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Definitive radiotherapy for head-and-neck cancer with radiographically positive retropharyngeal nodes: Incomplete radiographic response does not necessarily indicate failure

2006; Elsevier BV; Volume: 66; Issue: 4 Linguagem: Inglês

10.1016/j.ijrobp.2006.06.033

1879-355X

Stanley L. Liauw, Anthony Mancuso, Christopher G. Morris, Robert J. Amdur, William M. Mendenhall,

Head and Neck Surgical Oncology

Purpose: Our aim was to report the control rate of radiographically positive retropharyngeal (RP) nodes with radiation therapy (RT) and to correlate posttreatment imaging with clinical outcome.Methods and Materials: Sixteen patients treated with definitive RT for head-and-neck cancer had radiographically positive RP nodes (size >1 cm in largest axial dimension, or presence of focal enhancement, lucency, or calcification), and both pre-RT and post-RT image sets available for review. An additional 21 patients with unconfirmed radiographically positive RP nodes had post–RT imaging, which consisted of computed tomography (CT) at a median of 4 weeks after completing RT. Patients with positive post-RT RP nodes underwent observation with serial imaging.Results: Of 16 patients with pre-RT and post-RT images available for review, 9 (56%) had a radiographic complete response, and of 21 patients with unconfirmed positive RP nodes with post-RT images available for review, 14 (67%) had a radiographic complete response. In all, 14 patients with incomplete response on post–RT imaging experienced control of their disease with no further therapy, and no RP node or neck failures were noted during a median follow-up of 2.8 years. Six patients with positive post-RT RP nodes had serial imaging available for review, and none demonstrated radiographic progression of disease.Conclusions: Radiographic response at 4 weeks may not accurately reflect long-term locoregional control, as RP nodes may continue to resolve over time. The highest index of suspicion should be reserved for patients with progressive changes in size, focal lucency, or focal enhancement on serial imaging after RT. Purpose: Our aim was to report the control rate of radiographically positive retropharyngeal (RP) nodes with radiation therapy (RT) and to correlate posttreatment imaging with clinical outcome. Methods and Materials: Sixteen patients treated with definitive RT for head-and-neck cancer had radiographically positive RP nodes (size >1 cm in largest axial dimension, or presence of focal enhancement, lucency, or calcification), and both pre-RT and post-RT image sets available for review. An additional 21 patients with unconfirmed radiographically positive RP nodes had post–RT imaging, which consisted of computed tomography (CT) at a median of 4 weeks after completing RT. Patients with positive post-RT RP nodes underwent observation with serial imaging. Results: Of 16 patients with pre-RT and post-RT images available for review, 9 (56%) had a radiographic complete response, and of 21 patients with unconfirmed positive RP nodes with post-RT images available for review, 14 (67%) had a radiographic complete response. In all, 14 patients with incomplete response on post–RT imaging experienced control of their disease with no further therapy, and no RP node or neck failures were noted during a median follow-up of 2.8 years. Six patients with positive post-RT RP nodes had serial imaging available for review, and none demonstrated radiographic progression of disease. Conclusions: Radiographic response at 4 weeks may not accurately reflect long-term locoregional control, as RP nodes may continue to resolve over time. The highest index of suspicion should be reserved for patients with progressive changes in size, focal lucency, or focal enhancement on serial imaging after RT. IntroductionRetropharyngeal (RP) nodes, first described by Rouviére (1Rouviére H. Anatomy of the human lymphatic system. Edwards Brothers, Ann Arbor, MI1938: 44-56Google Scholar), lie in the retropharyngeal space medial to the internal carotid arteries at the level of vertebral bodies C1 to C3 (2Mancuso A.A. Harnsberger H.R. Muraki A.S. et al.Computed tomography of cervical and retropharyngeal lymph nodes: Normal anatomy, variants of normal, and applications in staging head-and-neck cancer Part I: normal anatomy.Radiology. 