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Modes of Therapy
PRIMARY RADIOTHERAPY
Key Points
• External beam radiotherapy, generally using 6-MV
x-rays with or without some components of electrons, has an important role in frontline therapy for
patients with carcinoma of the oropharynx, larynx,
or hypopharynx; its aim is to eradicate tumors while
preserving organ structure and function.
• Intensity-modulated radiation therapy (IMRT) has
been widely adopted because of its ability to better
target tumors and reduce late morbidity by diminishing the radiation dose to salivary glands and other
critical organs.
• Brachytherapy, alone or as a supplement to external
beam therapy, can yield high tumor control rates
with less toxicity in selected patients, but its use is
decreasing with the increasing use of IMRT.
• Chemotherapy is o en given, either concurrently
with radiation or before radiation, to improve control
of locally advanced carcinomas.
• Combination therapy with radiation and the
anti–epidermal growth factor receptor antibody
cetuximab has emerged as an alternative to chemoradiation, with a better toxicity pro le, for the frontline
treatment of patients with carcinoma of the oropharynx, larynx, or hypopharynx.
• Surgery remains the preferred therapy for cancers
of the oral cavity, paranasal sinuses, salivary glands,
and thyroid and also for less common head and
neck neoplasms.
• Postoperative radiation, alone or combined with
concurrent chemotherapy when indicated, is an
established adjuvant treatment for patients with
adverse surgical pathologic features, such as multiple
positive lymph nodes, extranodal disease extension,
positive surgical margins, and perineural invasion,
among others.
External Beam Irradiation (Teletherapy)
Primary frontline radiotherapy is generally preferred for the
treatment of patients with carcinoma of the oropharynx, larynx, or hypopharynx. Such therapy is most o en delivered
through external beam irradiation with 6- or 18-MV x-rays,
6- to 20-MeV electron beams, or a combination of both photons
and electrons of proper beam energies. e choice of the beam
type and energy is based on the location and geometric parameters of the target volumes. Occasionally, orthovoltage x-rays
can be useful, for example, for treatment of skin cancers or
for intraoral cone therapy for accessible, well-circumscribed
tumors of the oral cavity or anterior oropharynx.
e initial target volume for external beam therapy
includes both the gross tumor, as determined by clinical
examinations and diagnostic imaging, and the potential
routes of subclinical (microscopic) disease spread. Until
about a decade ago, a shrinking eld technique was widely
used in which the target volume is reduced a er a dose suf cient to sterilize subclinical disease is reached to deliver
an additional boost dose to the demonstrable gross tumor.
e boost dose may be given a er or concomitantly with
the initial large- eld target volume irradiations. In the latter
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scenario, the boost irradiations are administered as second
daily fractions.
1
e common practice in the United States until the
late 1990s was to administer primary radiotherapy in 2-Gy
fractions, once a day, 5 days a week, to total doses ranging
from 66 to 70 Gy depending on the tumor stage and site. As
summarized in Chapter 1, intensive clinical investigations
conducted during the past 3 decades revealed the superiority of hyperfractionation (e.g., 81.6 Gy given in 1.2 Gy per
fractions, twice a day with 6-hour intervals, over 7 weeks)
and two types of accelerated fractionation—concomitant
boost (54 Gy given in 30 fractions over 6 weeks, plus an
18-Gy boost dose given in 1.5-Gy fractions as second daily
fractions during the last 2.5 weeks) and six fractions of
2 Gy per week regimens—in yielding local–regional con-
2,3
trol.
Consequently, many centers have adopted one of
these regimens as the current standard for the treatment
of intermediate-stage head and neck carcinomas or locally
advanced cancers in patients who are not medically t to
receive chemotherapy.
Intensity-Modulated Radiation Therapy
As presented in Chapter 1, advances in computing and
engineering technologies have greatly improved the exibility and precision of aiming radiation beams at irregular
volumes. Such precision radiotherapy can be achieved with
intensity-modulated photon beams in IMRT. Intensitymodulated proton therapy is still in the developmental stage.
With IMRT, all target volumes are irradiated during
every radiation session but, with a properly shaped dose gradient, a higher dose per fraction (e.g., 2 Gy) is delivered to the
clinical target volume (CTV), which encompasses the gross
tumor (primary lesion and involved nodes) with 1- to 1.5-cm
margins (CTVHD), a lower elective dose (e.g., 1.6 Gy per fraction) to subclinical disease target volumes (CTVED), and,
when desired, an intermediate dose (e.g., 1.8 Gy per fraction)
to intermediary volumes (CTVID) surrounding the CTVHD.
