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Effective radiotherapy requires careful simulation and treatment planning. The patient generally lies supine while the head is immobilized with the neck extended using a headrest and customized mask. A tongue

N Stage Lymph Node Disease

M Stage

Distant Metastases

MO

Absent

M1

Present

Stage Group

T Stage N Stage

IIA T2a NO MO

IIB T2b NO MO

T1-T2b N1 MO

III T3 NO-1 MO

T1-T3 N2 MO

IVA T4 NO-2 MO

IVB T1-4 N3 MO

blade is inserted to depress the tongue away from the palate, and palpable lymph nodes are outlined with wires. The most common field arrangement consists of opposed lateral fields to encompass the primary tumor and upper neck (Figure 7-3). A third, anterior field is matched below the lateral fields to treat the lower cervical and supraclavicular lymph nodes. The larynx is generally shielded and care must be taken to avoid overlapping fields on the spinal cord. The treatment design must be individualized for each patient, depending upon disease distribution and stage. CT or MRI scans should be used to define the gross tumor volume and this should be expanded by 1 to 2 cm to define the planning target volume. It is important to adequately treat the skull base and anterior as well as posterior cervical lymph nodes.

Radiation therapy is most often delivered with a linear accelerator in fractions of 1.8 to 2 Gy per day. Various accelerated fractionation regimens have also been used.22,23 A shrinking field technique is used to give a range of doses to various regions. For instance, the optic nerves and spinal cord should be blocked from photon irradiation after a dose of 40 to 45 Gy. The posterior neck may then be treated to the appropriate total dose with electron beams. Elec-tively treated nodal regions should receive doses of

Figure 7-3. Initial lateral simulation film for a patient with a stage T3 nasopharyngeal cancer invading the skull base. The cavernous sinuses, posterior ethmoid sinuses and skull base are included in the treatment field. The eyes and oral cavity are shielded. A palpable lymph node is marked with a wire. The field should be reduced during the course of therapy to prevent overdosing critical structures such as the optic nerves, optic chiasm, brain stem, and spinal cord. Treatment fields must be customized for each patient based on the extent of disease.

Figure 7-3. Initial lateral simulation film for a patient with a stage T3 nasopharyngeal cancer invading the skull base. The cavernous sinuses, posterior ethmoid sinuses and skull base are included in the treatment field. The eyes and oral cavity are shielded. A palpable lymph node is marked with a wire. The field should be reduced during the course of therapy to prevent overdosing critical structures such as the optic nerves, optic chiasm, brain stem, and spinal cord. Treatment fields must be customized for each patient based on the extent of disease.

45 to 54 Gy. The portals may then be reduced to treat the primary tumor and gross adenopathy to total doses in the range of 65 to 75 Gy.

The appropriate radiation dose for an individual patient is derived by balancing the likelihood of achieving local control with the risks of radiation toxicity. Large tumors may require higher doses than small tumors. In general, several retrospective studies have shown improved local control using cumulative doses of > 70 Gy.24-26 Yan and colleagues conducted a study randomizing patients with residual disease after a dose of 70 Gy to receive a boost to 90 Gy or no additional treatment.27 Local failure was significantly lower for patients receiving the boost but there was an increase in radiation toxicity.

A variety of techniques exist for delivering higher doses of radiation to the nasopharynx while minimizing the dose to critical structures such as the brainstem, optic nerves, mandible, temporal lobes, and inner ears. Intracavitary brachytherapy is a traditional technique whereby radiation sources are placed within the nasopharynx (Figure 7-4).28,29 Alternative external beam techniques have also been used and this approach has been aided by the development of CT scan planning.30 Newer technologies for boosting this region include stereotactic radio-surgery and intensity modulated radiotherapy (IMRT) as demonstrated in Figure 7-5.31,32

Nasopharynx cancer responds to a wide variety of chemotherapy agents. The most commonly used

Figure 7-4. Verification film for a patient receiving an intracavitary brachytherapy boost for a stage T1 nasopharyngeal cancer. Radioactive sources are placed in catheters within the nasopharynx. In this case, the applicator has a thin metal shield inferiorly to allow relative sparing of the soft palate. The dose distribution is represented by the colored lines: red = 29 Gy, blue = 10 Gy, and brown = 5 Gy.

Figure 7-5. Axial and sagittal views of an intensity modulated radiotherapy (IMRT) plan for a stage T3 nasopharynx cancer. Seven beam angles are used in this case. Isodose curves are labeled by color. The target volume consists of the gross tumor plus a margin and is covered by the 100 percent dose level. The brain stem receives less than 50 percent of the prescribed dose.

Figure 7-5. Axial and sagittal views of an intensity modulated radiotherapy (IMRT) plan for a stage T3 nasopharynx cancer. Seven beam angles are used in this case. Isodose curves are labeled by color. The target volume consists of the gross tumor plus a margin and is covered by the 100 percent dose level. The brain stem receives less than 50 percent of the prescribed dose.

regimen for patients with advanced disease in the United States includes cisplatin and 5-fluorouracil, based on the Head and Neck Intergroup study.20 Patients should have measurement of creatinine clearance, an electrocardiogram, and an audiogram to ensure that they are appropriate candidates before starting this chemotherapy. Cisplatin 100 mg/m2 is generally given on days 1, 22, and 43 during radiotherapy, with appropriate hydration and supportive care. Following chemoradiotherapy, patients receive 3 cycles of cisplatin 80 mg/m2 and 5-fluorouracil 1000 mg/m2/day (96-hour infusion) every 4 weeks.

Local recurrence after primary radiotherapy may be managed with re-irradiation or nasopharyngec-tomy in selected cases.33,34 A discussion of these techniques is beyond the scope of this chapter. Regional nodal recurrence in the neck may be managed with a neck dissection. Most patients with locoregional recurrence and those with distant metastases should be offered systemic chemotherapy.

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