Glottic Larynx

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Squamous cell carcinoma in situ of the true vocal cords is initially treated surgically, and usually with micro-excision. However, if there is evidence of microinvasive squamous cell carcinoma in the specimen or if there are rapid or multiple recurrences, radiation therapy can be administered with an approach identical to that for T1 invasive lesions. Wang24 reported a 92 percent 5-year local control and a 98 percent 5-year disease-free survival. The results in voice quality are good.

T1 invasive vocal cord lesions are limited to the cord with a normal mobility and are treated with surgery or radiation therapy with equally high effectiveness. Generally, the treatment of choice is radiation therapy while surgery is reserved for salvage of radiation failures. Bulky lesions in general and especially those located in the anterior commissure as well as extension of glottic lesions to the far anterior and posterior aspects of the larynx can decrease local control rates with radiation therapy. Radiation and surgery both result in an equivalent high local control rate but irradiated patients have superior voice quality.62 The treatment field has a superior margin below the hyoid bone, an inferior margin at the bottom of the cricoid cartilage and an anterior margin with a 2 cm flash. The posterior margin is at the anterior 25 to 30 percent of the vertebral body for cobalt 60 teletherapy units; for 4 MV linear accelerators, anterior vocal cord lesions have a posterior portal margin at the anterior border of the vertebral body while posterior lesions have a portal margin similar to that noted for cobalt 60 teletherapy units. Because of the sparse lymphatics in the true vocal cords, the risk for nodal metastasis is quite low at 5 percent for T1 lesions63 and thus the regional lymph nodes are not included in the treatment field. The field arrangements are via the right/left lateral opposed portals. Treatment should be administered on a cobalt 60 teletherapy unit (Figure 21-8) with 1.25 MV gamma rays or a linear accelerator with 4 MV x-rays, since higher energy units (Figure 21 -9) may create a dosimetry problem, particularly for anterior commissure lesions with an underdosage to this region because of the greater maximum depth dose in this anatomically narrowed area.64 If a linear accelerator with 6 MV x-rays is used, a bolus of appropriate thickness will be needed to compensate for this dosimetry concern; however, this will be associated with an increased acute skin reaction. A

Figure 21-8.

gamma rays.

Cobalt 60 teletherapy unit administers 1.25 MV

Figure 21-8.

gamma rays.

Cobalt 60 teletherapy unit administers 1.25 MV

larynx compensator would be used to improve the dose homogeneity. The dose per fraction would be 200 cGy or higher as lower fraction sizes have been associated with higher local recurrence rates.65,66 The total dosage would be 6,600 cGy. Radiation therapy local control rates for T1 lesions have been reported at 93 percent, 91 percent and 93 percent (Figure 21-10A to C).246768

Surgery for T1 lesions is with a vertical hemi-laryngectomy with the removal of the involved vocal cord, the ipsilateral false cord and the adjacent thyroid cartilage. Local control rates have been reported at 78 percent69 and 87 percent.70 This procedure is most frequently used for salvage of radiation therapy failures.

T2 glottic lesions involve the transglottic extension of tumor to the supraglottis and/or subglottis with or without impaired vocal cord mobility. In general, the risk of lymph node metastasis is rather low at 8 percent.63 This is a heterogeneous group. C.C. Wang has advocated dividing this stage into a T2a with normal vocal cord mobility and T2b with impaired mobility. Primary radiation therapy results are quite good with T2a but suboptimal for T2b lesions which appear to behave more like T3 lesions.

