Comparison of the treatment outcomes of intensity-modulated radiotherapy and two-dimensional conventional radiotherapy in nasopharyngeal carcinoma patients with parapharyngeal space extension

Effect of radiotherapy interruption on nasopharyngeal cancer

Nasopharyngeal carcinoma (NPC) is a malignant tumor originating from the epithelial cells of the nasopharynx with a unique geographic distribution, and is particularly prevalent in East and Southeast Asia. Due to its anatomical location, the surgery is difficult to access and the high sensitivity of nasopharyngeal cancer to radiotherapy (RT) makes it the main treatment modality. Radical radiotherapy is the first-line treatment for early-stage nasopharyngeal carcinoma and the cornerstone of multidisciplinary treatment for patients with locally advanced nasopharyngeal carcinoma. Nevertheless, radiotherapy interruption is inevitable as a consequence of unavoidable factors such as public holidays, machine malfunction, patient compliance, and adverse response to treatment, which in turn leads to a reduction in bioactivity and causes sublethal loss of tumor cells to repair. Unirradiated tumor cells are more likely to repopulate at or near their original fastest growth rate during this interval. If no measures are taken after the radiotherapy interruption, such as increasing the dose of radiotherapy and systemic therapy, the tumor is most likely to go uncontrolled and then progress. This review describes the effects of radiotherapy interruption on nasopharyngeal carcinoma, the mechanism of the effect, and explores the measures that can be taken in response to such interruption.

Prognostic significance of cervical radiologic carotid artery invasion by lymph node on magnetic resonance imaging in nasopharyngeal carcinoma

PURPOSE

Carotid artery invasion (CAI) has been demonstrated to be an important prognosticator in some head and neck cancers. This study aimed to examine the prognostic value of radiologic CAI (rCAI) by cervical lymphadenopathy in nasopharyngeal carcinoma (NPC).

METHODS

NPC patients treated between January 2013 and December 2016 were included. Pre-treatment MRIs were reviewed for cervical rCAI according to the radiologic criteria. Univariate and multivariate models were constructed to assess the association between cervical rCAI and clinical outcomes. A new N classification system was proposed and compared to the 8th AJCC system.

RESULTS

The percentage of patients with MRI-positive lymph nodes was 84.7% (494/583), of whom cervical rCAI cases accounted for 42.3% (209/494). Cervical rCAI was associated with significantly poorer OS, DFS, DFFS and RFFS compared to non-rCAI (P < 0.05). Multivariate analyses confirmed that cervical rCAI was an independent prognosticator for DFS and DFFS, surpassing other nodal features, such as laterality, size, cervical node necrosis (CNN) and radiologic extranodal extension (rENE), while location of positive LNs remained independently associated with OS, DFS and DFFS. We propose a refined N classification: New_N1: upper neck LNs only without cervical rCAI; New_N2: upper neck LNs only with cervical rCAI; New_N3: upper and lower LNs. The proposed classification broadened the differences in OS, DFS and DFFS between N1 and N2 disease, and achieved a higher c-index for DFS and DFFS.

CONCLUSIONS

Cervical rCAI was an independent unfavorable indicator of NPC. Compared to the AJCC system, the proposed N category showed satisfactory stratification between N1 and N2 disease, and better prediction of distant metastasis and disease failure.

Efficacy and survival analysis of nimotuzumab combined with concurrent chemoradiotherapy in the treatment of locally advanced nasopharyngeal carcinoma

Objective

This study investigated the curative effect of adding nimotuzumab (NTZ) in patients with locally advanced nasopharyngeal carcinoma (NPC) who were treated with concurrent chemoradiotherapy (CCRT) and explored significant prognostic factors of NPC.

Materials and methods

The clinical data of 307 patients with NPC treated in the First Affiliated Hospital of Soochow University from January 2013 to December 2018 were retrospectively analyzed. The patients were divided into the NTZ-CCRT group and the CCRT group according to whether they were associated with NTZ. We applied propensity score matching to reduce the interference of biases and compared the short-term efficacy and long-term survival rate of the two groups. Moreover, univariate and multivariate analyses were performed for all patients, and subgroup analysis was used to compare the efficacy of therapy combined with NTZ in different subgroups.

