Treatment of oral and oropharyngeal epidermoid carcinomas
by means of CO₂ laser

VILLARREAL-RENEDO PM, MONJE-GIL F, JUNQUERA-GUTIÉRREZ LM, DE VICENTE -RODRÍGUEZ JC
MORILLO-SÁNCHEZ AJ. TREATMENT OF ORAL AND OROPHARYNGEAL EPIDERMOID CARCINOMAS
BY MEANS OF CO₂ LASER.. MED ORAL 2004;9:168-75.

SUMMARY

Introduction: The effect of the wide long-wave CO₂ laser is the thermal vaporization of the tissues, getting a maximum energy concentration with a minimum of tissue penetration. In oral surgery, it is generally used for the treatment of oral and oropharyngeal small mucous tumors, due to the scarce morbidity that takes place and the absence of reconstructive necessity.
Objective: To analyze the postoperative evolution, in the patients treated by oral and oropharyngeal epidermoid carcinomas, after CO₂ laser resection. To compare it with that of the patients treated by means of conventional surgical methods, achieving the reconstruction through direct suture or the employment of local, regional or distance flaps.
Methods: A prospective study was designed including 70 patients treated by oral and oropharyngeal epidermoid carcinomas. Thirty-five patients were treated by means of CO₂ laser, in 10 cases direct wound-closure was realized, and in the remaining 25 patients some local, regional or distance flap were used. There were analysed the presence of postoperative pain, the degree of cicatricial retraction, and the speech and swallowing functional results.
Results: We obtained a smaller painful degree and postoperative cicatricial retraction by the employment of CO₂ laser. It permits minimizing the functional speech sequels (better words articulation) and swallowing (effective and precocious functional recovery).
Conclusion: CO₂ laser resection has become the elective treatment for small oral and oropharyngeal epidermoid carcinomas. The reasons are the absence of reconstructive surgery necessity, the scarce cicatricial retraction, and the excellent postoperative evolution.

Key words: CO₂ laser, oral and oropharyngeal epidermoid carcinomas.

INTRODUCTION

The term LASER is the acronym of Light Amplification by Stimulated Emission of Radiation (1-3). The laser is a man created device, which produces a very special light (visible or invisible according to its long-wave) that acts as a solid matter. Einstein establishes the theoretical base with the Quantum Theory of the Radiation in 1917. In order to that, the energy (light) can be converted into mass, and the mass can be converted into energy, so that the laser light can act as a mass or a solid element. As light, it can be reflected, absorbed, burned and varies it's direction when passed through lenses. As a solid element, it can cut, melt, burn, and transmit (3,4).

Patel developed the CO₂ laser in 1964. Yahr and Strully (1966) experimented with it until finding the possibility to cut alive tissues. The CO₂ laser was the first laser in being adapted for its use in human surgical interventions. It has numerous types of applications at the present time. The light of the CO₂ laser is located in the infrared spectrum of lights (without colour), with a wide long-wave (l) of 10.600 nm. Therefore, a directional beam light of helium-neon (l =630nm) is required to guide it. The wide long-wave determines its biophysical properties of maximum absorption and minimum penetration in the tissues, which make the CO₂ laser the most useful laser in surgery (1,3).

The CO₂ laser has been employed in the superior aero-digestive tract surgery (2,5,6), ophthalmology (2), gynaecology (4), skin surgery (4), and intra-abdominal procedures (4). It can be used in endoscopic surgery like temporomandibular joint surgery, but conducted through rigid optic fiber. In oral surgery, it is generally used between 8 and 25 watts of power and it is considered the elective treatment in oral and oropharyngeal small mucous tumors, because the scarce morbidity that takes place and the absence of reconstructive necessity (2,5,6).

OBJECTIVE

To analyze the postoperative evolution, in the patients treated by oral and oropharyngeal epidermoid carcinomas, after CO₂ laser resection. To compare it with that of the patients treated by means of conventional surgical methods, achieving the reconstruction through direct wound-closure or the employment of local, regional or distance flaps.

MATERIAL AND METHODS

A prospective study was developed, between January 2000 and June 2002, in the Department of Oral and Maxillofacial Surgery of the Infanta Cristina hospital in Badajoz. It includes 70 patients with T1-T3 stage oral and oropharyngeal epidermoid carcinomas.

Thirty-five patients were treated by means of CO₂ laser leaving granulation and epithelization by second intention (section with 10-20 watts of power in continuous mode, followed by vaporization of the surgical field with an unfocused beam of light). In the remaining ones, 35 patients were treated by means of cold scalpel or cautery knife; in 10 cases direct wound-closure was realized, and in the remaining 25 patients some local (nasolabial flap or Bichat buccal fat pad), regional (temporal muscle flap) or distance flap (radial forearm cutaneous flap) were used.

The attainment of free margins after the histopathological study of the specimen, the local relapse and the postoperative evolution of the patients were analysed. The last one included the presence of pain during the postoperative period, functional alterations in swallowing and phonation, time of re-epithelization, degree of cicatricial retraction and presence of complications.