For T2a lesions, radiation therapy is generally the treatment of choice. With disease that is primarily on the vocal cord with low volume extension onto the adjacent supraglottis or subglottis, one would consider designing a generous treatment volume similar to a T1 glottis that would encompass 2 cm around all of the tumor. Generally, we would not include the regional lymph nodes in the treatment volume; however, with extensive moderate to high volume involvement of the adjacent supraglottis or sublottis, we would consider treatment of adjacent lymph nodes based on the extent of the disease. One should note that if there is such an extensive amount of bulk and volume in the adjacent supraglottic or subglottic subsites with respect to the true vocal cord involvement, one may need to reconsider whether this lesion may indeed be a primary site in these other structures rather than the true vocal cord, and thus be treated as such. This would include regional nodal irradiation. Field arrangements are via right/left lateral opposed portals. Substantial lesions involving these adjacent subsites that are rich in lymphatics will require that the regional lymph nodes be treated as well. For small volume, less bulky lesions, conventional fractionation radiation therapy can be considered at 200 cGy per fraction to a total dosage of

Figure 21-9. Linear accelerator with dual energy x-rays and multiple electron energy capabilities. Dynamic multi-leaf collimation allows for its use in IMRT cases.

7,000 cGy. However, for more extensive lesions, we would use accelerated fractionation with a delayed concomitant boost to a dosage of 7,000 cGy. Local control rates with radiation therapy have been reported at 86 percent.71 Primary surgery is usually a vertical hemilaryngectomy and has 3-year survival rates in the low 80 percent range.70 In men, surgery can be considered for lesions that involve one entire vocal cord and up to one-third of the opposite cord; however for women, one vocal cord and only a few millimeters of the opposite cord may be resected without causing airway compromise. For subglottic extension, the maximum extent allowable for a ver tical hemilaryngectomy is 9 mm anteriorly and 5 mm posteriorly in order to preserve the functional integrity of the cricoid cartilage. The postoperative voice quality is inferior to that of post-radiation therapy and the patient will have a persistent hoarseness. Therefore, surgery is usually reserved for salvage of radiation failures. However, if the lesion extends to involve the epiglottis, false cord, or both arytenoids, a total laryngectomy is needed if surgery is used. In such cases, we would consider initially treating the patient with a larynx preservation approach using chemotherapy and radiation therapy and saving surgery for salvage.

Wedge Vocal Cords
Figure 21-10. Patient with a T1aN0 squamous cell carcinoma of the right true vocal cord before (A) and several months after (B) full course external beam radiation therapy showing a complete clinical response. Treatment plan with the use of wedges to create a more homogenous dose distribution (C).

For T2b lesions, primary radiation therapy can be considered particularly for small, non-bulky lesions. Local control rates of radiation alone are in the range of 60 to 70 percent. Wang reported a local control rate of 63 percent.71 Large, bulky masses may be approached with surgery if a vertical hemi-laryngectomy can be performed. However, if a total laryngectomy is required, it would be reasonable to consider the laryngeal preservation approach with chemotherapy and radiation therapy, reserving surgery for salvage.

T3 lesions have a fixed vocal cord while T4 lesions involve extension into the thyroid cartilage, thyroid gland, and soft tissues of the neck and esophagus. The risk of lymph node metastasis is 15 percent for T3 lesions and 20 to 30 percent for T4 lesions.63 The initial therapeutic approach should be with larynx preservation as surgical therapy would require a total laryngectomy and this can be reserved for salvage. Data from the Veterans Affairs Laryngeal Cancer Study Group72 evaluating stage III and IV larynx cancers in 1991 is based on using neoadjuvant cisplatin and 5-FU chemotherapy for 2 to 3 cycles and then conventional fractionation radiation therapy to a total dosage of 7,000 cGy for partial or complete responders. They reported a 68 percent 2-year survival rate which was equivalent to that of the total laryngectomy-postoperative radiation therapy arm. However, there was a 64 percent larynx preservation in the chemotherapy-radiation therapy arm. At Memorial Sloan-Kettering Cancer Center, we have usually employed cisplatin chemotherapy on days 1 and 22 concurrent with radiation therapy using accelerated fractionation with a delayed concomitant boost to a total dosage of 7,000 cGy to the primary site and lymphadenopathy.61a When elective lymph node irradiation is administered, we would deliver 5,000 to 5,400 cGy.

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