Results

In primary nasopharyngeal tumors, the objective response rates in the NTZ-CCRT group and CCRT group were 95.8% and 85.7%, respectively (P =0.007). In cervical positive lymph nodes, the objective response rates in the NTZ-CCRT group and CCRT group were 98.3% and 87.4%, respectively (P =0.001). Compared with CCRT alone, the addition of NTZ significantly improved the 5-year OS (94.1% vs. 81.8%, P=0.014) and the 5-year DFS (84.2% vs. 75.5%, P=0.031) of NPC patients; however, the addition of NTZ was accompanied by more severe hematologic toxicity and acute oral mucositis. Multivariate analysis demonstrated that the addition of NTZ was an important prognostic factor for OS and DFS (HR 0.367, 95% CI 0.167-0.808, P=0.013 for OS and HR 0.536, 95% CI 0.312-0.919, P=0.023 for DFS) and the level of pretreatment LDH (HR 5.170, 95% CI 2.125-12.580, P<0.001 for OS and HR 2.421, 95% CI 1.027-5.707, P=0.043 for DFS). Moreover, patients with high levels of hsCRP before treatment (HR 0.389, 95% CI 0.177-0.853, P=0.018) may gain more benefits from combined treatment with NTZ.

Conclusions

For locally advanced NPC patients treated with concurrent chemoradiotherapy, the addition of NTZ can significantly improve their survival outcome. However, it is necessary to guard against the associated increase in hematological toxicity and acute oral mucositis.

Structural network alterations in patients with nasopharyngeal carcinoma after radiotherapy: A 1-year longitudinal study

This longitudinal study explored the changed patterns of structural brain network after radiotherapy (RT) in patients with nasopharyngeal carcinoma (NPC). Diffusion tensor imaging (DTI) data were gathered from 35 patients with NPC at four time points: before RT (baseline), 0∼3 (acute), 6 (early delayed), and 12 months (late-delayed) after RT. The graph theory was used to characterize the dynamic topological properties after RT and the significant changes were detected over time at the global, regional and modular levels. Significantly altered regional metrics (nodal efficiency and degree centrality) were distributed in the prefrontal, temporal, parietal, frontal, and subcortical regions. The module, that exhibited a significantly altered within-module connectivity, had a high overlap with the default mode network (DMN). In addition, the global, regional and modular metrics showed a tendency of progressive decrease at the acute and early delayed stages, and a partial/full recovery at the late-delayed stage. This changed pattern illustrated that the radiation-induced brain damage began at the acute reaction stage and were aggravated at the early-delayed stage, and then partially recovered at the late-delayed stage. Furthermore, the spearman’s correlations between the abnormal nodal metrics and temporal dose were calculated and high correlations were found at the temporal (MTG.R and HES.L), subcortical (INS.R), prefrontal (ORBinf.L and ACG.L), and parietal (IPL.R) indicating that these regions were more sensitive to dose and should be mainly considered in radiotherapy treatment plan.

MRI of nasopharyngeal carcinoma: parapharyngeal subspace involvement has prognostic value and influences T-staging in the IMRT era

OBJECTIVES

To identify the prognosis of parapharyngeal space involvement (PPSI) based on the number of subspaces involved (pre-styloid space, carotid space (CS), areas outside the CS) and explore its significance for current T-staging in patients with nasopharyngeal carcinoma (NPC).

METHODS

PPSI was retrospectively identified in 1224 patients with non-disseminated NPC at two centers on MRI and separated into four invasion patterns: pattern A (only post-styloid space), pattern B (post-styloid space, CS extension), pattern C (post-styloid space, pre-styloid space extension), and pattern D (all spaces). The Kaplan-Meier analysis and multivariate Cox regression models were used.

RESULTS

PPSI was diagnosed in 63.4% of cases, with patterns A, B, C, and D in 14.3%, 3.8%, 25.3%, and 18.6% of cases, respectively. No prognostic heterogeneity was observed between pattern B and pattern C (p > 0.05). Thus, the degree of PPSI was based on the number of subspaces involved: grade 0 (none), grade 1 (one), grade 2 (two), and grade 3 (three), which could independently predict overall survival (OS) (p < 0.001). T3 patients with grade 0/1 PPSI (slight-T3) had a better prognosis than those with grade 2/3 PPSI (severe-T3) in terms of OS, locoregional-free survival (LRFS), and progression-free survival (PFS) (all p < 0.001), whose hazard ratios were higher and lower than those with T1 and T2, respectively. Combining the T2 and slight-T3 groups as the proposed T2 provided significant differences in OS, LRFS, and PFS between T2 and T3 (all p < 0.05).