1983; 148: 709-714PubMed Google Scholar, 3Mancuso A.A. Harnsberger H.R. Muraki A.S. et al.Computed tomography of cervical and retropharyngeal lymph nodes: Normal anatomy, variants of normal, and applications in staging head-and-neck cancer Part II: pathology.Radiology. 1983; 148: 715-723PubMed Google Scholar, 4Gregoire V. Coche E. Cosnard G. et al.Selection and delineation of lymph node target volumes in head and neck conformal radiotherapy Proposal for standardizing terminology and procedure based on the surgical experience.Radiother Oncol. 2000; 56: 135-150Abstract Full Text Full Text PDF PubMed Scopus (299) Google Scholar, 5Chong V.F. Fan Y.F. Radiology of the retropharyngeal space.Clin Radiol. 2000; 55: 740-748Abstract Full Text PDF PubMed Scopus (47) Google Scholar). Given the potential to harbor disease in the case of head-and-neck cancer (6Ballantyne A.J. Significance of retropharyngeal nodes in cancer of the head and neck.Am J Surg. 1964; 108: 500-504Abstract Full Text PDF PubMed Scopus (109) Google Scholar, 7Ferlito A. Shaha A.R. Rinaldo A. Retropharyngeal lymph node metastasis from cancer of the head and neck.Acta Otolaryngol. 2002; 122: 556-560Crossref PubMed Scopus (29) Google Scholar), RP nodes are important to evaluate with imaging before definitive treatment, especially because they are inaccessible to physical examination. There are limited published data on the influence of metastatic RP nodes on clinical outcome and reports from the modern era are conflicting. The largest reported series suggests that patients treated with radiation therapy (RT) who have metastatic RP nodes have a higher rate of neck relapse and distant metastasis and a lower overall survival (8McLaughlin M.P. Mendenhall W.M. Mancuso A.A. et al.Retropharyngeal adenopathy as a predictor of outcome in squamous cell carcinoma of the head and neck.Head Neck. 1995; 17: 190-198Crossref PubMed Scopus (128) Google Scholar), but this association is not supported by smaller surgical series in which RP nodes at risk are primarily dissected (9Amatsu M. Mohri M. Kinishi M. Significance of retropharyngeal node dissection at radical surgery for carcinoma of the hypopharynx and cervical esophagus.Laryngoscope. 2001; 111: 1099-1103Crossref PubMed Scopus (70) Google Scholar, 10Gross N.D. Ellingson T.W. Wax M.K. et al.Impact of retropharyngeal lymph node metastasis in head and neck squamous cell carcinoma.Arch Otolaryngol Head Neck Surg. 2004; 130: 169-173Crossref PubMed Scopus (52) Google Scholar). Complicating this discrepancy is the uncertain ability of imaging to accurately identify pathologic involvement (11Morrissey D.D. Talbot J.M. Cohen J.I. et al.Accuracy of computed tomography in determining the presence or absence of metastatic retropharyngeal adenopathy.Arch Otolaryngol Head Neck Surg. 2000; 126: 1478-1481Crossref PubMed Scopus (31) Google Scholar), as radiographically positive RP nodes are not always pathologically involved. Regardless of these issues, it is accepted that RP nodes at risk for involvement should be properly evaluated and treated in patients receiving definitive RT (12Eisbruch A. Marsh L.H. Dawson L.A. et al.Recurrences near base of skull after IMRT for head-and-neck cancer: Implications for target delineation in high neck and for parotid gland sparing.Int J Radiat Oncol Biol Phys. 2004; 59: 28-42Abstract Full Text Full Text PDF PubMed Scopus (269) Google Scholar). There are no published data that address the response of involved RP nodes to RT, or the significance of radiographically abnormal RP nodes post-RT. The goal of this study is to characterize the radiographic response of RP nodes in patients treated with definitive RT for