It should be noted, however, that in addition to delivering
radiation in smaller fractions, the overall radiotherapy time
for treating subclinical disease is prolonged from the conventional 5 weeks (50 Gy in 25 fractions) up to 6 to 7 weeks
(30 to 35 fractions). erefore, it is prudent to adjust the
dose to the electively irradiated regions to correct for these
changes. Consequently, when IMRT is given in 6 weeks to
deliver a total dose of 66 Gy in 30 fractions to CTV
as in the treatment of T1 to T2 oropharyngeal carcinoma, we
currently prescribe 54 Gy (1.8 Gy per fraction) to the elective volume. When a total dose of 70 Gy is given in 35 fractions (2.0 Gy per fraction) to CTVHD for treatment of larger
tumors, we prescribe 56 Gy (1.6 Gy per fraction) to CTVED
and 63 Gy to CTVID. In the latter scenario, IMRT can be
given in conventional fractionation over 7 weeks by delivering ve daily fractions per week or in accelerated fractionation over 6 weeks by administering six fractions per week
HD
such
(usually by prescribing two fractions a day, with a 6-hour
interfraction interval, 1 day a week, for 5 weeks), a schedule
modeled a er the regimen used by Danish investigators.4 An
alternative strategy to complete treatment in 6 weeks is by
using a concomitant boost–type regimen1 in which all CTVs
receive daily fractions of 1.8 Gy, ve fractions per week for
6 weeks and the CTVHD receives second daily fractions of
1.8Gy each during the last 10 treatment days. e concomitant
boost–type regimen requires two dosimetric plans but has
the advantage of having generally smaller volumes receiving
radiation doses beyond the prescribed level (“hot spots”).
Brachytherapy
Brachytherapy is usually combined with external beam therapy. e rationale for this combination is that areas at risk
of harboring subclinical disease are irradiated with external
beams to a dose su cient to sterilize microscopic deposits
and that the gross lesion is boosted with a brachytherapy
system to higher doses. is approach results in exposing
a smaller volume of normal tissues to high radiation doses.
erefore, if applied appropriately by an experienced team,
high tumor control rates can be obtained with generally low
treatment morbidity.
Brachytherapy is used in the form of interstitial implants
(e.g., for primary cancer of the base of tongue or tonsillar
fossa extending into the base of tongue), molds (e.g., for
lesions of the hard palate), or intracavitary applicators (e.g.,
for recurrent nasopharyngeal cancer).
In selected situations, brachytherapy is used alone.
Examples of such applications include treatment of super cial lip cancers, small nasal vestibule neoplasms, and alveolar
ridge carcinomas.
High-precision external beam radiation techniques such
as IMRT can also better conform the high-dose region to the
tumor with narrow margins. erefore, IMRT has gradually
been substituted for brachytherapy in the treatment of head
and neck cancer.
CONCURRENT RADIATION
AND CHEMOTHERAPY
As presented in Chapter 1, data from several clinical trials
have demonstrated that concurrent radiation–chemotherapy
regimens improve the local–regional control of locally
advanced head and neck cancers, and some regimens also
improve survival rates over those of radiation alone. However, some of the combined regimens studied so far seem to
induce higher normal tissue toxicity as well. e challenge
is to develop mechanism-driven combined regimens with
chemotherapy, emerging novel biologic agents, or both to
yield e ects that are more pronounced on tumors than on
normal tissues. erefore, most patients with T3 to T4 N2 to
N3 head and neck carcinomas are being enrolled in clinical
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Part 1 General Principles of Head and Neck Radiotherapy
trials evaluating new radiation–chemotherapy regimens or
combinations of radiotherapy with biologic agents with or
without chemotherapy. Protocols focusing on reducing treatment morbidity are being designed for patients with human
papillomavirus (HPV)–associated oropharyngeal carcinoma.
