{"id":13906,"date":"2026-03-11T23:20:15","date_gmt":"2026-03-12T02:20:15","guid":{"rendered":"https:\/\/rtmedical.com.br\/tmp-en-1773282013520\/"},"modified":"2026-04-04T18:06:37","modified_gmt":"2026-04-04T21:06:37","slug":"unknown-primary-head-neck-rt","status":"publish","type":"post","link":"https:\/\/rtmedical.com.br\/en\/unknown-primary-head-neck-rt\/","title":{"rendered":"Unknown Primary Head &#038; Neck: RT Planning Guide"},"content":{"rendered":"<div class=\"toc\">\n<h2>In This Article<\/h2>\n<ul>\n<li><a href=\"#workup\">1. Diagnostic Workup and Primary Site Search<\/a><\/li>\n<li><a href=\"#hpv-ebv\">2. HPV, EBV Testing and Directed Biopsy<\/a><\/li>\n<li><a href=\"#treatment-decision\">3. Treatment Decision: Single vs. Combined Modality<\/a><\/li>\n<li><a href=\"#target-volumes\">4. Target Volumes and Pharyngeal Mucosal Coverage<\/a><\/li>\n<li><a href=\"#postop-case\">5. Postoperative Case: Practical Contouring<\/a><\/li>\n<li><a href=\"#definitive-case\">6. Definitive Case: Bilateral HPV-Negative Disease<\/a><\/li>\n<\/ul>\n<\/div>\n<h2 id=\"workup\">Diagnostic Workup and Primary Site Search<\/h2>\n<p>Labeling a cervical node metastasis as an unknown primary demands an exhaustive workup first. In practice, many cases initially classified as CUP reveal their origin when the investigation is aggressive enough.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/unknown-primary-head-neck-sagittal-landmarks-fig10-2.jpeg\" alt=\"Midline sagittal CT image showing anatomical landmarks demarcating nasopharynx, oropharynx, and larynx\/hypopharynx for unknown primary RT planning\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 461px; --smush-placeholder-aspect-ratio: 461\/580;\"><figcaption>Source: Target Volume Delineation and Field Setup, 2nd Edition \u2014 Fig. 10.2<\/figcaption><\/figure>\n<p>The minimum evaluation includes a thorough physical examination with cranial nerve testing, fiberoptic visualization of the nasopharynx, oropharynx, larynx, and hypopharynx, plus high-resolution contrast-enhanced CT. A detailed skin and scalp examination is essential \u2014 cutaneous malignancies are real differential diagnoses.<\/p>\n<p>Patient history deserves careful attention. Risk factors for thoracic, gynecologic, or gastrointestinal cancers should be evaluated, as cervical adenopathy may represent infraclavicular disease. PET\/CT adds sensitivity for detecting occult primaries but must be performed <strong>before biopsy<\/strong> to reduce false-positive inflammatory uptake. Panendoscopy remains a useful complement.<\/p>\n<p>For a comprehensive overview of all head and neck sites, see our <a href=\"https:\/\/rtmedical.com.br\/en\/target-volume-delineation-field-setup-2\/\">complete guide on target volume delineation in radiation therapy<\/a>.<\/p>\n<h2 id=\"hpv-ebv\">HPV, EBV Testing and Directed Biopsy<\/h2>\n<p>HPV and EBV testing directly guides pharyngeal coverage strategy and has changed how these tumors are classified. In the AJCC 8th edition, HPV-positive nodes are staged as T0 oropharynx, while EBV-positive nodes are classified as T0 nasopharynx. This distinction carries immediate planning implications.<\/p>\n<p>Directed biopsies of all suspicious lesions along the pharyngeal axis are mandatory. Blind biopsies of normal-appearing mucosa have been traditionally recommended but only occasionally identify the primary. A more effective approach: transoral tongue base mucosectomy (lingual tonsillectomy) combined with at least ipsilateral palatine tonsillectomy detects roughly <strong>80% of unknown primary cases<\/strong>, particularly HPV-related ones. Some centers perform bilateral palatine tonsillectomies and may omit lingual tonsillectomy.<\/p>\n<p>This matters because HPV-positive patients may need only oropharyngeal irradiation. EBV-positive patients \u2014 especially those of Asian ethnicity \u2014 may require treatment to the nasopharynx alone. The pattern of lymph node spread further refines the decision about pharyngeal coverage extent.<\/p>\n<h2 id=\"treatment-decision\">Treatment Decision: Single vs. Combined Modality<\/h2>\n<p>Patients with a single ipsilateral lymph node measuring 3 cm or smaller without extranodal extension may be candidates for single-modality therapy \u2014 surgery or radiation alone. This is a relatively favorable scenario that allows sparing patients the morbidity of combined treatment.<\/p>\n<p>When extended-field IMRT is planned, CT simulation with IV contrast is essential for delineating involved lymph nodes. The thermoplastic mask should immobilize the head, neck, <strong>and shoulders<\/strong> \u2014 not just the head and neck \u2014 to ensure positional reproducibility across fields extending inferiorly.<\/p>\n<p>In the postoperative setting, concurrent chemotherapy should be considered when <strong>extracapsular extension (ECE)<\/strong> is present. In the definitive setting, advanced nodal disease is an indication for concurrent chemotherapy. The dissected neck should receive 60\u201366 Gy in 2 Gy fractions. Related articles on other head and neck subsites provide complementary detail on site-specific anatomy and contouring.