Modified reduced-volume intensity-modulated radiation therapy in non-metastatic nasopharyngeal carcinoma: A prospective observation series

Research landscape of radiotherapy for nasopharyngeal carcinoma from 1959 to 2022: A bibliometric analysis

Background

Radiotherapy, as the main treatment method for nasopharyngeal carcinoma (NPC), has evolved over time, but there has been no bibliometric study on NPC radiotherapy to date. In our study, the scientific achievements of NPC radiotherapy around the world were evaluated by bibliometric analyses, and the previous research hotspots and future trends are described.

Methods

Original articles related to NPC radiotherapy were obtained from the Web of Science Core Collection. To identify research hotspots and future trends, countries/regions, institutions, journals, references, authors, and keywords were evaluated and visualized by Excel, VOSviewer, and CiteSpace.

Results

From 1959 to 2022, 7139 original articles were collected. The annual publications showed an increasing trend, especially after 2011. China had the most publications (n = 3719, 52.09 %). Sun Yat-sen University has the most publications and citations among institutions. Jun Ma is most productive and SR Baker has the highest co-cited centrality. International Journal of Radiation Oncology-Biology-Physics is the core journal, with most publications, citations and co-citations. Analysis of keywords showed intensity-modulated radiotherapy and chemoradiotherapy were the main keywords, and multicenter showed the strongest burst.

Conclusion

NPC radiotherapy has attracted increasing attention, and precision and artificial intelligence may be the future trends in this field.

Is a total dose of 54 Gy with radiochemotherapy sufficient for treatment of intermediate-risk volumes in nasopharyngeal cancer?

BACKGROUND

The mainstay treatment of nasopharyngeal cancer (NPC) is radiation therapy (RT). The doses and volumes may differ from center to center. Most studies and guidelines recommend a total dose of 60 Gy for elective nodal and peritumoral volume treatment. This retrospective analysis aimed to analyze whether a dose reduction to 54 Gy to this volume would be associated with a higher risk of recurrence.

METHODS

A total of 111 patients treated by intensity-modulated radiotherapy (IMRT) and concurrent chemotherapy were retrospectively analyzed. The recurrent tumor volume was classified as "in field" if 95% of the recurrent volume was inside the 95% isodose, as "marginal" if 20-95% of the recurrence was inside the 95% isodose, or as "outside" if less than 20% of the recurrence was inside the 95% isodose.

RESULTS

Median follow-up was 67 months (range 6-142). The 2‑ and 5‑year overall survival (OS) rates were 88.6% and 70%, respectively. The 2‑year locoregional control (LRC), disease-free survival (DFS), and distant metastasis-free survival (DMFS) were 93.3%, 89.3%, and 87.4%, and the 5‑year LRC, DFS, and DMFS were 86.8%, 74%, and 81.1%, respectively. Ten patients (9%) had a local and or regional recurrence. Half of the patients with locoregional failure had in-field recurrences. For primary tumor, there was no recurrence in the volume of 54 Gy. For regional lymph node volume, recurrence was detected in two (1.8%) patients in the volume of 54 Gy.

CONCLUSION

These retrospective data suggest that a dose reduction may be possible for intermediate-risk volumes, especially for the primary site.

The individualized delineation of clinical target volume for primary nasopharyngeal carcinoma based on invasion risk of substructures: A prospective, real-world study with a large population

BACKGROUND AND PURPOSE

The delineation of clinical target volume (CTV) for primary nasopharyngeal carcinoma (NPC) is currently controversial and the international guideline still recommend a uniform border for CTV regardless of the tumor extent. We conducted this prospective, real-world study to evaluate the clinical outcomes of our individualized CTV delineation method based on distance plus substructures.

MATERIALS AND METHODS

We preliminarily investigated the local extension patterns of NPC on 354 newly diagnosed patients and defined the structures surrounding the nasopharynx as Level-1 to Level-4 substructures stratified by the risk of invasion. We then enrolled patients with newly diagnosed NPC without distant metastasis to investigate our individualized CTV delineation protocol. All patients received intensity modulated radiotherapy. CTV1 and CTV2 were prescribed doses of 60 Gy and 54 Gy in 30 ∼ 33 fractions. The primary endpoint was local recurrence-free survival (LRFS); secondary endpoints included regional control and survival, estimated using the Kaplan-Meier method. The local failure patterns were also analyzed.