Outside of the protocol study setting, however, the combination of conventional fractionation (70 Gy in 35 fractions
over 7 weeks) with three cycles of cisplatin (100 mg/m2)
given during weeks 1, 4, and 7 is o en recommended, even
for patients with HPV-associated oropharyngeal carcinoma,
because this regimen has the longest and most solid track
record. Results of phase III trials have shown that as primary
therapy, this regimen improves local–regional control and
survival as compared with radiation alone for patients with
locally advanced nasopharyngeal carcinoma
5,6
and other
head and neck carcinomas.7 It also increases the likelihood of
laryngeal preservation.8 e combination of conventionally
fractionated radiotherapy with cisplatin given as postoperative adjunctive therapy also improves local–regional control,
disease-free survival
9,10
and survival10 in patients with highrisk surgical pathologic features, particularly the presence of
extracapsular extension of nodal disease and positive surgical margins.11 Recently published ndings from a phase
III trial showed that the combination of accelerated fractionation by concomitant boost (72 Gy in 42 fractions over
6 weeks) plus two cycles of cisplatin can serve as an alternative regimen12 because no di erences were detected between
this regimen and the conventional fractionation plus three
cycles of cisplatin in terms of tumor control or morbidity,
and compliance with the prescribed treatment was better
with two cycles of cisplatin than with three.
CONCURRENT RADIATION
AND CETUXIMAB
Data from a pivotal trial, launched based on strong preclinical evidence, showed that adding eight weekly doses
of cetuximab to radiation improves local–regional control
and survival rates without increasing radiation-induced side
13,14
e ects such as mucositis and dysphagia.
Consequently,
this novel, biologically oriented combined regimen has
become one of several currently approved standard frontline
therapies for locally advanced carcinoma of the oropharynx,
larynx, or hypopharynx.
RADIOTHERAPY AFTER
CHEMOTHERAPY
Neoadjuvant chemotherapy can produce complete tumor
responses in up to 20% of patients and partial tumor
response in up to 60% of patients. In spite of these occasional
impressive responses, overall control rates in randomized
trials of chemotherapy regimens that do not include taxanes
have been at most a few percentage points better than those
achievable with radiotherapy alone. However, as described in
Chapter 1, two recent phase III trials showed that neoadjuvant chemotherapy with the combination of docetaxel, cisplatin, and uorouracil, widely referred to as the TPF regimen,
given before radiation (with or without concurrent carboplatin) yielded superior overall survival rates compared with
cisplatin and uorouracil given before radiation
15,16
Findings
from one of these trials showed that this improvement in
overall survival came predominantly from an increase in the
local–regional tumor control rate rather than from a reduction in distant metastasis.16 Consequently, the TPF neoadjuvant regimen is increasingly being considered one of several
currently available standard therapies.
For patients receiving induction chemotherapy, our
policy is to irradiate the entire anatomical region containing the original tumor volume with adequate margins to
doses equivalent to those from primary radiotherapy alone.
A small dose reduction is sometimes made when the tumor
is adjacent to critical organs, such as locally advanced nasopharyngeal carcinoma, or when acute reactions are excessive.
ADJUVANT POSTOPERATIVE
RADIOTHERAPY
Surgery is the preferred treatment for cancer of the oral
cavity, paranasal sinuses, salivary glands, and thyroid.
Advanced carcinomas of the oropharynx, larynx, or
hypopharynx (e.g., those invading the mandible or neck
so tissues) are o en also treated with a combination of surgery and radiation. e general indications for postoperative radiotherapy include close or positive surgical margins,
perineural spread, lymphovascular invasion, contiguous
tumor extension into bone or neck so tissue, multiple positive nodes, and extracapsular extension of nodal disease.
Radiation with 6-MV x-rays o en include consideration
of using a 3-mm scar bolus to deliver su cient dose to the
subcutaneous tissues.
As a general principle, the entire operative bed is
included in the postoperative target volume. e donor
site(s) for skin gra s or myocutaneous aps are not considered part of the operative bed in this context. With conventional techniques, several eld reductions may be necessary
to deliver desired doses to the undissected nodal basins, surgical bed, and regions at high risk of recurrence, such as sites
of extensive extracapsular extension or positive margins.
IMRT is also being increasingly used for postoperative treatment because of its ability to better distribute radiation dose
according to high-risk features while sparing salivary glands
and other critical normal tissues. e target volume that is to
receive higher doses and the total doses prescribed are based
on surgical pathologic ndings.