<\/p>\n<h2 id=\"target-volumes\">Target Volumes and Pharyngeal Mucosal Coverage<\/h2>\n<p>Bilateral neck treatment with coverage of pharyngeal mucosal areas at risk is the standard recommendation. Some institutions have treated the ipsilateral neck alone; however, neck relapse and distant metastasis rates appear higher than with comprehensive radiotherapy.<\/p>\n<p>Traditionally, the entire pharynx was included. IMRT allows more specific targeting of pharyngeal portions most likely to harbor the primary, sparing normal structures and minimizing side effects. The pharyngeal extent to irradiate must be determined case by case. When in doubt, the entire pharynx should be treated. For cases with full TORS evaluation, emerging data suggests the pharyngeal axis may be safely spared, though this needs prospective validation.<\/p>\n<h3>Suggested Target Volume Definitions<\/h3>\n<p>The table below summarizes recommended volume definitions for unknown primary head and neck cancer.<\/p>\n<table>\n<thead>\n<tr>\n<th>Volume<\/th>\n<th>Definition and Description<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>GTV<sub>70<\/sub><\/strong><\/td>\n<td>All lymph nodes \u2265 1 cm in short axis, significantly FDG avid, or biopsy-positive. Contour any equivocal nodes as GTV. GTV = CTV<sub>70<\/sub><\/td>\n<\/tr>\n<tr>\n<td><strong>PTV<sub>70<\/sub><\/strong><\/td>\n<td>GTV<sub>70<\/sub> + 3\u20135 mm depending on institutional daily positioning accuracy<\/td>\n<\/tr>\n<tr>\n<td><strong>CTV nasopharynx<\/strong><\/td>\n<td>From skull base (superiorly) to soft palate (inferiorly). Anteriorly from the posterior choana to the posterior pharyngeal wall. Laterally: adequate coverage of the fossa of Rosenm\u00fcller<\/td>\n<\/tr>\n<tr>\n<td><strong>CTV oropharynx<\/strong><\/td>\n<td>From soft palate surface (superiorly) to floor of vallecula or hyoid bone (inferiorly). Tongue base covered anteriorly \u2014 oral tongue margin not necessary. Tonsils adequately covered laterally. Entire posterior pharyngeal wall included<\/td>\n<\/tr>\n<tr>\n<td><strong>CTV larynx &#038; hypopharynx<\/strong><\/td>\n<td>From hyoid bone (superiorly) to bottom of cricoid cartilage (inferiorly)<\/td>\n<\/tr>\n<tr>\n<td><strong>PTV mucosa<\/strong><\/td>\n<td>3\u20135 mm expansion on mucosal surface CTVs depending on institutional positioning accuracy<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Note: Suggested dose to gross disease: 70 Gy in 33\u201335 fractions. Dose to mucosal surfaces at risk: 54\u201360 Gy. Postoperative dissected neck: 60\u201366 Gy in 2 Gy fractions. Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 10.1)<\/em><\/p>\n<p>For the node-positive neck, cervical levels Ib\u2013V and retropharyngeal lymph nodes should be included. The contralateral neck receives prophylactic dose to levels II\u2013IV and retropharyngeal nodes. Some authors advocate sparing the larynx when no low lymph nodes are involved.<\/p>\n<h2 id=\"postop-case\">Postoperative Case: Practical Contouring<\/h2>\n<p>The first case illustrates a 62-year-old male with TxN2a unknown primary who underwent bilateral tonsillectomy and right neck dissection revealing a single 4.6 cm level II lymph node.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/unknown-primary-head-neck-postop-axial-fig10-1a.jpeg\" alt=\"Axial CT planning slices showing CTV66 in red, CTV54-60 in green, and CTV54 in blue for postoperative unknown primary head and neck contouring\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 691px; --smush-placeholder-aspect-ratio: 691\/941;\"><figcaption>Source: Target Volume Delineation and Field Setup, 2nd Edition \u2014 Fig. 10.1a<\/figcaption><\/figure>\n<p>Notice the difference between the contouring on the operated (ipsilateral) neck versus the contralateral side. The CTV<sub>66Gy<\/sub> (red) covers the high-risk surgical bed; the CTV<sub>54-60Gy<\/sub> (green) covers pharyngeal mucosa at risk for harboring the primary; and the CTV<sub>54Gy<\/sub> (blue) provides prophylactic coverage of the contralateral neck. This asymmetry reflects the principle of dose escalation according to actual risk.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/unknown-primary-head-neck-postop-axial-fig10-1b.jpeg\" alt=\"Continuation of postoperative axial planning slices for cervical unknown primary showing lymph node levels and pharyngeal coverage\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 691px; --smush-placeholder-aspect-ratio: 691\/503;\"><figcaption>Source: Target Volume Delineation and Field Setup, 2nd Edition \u2014 Fig. 10.1b<\/figcaption><\/figure>\n<p>Sagittal views (Fig. 10.2) are particularly helpful for confirming correct craniocaudal extent of mucosal volumes \u2014 nasopharynx, oropharynx, and larynx\/hypopharynx \u2014 and ensuring no gaps between adjacent CTVs. The radiographic isocenter serves as the geometric reference for planning.<\/p>\n<h2 id=\"definitive-case\">Definitive Case: Bilateral HPV-Negative Disease<\/h2>\n<p>The second case demonstrates a more aggressive scenario: a 50-year-old male with TxN2c, open biopsy of a left-sided node showing extranodal extension, HPV ISH and p16 negative. He received definitive chemoradiotherapy.