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Medicina Oral, Patología Oral y Cirugía Bucal (Ed. impresa)

versión impresa ISSN 1698-4447

Med. oral patol. oral cir. bucal (Ed.impr.) v.10 n.1 Valencia ene.-feb. 2005

 

Treatment of the carcinoma of the lip through high dose rate brachitherapy

FINESTRES-ZUBELDIA F, GUIX MELCIOR B, CLOQUELL DAMIÁN A, CHIMENOS KÜSTNER E, TELLO LUQUE JI. TREATMENT OF THE CARCINOMA OF THE LIP THROUGH HIGH DOSE RATE BRACHITHERAPY. MED ORAL PATOL ORAL CIR BUCAL 2005;10:17-24.

ABSTRACT

Objetives: The objetive of the present study is to value the results obtained in the treatment of 28 patients a prospective group, affected of upper lip carcinoma treated through external molds of high dose rate brachytherapy.
Design of the study: A total of 28 patients ffected of lip carcinoma were treated through superficial ready – made molds and high dose rate brachytherapy. The dose of radiation given was 6.000 to 6.500 cGy in 33 to 36 fractions of 180 cGy on tumors up to 4 centimeters of diameter. On the big tumors the dose given was 7.500 to 8.000 cGy in 43 to 46 fractions. The patients were followed every 3 months, evaluating in each visit the local control, regional and at distance of the tumor, the existence of complications or sequels and the aesthetic result obtained.
Results: All the patients completed the foreseen treatment. All the cases had complete remission of the tumor. During the period of pursuit local relapses were not detected neither regional or at distance. Patients did not present inmediate or late complications during the treatment. In the observations made 6 and 12 months after the treatment 27/28 patients had excellent or good aesthetic results.
Conclusions: Because of the high control of the tumor,good tolerance to therapy, absence of complications and reverts,easy employment of molds, accuracy in positioning the source in the daily repetition of the treatment and the security that offers for radioprotection,we conclude that this therapy will probably be of habitual use the next years.

Key words: Cancer of the lip, cutaneous carcinomas, cancer of skin, radiotherapy, brachytherapy, high rate dose.

 

INTRODUCTION

Cancer of the lip is relatively frequent tumor in our population (1). It is estimated that a total of 1500 cases are diagnosed anually in Spain. 75% of the cases are basacell carcinomas and most of the remaining 25% are squamous carcinomas (2). The more frequent ethiology of carcinomas of the lip is ultraviolet radiation, with the habit of smoking (3). Their behavior is locally destructive, rarely they give metastasis and have little effect over survival. According to the localization they can produce serious aesthetic effects, functional changes in swallowing of liquids, incontinence of oral fluids, and poor quality of life. These tumors can be treated by diverse forms: Surgical excision (4); chimio-surgery with paste of Mohs (5); electrofulguration (2); or radiotherapy (2,4.6.7). The superficial nature of these injures made them easily accesible to the physical exploration and for that reason tributary to their diagnosis and earlier cure. Dentists, dental hygienists and gum specialists have eminent rol in the early diagnosis of this type of cancer.

The aesthetic result of the treatment is very important. Surgery can produce major aesthetic and functional changes. For that reason , the practice of implants and tatters for repairing. On the other hand, to limit the aesthetic effects, the exeresis is less long than what would advise an oncologic criterion,for that the healthy tissue limits are not frequently enough and the local relapses are not rare. The chimiosurgery offers not so satisfactory results as the rest of theurapeutical agents, with high rate of local relapses.

The electrofulguration destroys locally the tissue; for that it does not allow neither anatomo-pathological exam or the study of the resection edge. Besides, it produces an injury which heals with a poor aesthetic result. The radiotherapy has been employed many years ago in the treatment of these injuries with excellent results (2,4,6,7). Its capacity of treating a wide area with a mínimum alteration of the healthy tissue allows high probability of cure with excellent aesthetic results. In the use of radiotherapy, it must be considered the following technical parameters: total dose, dose by fraction, type of frequency used, utilization of bolus, and size of the treated region, because they have impact on the results.

Radiotherapy of cutaneous carcinomas has been made generally through x ray of scarce energy (to 90 kV) or electrons of a lineal accelerator (2). Some cases have been treated through intersticial brachytherapy with Iridium sources192, that were positioned crossing the tumoral volume (7,8),or wax molds with sources of gamma rays (Ra, Co, Au, Rn, Cs) (9). Continuos technological advances produced in the field of brachytherapy, have made possible disposing recently of highly precise load equipment, endowed with radio-active sources, generally few milimiters long of Iridium 192, and high activity (10). These radio-active load equipment differed of high dose rate usually giving informatic programs specific for treatment planification and calculation of the dose distribution, which allows to determine with precision parameters of treatment and dose given to the patients in different points (11-14). Also, they incorporate sophisticated algorithms of optimization of the dose distribution, wich allows to modify the dose so it can adapt better to the current volume, getting distribution of an individualized dose according to the needs of every case (13).