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27
In the presence of perineural invasion of major or
named nerves, our general policy is to treat the course of
involved major nerves at least to the skull base. However,
if only minor unnamed nerves are histologically involved,
slightly larger portals (e.g., with margins of an additional
2 or 3 cm) are generally selected and no attempt is made to
trace the course of major nerves to the skull base.
e general rule is to start radiotherapy as soon as the
surgical wound has healed, usually 3 to 4 weeks a er surgery. With good communication between surgical, radiation,
and dental oncologists, treatment simulations generally can
take place 3 to 4 weeks a er surgery, and radiotherapy can
start within a week for most patients. is approach requires
that dental assessment occur before surgery to determine
the need for extractions when postoperative radiotherapy is
contemplated. When postoperative radiotherapy is recommended, dental care can be provided at the time of cancer
surgery to avoid the need for a second anesthesia for fullmouth teeth extraction and unnecessary delay in initiating
radiotherapy.
Our series revealed that completion of combined therapy within 11 weeks yielded better local–regional control
and better survival rates than completion of treatment in
11 to 13 weeks, and nishing combined therapy in more
than 13 weeks resulted in a much worse outcome.
17
When
delayed wound healing postpones postoperative radiation
beyond 5 to 6 weeks a er surgery, we prescribe accelerated
fractionation to reduce the overall treatment time by 1 week
to avoid the potential deleterious e ects of prolonged cumulative treatment time. Using this strategy, a dose of 60 Gy is
given in 5 weeks, which may induce more severe mucositis
but does not increase the rate of late complications.
PREOPERATIVE RADIOTHERAPY
Preoperative radiotherapy is rarely used in our practice
because of the surgeons’ preference to operate in an unirradiated eld where frozen section control of surgical margins
can be obtained. In certain circumstances, however, planned
preoperative radiotherapy may be given.
ese include situations in which the cancer is marginally resectable or has a very rapid growth history. Patients
with small radiocurable primary tumors and large adenopathy may be treated with de nitive radiation to the primary
tumor and preoperative radiation to the neck with a planned
neck dissection to follow radiation. is strategy is particularly appealing for patients with bulky disease in the level IV
nodal region, to eliminate the need to administer a total dose
of 70 Gy to the brachial plexus. Neck dissection is performed
approximately 6 weeks a er radiotherapy.
For most preoperative treatments, the dose is limited
to that required for sterilization of subclinical disease, that
is, 50 Gy in 25 fractions over 5 weeks. For very advanced
tumors, a dose of 60 Gy in 30 fractions over 6 weeks may be
administered. Surgery may also be performed, however, a er
full-dose primary radiotherapy if residual disease persists at
6 or more weeks a er completion of treatment. is situation
occurs mostly in the presence of a large nodal mass. e timing for surgery is generally about 6 weeks a er completion
of radiation.
REFERENCES
1. Ang KK, Peters LJ, Weber RS, et al. Concomitant boost
radiotherapy schedules in the treatment of carcinoma of the
oropharynx and nasopharynx. Int J Radiat Oncol Biol Phys
1990;19:1339–1345.
2. Bourhis J, Overgaard J, Audry H, et al. Hyperfractionated or
accelerated radiotherapy in head and neck cancer: a metaanalysis. Lancet 2006;368:843–854.
3. Fu KK, Pajak TF, Trotti A, et al. A radiation therapy oncology
group (RTOG) phase III randomized study to compare hyperfractionation and two variants of accelerated fractionation to
standard fractionation radiotherapy for head and neck squamous cell carcinomas: rst report of RTOG 9003. Int J Radiat
Oncol Biol Phys 2000;48:7–16.
4. Overgaard J, Hansen HS, Specht L, et al. Five compared with
six fractions per week of conventional radiotherapy of squamous-cell carcinoma of head and neck: DAHANCA 6 and
7 randomised controlled trial. Lancet 2003;362:933–940.
5. Al-Sarraf M, LeBlance M, Shanker PG, et al: Chemoradiotherapy versus radiotherapy in patients with advanced nasopharyngeal cancer: phase III randomized intergroup study 0099. J Clin
Oncol 1998;16:1310–1317.
6. Wee J, Tan EH, Tai BC, et al. Randomized trial of radiotherapy
versus concurrent chemoradiotherapy followed by adjuvant
chemotherapy in patients with American Joint Committee on
Cancer/International Union against cancer stage III and IV
nasopharyngeal cancer of the endemic variety. J Clin Oncol
2005;23:6730–6738.