CONCLUSIONS

The risk of death increased with the number of parapharyngeal subspaces involved. The degree of PPSI is recommended to optimize T3 heterogeneity.

KEY POINTS

• Parapharyngeal space involvement was proposed to differentiate patient risk groups based on the number of involved subspaces: grade 0 (none), grade 1 (one), grade 2 (two), or grade 3 (three). • The degree of parapharyngeal space involvement was an independent negative prognosticator for OS. • The degree of parapharyngeal space involvement may influence T-staging in patients with nasopharyngeal carcinoma.

Altered properties of brain white matter structural networks in patients with nasopharyngeal carcinoma after radiotherapy

Previous neuroimaging studies revealed radiation-induced brain injury in patients with nasopharyngeal carcinoma (NPC) in the years after radiotherapy (RT). These injuries may be associated with structural and functional alterations. However, differences in the brain structural connectivity of NPC patients at different times after RT, especially in the early-delayed period, remain unclear. We acquired diffusion tensor imaging (DTI) data from three groups of NPC patients, 25 in the pre-RT (before RT) group, 22 in the early-delayed (1-6 months) period (post-RT-ED) group, and 33 in the late-delayed (>6 months) period (post-RT-LD) group. Then, we constructed brain white matter (WM) structural networks and used graph theory to compare their between-group differences. The NPC patients in the post-RT-ED group showed decreased global properties when compared with the pre-RT group. We also detected the nodes with between-group differences in nodal parameters. The nodes that differed between the post-RT-ED and pre-RT groups were mainly located in the default mode (DMN) and central executive networks (CEN); those that differed between the post-RT-LD and pre-RT groups were located in the limbic system; and those that differed between the post-RT-LD and post-RT-ED groups were mainly in the DMN. These findings may indicate that radiation-induced brain injury begins in the early-delayed period and that a reorganization strategy begins in the late-delayed period. Our findings may provide new insight into the pathogenesis of radiation-induced brain injury in normal-appearing brain tissue from the network perspective.

Cost-effectiveness of treating head and neck cancer using intensity-modulated radiation therapy: implications for cancer control program in India

Background

The newer cancer treatment technologies hold the potential of providing improved health outcomes at an additional cost. So it becomes obligatory to assess the costs and benefits of a new technology, before defining its clinical value. We assessed the cost-effectiveness of intensity-modulated radiotherapy (IMRT) as compared to 2-dimensional radiotherapy (2-DRT) and 3-dimensional radiotherapy (3D-CRT) for treating head and neck cancers (HNC) in India. The cost-effectiveness of 3-DCRT as compared to 2-DRT was also estimated.

Methods

A probabilistic Markov model was designed. Using a disaggregated societal perspective, lifetime study horizon and 3 percent discount rate, future costs and health outcomes were compared for a cohort of 1000 patients treated with any of the three radiation techniques. Data on health system cost, out of pocket expenditure, and quality of life was assessed through primary data collected from a large tertiary care public sector hospital in India. Data on xerostomia rates following each of the radiation techniques was extracted from the existing randomized controlled trials.

Results

IMRT incurs an incremental cost of $7,072 (2,932–13,258) and $5,164 (463–10,954) per quality-adjusted life year (QALY) gained compared to 2-DRT and 3D-CRT, respectively. Further, 3D-CRT as compared to 2-DRT requires an incremental cost of $8,946 (1,996–19,313) per QALY gained.

Conclusion

Both IMRT and 3D-CRT are not cost-effective at 1 times GDP per capita for treating HNC in India. The costs and benefits of using IMRT for other potential indications (e.g. prostate, lung) require to be assessed before considering its introduction in India.

Staging of T2 and T3 nasopharyngeal carcinoma: Proposed modifications for improving the current AJCC staging system

Objectives

We aimed to reconstitute T2 and T3 stage classification in nasopharyngeal carcinoma (NPC) cases and verify its utility in clinical settings.

Materials and Methods

We enrolled 792 NPC patients. Cox proportional hazards model was used to compare the effect sizes (hazard ratio [HR]) of the cranial structure invasion on survival and select the structures for up‐staging or downstaging T2 and T3 NPC. The samples were reclassified and the survival curves for T2 and T3 stages were analyzed. The proposed new staging system was validated on an external sample (n = 433).

