed with the patient. Phonomicrosurgical resection preserves all treatment options, including further transoral resections. Radiotherapy treats all normal glottal tissue, including its saccular glands, which provide the mucociliary blanket that keeps the vocal cords moist and lubricated. It also induces fibrotic changes and impaired mucosal oscillation in both normal and cancerous tissues. The use of radiotherapy precludes its further use for tumor recurrence and for new primaries. The cost of endoscopic excision is significantly lower than that of irradiation, and the patient avoids an increased burden of time and travel commitments.
In contrast, resection of most of the vocal muscle and of the anterior commisure has been demonstrated to worsen postoperative voice in comparison with normal controls. ,,, Patients with types III-V cordectomies often had a tendency toward a permanent dysphonia and an important subjective voice-related disability. As the depth of the resection margin extends to include the paraglottic musculature, there is further danger of aerodynamic and acoustic impairment. This leads to deteriorating vocal function with an inefficient glottal closure and a loss of epithelial pliability. These patients are optimal candidates for phonosurgical reconstruction in order to reduce the dysphonia resulting from such endoscopic treatments.  A span of disease-free interval between endoscopic cordectomy and the reconstructive procedure is always mandatory. Moreover, further treatments, both endoscopic and external approaches, are often necessary in order to obtain adequate vocal results; these treatments reduce patient compliance and the cost-effectiveness ratio.
Types I and II excisions can therefore be regarded as a functionally adequate treatment, even for professional voice users. By contrast, accurate counseling is mandatory in patients with tumors requiring more extended cordectomies, for whom the disadvantages inherent to radiotherapy (duration of treatment, loss of time for work and social activities, higher rate of complications, and partial preclusion of further conservative salvage surgery) could become acceptable. 
| Discussion|| |
Although both external beam radiotherapy and endoscopic carbon dioxide laser excision of early glottic cancer will affect voice quality, it is difficult to compare them. The main problem of the few available comparative studies on functional outcome is that they are affected by selection bias by including only midcord lesions for laser surgery, large variations in follow-up periods as a consequence of retrospective designs, and small size sample. Another problem of the comparative studies is that the surgical arm did not include the most recent developments; some patients probably underwent more extensive resections than necessary, and others did not undergo surgical reconstruction of the glottal competency.  In addition, the voice analysis methods used lacked uniformity, reliability, and validity. 
A complete voice assessment including perceptual, objective, and subjective evaluation is mandatory whenever a meaningful analysis of the pathological voice is to be accomplished. Meta-analyses of the results of voice treatments are generally limited and may even be impossible owing to the major diversity in the ways functional outcomes are assessed. The European Laryngological Society (ELS) concluded in 2000 that there is no single voice analysis method that adequately describes voice function and that the assessment of the dysphonia needs to be multidimensional.
While acoustic, physiological, and perceptual measurements are important parameters in assessing vocal function, they do not provide information about the patients' perception of their own voice quality. Given that voice quality, because of its potential impact on life quality, can be an important factor in the choice of treatment, it is important to include this information when evaluating results. Not only should dysphonia as a by-product of laryngeal physiology be considered, but also the effects on patients' life quality.
Sjögren et al.  performed the first study with consecutive and comparable T1 lesions in a laser surgery group and a radiation group using a multidimensional assessment protocol based on ELS recommendations. They found that there is no statistical difference in the severity and type of voice dysfunction between both groups, although voice dysfunction profiles may be different, with voices of irradiated patients showing more roughness and the voices of laser surgery treated patients being mainly breathy.
It is important to emphasize that the postsurgical voice outcome depends upon having a straight postoperative vocal fold for glottic closure and intact vibration from the contralateral vocal fold. Peretti et al.  demonstrated that the mean VHI scores doubled when resection included more than the superficial vocalis muscle. Subepithelial and subligamental cordectomies are oncologically safe resections and have a quality of voice comparable to that of controls. Types I and II excisions can therefore be regarded as functionally adequate treatments, even for professional voice users. By contrast, with wider resections (types III-V cordectomies), a concave neocord may form resulting in an aerodynamic glottic incompetence. In order to select the most appropriate treatment modality according to the patient's age, gender, compliance, and professional activity, a detailed preoperative counseling concerning vocal outcome is recommended. After phonosurgical resection, patients who have lost paraglottic musculature may benefit from medialization and augmentation procedures to re-establish glottic competence.