head-and-cancer, and correlate posttreatment imaging with clinical outcome.Methods and materialsThis was an institutional review board–approved, retrospective review of 550 consecutive patients with lymph node–positive head-and-neck cancer treated at the University of Florida with definitive RT with curative intent between 1990 and 2002. Patient characteristics and treatment techniques for this set of patients are discussed in detail elsewhere (13Liauw S.L. Mancuso A.A. Amdur R.J. Postradiotherapy neck dissection for lymph node-positive head-and-neck cancer: The use of computed tomography to manage the neck.J Clin Oncol. 2006; 24: 1421-1427Crossref PubMed Scopus (131) Google Scholar). RT was generally prescribed using lateral, opposed head-and-neck fields to a dose of 74.4 Gy at 1.2 Gy/fraction twice daily. Radiographically positive RP nodes were covered by extending the superior border of the treatment fields to include the retropharyngeal space anterior to C1 to C3, using the superior landmark of the auditory meatus on conventional planning. Of 550 patients, 88 had radiographically positive RP nodes at initial presentation as dictated in tumor board notes or radiographic reports in each patient’s chart. Retropharyngeal nodes were assessed at 3-mm intervals using a scanning plane perpendicular to vertebral bodies C1 to C4, according to an institutional protocol for all head-and-neck cancer patients staged with contrast-enhanced computed tomography (CT). Pre-RT images were available for recall from radiology archives for 27 patients. Soft-copy images were then reviewed jointly by a radiation oncologist and a neuroradiologist on a computer workstation with outcomes blinded during review. RP nodes were characterized on the basis of size (largest axial dimension) or focal abnormality (lucency, enhancement, or calcification) and graded on a five-point scale: 0 = definitely normal; 1 = probably normal; 2 = indeterminate; 3 = probably abnormal; and 4 = definitely abnormal. Radiographically positive RP nodes were defined as any retropharyngeal lymph node >1 cm or with any Grade 3 or 4 focal abnormality. Examples are included in Fig. 1, Fig. 2, Fig. 3. Of 27 patients, 11 were subsequently excluded from this study because of an inability to identify a radiographically positive RP node with these criteria (n = 4), involvement of a high-level II lymph node lateral to the internal carotid arteries rather than an RP node (n = 3), difficulty in distinguishing an RP node from the primary disease (n = 2), lack of i.v. contrast (n = 1), or no post–RT imaging available for review (n = 1). A total of 16 patients had 17 confirmed radiographically positive RP nodes and subsequent post–RT imaging (median 28 days, range, 15 to 42 days after completing RT). Patient and treatment characteristics for this group are described in Table 1.Fig. 2Patient with a T2N2B tonsil cancer who had a pretreatment scan showing a 1.7-cm left retropharyngeal node with a definite focal lucency. Imaging 29 days after radiation therapy shows a 0.9-cm retropharyngeal node with residual definite focal lucency.View Large Image Figure ViewerDownload (PPT)Fig. 3Patient with a T3N2B tonsil cancer had a pretreatment scan showing a 1.5-cm left retropharyngeal node with a definite focal lucency and calcification. Imaging 24 days after radiation therapy (RT) shows a 0.9-cm retropharyngeal node with residual calcification; imaging 8 months after RT continues to show residual calcification.View Large Image Figure ViewerDownload (PPT)Table 1Characteristics of 16 patients with confirmed radiographically involved retropharyngeal (RP) nodes and post–radiation therapy (RT) imagingCharacteristicNumber (%)Primary site Oropharynx14 (88%) Tonsil9 Base of tongue4 Soft palate1 Hypopharynx1 (6%) Posterior pharyngeal wall1 Multiple synchronous primaries1 (6%)T stage T24 (25%) T34 (25%) T48 (50%)N stage N11 (6%) N2A0 (0%) N2B6 (38%) N2C4 (25%) N35 (31%)Fractionation Conventional (once-daily)5 (31%) Hyperfractionation11 (69%)Chemotherapy10 (63%) Neoadjuvant2 Concurrent7 Neoadjuvant and concurrent1Pretreatment RP node abnormality⁎Numbers do not add up to 16 because each positive node can have multiple abnormalities. Size >1 cm11 (69%) Focal lucency6 (38%) Focal enhancement2 (13%) Focal calcification2 (13%) Numbers do not add up to 16 because each positive node can have multiple abnormalities. Open table in a new tab Computed tomography (CT) was used to assess RP nodes at presentation and after RT in all cases. One patient also had magnetic resonance imaging at presentation to better define the disease extending into the nasopharynx, and this was the only set of images available for review on this patient. Images were on hand for an additional 21 patients who did not have available pre-RT images, leaving a total of 37 patients with CT data after treatment of a presumed radiographically positive RP node. As a general rule, patients with radiographically positive RP nodes after treatment were observed with serial imaging with the understanding that more aggressive therapy (salvage dissection or stereotactic radiosurgery) would be considered for progressive disease in the RP node if the patient had the disease controlled elsewhere. The timing of serial imaging was not strictly defined at the outset of the study period, but tended to be at every 3 to 4 months until radiographic resolution, declining index of suspicion for disease, or progression of disease elsewhere.ResultsRadiographic responseCharacteristics of radiographically positive RP nodes, along with post-RT response, are described in Table 2. Of 16 patients with radiographically positive RP nodes as well as pre-RT and post-RT images available for review, 9 (56%) had a complete radiographic response on post-RT CT. Incomplete response was usually a result of a focal abnormality (n = 6) rather than large size alone, as only 2 patients had post-RT size >1 cm. Most focal abnormalities detected on post-RT CT were identical on pretreatment imaging (n = 5), although 2 patients developed a new focal abnormality (calcification) after RT.Table 2Response of radiographically involved retropharyngeal (RP) nodes to radiation therapy in 16 patientsStage and primary siteImaging characteristicsResponsePre-RT studyPost-RT studyT2N3 tonsil1.0 cm G4 lucNegative – not measurableCompleteT4N2B tonsil1.0 cm G3 lucNegative – not measurableCompleteT2N3 base of tongue0.5 cm G4 enhNegative – 0.5 cmCompleteT4N3 tonsil1.1 cmNegative – 0.5 cmCompleteT3N2C tonsil1.2 cmNegative – 0.6 cmCompleteT4N3 base of tongue1.1 cmNegative – 0.6 cmCompleteT4N2B pharyngeal wall1.4 cmNegative – 0.7 cmCompleteT3N2B base of tongue1.8 cm G4 lucNegative – 0.8 cmCompleteT4N2C tonsil1.7 cm (R)Negative – 0.9 cm (R)Complete1.3 cm (L)Negative – 0.9 cm (L)T4N2B soft palate2.6 cm with carotid encasement⁎Only case in which imaging was done by magnetic resonance imaging and not computed tomography.1.2 cmIncomplete by sizeT4N2C base of tongue0.9 cm G3 enh0.6 cm G3 enhIncomplete by enhT2N2B tonsil1.7 cm G4 luc0.9 cm G4 lucIncomplete by lucT2N3 multiple synchronous1.7 cm G4 luc1.6 cm G4 lucIncomplete by size and lucT3N2B tonsil1.5 cm G4 calc and luc0.9 cm G4 calcIncomplete by calcT3N1 tonsil1.1 cm0.8 cm G4 calcIncomplete by new calcT4N2C tonsil0.8 cm G4 calc (R)0.8 cm G4 calc (R);0.9 cm G4 calc (L)Incomplete by calc (and new calc)Abbreviations: calc = focal calcification; enh = focal enhancement; G3 = Grade 3, G4 = Grade 4; L = left (in cases of bilaterally positive retropharyngeal nodes); luc = focal lucency; R = right (in cases of bilaterally positive retropharyngeal nodes); RT = radiation therapy. Only case in which imaging was done by magnetic resonance imaging and not computed tomography. Open table in a new tab Review of an additional 21 sets of post-RT CT scans with radiographically positive RP nodes by report demonstrated complete radiographic response in 14 patients (67%). Of 7 patients with incomplete response, 2 had nodes >1 cm post-RT but none were radiographically positive by