Radiation Oncology/Head & Neck/Larynx/Subglottis

Subglottic Larynx

Overview

• Anatomy - 5mm below the free margin of true vocal cords to inferior margin of cricoid cartilage
• Primary lesions are rare (<3%); usually extension from glottis. 50-70% are SCC
• Symptoms - usually asymptomatic, but can present with horseness, dyspnea, stridor
• Disease often advanced at presentation; thorcacic cavity involved in T3-T4(~50%)
• Staging
  • T1 - subglottis only
  • T2 - extension to vocal cords, with normal or impaired mobility (no fixation)
  • T3 - vocal cord fixation
  • T4 - invades through cricoid or thyroid cartilage, or other tissues
    • T4a - invades cricoid or thyroid cartilage or tissues beyond the larynx
    • T4b - invades prevertebral space, carotid, or mediastinum
• Lymphatics - channel unite to form one anterior and two posterolateral pedicles. Anterior drains through cricothyroid membrane into mid- and lower jugular nodes, or via prelaryngeal node into pretracheal and supraclavicular LNS. Posterior drains through cricotracheal membrane into paratracheal nodes
  • LN+ in 20-50%
• Treatment - no consensus due to small numbers, but Toronto reports good experience with primary RT
  • Stage I-II: RT (include lower neck and mediastinum)
  • Stage III-IV: surgery (include larynx, thyroid, parastomal LNs), post-op RT if LN+ (include lower neck and mediastinum)
• RT fields - lateral opposed fields inferiorly 2cm below primary tumor, superiorly encompassing upper jugular nodes. Also an anterior low neck and upper mediastinum T-field

Radiation

• 2006 Ocshner Clinic PMID 16360814 -- Squamous cell carcinoma of the subglottis. (Garas J, Am J Otolaryngol. 2006 Jan-Feb;27(1):1-4.)
  • Retrospective. 15 patients over 25 years. 20% T1-2, 80% T3-4
  • 3-year OS: 25%
  • Recommend:
    • Stage I-II: RT (include lower neck and mediastinum)
    • Stage III-IV: surgery (include larynx, thyroid, parastomal LNs), post-op RT if LN+ (include lower neck and mediastinum)

• Toronto
  • 2002 PMID 11955735 -- Results of radiotherapy for primary subglottic squamous cell carcinoma. (Paisley S, Int J Radiat Oncol Biol Phys. 2002 Apr 1;52(5):1245-50.
    • Retrospective. 43/55 (9 palliative, 3 laryngectomy) patients treated (1971-1996) with radical RT and surgical salvage. 54% T1-2, 46% T3-4, clinical N0. Median follow-up 4.2 years
    • RT: 50-52 Gy in 20 fxs (2.5 Gy/fx) over 4 weeks. Fields: Lateral oblique fields directed caudally (angled-down wedge pair technique), typically included the primary site alone, although in most cases, the first echelon nodes were encompassed in this volume. The median field size was 96 cm2 (8 cm wide by 12 cm long) and usually extended superiorly to above the hyoid, inferiorly to encompass known disease with a margin, posteriorly to the mid-vertebral body and anteriorly out beyond the skin. No severe late radiation morbidity. Authors note the dose would now be considered low (compared with current higher fractionated therapy for larynx)
    • Local RT control 56% (82% including surgical salvage)
    • 5-year OS: 50%
    • Note: As per Garas above, much better RT results than others
  • 1987 PMID 3117073 -- Carcinoma of the subglottis. Results of initial radical radiation. (Warde P, Arch Otolaryngol Head Neck Surg. 1987 Nov;113(11):1228-9.)
    • Retrospective. 23 patients (1971-1982), 40% T1-T2, 60% T3-T4
    • Local RT control 70% (74% including surgical salvage)

• 2000 Florence PMID 11195034 -- Primary carcinoma of the subglottic larynx. (Santoro R, Eur Arch Otorhinolaryngol. 2000 Dec;257(10):548-51.)
  • Retrospective. 49 patients (1969-1993), 35% T1-T2, 65% T3-T4
  • 5-year OS: surgery 47%, RT alone 0%, surgery + RT 83%

• 1999 London PMID 10229604 -- Submucosal squamous cell carcinoma of the subglottis. (Porter GC, Otolaryngol Head Neck Surg. 1999 May;120(5):745-6.)

• 1998 Washington U PMID 9591557 -- Primary subglottic cancer. (Dahm JD, Laryngoscope. 1998 May;108(5):741-6.)
  • Retrospective. 39 patients with primary subglottic cancer, 1955-1988
  • 5-year OS: 58%
  • 5-year DFS: 46% (RT alone 22%, surgery alone 42%, surgery + RT 100%)

• 1993 Sussex PMID 8347536 -- Primary radiotherapy for subglottic carcinoma. (Haylock BJ, Clin Oncol (R Coll Radiol). 1993;5(3):143-6.)
  • Retrospective. 23 patients treated 1976-1990 by one therapist. Mean follow-up 5.6 years
  • RT: Small parallel opposed wedged fields to the neck. No mediastinal radiotherapy used.
  • 2-year OS: 69%, failure due to persistent disease (22%) or recurrence (10%)
  • Questionnaire to ENTs: surgeons have a pessimistic perception of the value of radiotherapy in this condition

• 1982 MSKCC PMID 7125077 -- Carcinoma of the subglottic larynx. (Shaha AR, Am J Surg. 1982 Oct;144(4):456-8.)
  • Retrospective. 16 patients over 25 years. 25% T1-T2, 75% T3-T4
  • 5-year OS: 70%
  • Treatment: primary surgery (wide-field laryngectomy, thyroidectomy, node dissection), followed by RT in advanced cases

Review

• 2000 PMID 10839493 -- The pathology and management of subglottic cancer. (Ferlito A, Eur Arch Otorhinolaryngol. 2000;257(3):168-73.)