RESULTS

From January 2008 to December 2012 and from January 2013 to September 2019, 356 and 648 patients were enrolled, named as training set and validation set, respectively. With a median follow-up of 104.6 (interquartile, 73.1-126.9) and 51.4 (39.5-78.5) months, 31 (8.7 %) and 38 (5.9 %) patients in training and validation sets experienced local recurrence, and the 5-year LRFS was 93.0 % and 93.2 %, respectively; 63 (17.7 %) and 39 (6 %) patients died in training and validation sets, and the 5-year overall survival (OS) was 88.5 % and 93.4 %, respectively. For the whole study cohort (N = 1004) with a median follow-up of 66.6 (41.5-98.0) months, the 5-year LRFS and OS was 93.2 % and 91.5 %. The grade 3 late toxicities included xerostomia, subcutaneous fibrosis, hearing impairment, trismus, visuality impairment and skin atrophy, with a total incidence of 1.5 %. Sixty-seven of 69 (97.1 %) local recurrence was in high-dose area.

CONCLUSION

Our individualized CTV delineation method can achieve favorable local tumor control and long-term survival outcomes with acceptable late toxicities.

Efficacy of salvage surgery versus re-irradiation for isolated regional lymph node recurrence in patients with nasopharyngeal carcinoma

BACKGROUND

To compare the clinical characteristics and prognoses of patients with isolated regional lymph node recurrent nasopharyngeal carcinoma (irrNPC) who underwent surgery or re-irradiation treatment.

METHODS

We retrospectively reviewed 124 irrNPC patients who underwent initial radiotherapy between January 2010 and December 2020. The staging of regional lymph node recurrence was as follows: 75.8% for rN1, 14.5% for rN2, and 9.7% for rN3. Fifty-five patients underwent regional lymph node surgery (Surgery group), and sixty-nine patients received salvage radiotherapy with or without chemotherapy (Re-irradiation group). The survival rate was compared using Kaplan‒Meier analysis and evaluated by the log-rank test. Cox proportional hazard models were used to analyze prognostic factors.

RESULTS

The median follow-up time was 70 months, the 5-year overall survival (OS) was 74%, and the median survival time was 60.8 months. There were no significant differences in 5-year OS (75.6% vs. 72.4%, P = 0.973), regional recurrence-free survival (RRFS, 62.7% vs. 71.1%, P = 0.330) or distant metastasis-free survival (DMFS, 4.2% vs.78.7%, P = 0.677) between the Surgery group and Re-irradiation group. Multivariate analysis revealed age at recurrence, radiologic extra-nodal extension (rENE) status, and recurrent lymph node (rN) classification as independent prognostic factors for OS. The rENE status was an independent prognostic factor for DMFS. Subgroup analysis of the Surgery group revealed that the rN3 classification was an adverse prognostic factor for OS. Age at recurrence ≥ 50 years, GTV-N dose, and induction chemotherapy were found to be independent prognostic factors for OS, RRFS, and DMFS, respectively, in the Re-irradiation group.

CONCLUSIONS

For NPC patients with isolated regional lymph node recurrence after initial radiotherapy, those who underwent surgery had survival prognosis similar to those who underwent re-radiotherapy with or without chemotherapy. A prospective study is needed to validate these findings.

Selectively sparing of the supraclavicular area during intensity-modulated radiotherapy in nasopharyngeal carcinoma: A double-center observation study

BACKGROUND AND PURPOSE

This study was aimed at evaluating the feasibility of sparing the supraclavicular area, namely levels IVb and Vc, during intensity-modulated radiotherapy (IMRT) in nasopharyngeal carcinoma (NPC) patients with N1-2 disease[except N1 disease with purely restropharyngeal lymph nodes(RPN) involvement], and providing a basis for the revision of International Guideline for the delineation of the clinical target volume (CTV).

