Oral Carcinoma of the Retromolar Trigone, Maxillary Alveolus and Palate: Considerations in Surgical Management

Abstract

Suun alueen syöpä on haastava tauti koska se ei vaikuta ainoastaan toimintaan vaan myös potilaan ulkonäköön. Parantuneesta diagnostiikasta ja hoitomenetelmistä huolimatta suusyövän kulkua on edelleen vaikea ennustaa.

Tässä väitöskirjassa tutkittiin suun alueen levyepiteelisyövän käyttäytymistä ja hoitoa alueilla joista ei aikaisemmin ole ollut paljon tietoa; kyseessä oli alaleuan retromolaari- eli poskihampaiden takana oleva alue sekä yläleuan hammasharjanne/kovan suulaen alue. Lisäksi tutkittiin yläleuan maksillaariarterian ja alaleuan kasvohermon anatomista kulkua; usein nämä rakenteet sijaitsevat operoitavalla alueella tai heti sen läheisyydessä. Tutkimuksessa käsiteltiin myös leikkauksessa poistetun eli resekoidun alueen reunamarginaalin histologisen tutkimuksen tärkeyttä.

Tutkimusten perusteella tehtiin seuraavat johtopäätökset: Retromolaarialueen levyepiteelisyövän ennuste on huono jo syövän varhaisessa vaiheessa. Riittävä kirurginen reunamarginaali voi parantaa ennustetta. Yläleuan hammasharjanteen ja suulaen levyepiteelisyöpä eroaa muista suun alueen syövistä siinä että potilaat ovat suhteellisesti vanhempia ja useammin naisia. Kirurginen hoito sädehoidon kanssa tai ilman sädehoitoa näyttäisi helpottavan taudin hallintaa.

Yläleuan maksillaariarteria sijaitsi useammin lateraalisen pterygoideus-lihaksen alaosan päällä kuin sen alla. Se on tärkeää tietää jotta voidaan välttää sen vaurioituminen leikkauksen aikana. Kasvohermon osalta todettiin että kun se pyrittiin säästämään leikkauksessa, hermon toimintahäiriötä esiintyi 16/101 tapauksessa (16%). Kun analysoitiin 425 potilasta, kirurginen reunamarginaali todettiin tärkeäksi tekijäksi ennusteen kannalta. Tämä, toisin kuin muut ennusteeseen vaikuttavat tekijät, on asia johon kirurgi voi suoraan vaikuttaa.

Cancer of the oral cavity is a most devastating disease that causes a significant disfigurement of the patient with severe morbidity and mortality. It is a challenging disease in it is nature and management that affects not only the function but also the cosmesis of the afflicted patients. Despite improvement in the diagnostic and management methods, the prognosis of oral cancer is still unpredictable. This series of works seeks to examine the behaviour and management of oral Squamous cell carcinoma at two uncommon sites for which data is lacking; namely the retromolar trigone and the maxillary alveolus / hard palate. Additionally the thesis examines the anatomy of two important neighbouring structures which may be affected by surgical treatment; namely the maxillary artery and the marginal mandibular branch of the facial nerve. Finally the importance of the histological status of the resection margin is examined.

The cohort with Squamous cell carcinoma involving the retromolar trigone consisted of 76 cases. The absolute and disease specific survivals at 5 years were 51.4% and 67.7%. In patients treated with surgery, the resection margin status predicted the overall 5- year survival (P= 0.027) with 75% of patients with negative margins surviving 5 years versus a survival of 0% of patients with involved margins. Squamous cell carcinoma of the retromolar trigone has a poor survival for early stage disease. Adequate surgical margins can improve survival.

In analysis of the cohort of 37 patients with tumors involving the maxillary alveolus and hard palate, there was a female predilection. Local recurrence was observed in ten patients with 6 failing at the primary site. The absolute and disease free survival at 5-years was 33% and 62% respectively. The 5-year disease-free survival was 82% for stage I & II and 48% for stage III and IV (P=0.056). No patient treated with radiotherapy as a single treatment modality survived 5 years. Disease free survival for patients treated with surgery, and surgery± radiotherapy, was 69% and 73% at 5 years respectively. (P=0.001). Squamous cell carcinoma of the maxillary alveolus and palate differs from other oral cancers in that the patients are relatively older with a slight female predilection. Treatment with surgery, with or without radiotherapy, appears to improve disease control.

The course of the maxillary artery relative to the lateral pterygoid muscle was dissected in 44 cadaver specimens. In the majority of the cases (30), the artery was found lateral to the lower head of the lateral pterygoid muscle (71% in males and 65% in females). The maxillary artery was found medial to the lower head of the lateral pterygoid muscle in only 14 of the cases (29% in males and 35% in females). No variations in the course of maxillary artery were noted between the two sides and between both sexes. This study shows that the lateral or superficial course of the maxillary artery relative to the lower head of the lateral pterygoid muscle to be more prevalent than the medial or deep course. The anatomy and function of the facial nerve was studied in 133 patients undergoing neck dissections. When the neck was extended the nerve was displaced in an anterior and downwards direction with the lowest point 1.25 +/- 0.07 cm below the mandible between the posterior and anterior facial veins. When the intent was to preserve the nerve, dysfunction was seen in 16 of 101 dissections (16%).

A total of 425 patients were assessed for adequacy of the margins at the time of resection. After controlling for significant prognostic factors, involved surgical margins increased the risk of death at 5 years by 90%. The status of the surgical margin is an important predictor of outcome. The surgical margin, unlike other prognostic factors is under the direct control of the surgeon.