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

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.

Long-term Patterns of Regional Failure for Nasopharyngeal Carcinoma following Intensity-Modulated Radiation Therapy

“…By the last follow-up visit, only two patients (1.6%) had developed failures at level Ib, so the authors suggested omitting elective neck irradiation of level Ib in Ib-negative patients. Results from other prospective and retrospective studies also showed that recurrence in unirradiated level Ib is acceptably low 26-28. Our findings showed no nodal failures in level Ib in the absence of prophylactic level Ib irradiation, in accord with the above reports.…”

Patterns of nodal failure after intensity modulated radiotherapy for nasopharyngeal carcinoma

“…Metastatic nodes in level Ib are extremely rare in treatment‐naive patients with NPC and account for 0.3% on CT, 3.1% on MRI, and 2.2% on PET imaging . Results from prospective and retrospective studies show that relapse in the unirradiated Ib nodal region is acceptably low . However, controversy remains regarding the necessity of irradiating level Ib nodes.…”

“…6 Results from prospective and retrospective studies show that relapse in the unirradiated Ib nodal region is acceptably low. 26,27 However, controversy remains regarding the necessity of irradiating level Ib nodes. Our finding that no Ib nodal failures occurred supports the practice that Ib nodes may be safely excluded from the prophylactic target volumes, unless risk factors are present before treatment.…”

Can Parameters Other Than Minimal Axial Diameter in MRI and PET/CT Further Improve the Diagnostic Accuracy of Equivocal Retropharyngeal Lymph Nodes in Nasopharyngeal Carcinoma?

“…The clinical significance of this criterion is that it can prevent radiation oncologists from prescribing RT doses greater than 60 Gy for negative LRPL nodes, and it is more straightforward than an MIAD ranging from 5.0 to 5.9 mm. Excessive RT doses, especially 66 to 70 Gy, cause a higher incidence of complications such as internal carotid artery injury [24] and swallowing dysfunction [25] and more severe dryness of mouth [26][27][28]. If a LRPL node is the only node with suspected involvement, our criteria can prevent patients from undergoing unnecessary chemotherapy.…”