size criteria alone. All patients had a focal lucency with (n = 1) or without (n = 6) calcification.Serial imaging of radiographically abnormal post-RT RP nodesSix patients with radiographically positive post-RT RP nodes had at least one subsequent CT scan available for review. No patient demonstrated progressive disease in the RP nodes. Two patients with focal calcification had persistent calcification on serial imaging up to 4 months and 8 months. Three patients with focal lucency had resolution of lucency by 2 months, 3 months, and 1 year with further follow-up. One patient with a post-RT RP node of 1.2 cm had regression to normal size on the only available follow-up study 2 years later.Clinical outcomeAll 14 patients with incomplete response in the RP nodes after RT were observed rather than subjected to a salvage procedure for presumed disease. None of these patients with post-RT radiographic abnormalities had disease recurrence in the retropharyngeal nodes or neck, with a median follow-up of 2.8 years in all patients (range, 0.4–7.9 years) and 5 years in living patients. Two patients experienced failure with disease recurrence elsewhere; of these, 1 had distant disease 1 month after RT and local disease 4 months later, and the other with distant disease alone 11 months after RT.DiscussionInvolvement of retropharyngeal nodes with head-and-neck cancer is highest for cancers arising in the nasopharynx, pharyngeal wall, soft palate, tonsil, hypopharynx, and cervical esophagus (7Ferlito A. Shaha A.R. Rinaldo A. Retropharyngeal lymph node metastasis from cancer of the head and neck.Acta Otolaryngol. 2002; 122: 556-560Crossref PubMed Scopus (29) Google Scholar). Despite the possibility that imaging can lead to overdiagnosis of pathologic involvement (11Morrissey D.D. Talbot J.M. Cohen J.I. et al.Accuracy of computed tomography in determining the presence or absence of metastatic retropharyngeal adenopathy.Arch Otolaryngol Head Neck Surg. 2000; 126: 1478-1481Crossref PubMed Scopus (31) Google Scholar), surgical series (9Amatsu M. Mohri M. Kinishi M. Significance of retropharyngeal node dissection at radical surgery for carcinoma of the hypopharynx and cervical esophagus.Laryngoscope. 2001; 111: 1099-1103Crossref PubMed Scopus (70) Google Scholar, 10Gross N.D. Ellingson T.W. Wax M.K. et al.Impact of retropharyngeal lymph node metastasis in head and neck squamous cell carcinoma.Arch Otolaryngol Head Neck Surg. 2004; 130: 169-173Crossref PubMed Scopus (52) Google Scholar, 11Morrissey D.D. Talbot J.M. Cohen J.I. et al.Accuracy of computed tomography in determining the presence or absence of metastatic retropharyngeal adenopathy.Arch Otolaryngol Head Neck Surg. 2000; 126: 1478-1481Crossref PubMed Scopus (31) Google Scholar, 14Hasegawa Y. Matsuura H. Retropharyngeal node dissection in cancer of the oropharynx and hypopharynx.Head Neck. 1994; 16: 173-180Crossref PubMed Scopus (93) Google Scholar) still report rates of involvement greater than 20% upon dissecting retropharyngeal nodes for patients with certain cancers of the head and neck. RT may be a preferred modality to treat retropharyngeal nodes at risk at initial presentation given the difficulty of retropharyngeal node dissection as the nodes may be adherent to pharyngeal musculature and difficult to access near the base of skull. Furthermore, treatment with primary RT with or without chemotherapy can potentially spare the patient from surgery and the associated morbidity of primary resection or neck dissection (15Department of Veterans Affairs Laryngeal Cancer Study GroupInduction chemotherapy plus radiation compared with surgery plus radiation in patients with advanced laryngeal cancer.N Engl J Med. 1991; 324: 1685-1690Crossref PubMed Scopus (2240) Google Scholar, 16Forastiere A.A. Goepfert H. Maor M. et al.Concurrent chemotherapy and radiotherapy for organ preservation in advanced laryngeal cancer.N Engl J Med. 2003; 349: 2091-2098Crossref PubMed Scopus (2387) Google Scholar).This study shows that the