A 59-year-old man presented with a 1-month history of sore mouth. Physical examination revealed a 2.5-cm ulcerative, mobile lesion in the right anterior part of the floor of mouth. The tumor involved the frenulum of the tongue, but did not cross the midline. The mobility of the tongue was normal. A 1.5-cm mobile lymph node was palpated at the right submandibular area. Biopsy of the primary tumor showed moderately differentiated SCC. Stage: T2 N1 M0. This patient underwent a wide local excision of the primary tumor and bilateral supraomohyoid neck dissections. The defect in the floor of mouth was repaired with a split-thickness skin graft. At the time of surgery, the tumor was found to involve the sublingual gland and the deep musculature. The initial deep margin was positive, but was converted to negative by further excision of the muscle. Of the five nodes recovered from the right neck specimen, one submandibular node measuring 2 cm was involved with carcinoma without evidence of ECE. Seven lymph nodes recovered from the left side were all free of tumor. Pathologic stage: p T4 N1. The patient received postoperative radiotherapy.

The primary site and upper neck were treated with parallel opposed-lateral photon fields (Fig. 6.1). By using a tongue depressor, the hard palate and part of the soft palate and upper gums could be excluded from the radiation field. The mid and lower neck nodes were treated with an anterior appositional photon field with a midline block to shield the larynx. This block was placed just above the surgical scar in the neck, which is marked with a wire. The primary tumor bed and uninvolved nodal areas received 56 Gy in 28 fractions. The involved nodal area was boosted to 60 Gy in 30 fractions. The boost dose to the right upper neck was delivered with an appositional electron field. He had no evidence of disease and was free of complications 2 years after treatment.

A 65-year-old man presented with ill-fitting dentures and oral pain. Physical examination revealed a 4-cm tumor on the right lateral tongue, an enlarged submandibular gland, and a 3.5-cm conglomerate nodal mass in right level II. Stage T2 N2b M0. He underwent a partial glossectomy and selective right neck dissection. Histologic examination showed an SCC of the tongue with negative section margins but presence of perineural invasion. Five of forty dissected nodes were positive, and there was ECE. He received adjunctive postoperative radiotherapy delivered with 6-MV photons for the entire treatment using an isocentric technique. A 3-mm tissue-equivalent bolus was placed over the scar.

A digitally reconstructed radiograph with the fields is shown in Figure 6.2A. An off-spinal cord reduction was made at 42 Gy and a boost cone-down at 56 Gy. The posterior cervical strips were supplemented with 9-MeV electrons, 18 Gy to the right strip and 8 Gy to the left strip. Figure 6.2B,C: show axial and sagittal isodose distributions through the tongue. The supraclavicular field had a larynx (and spinal cord safety) block. Both sides of the lower neck received 50 Gy. The right mid and lower neck received 6-Gy boost dose. These fields were further reduced off the inferior border to take the right neck at risk to 60 Gy.

A 38-year-old man treated with a limited resection of an oral tongue SCC presented 2 years following surgery with a recurrence. He underwent a left partial glossectomy with a radial forearm graft reconstruction and left neck dissection. The tumor had 1.3-cm depth of invasion, section margins were negative (deep margin 0.6 cm) and nodes were not involved. Due to the recurrent nature and depth of invasion, he was treated with postoperative radiation using IMRT.

Figure 6.3A shows an axial view with contours of target volumes. The green volume represents the preoperative disease (vGTV) and blue volume the CTV to receive 60 Gy (CTV_HD). The purple volume represents the remaining operative bed (including a wired scar), planned to 57 Gy (CTV_ID), while the orange contour represents the remaining tongue and contralateral neck nodes planned to 54 Gy (CTV_ED). Figure 6.3B,C show isodose distributions through a superior axial cut and a sagittal view through midplane, respectively. The patient remains well 2 years from all therapy with good speech and oral comfort.

A 47-year-old man presented with biopsy-proven SCC of the left oral tongue. He underwent a partial glossectomy with selective left neck dissection. The primary tumor was 1.2 cm in size and had negative margins. The neck dissection yielded 3 positive nodes in levels II and III without ECE. He was treated with postoperative radiation. The tumor bed, consisting of the left lateral tongue and left upper neck, with margin was identified as CTV_HD (60 Gy). The undissected right neck and right hemitongue was contoured as CTV_ED (54 Gy).

Figure 6.4 shows CTV_HD (red) and CTV_ED (blue) paired with isodose distributions at the level of the tongue (Fig. 6.4A,B) and upper neck (Fig. 6.4C,D). Figure 6.4E,F: show isodose distributions on a sagittal view through the midtongue and a coronal view, respectively. An intraoral stent opens the mouth and separates the palate from the tongue (Fig. 6.4E). The isocenter was placed just above the thyroid notch (Fig 6.4F). IMRT was delivered to fields above the isocenter. Level III and IV nodes were treated with an anterior beam with a larynx block to 40 Gy and with a full midline block to 50 Gy. Right level III was boosted to a total of 60 Gy with glancing photon beams. The patient remains without disease 5 years later.

A 78-year-old man presented with an anterior oral tongue tumor and a palpable left level IB node, also detected on the staging CT scan (Fig. 6.5A). Biopsy of the primary tumor was positive for SCC. He underwent a partial glossectomy and left selective neck dissection. Histologic examination revealed a 2.5-cm carcinoma with negative margins. The neck dissection revealed only 1 positive lymph node, 2.5 cm in size consistent with the clinical findings. There was ECE. He was treated with postoperative IMRT. Concurrent chemotherapy was indicated but not given due to concern about tolerance secondary to overall performance status and age.