Results

Thirteen cranial structures were examined. American Joint Committee on Cancer (AJCC) T3 stage patients with the invasion of the base of the sphenoid (HR = 2.58, 95% CI = 1.16‐5.77) or base of the pterygoid (HR = 2.00, 95% CI = 0.84‐4.77) had significantly lower hazard ratios than T2 stage patients with the invasion of soft tissues in the bilateral parapharyngeal space (HR = 5.26, 95% CI = 2.02‐13.68) and single/bilateral carotid sheath (HR = 7.78, 95% CI = 3.06‐19.76). T3 stage with the invasion of the above‐mentioned bones was reclassified as T2, and T2 stage with the invasion of the above‐mentioned soft‐tissue structures was reclassified as T3. Survival analysis showed a significant difference between the reclassified T2 and T3 stages (P < 0.001). The results were replicated in the validation samples.

Conclusion

The proposed staging system for defining T2 and T3 stage NPC appears to be superior to the AJCC 8th edition. It could improve prognosis and optimize the treatment selection.

A knowledge-based intensity-modulated radiation therapy treatment planning technique for locally advanced nasopharyngeal carcinoma radiotherapy

Background

To investigate the feasibility of a knowledge-based automated intensity-modulated radiation therapy (IMRT) planning technique for locally advanced nasopharyngeal carcinoma (NPC) radiotherapy.

Methods

One hundred forty NPC patients treated with definitive radiation therapy with the step-and-shoot IMRT techniques were retrospectively selected and separated into a knowledge library (n = 115) and a test library (n = 25). For each patient in the knowledge library, the overlap volume histogram (OVH), target volume histogram (TVH) and dose objectives were extracted from the manually generated plan. 5-fold cross validation was performed to divide the patients in the knowledge library into 5 groups before validating one group by using the other 4 groups to train each neural network (NN) machine learning models. For patients in the test library, their OVH and TVH were then used by the trained models to predict a corresponding set of mean dose objectives, which were subsequently used to generate automated plans (APs) in Pinnacle planning system via an in-house developed automated scripting system. All APs were obtained after a single step of optimization. Manual plans (MPs) for the test patients were generated by an experienced medical physicist strictly following the established clinical protocols. The qualities of the APs and MPs were evaluated by an attending radiation oncologist. The dosimetric parameters for planning target volume (PTV) coverage and the organs-at-risk (OAR) sparing were also quantitatively measured and compared using Mann-Whitney U test and Bonferroni correction.

Results

APs and MPs had the same rating for more than 80% of the patients (19 out of 25) in the test group. Both AP and MP achieved PTV coverage criteria for no less than 80% of the patients. For each OAR, the number of APs achieving its criterion was similar to that in the MPs. The AP approach improved planning efficiency by greatly reducing the planning duration to about 17% of the MP (9.85 ± 1.13 min vs. 57.10 ± 6.35 min).

Conclusion

A robust and effective knowledge-based IMRT treatment planning technique for locally advanced NPC is developed. Patient specific dose objectives can be predicted by trained NN models based on the individual’s OVH and clinical TVH goals. The automated planning scripts can use these dose objectives to efficiently generate APs with largely shortened planning time. These APs had comparable dosimetric qualities when compared to our clinic’s manual plans.

Low Skeletal Muscle Mass Impairs Quality of Life in Nasopharyngeal Carcinoma Patients Treated With Concurrent Chemoradiotherapy

Background: Nasopharyngeal carcinoma (NPC) patients receiving concurrent chemoradiotherapy (CCRT) frequently develop low skeletal muscle mass (SMM), but, little is known about the impacts of low SMM on health-related quality of life (QOL).

Methods: We retrospectively assessed 56 patients with locoregionally advanced NPC enrolled in a prospective trial. Low SMM was determined on routine computed tomography simulation (CT-sim) scans taken before radiotherapy, at the third cervical (C3) vertebral level with validated sex-specific cutoffs. QOL was assessed using the World Health Organization Quality of Life Questionnaire-100 at baseline and after 3 weeks. Pain was scored every 24 h using a numerical rating scale (NRS). Characteristics related to low SMM were identified by logistic regression. The chi-square test was used to examine the association of low SMM with QOL and pain.