control rate of radiographically positive RP nodes is high with primary RT as long as treatment volumes provide adequate coverage of the area at risk. A total of 37 patients who had imaging of the retropharyngeal nodes before and/or after RT were controlled in the RP nodes and neck. The high rate of locoregional control did not correlate with the relatively low complete radiographic response rate 4 weeks after RT (56% in patients with confirmed disease on pretreatment scan, 67% in patients with unconfirmed initial radiographically positive RT nodes). The results suggest that radiographic abnormalities including large size or focal lucency in the RP nodes may require more time after RT to completely resolve (although calcifications may persist for >1 year after treatment). Given this finding, it may be best to defer salvage treatment for incompletely responding RP nodes until serial imaging shows progression, unless clinical suspicion for disease is high. Risks of delaying salvage treatment include limiting the chance of curing the disease and making surgical dissection more difficult as radiation fibrosis progresses after RT. For patients with neck disease who are treated with primary RT, we evaluate the neck for post-RT neck dissection 4 weeks after RT to avoid these risks.It may be surprising that none of the 14 patients with an incomplete radiographic response experienced locoregional failure, but radiographic abnormalities are likely to overcall the true rate of pathologic involvement. Morrissey et al. correlated radiographically positive RP nodes (size >8 mm or with focal lucency or enhancement) with pathologic findings on RP node dissection in 26 patients and found a positive predictive value of 33% (11Morrissey D.D. Talbot J.M. Cohen J.I. et al.Accuracy of computed tomography in determining the presence or absence of metastatic retropharyngeal adenopathy.Arch Otolaryngol Head Neck Surg. 2000; 126: 1478-1481Crossref PubMed Scopus (31) Google Scholar). This number is similar to the positive predictive values of 31% to 43% that we found on correlating radiographically abnormal cervical neck nodes (size >1.5 cm or with focal lucency, enhancement, or calcification) with pathologic findings on neck dissection in 193 hemi-necks (13Liauw S.L. Mancuso A.A. Amdur R.J. Postradiotherapy neck dissection for lymph node-positive head-and-neck cancer: The use of computed tomography to manage the neck.J Clin Oncol. 2006; 24: 1421-1427Crossref PubMed Scopus (131) Google Scholar). Clinical control rates are high in part because involved RP nodes are usually 1 cm or with focal abnormality) (8McLaughlin M.P. Mendenhall W.M. Mancuso A.A. et al.Retropharyngeal adenopathy as a predictor of outcome in squamous cell carcinoma of the head and neck.Head Neck. 1995; 17: 190-198Crossref PubMed Scopus (128) Google Scholar). Multivariate analysis indicated decreased neck control, distant control, and overall survival for all primary head-and-neck sites analyzed, except the nasopharynx, in patients with positive RP nodes. Although it is possible that the use of concurrent chemotherapy may increase the efficacy of RT and thereby slightly diminish the prognostic value of radiographically positive RP nodes, coverage of RP nodes should continue to be common practice when at risk of involvement.ConclusionRadiographically positive RP nodes are highly controlled in patients treated with definitive RT for head-and-neck cancer. Radiographic response at 4 weeks may not accurately reflect long-term locoregional control, and RP nodes may continue to regress over time. The most appropriate criteria to diagnose positive RP nodes with CT after RT may be a progressive change in size, focal lucency, or focal enhancement on serial imaging. IntroductionRetropharyngeal (RP) nodes, first described by Rouviére (1Rouviére H. Anatomy of the human lymphatic system. Edwards Brothers, Ann Arbor, MI1938: 44-56Google Scholar), lie in the retropharyngeal space medial to the internal carotid arteries at the level of vertebral bodies C1 to C3 (2Mancuso A.A. Harnsberger H.R. Muraki A.S. et al.Computed tomography of cervical and retropharyngeal lymph nodes: Normal anatomy, variants of normal, and applications in staging head-and-neck cancer Part I: normal anatomy.Radiology. 