Treatments of high dose brachytherapy is done in few minutes. For lip carcinomas it is not necessary the introduction of any vectryz needle inside the tumor, but rather the radio-active source can lodge in an external applicator specially built for every patient. Irradiation is made in few seconds, fact that allows to maintain the daily activity of the patient. On the other hand, it offers a total radioproctection of the professional staff exposed, so they have total radiactive load which is differed, giving this way execution to the more strict norms of protection (11). This characteristic makes it specially attractive.

Radiology of high dose rate makes the difference in radiodenditivity between the healthy tissues and the neoplastic small (11). This is why treatments with high activity sources should be made with special precision, in the calculation of the dose distribution, times of treatment and in the daily positioning of the applicator and the radio-active source. To guarantee the constant execution of the treatment parameters, it is necessary to carry out a continuos and strict quality control.

MATERIALS AND METODS

Since March 1992 to Mrach 1997 a serie of 28 patients who suffered basalcell or squamous-cell carcinomas of lip, which were confirmed histologically, have been treated with brachytherapy equipment of high dose rate. All the patients were followed through March 1998, with a minimum follow up of 12 months.

The radiotherapy, medical reports, pathological anatomy and previous and later photos were revised to obtain information about the local control, aesthetic, and local complications and relapses.

Twenty eight patients were studied, 17 women (62%) and 11 men (38%). There were 27 Basalcell carcinomas and 1 scalycell carcinomas. The average age of the patients was 67 years old with an interval of 23 to 91 years old. All the patients were treated by first intention, after the biopsy. The cases of realapses after surgery were excluded from the analysis. The 92% of all lesions was localizated on inferior lip. In 6 cases (22%) the injuries were of 2 centimeters of diameter, 2 cases were of 1 centimeter or less, 19 cases (68%) were 2 to 5 centimeters of diameter and 3 (10%) patients suffered injuries up to 5 centimeters of diameter. Not patient presented ganglionar metastasis at distance in the time of diagnosis.

The treatment of 28 patients was carried out through cutaneous applicators connected to a brachytherapy equipment of high dose rate (Microselectron, Nucletron Int. BV). To apply the source in the same daily position, acrilic applicators were built according to the plaster models obtained from the impression of the interested zone of the patient and carried out with condesated silicon, putty texture, trade mark OPTOSIL (Bayer). On these applicators were fixed 3 to 7 pastic tube that serve as guides in parallel and halfway form, with instantaneous adhesive, as the curve of the zone to treat. The distance between tubes was 5 to 10 milimeters. Through the introduction of an inactive source, the bending was corrected softening it. In the ends of the applicators were built buttonholes to fixe elastic tips of subjection in order to guarantee the right daily positioning of the applicator and its total inmobility during the treatment (figure 1). Subsequently orthogonal x ray were obtained of the applicator with graduated metallic shammers from the radio-active source (figure 2), in order to introduce the data inside the planning system of the treatment (Silicon graphics).Next, treatment parameters were calculated through the planning 3d software (Plate, Nucletron Int. BV) and distribution of dose was calculated (figure 3). Before the treatment of the patients a treatment essay was carried out positioning the plaster mold and an autoradiography was obtained to file the verification (figure 4). The set of the individualized applicator built,calculation of the treatment parameters and verification of dose was carried out in 3 days, requiring 2 visits of the patient before starting the treatment, one in order to make the impression of the lip zone and the other to draw on the plaster mold the tumor volume and the volume to treat.

In all the cases the minimum dose administered was 6.000 to 6.500 cGy in 33 to 36 fractions of 180 cGy calculated up to 5 milimeters of deep from the cutaneous surface, with correction of the dose distribution because of geometry. Patients with injuries larger than 4 centimeters of diameter had a overimpression of 1800 cGy in 10 fractions, after a rest of 3 weeks, being the administered total dose 7500 to 8000 cGy.

The local control was calculated through the actuarial method of Kaplan and Meier (15), using a statistic package (SPSS). The aesthectic result and complications were measured according to the SOMA-LENT scale (16-19) based in the value of different parameters, not necessarily subordinate one to the other, such as subjetive, objetive, treatment, analytic and late effects on normal tissues. Three measurements were carried out: at six months, 12 months and at the end of the treatment. (figure 5)

RESULTS

A uniform dose distribution was obtained on the surface of the applicator and 5 milimeters deep, in the all area of the applicator. The maximum dose were in the zones next to the guide catheters and the minimum dose in the space between 2 plastic tubes next to each other. The difference between the points of maximum and minimum dose never surpassed 5% of the prescribed dose.

On the end of the treated surface the dose gradient was big enough to include a part of healthy tissue almost worthless, as we can verify in one of the applicators auto x ray (figure 4).

All the patients reached complete remission of their tumor. There were not local or regional relapses. The complete macroscopic remission of the tumor was obtained before the treatment ended in 23 cases, in 3 patients before of the 4 weeks of the treatment end, 1 between 4 and 8 weeks and in one patient between 8 and 12 weeks after treatment. All the patients presented certain grade of cutaneous erythema at the end of the treatment with intensity 1 ( no symptom present) in 24 cases and intensity 2 (minimum functional alteration present) in 4 cases. In 3 patients ulcer grade 1 was present. (limited to the epydermis).