PATIENTS AND MATERIALS

Patients with NPC (stage TanyN1-2M0) diagnosed pathologically in Fujian Cancer Hospital (Center 1, Only Lin SJ's attending group) from January 2014 to March 2018 and Jiangxi Cancer Hospital(Center 2) from January 2014 to December 2015 were included. According to our principle, the supraclavicular area (levels IVb and Vc) were excluded from the CTVnd. Survival outcomes focused on regional recurrence-free survival (RRFS) and recurrence rates of levels IVb and Vc were analysed.

RESULTS

A total of 672 eligible patients were recruited (Center 1, n = 362; Center 2, n = 310). There was no significant difference in 5-year RRFS (97.33 % vs. 97.24 %, p = 0.980), overall survival (OS) (89.14 % vs. 88.56 %, p = 0.327), local recurrence-free survival (LRFS) (94.90 % vs. 95.30 %, p = 0.593) and distant metastasis-free survival (DMFS) (89.38 % vs. 86.60 %, p = 0.130) between Center 1 and Center 2. Twenty patients developed regional failure (median: 36 months), among them, only one case (0.15 %) was recorded as levels IVb and Vc recurrence.

CONCLUSION

Omitting the supraclavicular area (levels IVb and Vc) during IMRT should be safe and feasible for N1-2 disease (except N1 disease with purely RPN involvement). Well-designed multicenter prospective trials should be conducted to confirm our findings.

Deletion of concurrent chemotherapy on the basis of sequential chemoradiotherapy for non-metastatic stage T4 nasopharyngeal carcinoma in IMRT era

PURPOSE

Intensity-modulated radiotherapy (IMRT) combined with concurrent chemotherapy is deemed as the mainstay treatment in locoregionally advanced nasopharyngeal carcinoma (NPC). Nevertheless, the tolerance of severe acute toxicity of concurrent chemotherapy was unsatisfied. In addition, T4 is the predicting factor of poor prognosis for NPC patients. In this retrospective analysis, the long-term outcomes IMRT combined by induction chemotherapy deleting concurrent chemotherapy with or without adjuvant chemotherapy for T4 non-metastatic NPC were analyzed.

MATERIALS AND METHODS

From January 2005 to November 2016, a total of 145 biopsy-proven non-metastatic T4 NPC was treated with IMRT combined by induction chemotherapy with or without adjuvant chemotherapy. The survival and side effects of the patients were analyzed.

RESULTS

Median follow-up time was 74 months (ranges, 8-186 months). 10.0%, 61.3%, 27.3%, and 1.3% developed grade 1, 2, 3, and 4 mucositis during IMRT, respectively. 5.5% and 2.0% patients experienced grade 1 and 2 nausea and vomiting; no patients developed grade 3 or 4 nausea and vomiting. Of 145 patients enrolled, 5-year and 10-year overall survival(OS) rates were 73.7% and 53.9%, local progression-free survival(LPFS) rates were 86.1% and 71.6%, regional progression-free survival(RPFS) rates were 96.7% and 92.8%, distant metastasis-free survival (DMFS) rates were 86.7%, 78.2%, respectively. At the last follow-up, five patients developed cranial nerve injury, one patient developed mandibular bone necrosis, four patients developed temporal lobe injury, four patients developed nasopharyngeal massive hemorrhage (three cases after recurrence and one case without recurrence), and five patients developed second primary tumor.

CONCLUSION

The survival outcomes of treating T4 NPC IMRT combined by induction chemotherapy deleting concurrent chemotherapy with or without adjuvant chemotherapy are encouraging. Moreover, mucosal reaction, nausea, and vomiting reaction were reduced during IMRT.

Constructing an individualized surveillance framework for nasopharyngeal carcinoma based on a dynamic risk-adapted approach

BACKGROUND AND PURPOSE

This study aims to evaluate the dynamic survival and recurrence hazard of nasopharyngeal carcinoma(NPC) patients after definitive chemoradiotherapy utilizing conditional survival(CS) analysis, and to propose a personalized surveillance strategy at different clinical stages.

MATERIALS AND METHODS

Non-metastatic NPC patients who received curative chemotherapy between June 2005 and December 2011 were included. The Kaplan-Meier method was used to calculate the CS rate.