The statistical analysis was realized by non-parametric tests using the software SPSS 10.0 for Windows. Chi-square's test was used to analyse the relationship between the qualitative variables. The relationship between a qualitative variable (with more than two categories) and a quantitative one was analysed by the Kruskall-Wallis' test. The differences were considered significant when p < 0.05.

RESULTS

Fifty-nine males and 11 females composed the final sample (ratio = 5.36). The age range was between the 28 and 87 years, with a 59 year-old average. The relation between the tumour localization and the treatment is represented in the Table 1. Treatment by laser and direct wound-closure prevailed in the lingual tumours. Flaps were the therapeutic option more usually employed in the floor of the mouth, retromolar trigone and tonsillar tumours (Chi-square, p = 0.0001). The flaps used in the diverse tumor localizations are represented in the Table 2. The majority of T1 stage tumors were treated by CO₂ laser (25/38, 66%). Flaps reconstructed the majority of T2 stage tumors (15/22, 68%). The proportion was balanced in T3 stage tumors (5 patients with both methods of treatment) (Chi-square, p = 0.001).

We obtained free margins, (in the pathological study), in 97% (34/35) of the patients treated by CO₂ laser, in 100% of the cases treated by direct suture, and in 88% (22/25) of those reconstructed by flaps (Chi-square, p = 0.22). The percentages of cases with free margins according to the tumor localization were: anterior tongue 100% (32), posterior tongue 88,9% (8/9), floor of the mouth 100% (13), retromolar trigone 100% (8) and tonsil 62,5% (5/8) (Chi-square, p= 0.001).

The rate of local relapse during pursuit period was of 5.7% (4 cases). None of them were treated by CO₂ laser (0%), 3 by flaps (12%), and one with direct suture (10%) (Chi-square, p = 0.11).

The postoperative pain was classified as null or light in majority of the patients treated by CO₂ laser (34/35, 97%) and direct suture (7/10, 70%). On the contrary, most of the patients treated by flaps suffered a pain classified as moderate or intense (21/25, 84%) (Fig. 1) (Chi-square, p = 0,001).

Diverse degrees of cicatricial retraction occurred in all cases, being categorized as light, moderate or intense. The majority of the patients treated by CO₂ laser had a light cicatricial retraction (27 patients, 77%). In 8 patients (23%) it was moderate. In the cases treated by direct suture it was light (6 cases, 60%) or moderate (4 cases, 40%). In 5 patients treated by flaps it was intense (20%), in 10 cases moderate (40%), and in other 10 patients light (40%) (Fig. 2) (Chi-square, p = 0.008).

To evaluate the postoperative swallowing a scale was used with 4 categories: 1. "equal to preoperative", 2. "difficulty to swallow solids", 3. "difficulty to ingest liquids", and 4. "impossible to swallow". The relation with the tumor localization is represented in Table 3 (Chi-square, p = 0,001), and with the treatment applied in Figure 3. Swallowing was not altered in any patient treated by direct closure. Six patients treated by laser (17%) and 8 cases treated by flaps (32%) had difficulty to swallow solids. Other 6 patients presented difficulty to swallow liquids, 2 of them were treated by laser (5,7%) and 4 by flaps (16%). Only 1 patient was unable to swallow having been treated by a distance flap (Chi-square, p = 0,127).

Postoperative phonation was evaluated by means of a scale that included: 1. "equal to preoperative", 2. "comprehensible", 3. "comprehensible solely by the relatives" and 4. "incomprehensible". In any patient it was classified as "incomprehensible". Phonation was only "comprehensible by the relatives" in 3 cases of tonsillar and 2 cases of tongue base tumors. It was "comprehensible" in 5 cases of tonsilar tumors, 6 from retromolar trigone, 11 from the floor of the mouth, and 6 from tongue base. Lastly, it was classified as "equal to preoperative" in the 32 cases of anterior tongue, 2 from floor of the mouth, 1 from lingual base, and 2 from retromolar trigone (Chi-square, p = 0,001).

In all the patients treated by direct suture and in majority of the ones treated by laser (23/35, 66%) the postoperative phonation was "equal to preoperative" (12 "comprehensible", 34%). In the patients treated by flaps, it was "equal to preoperative" in 4 cases (16%), "comprehensible" in 16 (64%), and "solely comprehensible for the relatives" in 5 cases (20%). (Chi-square's test, p = 0.001, Figure 4).

The time to obtain the complete re-epithelization in the cases treated by laser varied between 4 and 6 weeks, according to the tumor localization, and without statistical significant differences (anterior tongue and retro molar trigone 4 weeks and 3 days; posterior tongue 4 weeks and 6 days; tonsil 5 weeks; floor of the mouth 5 weeks and 2 days) (Kruskall-Wallis' test, p = 0.356).

In relation to the complications during the postoperative period, one patient treated by a nasolabial flap suffered a postoperative infection. Five patients had a partial wound dehiscence (4 cases with flaps and 1 with direct suture), and 4 ones had postoperative paresthesias (3 with flaps and one with direct closing). No patient suffered haemorrhages or pyogenic granulomas during the postoperative period.