1983; 148: 709-714PubMed Google Scholar, 3Mancuso A.A. Harnsberger H.R. Muraki A.S. et al.Computed tomography of cervical and retropharyngeal lymph nodes: Normal anatomy, variants of normal, and applications in staging head-and-neck cancer Part II: pathology.Radiology. 1983; 148: 715-723PubMed Google Scholar, 4Gregoire V. Coche E. Cosnard G. et al.Selection and delineation of lymph node target volumes in head and neck conformal radiotherapy Proposal for standardizing terminology and procedure based on the surgical experience.Radiother Oncol. 2000; 56: 135-150Abstract Full Text Full Text PDF PubMed Scopus (299) Google Scholar, 5Chong V.F. Fan Y.F. Radiology of the retropharyngeal space.Clin Radiol. 2000; 55: 740-748Abstract Full Text PDF PubMed Scopus (47) Google Scholar). Given the potential to harbor disease in the case of head-and-neck cancer (6Ballantyne A.J. Significance of retropharyngeal nodes in cancer of the head and neck.Am J Surg. 1964; 108: 500-504Abstract Full Text PDF PubMed Scopus (109) Google Scholar, 7Ferlito A. Shaha A.R. Rinaldo A. Retropharyngeal lymph node metastasis from cancer of the head and neck.Acta Otolaryngol. 2002; 122: 556-560Crossref PubMed Scopus (29) Google Scholar), RP nodes are important to evaluate with imaging before definitive treatment, especially because they are inaccessible to physical examination. There are limited published data on the influence of metastatic RP nodes on clinical outcome and reports from the modern era are conflicting. The largest reported series suggests that patients treated with radiation therapy (RT) who have metastatic RP nodes have a higher rate of neck relapse and distant metastasis and a lower overall survival (8McLaughlin M.P. Mendenhall W.M. Mancuso A.A. et al.Retropharyngeal adenopathy as a predictor of outcome in squamous cell carcinoma of the head and neck.Head Neck. 1995; 17: 190-198Crossref PubMed Scopus (128) Google Scholar), but this association is not supported by smaller surgical series in which RP nodes at risk are primarily dissected (9Amatsu M. Mohri M. Kinishi M. Significance of retropharyngeal node dissection at radical surgery for carcinoma of the hypopharynx and cervical esophagus.Laryngoscope. 2001; 111: 1099-1103Crossref PubMed Scopus (70) Google Scholar, 10Gross N.D. Ellingson T.W. Wax M.K. et al.Impact of retropharyngeal lymph node metastasis in head and neck squamous cell carcinoma.Arch Otolaryngol Head Neck Surg. 2004; 130: 169-173Crossref PubMed Scopus (52) Google Scholar). Complicating this discrepancy is the uncertain ability of imaging to accurately identify pathologic involvement (11Morrissey D.D. Talbot J.M. Cohen J.I. et al.Accuracy of computed tomography in determining the presence or absence of metastatic retropharyngeal adenopathy.Arch Otolaryngol Head Neck Surg. 2000; 126: 1478-1481Crossref PubMed Scopus (31) Google Scholar), as radiographically positive RP nodes are not always pathologically involved. Regardless of these issues, it is accepted that RP nodes at risk for involvement should be properly evaluated and treated in patients receiving definitive RT (12Eisbruch A. Marsh L.H. Dawson L.A. et al.Recurrences near base of skull after IMRT for head-and-neck cancer: Implications for target delineation in high neck and for parotid gland sparing.Int J Radiat Oncol Biol Phys. 2004; 59: 28-42Abstract Full Text Full Text PDF PubMed Scopus (269) Google Scholar). There are no published data that address the response of involved RP nodes to RT, or the significance of radiographically abnormal RP nodes post-RT. The goal of this study is to characterize the radiographic response of RP nodes in patients treated with definitive RT for head-and-cancer, and correlate posttreatment imaging with clinical outcome.