RESULTS

A total of 1616 patients were analyzed. With the prolongation of survival time, both conditional locoregional recurrence free survival and distant metastatic free survival increased gradually. Changing pattern of annual recurrence risk over time varied among different clinical stages. The annual locoregional recurrence(LRR) risk in stage I-II was always less than 2%, while in stage III-IVa, it was greater than 2% for the first three years and decreased to below 2% only after the third year. The annual distant metastases (DM) risk was always less than 2% in stage I, but higher than 2% in stage II for the first 3 years (2.5-3.8%). For those with stage III-IVa, the annual DM risk retained at a high level(>5%), and only decreased to < 5% after the third year. Based on the dynamic changes in survival probability over time, we established a surveillance plan with different follow-up intensities and frequencies for different clinical stages.

CONCLUSION

The annual risk of LRR and DM decrease over time. Our individual surveillance model will provide critical prognostic information to optimize clinical decision-making, and promote to formulate surveillance counseling and help with resources allocation.

Why subclinical involvement is prescribed the same high dose as gross tumor volume: A study on high-dose clinical target volume in intensity-modulated radiotherapy plan of nasopharyngeal carcinoma

BACKGROUND

Most nasopharyngeal carcinoma (NPC) protocols define primary gross tumor volume (GTVnx) plus a range from 2 to 5 mm as the high-dose clinical target volume (hd-CTV). However, in China, hd-CTV is defined as GTVnx plus 0 mm.

METHODS

A total of 40 patients with newly diagnosed nonmetastatic NPC (T1-T4 ten cases each) treated with IMRT were consecutively enrolled. Real and virtual treatment plans were designed according to the definitions of hd-CTV recommended by China and Radiation Therapy Oncology Group (RTOG), respectively.

RESULTS

The hd-CTV in China was significantly smaller than that of RTOG. Exposure doses to 5 mm subclinical involvement and OARs as well as NTCP in the China treatment plan were significantly lower than those of RTOG.

CONCLUSION

It could be recommended to divide the hd-CTV into GTV and subclinical target volume and to prescribe different doses for the GTV and subclinical involvement in the IMRT plan of NPC.

Current Radiotherapy Considerations for Nasopharyngeal Carcinoma

Radiotherapy is the primary treatment modality for nasopharyngeal carcinoma (NPC). Successful curative treatment requires optimal radiotherapy planning and precise beam delivery that maximizes locoregional control while minimizing treatment-related side effects. In this article, we highlight considerations in target delineation, radiation dose, and the adoption of technological advances with the aim of optimizing the benefits of radiotherapy in NPC patients.

Is a high-risk clinical target volume required? Evaluation of the dosimetric feasibility based on T staging

Background

Clinical target delineation is a primary focus in the field of radiotherapy. This study aimed to investigate whether high-risk clinical target volume can be removed in nasopharyngeal carcinoma patients with different T stages.

Materials and methods

We designed a test plan without the high-risk clinical target volume for 111 nasopharyngeal carcinoma patients and further compared the test plans with the treatment plans in the parameters of planning target volumes and the radiation dose to normal organs.

Results

Our data showed that when high-risk clinical target volume was abnegated, target coverage, conformity indices, and homogeneity indices of planning target volumes and doses of normal organs were not influenced in the T4 nasopharyngeal carcinoma patients, and more than 95% of the high-risk planning target volume area could still be covered by the 60 Gy dose line. However, only some T1–3 patients achieved the ideal dose coverage, and even fewer after induction chemotherapy (62.8% vs. 41.2%, p = 0.018). Gross tumor volume was positively correlated with the target coverage of the original high-risk planning target volume in the test-plan (p = 0.0001). Gross tumor volume can be used to predict whether the target coverage of high-risk planning target volume is more than 95% (area under the curve = 0.868).

Conclusion

Omitting high risk clinical target volume can be considered in patients with T4 nasopharyngeal carcinoma according to physical evaluations. However, this approach is only suitable for a specific subset of T1–3 patients.

Influence of beamlet width on dynamic IMRT plan quality in nasopharyngeal carcinoma

Objective

This study aimed to identify the effects of beamlet width on dynamic intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) and determine the optimal parameters for the most effective radiotherapy plan.