DISCUSSION

The laser energy is a form of monochrome electromagnetic radiation, collimated (it doesn't diverge) and coherent or additive (all the waves are coupled to each other in longitude, width and number). These properties determine its particular clinical utility. (3,4) The CO₂ laser energy or light is absorbed by the tissues' water. It produces tissue destruction by instantaneous cellular vaporization, with a minimal tisular penetration (1,3,4,7).

The CO₂ laser produces 3 tisular effects: section, coagulation and sterilization (3,4,8). The laser is able to produce a narrower cut than a conventional scalpel, with the light-beam focused. The incision has a characteristic crater form, with a proximal region of necrosis (100-300 microns) followed by a limited region of reversible cellular damage in the adjacent tissues. Lingering expositions produce deeper incisions, but with bigger thermal damage on the adjacent tissues (3,4).

The haemostatic or coagulative effect is gotten with the unfocused light-beam, being able to seal small blood and lymphatic vessels (0,5 - 1 mm) during the incision or the vaporization (8,9). This diminishes the intra-operative bleeding allowing the re-epithelization of the intra-oral mucous wound from the adjacent epithelium. It reduces the surgical time, the inflammation (8,9), the postoperative pain (6,8), and the cicatricial retraction (8), besides avoid the morbidity on the donating area of the flap (3,4,8).

The postoperative pain is reduced by minimizing the surgical trauma and by the coagulating and sealing effect over the free nerve endings. This also avoids paresthesias and neuromas production during the postoperative period. (3,4,6,8). The significant differences obtained in our study corroborate these arguments.

The absence of lesions in the adjacent tissues to the resection allows a quick wound re-epithelization. This would be favoured by the germicide action or sterilization capacity of the laser (4,8,10). The necessary time to get a complete re-epithelization of the oro-pharyngeal mucous epithelium after laser resection has been established between 4 and 6 weeks (10), depending of the defect width and localization, figures that coincide with our results. However, this delay in the complete re-epitelization doesn't commit the masticatory, swallowing and phonatory residual functional activity of the oral cavity during this period (11).

The postoperative swallowing is directly related with the tumoral localization (11). The resections that imply the tonsillar and the tongue base regions, present the biggest risk to produce functional alterations. Our results demonstrate no significant differences in postoperative swallowing in relation to the applied treatment. Although the patients treated by flaps had more swallowing severe problems than the ones treated by laser, it is also true that most of the tonsillar tumors required some flap for the reconstruction.

Tonsillar and lingual base tumors produced the most severe phonatory alterations. The treatment with laser seems, at the light of our results, produces lesser phonatory alterations than the reconstruction by flaps. It seems reasonable that the reconstruction by flaps reproduces with more reliability the previous oropharyngeal anatomy than the re-epithelization of the defect after laser resection. However, many times the flaps are redundant, others have an insufficient volume, in occasions have a scarce or null sensibility, and almost always have an different elasticity to the original tissue that replace. These circumstances could cause speech and swallowing functional alterations.

Diverse authors (3,4,10) affirm that the CO₂ laser energy is able to destroy tumoral tissues and to seal the lymphatic vessels. This capacity would allow us to cut through the tumors without producing local or regional metastatic spreading. It allows the resection of big tumors excising small fragments, simplifying the surgical approaches. This could be confirmed by the low local recurrences rate obtained in several studies (10-13) including this one (cases treated by laser 0%, cases treated by conventional scalpel between 10 and 12%). However, these differences are not statistically significant, and in other studies (9,14,15) the laser doesn't seem to offer an evident advantage over the conventional resection methods. Also, other factors like the tumoral stage, the tumor localization, and the degree of tumoral differentiation could influence in these rates.

For further controversy, some authors (16) have alerted on the possible cancerigenic effect of the laser radiation through cellular growth factors output. However, it is important to point out, that there should be present high-energy photons in order to produce that biological effects like the genetic mutation or carcinogenesis. These correspond to the ultraviolet spectrum photons and the ionizing radiation. Most of the laser devices don't produce ionizing radiation and are unable to produce these effects.

The employment of the laser energy is not exempt from diverse inconveniences such as the high price of the device and the necessity of previous training in its use. It is a no-contact surgery instrument where the tactile references that help in the control of the device are lost. Today doesn't exist a single laser type, which is used for all kinds of applications. Each laser type has its owns special indications, many of which are exclusive. The CO₂ laser should be managed with supreme care. The complications that can arise during its employment are cutaneous, corneal, and crystalline lens burns, viral or tumoral diseases dissemination through the resulting steam of vaporization, and the possible ignition and combustion of the anesthetic gas (O2) (17).

CONCLUSION

CO₂ laser resection has become the elective treatment for small oral and oropharyngeal mucous tumors. The reasons are the absence of surgical reconstruction necessity, the light cicatricial retraction, and the good postoperative evolution. The most important advantages of the laser are the scarce inflammation degree and tisular edema that takes place, the quick re-epithelization, the sealing of blood, lymphatic vessels and free nerve ending and capacity to destroy tumoral tissues.

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