Treatment Outcome of Combined Modalities for Buccal Cancers: Unilateral or Bilateral Neck Radiation?
IJROBP Volume 70, Issue 5, Pages 1373-1381 (1 April 2008)
Purpose
To evaluate the outcome of treatment for buccal cancers and assess the impact of unilateral vs. bilateral adjuvant neck radiation. We retrospectively reviewed the course of 145 patients newly diagnosed with buccal squamous cell carcinoma without distant metastases who completed definitive treatment between January 1994 and December 2000. Of 145 patients, 112 (77%) had Stage III or IV disease. All underwent radical surgery with postoperative radiotherapy (median dose, 64 Gy), including unilateral neck treatment in most (n = 120, 82.8%). After 1997, cisplatin-based concomitant chemoradiotherapy was given for high-risk patients with more than two involved lymph nodes, extracapsular spread, and/or positive margins.
Results
The 5-year disease-specific survival rate for Stages I–IV was 87%, 83%, 61%, and 60%, respectively. The most significant prognostic factor was N stage, with the 5-year disease-specific survival rate for N0, N1, and N2 being 79%, 65%, and 54%, respectively. For patients with more than two lymph nodes or positive extracapsular spread, cisplatin-based concomitant chemoradiotherapy improved locoregional control. Locoregional control did not differ between patients undergoing unilateral or bilateral neck treatments (p = 0.95). Contralateral neck failure occurred in only 2.1%.
Conclusions
In patients with buccal carcinoma after radical resection, ipsilateral neck radiation is adequate. Bilateral prophylactic neck treatment does not confer an added benefit.
Lymph node involvement in the neck was most commonly found in Level I, followed by both Levels I and II. This makes sense anatomically because it is likely that drainage occurs first to Level I and from there to Level II, or less commonly directly from Level I to III. Only 2.5% of our patients had involvement of Level II exclusively. At any rate, if Level I is involved, it is reasonable to include both Levels II and III in the prophylactic irradiation fields.
The reported incidence of contralateral neck metastasis from oral carcinomas varies from 0.9% to 34.7%. The differences may be attributed to variations in anatomy, etiology, and distinct tumor behavior. The need for contralateral neck elective treatment for oral cavity cancers is debatable. Kurita found that the incidence of contralateral neck metastasis increased with T4 tumors, multiple ipsilateral neck metastases, high grade, and lesions that cross the midline. Koo reported 25% of T3 patients (2 of 8) as having occult contralateral neck metastasis, and they recommended prophylactic neck treatment for lesions greater than T3 that cross the midline. Kowalski provided a useful multivariate model for prognostication. They stated that high-risk patients (i.e., those with tumors crossing the midline, extension to the floor of the mouth, or clinical Stage IV) have at least a 20% chance of having contralateral neck metastasis. These patients should therefore have prophylactic contralateral neck radiotherapy. However, in these studies, mobile tongue or mouth floor cancers were the commonest lesion, tumors in which the risk of neck metastasis is already relatively high. Advanced tongue and mouth floor cancers are in closer proximity to the midline and thus potentially more apt to cross it than are buccal lesions. It is therefore hard to know whether similar recommendations should apply to tumors involving the buccal mucosa. In the present study most patients received only unilateral prophylactic treatment, even though three quarters of them already had advanced disease (Stages III and IV). Bilateral treatment was given more often to patients with N2 disease or ECS, but it conferred no significant benefit over unilateral treatment in terms of LRC or RC in patients with N2 disease. These results make sense: buccal cancer rarely metastasizes to the contralateral side because there is little lymphatic drainage in that area that crosses the midline. Because of the risk of severe pharyngitis and mucositis with bilateral radiation, especially with CCRT, we recommend unilateral radiation only in patients with buccal tumors, even if there is ipsilateral neck node metastasis. Bilateral prophylactic radiation should be reserved for patients whose tumor crosses the midline.
he most important prognostic factor in our study was N2 nodal stage, similar to the results of other investigators. Extracapsular spread, usually thought to be a poor prognostic factor, was significant in univariate but not multivariate analysis. Because our study was retrospective, the effects of ECS might have been confounded by other factors. Because ECS is often present when multiple lymph nodes are involved, its contribution to outcome may have been masked by the N stage. Most patients (70%, 40 of 57) with positive ECS had CCRT, in contrast to only 54% of those with N2 disease. This also might have diminished the apparent impact of ECS on outcome.
The status of the resected tissue margins reportedly correlates with tumor control. We found it to be correlated with local or locoregional control but not with survival. The control rate decreased by approximately 10–15% in patients with close margins, despite adjuvant treatment. Our plastic surgeons strongly recommend immediate free-flap reconstruction for buccal cancer, so the initial radical excision almost always results in adequate margins, even with bulky tumors. Only 1 patient had positive margins in this study, which contrasts with the results of several other groups, whereby 20% or more of the patients had positive margins. The extensive resection our patients undergo, therefore, may account for a better outcome.