Other uncontrollable factors inherent to outcomes studies may be related to how patients view their voice after treatment. The sound of the voice, patient's expectative, cultural influences, personality, professional requirements, social activities, existence of gastroesophageal reflux, tobacco use, voice therapy, and age may all affect patients' perception of their voice and could not be assessed. [ 20]
| References|| |
|1.||Higgins KM, Shah MD, Maurice MP, Ogaick MJ, Enepekides D. Treatment of early-stage glottic cancer: Meta-analysis comparision of laser excision versus radiotherapy. J Otolaryngol Head Neck Surg 2009;38:603-12. |
|2.||Delsupehe KG, Zink I, Lejaegere M, Bastian RW. Voice quality after narrow-margin laser cordectomy compared with laryngeal irradiation. Otolaryngol Head Neck Surg 1999;121:528-33. |
|3.||Smith JC, Johnson JT, Myers EN. Management and outcome of early glottic carcinoma. Otolaryngol Head Neck Surg 2002;126:356-64. |
|4.||Mahler V, Boysen M, Brondbo K. Radiotherapy or CO2 laser surgery as treatment of T1a glottic carcinoma? Eur Arch Otorhinolaryngol 2010;267:743-50. |
|5.||Smith J, Jonhson J, Cognetti D, Landsittel D, Gooding W, Cano E, et al. Quality of life, functional outcome, and costs of early glottic cancer. Laryngoscope 2003;113:68-76. |
|6.||Keilmann A, Bergler W, Artzt M, Hormann K. Vocal function following laser and conventional surgery of small malignant vocal fold tumours. J Laryngol Otol 1996;110:1138-41. |
|7.||Schindler A, Palonta F, Preti G, Ottaviani F, Schindler O, Cavalot AL. Voice quality after carbon dioxide laser and conventional surgery for T1A glottic carcinoma. J Voice 2004;18:545-50. |
|8.||Gallo A, Vincentiis M, Manciocco V, Simonelli M, Fiorella ML, Shah JP. CO2 laser cordectomy for early-stage glottic carcinoma: A long-term follow-up of 156 cases. Laryngoscope 2002;112:370-4. |
|9.||Piazza C, Villaret AB, De Zinis LO, Cattaneo A, Cocco D, Peretti G. Phonosurgery after endoscopic cordectomies. II Delayed medialization techniques for major incompetence after total and extended resections. Eur Arch Otorhinolaryngol 2007;264:1185-90. |
|10.||Tamura E, Kitahara S, Ogura M, Kohno N. Voice quality after laser surgery or radiotherapy for T1a glottic carcinoma. Laryngoscope 2003; 113: 910-914. |
|11.||Wedman J, Heimdal J, Elstad I, Olofsson J. Voice results in patients with T1a glottic cancer treated by radiotherapy or endoscopic measures. Eur Arch Otorhinolaryngol 2002;259:547-50. |
|12.||Krengli M, Policarpo M, Manfreda I, Aluffi P, Gambaro G, Panella M, et al. Voice quality alter treatment for T1a glottic carcinoma-radiotherapy versus laser cordectomy. Acta Oncol 2004;43:284-9. |
|13.||Pellitteri PK, Kennedy TL, Vrabec DP, th Beiler D, Hellstrom M. Radiotherapy: The mainstay in the treatment of early glottic carcinoma. Arch Otolaryngol Head Neck Surg 1991;117:297-301. |
|14.||Verdonck-de Leeuw IM, Keus RB, Hilgers FJ, Koopmans-van Beinum FJ, Greven AJ, De Jong JM, et al. Consequences of voice impairment in daily life for patients following radiotherapy for early glottic cancer: Voice quality, vocal function, and vocal performance. Int J Radiat Oncol Biol Phys 1999;44:1071-8. |
|15.||Núñez-Batalla F, Caminero-Cueva MJ, Señaris González B, Llorente Pendás JL, Gorriz Gil C, López Llames A, et al. Voice quality after endoscopic laser surgery and radiotherapy for early glottic cancer. Objective measurements emphasizing the voice handicap index. Eur Arch Otorhinolaryngol 2008;265:543-8. |