Aesthetic was evaluated in relation to the existence of edema, alopecia, hypo or hyperpigmentation, telegiectasias, fibrosis, scars, atrophy and retraction. At 3 months of treatment 92% of the patients had excellent or good aesthesic and 8 % bad. At 6 months of treatment it was considered excellent (not sequels of the treatment) or good (minimum sequels) in 98 % of the cases. Only one patient had unfavorable aesthetic result. There were not severe late complications of the treatment.

DISCUSSION

Since the discovery of the radio, paraffin molds and applicators were used to treat skin tumors, but they fell in disuse because of radio-protection problems related to the need of manually load them. The last important study that has been published on this tecnique was Ashby and cols. (1989) (9). These authors treated 642 patients with skin cancer not melanomas, using wax molds and radon sources. The local control obtained was 96.8% with a low tension rate of long term complications (less than 1%).

Lovett and cols. (2) published the results obtained in 339 patients with cutaneous epitheliomas treated through external radio-therapy, of which 189 were treated through superficial x rays, 57 with megavoltage and 78 with a combination of beams. The local control in patients treated with superficial radio-therapy was 95.2% (180/189) and in the patients treated with electrons was 77.2% (44/57). The minor control obtained through the beam of electrons could be because of technical factors such as: colimation of beams that produces insufficient size of the irradiation campus and the use of bolus that can produce a insufficient superficial dose. The superficial x ray beam offered a better local control, but it required the exclusive use of a machine for the treatment of the cancer of the skin which produced an excessive dose close to the bone and cartilage, which brought sequels and complications of the treatment of 6% (18/310), some of them serious such as bony necrosis, soft tissues necrosis o cerebral necrosis.

A way to compensate the limitations of the external radio-therapy beams, is using intersticial brachytherapy with Iridium threads 192 (11, 20, 21). Daly and cols. (8,22) published the results obtained through intersticial brachitherapy. The local control obtained was 96.4% (6/165 relapses). There were present evident niusances in the intersticial application, besides a high rate of long term complications, which appeared in 18.2% of the cases (30/165).

The new high dose brachytherapy equipments, made possible again the use of molds or external superficial applicators, with the objective of obtaining the maximum local control and minimum complications. Brock and cols. (23) designed in 1992 a Superficial applicators to use with microselectron. Inside, it the radio-active source occupied an unique active position, situated 15 milimeters from the cutaneous surface. The dose in deep increased, but the maxim size of the applicator was 30 milimeters, which limited the application only to treat injuries up to 2 centimeters maximum diameter.

Svoboda and cols. (24) described in 1995 an applicator in wich the vectorial tubes were inserted in a block of expanded silicone of 0.75 thickness. The separation between tubes was 15 milimeters, 2 to 5 tubes were positioned according to the size of the treated zone. The silicone block was slightly elastic and it was used only to treat flat surfaces 24 squares centimeters far away from the eyes, that is to say tumors 4x4 centimeters of maximum diameter and 1 centimeter of security margin.

Using the applicator which we described in the present study it is possible to avoid the limitations of earlier works. Building on a wax mold multiple essays can be carried out with diverse geometry to find out the best one adaptable in every case. Before we start the treatment, it is possible to check the precise dose distribution calculus, using computer carring out auto x rays. Besides, inside the wax mold of the patient we can make perforations in order to put dosimeters of termoluminiscence and proving the accuracy of the dose distribution, with the same presicion that if we would make measures directly on the patient.

The applicator built this way is easy to use and there is not possibility of error in the daily positioning by the technicians, because it only can fit in one position, which the same patient can adjust. The inmovility of the applicator is secured using elastic rubbers during the few minutes of treatment duration.

With the rutines of optimization in dose distribution and positioning the plastic tubes next enough to each other, we can get uniform distribution of dose on the surface of the personalized applicator. The uniformity increases to 5 milimeters deep. The difference between the values of maximum and minimum dose is down 3%, using superficial x rays or electrons. This value is almost impossible to obtain with external radiotherapy in these cases of not flat surfaces, on which always there is a skin zone closer to the radiation focus. From this point of view, the cutaneous molds are an ideal from of treatment of skin carcinomas (25), of buccal cavity (25), or of palate (26).

In a recently published study (25), 46% on the patients that suffered skin cancer were treated because they presented relapses from previous treatment, such as sugery, electrodisection or chimiosurgery with Mohs paste. These patients with relapsed tumors had the worst local control because 2 of 3 recurrent patients presented relapses, being the actuarial local control 4 years in 87% of them. These values were similar to the published by Lovett and cols. (2), Menn and cols. (27), Sakkura and cols. (28) and Griep and cols. (29), which oscillated between 73% and 89%. If we only consider patients treated by first intention, the actuarial local control was 99%, data that compares favorably with 95% of Lovett and cols (2) and 94% of Fitzpatrick (30,31).

In our study there were not cases which presented late complications to the treatment (figure 5). Lovett and cols (2) found a total of 18 severe complications in a group of 310 patients with skin cancer using radiotherapy. Our study data confirm the opinion of Brady (32) which talks about the use of appropiate irradiation technique to get an excellent local control with best aesthetics and functional results.

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