Characteristics of locoregional extension of unilateral nasopharyngeal carcinoma and suggestions for clinical target volume delineation

Abstract

Background To summarize the characteristics of local invasion and distribution of metastatic lymph nodes in unilateral nasopharyngeal carcinoma (NPC) by magnetic resonance imaging (MRI) to provide references for the optimization of clinical target volume. Methods MRI and clinical data of 176 cases of unilateral NPC admitted to the Hunan Cancer Hospital from January 2019 to December 2019 were collected. Unilateral NPC was defined as a lesion confined to the one side of the nasopharynx and had not exceeded the midline as judged by MRI. Results Ipsilateral levator veli muscle (63.1%, 111/176), tensor veli palatini muscle (55.7%, 98/176), parapharyngeal space (50.0%, 88/176), and prevertebral muscle (43.7%, 77/176) were more likely to be invaded. Contralateral parapharyngeal space and skull base foramina were not invaded. All local invasions presented as continuous invasion from gross lesions and discontinuous invasions were not observed. The overall lymph node metastatic rate was 89.8% (158/176), of which bilateral metastasis accounted for 56.3% (89/158), and ipsilateral metastasis accounted for 88.1% (155/176), which was higher than the contralateral metastatic rate (55.4%, 94/176) (P < 0.001). The most common regions of lymph node metastasis were level IIb (82.4%), VIIa (69.9%), IIa (54.0%), and III (54.0%). Only one patient had skipping lymph node metastasis (0.6%). Conclusion Local invasion of unilateral NPC was characterized by continuous invasion from proximal to distal sites, and lymph node metastasis occurred from the upper to lower neck. Contralateral parapharyngeal space and skull base foramina had a very low probability of invasion, and routine prophylactic radiation may not be necessary.

Unraveling the patterns and pathways of local recurrence of nasopharyngeal carcinoma: evidence for individualized clinical target volume delineation

“…Sanford et al [ 19 ] advocated covering the Meckel’s cave and cavernous sinus ipsilaterally for lateralized tumors. Wu et al [ 21 ] recently characterized the locoregional extension patterns of unilateral NPC and demonstrated that contralateral skull base was not invaded in this case. In accordance with these, our study showed all cases relapsed at unilateral cavernous sinus, most cases at the same side of the primary tumor.…”

Distribution of regional lymph lode metastasis in unilateral nasopharyngeal carcinoma and the suggestions for selective prophylactic irradiation with intensity‐modulated radiotherapy

“…Tomita et al 16 reported a bilateral RLN metastasis rate of 18% in 76 patients with unilateral NPC on the patterns of RLN metastasis in newly diagnosed NPC patients. Wu et al 18 reported a bilateral RLN metastasis rate of 56.3% in 176 patients. In our study, the bilateral lymph node metastasis rate was 57.9%, indicating that unilateral NPC also carries a higher risk of bilateral RLN metastasis.…”

“…reported a bilateral RLN metastasis rate of 18% in 76 patients with unilateral NPC on the patterns of RLN metastasis in newly diagnosed NPC patients. Wu et al 18 . reported a bilateral RLN metastasis rate of 56.3% in 176 patients.…”

“…confirmed that about 37.5% had bilateral RLN metastasis. Wu et al 18 . reported that the rate of bilateral RLN metastasis in unilateral NPC was 53.4%.…”

Current Radiotherapy Considerations for Nasopharyngeal Carcinoma

“…An endoscopic biopsy study has revealed a low incidence of occult microscopic disease in the contralateral nasopharyngeal mucosa in unilateral NPC which did not cross the midline [ 8 ]. The risk of skipped discontinuous invasion to the contralateral parapharyngeal space and skull base is also exceedingly low in unilateral NPC, making unilateral irradiation an attractive option to reduce radiation side effects, such as trismus and xerostomia [ 10 ].…”