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/unknown-primary-head-neck-definitive-axial-fig10-3a.jpeg\" alt=\"Axial CT slices for definitive TxN2c HPV-negative case showing CTV70 in red, CTV60 in green, and CTV54 in blue with bilateral neck and pharyngeal coverage\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 691px; --smush-placeholder-aspect-ratio: 691\/980;\"><figcaption>Source: Target Volume Delineation and Field Setup, 2nd Edition \u2014 Fig. 10.3a<\/figcaption><\/figure>\n<p>Here the CTV<sub>70Gy<\/sub> (red) encompasses bilateral gross disease; the CTV<sub>60Gy<\/sub> (green) covers pharyngeal mucosa at risk; and the CTV<sub>54Gy<\/sub> (blue) includes the entire bilateral neck prophylactically. HPV negativity justifies comprehensive pharyngeal coverage \u2014 without viral guidance toward a specific subsite, risk is distributed along the entire mucosal axis.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/unknown-primary-head-neck-definitive-axial-fig10-3b.jpeg\" alt=\"Continuation of definitive planning axial slices for bilateral HPV-negative unknown primary with extranodal extension\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 691px; --smush-placeholder-aspect-ratio: 691\/897;\"><figcaption>Source: Target Volume Delineation and Field Setup, 2nd Edition \u2014 Fig. 10.3b<\/figcaption><\/figure>\n<p>ECE in this case reinforces the indication for concurrent chemotherapy. The dose of 70 Gy to gross disease and 54\u201360 Gy to at-risk mucosa follows the standard dose-escalation paradigm.<\/p>\n<p>Managing unknown primary head and neck cancer requires aggressive investigation before diagnosis, personalized treatment decisions based on HPV\/EBV status and nodal disease extent, and careful RT planning that balances adequate coverage with normal tissue preservation. For the full picture of all head and neck sites covered in this series, visit the <a href=\"https:\/\/rtmedical.com.br\/en\/target-volume-delineation-field-setup-2\/\">complete guide on target volume delineation<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Workup, target volumes, and RT planning for squamous cell carcinoma of unknown primary in the head and neck. Clinical cases and dose table included.<\/p>\n","protected":false},"author":1,"featured_media":16475,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"ngg_post_thumbnail":0,"fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[266,265,99],"tags":[],"class_list":{"0":"post-13906","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-delineamento-cabeca-pescoco","8":"category-delineamento-volumes","9":"category-radiotherapy"},"aioseo_notices":[],"rt_seo":{"title":"Unknown Primary Head & Neck: RT Delineation","description":"Target volume delineation for unknown primary head and neck cancer. CTV for mucosal sites, bilateral nodal coverage and dose levels.","canonical":"","og_image":"","robots":"default","schema_type":"MedicalWebPage","include_in_llms":false,"llms_label":"","llms_summary":"","faq_items":[{"q":"How is the CTV defined for unknown primary head and neck?","a":"The CTV includes potential mucosal primary sites (nasopharynx, oropharynx, hypopharynx) and bilateral cervical nodal levels. PET\/CT and examination under anesthesia with directed biopsies help narrow the likely primary site and may allow omission of certain mucosal volumes."},{"q":"Can the mucosal CTV be reduced in HPV-positive unknown primary?","a":"In HPV-positive unknown primary with isolated level II-III nodal disease, some protocols allow limiting the mucosal CTV to the ipsilateral oropharynx (tonsil and base of tongue). This reduces toxicity while maintaining excellent control rates in carefully selected patients."},{"q":"What dose levels are used for unknown primary?","a":"A three-tier dose approach is common: high dose to involved nodes (70 Gy), intermediate dose to high-risk mucosal sites and adjacent nodal levels (59.4-63 Gy), and low dose to elective nodal regions (54 Gy). Simultaneous integrated boost with IMRT is the preferred technique."}],"video":[],"gtin":"","mpn":"","brand":"","aggregate_rating":[]},"_links":{"self":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/13906\/"}],"collection":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/"}],"about":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/types\/post\/"}],"author":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/users\/1\/"}],"replies":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/comments\/?post=13906"}],"version-history":[{"count":2,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/13906\/revisions\/"}],"predecessor-version":[{"id":16491,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/13906\/revisions\/16491\/"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/media\/16475\/"}],"wp:attachment":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/media\/?parent=13906"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/categories\/?post=13906"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/tags\/?post=13906"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}