Investigation of the feasibility of elective irradiation to neck level Ib using intensity-modulated radiotherapy for patients with nasopharyngeal carcinoma: a retrospective analysis.

Fan Zhang,Ai-Hua Lin,Xu Liu,Guan-Qun Zhou,Yan-Ping Mao,Wen-Fei Li,Jun Ma,Lei Chen,Li-Zhi Liu,Ling-Long Tang,Ying Sun,Yi-Kan Cheng,Rui Guo

doi:10.1186/s12885-015-1669-z

Fan Zhang, Ai-Hua Lin + Show 11 more

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https://doi.org/10.1186/s12885-015-1669-z

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Abstract

BackgroundTo assess the feasibility of elective neck irradiation to level Ib in nasopharyngeal carcinoma (NPC) using intensity-modulated radiation therapy (IMRT).MethodsWe retrospectively analyzed 1438 patients with newly-diagnosed, non-metastatic and biopsy-proven NPC treated with IMRT.ResultsGreatest dimension of level IIa LNs (DLN-IIa) ≥ 20 mm and/or level IIa LNs with extracapsular spread (ES), oropharynx involvement and positive bilateral cervical lymph nodes (CLNs) were independently significantly associated with metastasis to level Ib LN at diagnosis. No recurrence at level Ib was observed in the 904 patients without these characteristics (median follow-up, 38.7 months; range, 1.3–57.8 months), these patients were classified as low risk. Level Ib irradiation was not an independent risk factor for locoregional failure-free survival, distant failure-free survival, failure-free survival or overall survival in low risk patients. The frequency of grade ≥ 2 subjective xerostomia at 12 months after radiotherapy was not significantly different between low risk patients who received level Ib-sparing, unilateral level Ib-covering or bilateral level Ib-covering IMRT.ConclusionLevel Ib-sparing IMRT should be safe and feasible for patients without a DLN-IIa ≥ 20 mm and/or level IIa LNs with ES, positive bilateral CLNs or oropharynx involvement at diagnosis. Further investigations based on specific criteria for dose constraints for the submandibular glands are warranted to confirm the benefit of elective level Ib irradiation.

Highlights

To assess the feasibility of elective neck irradiation to level Ib in nasopharyngeal carcinoma (NPC) using intensity-modulated radiation therapy (IMRT)
Multivariable analysis to adjust for various risk factors demonstrated a Greatest dimension of level IIa LNs (DLN-IIa) ≥ 20 mm or level IIa lymph nodes. DLN-IIa (LNs) with extracapsular spread (ES) (HR 2.21; 95 % confidence interval [CI] 1.10–4.46; P = .026) and oropharynx involvement (HR 2.59; 95 % CI 1.18–5.69; P = .018) were independently significantly associated with metastasis to the level Ib LNs at diagnosis, while positive bilateral cervical lymph nodes (CLNs) (HR 1.95; 95 % CI 0.97–3.92; P = .061) had a borderline significant association with metastasis to the level Ib LNs at diagnosis (Table 2)
In the 1193 patients with positive LNs in this series, univariable and multivariable analyses confirmed that a DLN-IIa ≥ 20 mm and/or level IIa LNs with ES (HR 2.41; 95 % CI 1.22–4.76; P = .011), oropharynx involvement (HR 2.50; 95 % CI 1.13–5.56; P = .024) and positive bilateral CLNs (HR 2.11; 95 % CI 1.06–4.20; P = .034) were independently significantly associated with metastasis to the level Ib LNs at diagnosis

Summary

Introduction

To assess the feasibility of elective neck irradiation to level Ib in nasopharyngeal carcinoma (NPC) using intensity-modulated radiation therapy (IMRT). Some studies routinely irradiate level Ib [1, 16,17,18], which exposes the SMGs to radiation; whereas others selectively spare level Ib with different criteria [11, 19,20,21]. Data on elective neck irradiation to level Ib in patients with NPC treated with IMRT is scarce. Chen and colleagues [22] reported that regional LN recurrence alone is rare in patients with negative level Ib LNs after level Ib-sparing IMRT; suitable criteria for elective irradiation of neck level Ib need to be re-evaluated due to the small sample size investigated

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