The tumor bed, consisting of the anterior tongue and left upper neck, with margin was identified as CTV_HD (60 Gy—orange). Dissected ipsilateral level IIb was contoured
as CTV_ID (57 Gy—blue). The undissected right neck and an additional 0.5 to 1 cm on the tongue were identified as CTV_ED (54 Gy—yellow). The region of the positive node at left level IB was delineated to give a simultaneous integrated boost to a total dose of 65 Gy (red). Representative axial slices of the contours and isodose distribution from the level of the midtongue to inferior level II of the neck are shown in Figure 6.5B-D. The isocenter was placed just above the thyroid notch. IMRT was delivered to fields above the isocenter. Level III and IV nodes were treated with an anterior beam with a larynx block to 40 Gy and with a full midline block to 50 Gy. Right level III was boosted to 60 Gy with glancing photon beams. Also shown are isodose distributions through the isocenter in sagittal (Fig. 6.5E) and coronal (Fig. 6.5F) view and through the midtongue and level IB in coronal view (Fig. 6.5G). The patient remains without disease 3 years later.

A 66-year-old man presented with a 2.5-cm anterior floor of mouth tumor with extension onto the ventral tongue without palpable lymph adenopathy (T2 N0). He underwent a partial glossectomy and bilateral supraomohyoid neck dissections. Histologic examination revealed a 1.8-cm SCC with negative margins. The neck dissection specimen contained 5 positive nodes, 2 in left level III, 2 in right level I, and 1 in right level II compartments. There was no ECE. He received postoperative radiation using IMRT to the primary tumor bed and upper neck and a matching anterior portal for lower neck as described Case Study 6.7.

Since the positive nodes were scattered through the neck, and were not well identified on preoperative imaging,
bilateral level I and II nodes, the floor of mouth and anterior tongue, and the musculature that inserts onto the hyoid bone were defined as CTV_ED (60 Gy).

Figure 6.6 shows target volumes on 2 axial images at the levels of the mandible (Fig. 6.6A) and upper neck (Fig. 6.6B) and sagittal image (Fig. 6.6C) along with isodose distributions on axial (Fig. 6.6D), sagittal (Fig. 6.6E), and coronal (Fig. 6.6F) views. The patient is without disease 2 years later.

A 67-year-old man who presented with oral pain was found to have a tumor of the anterior floor of mouth that spilled over the anterior gingiva. CT scan revealed a lesion in the floor of mouth eroding the mandible (Fig. 6.7A). He underwent surgical resection, including an anterior mandibulectomy, and bilateral supraomohyoid neck dissections followed by reconstruction with a fibula free flap. Histologic examination revealed SCC, poorly differentiated, invading the bone. There was carcinoma in situ at the tongue margin.

He received postoperative IMRT to the primary tumor bed and upper neck. The tumor bed, consisting of the floor of mouth, resected right mandibular bed and anterior tongue with margin was identified as CTV_HD (60 Gy). The dissected necks that did not harbor disease were contoured as CTV_ID (57 Gy).

Figures 6.7B-D show isodose distributions on axial images at the level of the reconstructed mandible and flap (Fig. 6.7B) and upper neck (Fig. 6.7C), and a sagittal view through midplane (Fig. 6.7D).

The IMRT beams were matched at an isocenter, placed above the thyroid notch, to an anterior portal for treating the lower nodal stations. The initial anterior beam had a larynx block and was treated to 40 Gy (Fig. 6.7E). A full midline block was added and the fields treated to 50 Gy (Fig. 6.7F). Bilateral level III, part of the operative bed, was boosted to 56 Gy with an anterior beam (Fig. 6.7G). The patient remains without disease 3 years later.

A 49-year-old man presented to his dentist with left-sided oral pain and was found to have a lesion of the left alveolar ridge. A biopsy was positive for SCC.

A diagnostic CT scan revealed an invasive primary tumor eroding the left mandible as shown in Figure 6.8A (green arrows). Treatment began with a wide local resection, including left mandibulectomy, and left neck dissection followed by reconstruction using an osteocutaneous free-fibular flap and skin graft. The fibula replaced the horizontal ramus whereas the soft tissue filled in the space of the resected left ascending ramus. Histologic examination revealed a 2.9-cm poorly differentiated SCC with bone invasion, but margins were negative. None of 28 nodes were positive for disease. Stage pT4 N0.

He was treated with adjuvant ipsilateral IMRT because the tumor was well lateralized and there was no nodal involvement. Figure 6.8B shows a coronal view through the right ascending ramus of the mandible with CTV_HD (red) and CTV_ID (blue) outlined. CTV_HD encompasses the preoperative tumor volume with generous margins, and CTV_ID covers the operative bed including generous coverage of the masticator space. The absence of the left ascending mandibular ramus can be appreciated on this coronal view. Figure 6.8C-F: show axial isodose distributions along with CTV_HD (red) and CTV_ID (blue) at the level of the inferior maxilla and masticator space, the superior aspect of the horizontal ramus of the mandible, the fibula graft and epicenter of the original tumor, and level II nodal region, respectively. Note that CTV_HD includes 1 cm of the residual mandible across midline and the upper neck to encompass soft tissues of the inferior-lateral portion of the floor of mouth musculature and tissues inferior to the angle of the mandible. The left level III and IV nodes were treated with a matching anterior beam to a dose of 50 Gy in 25 fractions. The patient had no evidence of disease 2 years after treatment.