7. Adelstein DJ, Li Y, Adams GL, et al. An Intergroup Phase III
Comparison of standard radiation therapy and two schedules
of concurrent chemoradiotherapy in patients with unresectable
squamous cell head and neck cancer. J Clin Oncol 2003;21:92–98.
8. Forastiere AA, Goepfert H, Maor M, et al. Concurrent chemotherapy and radiotherapy for organ preservation in advanced
laryngeal cancer. N Engl J Med 2003;349:2091–2098.
9. Cooper JS, Pajak TF, Forastiere AA, et al. Postoperative
concurrent radiotherapy and chemotherapy for high-risk
squamous-cell carcinoma of the head and neck. N Engl J Med
2004;350:1937–1944.
10. Bernier J, Domenge C, Ozsahin M, et al. Postoperative irradiation with or without concomitant chemotherapy for locally
advanced head and neck cancer. N Engl J Med 2004;350:
1945–1952.
11. Bernier J, Cooper JS, Pajak TF, et al. De ning risk levels in
locally advanced head and neck cancers: a comparative analysis of concurrent postoperative radiation plus chemotherapy
trials of the EORTC (#22931) and RTOG (# 9501). Head Neck
2005;27:843–850.
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Part 1 General Principles of Head and Neck Radiotherapy
12. Ang KK, Harris J, Wheeler R, et al. Human papillomavirus
(HPV) and survival of patients with oropharynx cancer. N Engl
J Med 2010;363:24–35.
13. Bonner JA, Harari PM, Giralt J, et al. Radiotherapy plus cetuximab for squamous-cell carcinoma of the head and neck. N Engl
J Med 2006;354:567–578.
14. Bonner JA, Harari PM, Giralt J, et al. Radiotherapy plus cetuximab for locoregionally advanced head and neck cancer: 5-year
survival data from a phase 3 randomised trial, and relation
between cetuximab-induced rash and survival. Lancet Oncol
11:21–28, 2010
15. Vermorken JB, Remenar E, van Herpen C, et al. Cisplatin, uorouracil, and docetaxel in unresectable head and neck cancer.
N Engl J Med 2007;357:1695–1704.
16. Posner MR, Hershock DM, Blajman CR, et al. Cisplatin and
uorouracil alone or with docetaxel in head and neck cancer.
N Engl J Med 2007;357:1705–1715.
17. Ang KK, Trotti A, Brown BW, et al. Randomized trial addressing risk features and time factors of surgery plus radiotherapy
in advanced head and neck cancer. Int J Radiat Oncol Biol Phys
2001;51:571–578.
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Practical Aspects of External
Beam Therapy
Key Points
• Patient positioning, immobilization, and placement
of an isocenter (or a reference point) are critical components for planning external beam radiotherapy.
• Supine position is most desirable for the vast major-
ity of patients.
• Use of radiopaque markers can aid delineation of
target volume.
• Positional or shielding stents are useful for decreas-
ing radiation dose to normal tissues in certain cases.
• CT-based plan with heterogeneity correction is the
current standard method.
• Intensity-modulated radiation therapy (IMRT) is increas-
ingly used for treating head and neck cancer for
improving target volume coverage around the skull base
(e.g., nasopharyngeal and sinonasal carcinomas) and for
reducing radiation exposure of normal tissues such as salivary glands, cranial nerves, spinal cord, brain stem, etc.
• Unilateral radiation is preferred for selected patients
with lateralized neoplasms such as cancer of the buccal mocosa, retromolar trigone, parotid, etc.
• Bolus, missing tissue compensator, and other devices
can improve dose distribution but their use is diminishing with the introduction of IMRT that provides
better conformation of radiation to the target volumes.
radiation therapy (IMRT). An isocentric technique is applied
for matching opposed–lateral elds or IMRT upper neck
portals to an anterior or anterior–posterior (AP-PA) lower
neck portal(s).
e “open neck” position, in which the head is rotated
on the trunk, resulting in attening of the contours of the
neck, is used for irradiating lateralized tumors and the ipsilateral neck. is position is suitable for irradiations with
adjoining appositional electron elds or with a wedge-pair
photon portal matched to an appositional electron eld for
lower neck.
e true lateral position is used in very select cases, for
example, postoperative situations in which patients are unable to control secretions in the supine position but nonetheless need to be treated with opposed–lateral elds.
e seated position is used very rarely, primarily for
those who have di culty managing their secretions or
those who have di culty breathing in the supine position.