|16.||Loughran S, Calder N, MacGregor FB, Carding F, Mackenzie K. Quality of life and voice following endoscopic resection or radiotherapy for early glottic cancer. Clin Otolaryngol 2005;30:42-7. |
|17.||Peeters AJ, van Gogh CD, Goor KM, Verdonck-de Leeuw IM, Langendijk JA, Mahieu HF. Health status and voice outcome after treatment for T1a glottic carcinoma. Eur Arch Otorhinolaryngol 2004;261:534-40. |
|18.||Stoeckli SJ, Guidicelli M, Schneider A, Huber A, Schmid S. Quality of life after treatment for early laryngeal carcinoma. Eur Arch Otorhinolaryngol 2001;258:96-9. |
|19.||Peretti G, Piazza C, Balzanelli C, Mensi MC, Rossini M, Antonelli AR. Preoperative and postoperative voice in Tis-T1 glottic cancer treated by endoscopic cordectomy: An additional issue for patient counseling. Ann Otol Rhinol Laryngol 2003;112:759-63. |
|20.||Cohen SM, Garrett CG, Dupont WD, Ossoff RH, Courey MS. Voice related quality of life in T1 glottic cancer: Irradiation versus endoscopic excision. Ann Otol Rhinol Laryngol 2006;115:581-6. |
|21.||Zeitels SM, Hillman RE, Franco RA, Bunting GW. Voice and treatment outcome from phonosurgical management of early glottic cancer. Ann Otol Rhinol Laryngol 2002;111:3-20. |
|22.||Remacle M, Lawson G, Morsomme D, Jamart J. Reconstruction of glottic defects after endoscopic cordectomy: Voice outcome. Otolaryngol Clin North Am 2006;39:191-204. |
|23.||Dejonckere PH, Bradley P, Clemente P, Cornut G, Crevier-Buchman L, Friedrich G, et al. A basic protocol for functional assessment of voice pathology, especially for investigating the efficacy of (phonosurgical) treatments and evaluating new assessment techniques. Guideline elaborated by the Committee on Phoniatrics of the European Laryngological Society (ELS). Eur Arch Otorhinolaryngol 2001;258:77-82. |
|24.||Hirano M. Clinical examination of voice. New York: Springer Verlag; 1981. p. 81-4. |
|25.||Yanagihara N. Significance of harmonic changes and noise components in hoarseness. J Speech Hear Res 1967;10:531-41. |
|26.||Jacobson BH, Jonson A, Grywalski C. The Voice Handicap Index (VHI): Development and validation. Am J Speech Language Pathol 1997;6:66-70. |
|27.||Rydell R, Schalen L, Fex S, Elner A. Voice evaluation before and after laser excision vs radiotherapy of T1a glottic carcinoma. Acta Otolaryngol (Stokh) 1995;115:560-5. |
|28.||McGuirt WF, Blalock D, Koufman JA, Feehs RS, Hilliard AJ, Greven K, et al. Comparative voice results after laser resection or irradiation of T1 vocal cord carcinoma. Arch Otolaryngol Head Neck Surg 1994;120:951-5. |
|29.||Epstein BF, Lee DJ, Kashima H, Johns ME. Stage T1 glottic carcinoma: Results of radiation therapy or laser excision. Radiology 1990;175:567-70. |
|30.||Elner A, Fex S. Carbon dioxide laser as primary treatment of glottic Tis and T1a tumors. Acta Otolaryngol (Stockh) 1988;449:135-9. |
|31.||Hirano M, Hirade Y, Kawasaki H. Vocal function following carbon dioxide laser surgery for glottic carcinoma. Ann Otol Rhinol Laryngol 1985;94:232-5. |
|32.||Sjögren EV, van Rossum MA, Langeveld TP, Voerman MS, van de Kamp VA, Friebel MO, et al. Voice outcome in T1a midcord glottic carcinoma. Laser surgery vs radiotherapy. Arch Otolaryngol Head Neck Surg 2008;134:965-72. |
|33.||Mlynarek A, Kost K, Gesser R. Radiotherapy versus surgery for early T1-T2 glottic carcinoma. J Otolaryngol 2006;35:413-9. |
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