Results: Of the 56 participants (mean age 44.20 ± 10.93 years), over half (60.71%) developed low SMM. Patients with low SMM were more likely to be older (P = 0.035), male (P = 0.066), have a lower body-mass index (BMI; P = 0.091), and have a higher pain score (P = 0.001). Older age (hazard ratio [HR] = 1.788, P = 0.016), being male (HR = 3.145, P = 0.010), lower BMI (HR = 0.761, P = 0.033), and lower prognostic nutritional index (HR = 0.186, P = 0.034) were associated with higher risk of low SMM. Low SMM was associated with poorer baseline QOL scores (P = 0.072), especially in the physical domain (P = 0.002) and its three facets: pain (P = 0.003), energy (P = 0.021), and sleep (P = 0.007). Low SMM was also associated with significantly worse QOL scores (P = 0.006) at 3 weeks, especially in the physical (P = 0.002), psychological (P = 0.046), independence (P = 0.003), social domains (P = 0.023), and in general health condition (P = 0.043). For pain score, low SMM group had worse overall changes from baseline to week 3 (P = 0.011).

Conclusions: The incidence of low SMM, as evaluated using routine CT-sim scans, is high in patients receiving CCRT for locoregionally advanced NPC. Low SMM results in poorer QOL and higher pain scores, which underscores the requirement for nutritional and functional interventions to address low SMM early in the treatment course.

Stage-specific concurrent chemoradiotherapy with or without induction chemotherapy for locoregionally advanced nasopharyngeal carcinoma: a retrospective, population-based study

Purpose

This large population-based analysis aims to investigate whether the additional induction chemotherapy to concurrent chemoradiotherapy improved overall survival (OS) and disease-free survival (DFS) for locoregionally advanced nasopharyngeal carcinoma (LRANPC).

Patients and Methods

The study group comprised 3,980 patients who were treated either with IC+CCRT (1,888 patients) or CCRT alone (2,092 patients) between January 1998 and June 2013. Survival outcomes were compared using Cox proportional hazards regression models with adjustments for confounding provided by propensity score methods. Primary outcome variables included OS and DFS.

Results

Kaplan–Meier analysis showed that CCRT and IC+CCRT were of similar benefit to OS (P=0.099), whereas there was a marginal benefit of CCRT to DFS (P=0.063) in the overall cohort, which showed no differences between the two treatment regimens using multivariate Cox analysis and propensity score. Interestingly, for patients with 2D radiationtherapy (2DRT), CCRT had OS and DFS benefits for stage III, with 5-year and 10-year OS for CCRT vs IC+CCRT being 88% and 75% vs 81% and 67%, respectively (P=0.002); 5-year and 10-year DFS for CCRT vs IC+CCRT being 84% and 74% vs 76% and 66%, respectively (P=0.002). In contrast, IC + CCRT had OS and DFS benefits for stage IVa-b, with 5-year and 10-year OS for CCRT vs IC+CCRT being 71% and 55% vs 76% and 60%, respectively (P=0.037, HR=0.786); 5-year and 10-year DFS for CCRT vs IC+CCRT were 64% and 50% vs 69% and 58%, respectively (P=0.038, HR=0.801). No difference was found in intensity-modulated radiotherapy (IMRT) subgroup.

Conclusion

Our study indicates that CCRT and IC+CCRT may have similar OS and DFS benefits for overall LRANPC. Stage-specific chemoradiotherapy may be administered based on the greatest benefit of IC+CCRT for stage IVa-b patients and CCRT alone for stage III patients received 2DRT. The optimal chemotherapy pattern in combination with IMRT needs further investigation.

Trial registration

 ClinicalTrials.gov ID: NCT02604472

The effectiveness of intensity-modulated radiation therapy versus 2D-RT for the treatment of nasopharyngeal carcinoma: A systematic review and meta-analysis

BACKGROUND

At present, the management of nasopharyngeal carcinoma (NPC) is mainly based on radiotherapy, but there are many radiation delivery techniques such as intensity-modulated radiotherapy (IMRT) and 2-dimensional radiotherapy (2D-RT).

MATERIALS AND METHODS

We searched all the eligible studies through the PubMed, Cochrane Library, Medline, and Embase. The endpoint events in meta-analysis were overall survival (OS), tumor local control including local-regional free survival (LRFS), progression-free survival (PFS), and distant metastasis-free survival (DMFS), and late toxicities.