Treatment is accomplished using a specially designed chair
mounted to the treatment couch. is chair enables the same
immobilization and allows the same treatment accessories
to be used as in the supine position. e chair is used only
if other options are not feasible because complex treatment
planning and dosimetry are di cult and because computed
tomography (CT) scanners cannot accommodate patients in
this position.
PATIENT POSITIONING
e supine position is most frequently used to deliver radiation with the conventional technique or intensity-modulated
PATIENT IMMOBILIZATION
Virtually all patients nowadays are immobilized with
thermoplastic masks that are individually made in the
desired treatment position. A variety of commercial
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Part 1 General Principles of Head and Neck Radiotherapy
neck pads and head holders are available for the purpose
of immobilization in different positions. When making a mask, care should be taken to stretch the thermoplastic sufficiently thin to avoid unwanted bolus effect.
A
For treatments limited to the neck region, the mask
can be constructed so as to avoid the portals altogether.
Figures3.1 and 3.2 outline briefly the general procedure
of constructing immobilization devices.
B
C
E
Figure 3.1
of the patient, aligned in the desired position, and the frames are then fi xed to a head holder by clamps. Care is taken to stretch
the thermoplastic sheet suffi ciently thin to avoid unwanted bolus effect. D: Gentle pressure is applied to make the thermoplastic
sheet conform to the contours of the head and shoulder while cooling off and becoming more rigid. E,F: Isocenter or reference
point is marked and thin-slice CT images are obtained for delineation of target volumes or portals and dosimetric planning.
Procedure for making a thermoplastic mask in a supine position. A: Thermoplastic sheet is submerged in a warm
water bath (72°C) until it becomes fl exible. B,C: The thermoplastic sheet is placed over the head and shoulders
D
F
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Introduction of IMRT to reduce radiation morbidity or
to escalate radiation dose to improve tumor control demands
more precise and reproducible immobilization technology.
Several methods have been introduced, which can be grouped
A
into invasive and noninvasive techniques. Invasive techniques
use head immobilization frames similar to those used for stereotactic radiosurgery. e frame is a xed to the patient’s
skull by several screws, usually placed by a neurosurgeon.
B
C
E
Figure 3.2
over the head of the patient and the frame is then fi xed to a head holder. E,F: Gentle pressure is applied to make the thermoplastic sheet conform to the contour of the patient and the sheet is rolled up cranially to expose the area of irradiation to minimize
perturbation of electron beams. Simulation can take place while the mask is cooling down and becoming more rigid.
Procedure for making a thermoplastic mask for treatment in an open neck position. A: The patient is positioned
with the head rotated on the trunk to fl atten the contours of the neck. B–D: The thermoplastic sheet is stretched
D
F
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Part 1 General Principles of Head and Neck Radiotherapy
Numerous noninvasive immobilization techniques
have been described. ey are based on thermoplastic mask
immobilization or customized polyurethane cradles. ermoplastic masks can be reinforced with additional straps to
increase rigidity. Some systems add individualized cradles
for support of the occiput. We currently use a longer headboard for attachment of a mask that extends from the vertex
of the scalp to the upper chest, giving additional support to
the upper neck and shoulder (Fig. 3.1).
RADIOPAQUE MARKERS
AND STENTS
Although CT scan–based simulation and dosimetry are
widely used, radiopaque markers can still be useful for delineating the scars and, in select cases, the primary lesion. It
is important to realize that it is o en di cult to visualize
super cial tumors in the diagnostic or planning CT scan.
is simple procedure helps in designing treatment portals to minimize the risk of a geographic miss and to avoid
unnecessary inclusion of normal tissues. Several types of
custom-made stents are useful in reducing the volume of
normal tissues irradiated.
Wires and seeds placed on the skin, on the thermoplastic mask, or inserted into the tissue are helpful in marking
the boundaries of the primary tumor, nodal biopsy sites, or
surgical scar.
Stents can be custom-made, such as those used to
depress or shield the tongue or to protrude the lip. In general,
these devices can be categorized into two basic types: shielding stents and positional stents. A shielding device serves to
reduce the radiation dose administered to normal tissues by
incorporating shielding material, whereas a positional device
serves to displace normal tissues out of the treatment elds
(Figs. 3.3–3.7).
A
Figure 3.3
cytologic study was obtained by fi ne needle aspiration and was interpreted as pleomorphic adenoma. At surgery, the
tumor was found to be mainly located in the deep lobe of the parotid gland. It was well encapsulated and was
dissected out along with the surrounding normal parotid tissue. The facial nerve was preserved. Pathologic examination revealed an acinic cell carcinoma measuring 2.4 cm in maximum diameter. All gross tumor was resected, but
tumor cells extended to the surgical margin. Therefore, postoperative radiotherapy was recommended. The left
parotid bed was treated with an ipsilateral appositional fi eld using a combination of 20-MeV electrons and 18-MV
photons, weighted 4:1, respectively. A dose of 56 Gy was delivered in 2-Gy fractions, specifi ed at the 90% isodose
line. To reduce the dose to the underlying brain during the electron treatments, 2 cm of beveled bolus was placed
over the superior part of the fi eld. After a dose of 44 Gy, the fi eld was reduced off the spinal cord, and treatment to
the postauricular and posterior cervical area was completed with 12-MeV electrons. A custom-made intraoral stent
containing cerrobend (Lipowitz’s metal, Cerro Metal Product, Bellefonte, PA, or Belmont Metal Inc, Brooklyn, NY) with
a fl ange containing occlusal registration (A) was used to shield the tongue and contralateral oral mucosa from the
electron beam treatments. The stent was held in place by the teeth fi tting in the fl ange on the lateral side (B), which
positioned the main stent between the alveolar processes and the tongue and, thereby, shielding as shown on the
portal image
A 37-year-old woman presented with a 1.5-cm mass at the left angle of the mandible. The head and
neck examination was otherwise unremarkable, and the facial nerve function was intact. Material for
B
C
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D
Figure 3.3
tongue and contralateral oral mucosa so that mucositis could be prevented.
A
(Continued) (C) and displacing the tongue toward the contralateral side as shown on planning CT scan (green
arrow) (D). Because 80% of the dose was delivered by electrons, there was still a signifi cant protection of the
B
C
Figure 3.4
oral commissure. The tumor was 1.0 to 1.5 cm thick, without apparent skin involvement. There were two right submandibular
nodes palpable, the largest measuring 2 cm in diameter. Biopsy revealed squamous cell carcinoma. The patient underwent
resection of the tumor and a right modifi ed neck dissection. Pathologic examination revealed a well-differentiated squamous cell
carcinoma of the buccal mucosa with microscopic extension into the skeletal muscle and skin of the cheek. Nine lymph nodes
were recovered in the surgical specimen, four of which contained metastatic squamous cell carcinoma with extension beyond
the capsule. The patient received postoperative radiotherapy. The tumor bed and right upper neck were subjected to an ipsilateral appositional 13-MeV electron fi eld to a given dose of 60 Gy in 30 fractions. The ipsilateral mid and lower jugular nodes and
the posterior cervical chain were encompassed by a 9-MeV electron fi eld. These areas were treated to a given dose of 50 Gy in
25 fractions. The scar extending into the mid neck was given a 4-Gy boost with 6-MeV electrons. A variation of the stent as
described in Figure 3.3 was used for this patient. As in the previous case, the stent-containing cerrobend was placed between
the alveolar processes and the tongue, serving to displace the tongue and to shield the tongue and contralateral oral mucosa. In
this case, the right oral commissure needed to be included in the fi eld and, therefore, fall off was required anteriorly. The stent
protruded anteriorly to shield the contralateral part of both lips and the left oral commissure. A: Lateral view. B: Stent mounted on
an articulator. C: Anterior end of the stent protrudes through the mouth for shielding part of the lips and the left oral commissure.
(From Kaanders JHAM, et al. Devices valuable in head and neck radiotherapy. Int J Radiat Oncol Bio Phys 1992;23:639–645.)
A 66-year-old woman presented with a right buccal mucosa lesion. On physical examination, she was found to
have an infi ltrative tumor measuring approximately 3.5 cm in largest diameter, extending anteriorly almost to the
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