RESULTS

A total of ten publications met the criteria and were identified through searches of the databases and references. We included 13304 patients in the meta-analysis, of whom 5212 received IMRT and 8092 were allocated to 2D-RT alone group. Compared with 2D-RT treatment, the IMRT group was associated with a better 5-year OS (OR = 1.70; 95% CI = 1.36-2.12), LRFS (OR = 2.08; 95% CI = 1.82-2.37), and PFS (OR = 1.40; 95% CI = 1.26-1.56). Additionally, the incidence of late toxicities such as late xerostomia (OR = 0.21; 95% CI = 0.09-0.51), trismus (OR = 0.16; 95% CI = 0.04-0.60), and temporal lobe neuropathy (TLN) (OR = 0.40; 95% CI = 0.24-0.67) for NPC patients in IMRT group were significantly lower than 2D-RT.

CONCLUSIONS

The meta-analysis demonstrates that IMRT provides improved long-term tumor overall survival and local control including LRFS and PFS. Additionally, IMRT yields a lower incidence of late toxicities induced by irradiation in NPC patients. Compared to 2D-RT, IMRT may be an effective treatment for patients with NPC. Further intensive studies should be pursued to examine the association.

Validation of the 8th edition of the UICC/AJCC staging system for nasopharyngeal carcinoma treated with intensity-modulated radiotherapy

An accurate TNM staging system is crucial for treatment guidance and prognosis prediction in nasopharyngeal carcinoma (NPC) patients. In this retrospective study, we evaluated the 8th edition of the Union for International Cancer Control/American Joint Committee on Cancer (UICC/AJCC) staging system for NPC treated with intensity-modulated radiotherapy (IMRT). A total of 608 patients with biopsy-proven, non-metastatic NPC, treated with IMRT between January 2008 and March 2010, were enrolled. The 5-year overall survival (OS), disease-free survival (DFS), local relapse-free survival (LRFS), and distant metastasis-free survival (DMFS) rates were 81.5%, 80.1%, 86.0%, and 81.1%, respectively. The LRFS rates of patients with stages T1 vs. T2, T2 vs. T3, and T1 vs. T3 did not differ between the 7th and 8th editions. By contrast, the DMFS rates of patients with N0 vs. N1, N1 vs. N2, and N2 vs. N3 differed between the 8th and the 7th editions, though no difference was observed between N3a and N3b, according to the 7th edition. The difference in OS between stages II and III, and between stages III and IVa, was larger according to the 8th edition than the 7th edition. There was no difference in the OS between stages I and II. These data indicate that in the IMRT era, the 8th edition staging system can predict the prognosis of NPC patients more accurately than the 7th edition.

The feasibility of contralateral lower neck sparing intensity modulation radiated therapy for nasopharyngeal carcinoma patients with unilateral cervical lymph node involvement

OBJECTIVES

To investigate the feasibility of contralateral lower neck sparing intensity modulation radiated therapy (IMRT) for nasopharyngeal carcinoma patients (NPC) with unilateral cervical lymph node metastasis.

MATERIALS AND METHODS

Retrospective review of 546 patients with unilateral cervical lymph node metastasis treated between November 2009 and February 2012 at one institution. All patients were staged using magnetic resonance imaging and received radical IMRT. Patients were classified into two groups: the inferior border of the negative neck irradiation field only covered Levels III to Va in Group 1; the inferior border covered entire neck down to Levels IV to Vb in Group 2.

RESULTS

Median follow-up was 49.9months (range, 1.3-69.2months). Four-year overall survival (OS:89.3% vs. 88.9%, P=0.91), disease-free survival (DFS:81.7% vs. 81.0%, P=0.91), distant metastasis-free survival (DMFS:88.2% vs. 87.9%, P=0.95), local relapse-free survival (LRFS:96.7% vs. 94.7%, P=0.70) and nodal relapse-free survival (NRFS: 96.1% vs. 95.9%, P=0.94) were not significantly different between Group 1 and Group 2. Twenty-two patients developed cervical lymph node relapse; of whom 20/22 (91.0%) developed unilateral relapse within pretreatment positive neck. Only one patient developed out-of-field relapse, though this patient also relapsed within the neck irradiation field (Level II). No clinicopathological feature tested had significant prognostic value for NRFS in multivariate analysis.

CONCLUSIONS

In the IMRT and MRI era, contralateral lower neck sparing IMRT seems to be feasible for NPC patients with unilateral cervical lymph node metastasis.