Methods

This study evaluated 20 patients with NPC were selected for dynamic IMRT. Only the beamlet width in the optimization parameters was changed (set to 2, 4, 6, 8, and 10 mm that were named BL02, BL04, BL06, BL08, and BL10, respectively) to optimize the results of the five groups of plans. Using the plan quality scoring system, the dose results of the planning target volumes (PTVs) and organs at risks (OARs) were analyzed objectively and comprehensively. The lower the quality score, the better the quality of the plan. The efficiency and accuracy of plan execution were evaluated using monitor units (MUs) and plan delivery time (PDT).

Results

The BL04 mm group had the lowest quality score for the targets and OARs (0.087), while the BL10 mm group had the highest total score (1.249). The BL04 mm group had the highest MUs (837 MUs) and longest PDT (358 s). However, the MUs range of each group plan was below 100 MUs, and the PDT range was within 30 s. In the BL02, BL04, BL06, BL08, and BL10 plans, <5 MUs segments accounted for 33%, 16%, 24%, 33%, and 40% of total segments, respectively, with which the lowest was in the BL04 mm group.

Conclusion

Smaller beamlet widths have not only reduced OARs dose while maintaining high dose coverage to the PTVs, but also lead to more MUs that would produce greater PDT. Considering the quality and efficiency of dynamic IMRT, the beamlet width value of the Monaco treatment planning system set to 4 mm would be optimal for NPC.

Effect of Body Size Change on Off-Center Cervical Point and Face Doses in Patients Undergoing Nasopharyngeal Carcinoma Radiotherapy

Nasopharyngeal carcinoma (NPC) is a clinically multiple malignant tumor. At present, with the increase in the infection rate of Epstein-Barr virus, the incidence of nasopharyngeal carcinoma is also increasing day by day. To explore the effect of body size change on off-center cervical point and face doses in patients with nasopharyngeal carcinoma (NPC) undergoing radiotherapy, in total, 100 patients with NPC from January 2019 to May 2020 in our hospital were selected for retrospective analysis, and they all received intensity-modulated radiation therapy. Bodyweight, horizontal longitudinal diameter of the odontoid process, longitudinal diameter of the third cervical spine, maximum radiation dose, and average radiation dose of normal organs in the first and last treatments were assessed, and the correlation between normal organ irradiation dose and body size was analyzed. Bodyweight, horizontal longitudinal diameter of the odontoid process, and longitudinal diameter of the third cervical spine in the last treatment were lower than those in the first treatment, with a statistically significant difference. There was no statistically significant difference in the maximum normal organ irradiation dose to the left eyeball, right eyeball, left crystalline lens, right crystalline lens, and maximum irradiation dose to optic nerve between the last treatment and the first treatment. In the last treatment, the maximum dose to the left parotid gland, right parotid gland, spinal cord, and brain stem was higher than that in the first treatment. The average irradiation dose to the left eye bulb, right eye bulb, left lens, right lens, optic nerve in the last treatment, and that in the first treatment showed no significant difference. The average dose to the left parotid gland, right parotid gland, spinal cord, and brain stem in the last treatment was higher than that in the first treatment. The irradiation dose to the left parotid gland, right parotid gland, spinal cord, and brain stem was significantly negatively correlated with body weight, horizontal longitudinal diameter of the odontoid process, and longitudinal diameter of the third cervical spine. After NPC radiotherapy, the body size of patients can change, which can have different effects on irradiation doses. Therefore, the target area and dose should be corrected during treatment to ensure the efficacy and safety of the treatment.

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

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.

Locoregional Extension Patterns of Nasopharyngeal Carcinoma Detected by FDG PET/MR

Purpose

We sought to define the locoregional extension patterns of nasopharyngeal carcinomas (NPCs) by positron emission tomography (PET)/magnetic resonance imaging (MRI) and to improve clinical target volume (CTV) delineation.

Methods

Between May 2017 and March 2021, 331 consecutive patients with nonmetastatic NPCs who underwent pretreatment, simultaneous whole-body PET/MRI for staging were included in this study.

Results

The high-risk regions included the base of the sphenoid bone, the prestyloid compartment, prevertebral muscle, foramen lacerum, medial pterygoid plate, sphenoidal sinus, clivus, petrous apex, and foramen ovale. When the high-risk regions were invaded, the incidence rates of tumor invasion into the medium-risk regions increased. In contrast, when the high-risk regions were not involved, the incidence rates of tumor invasion into the medium-risk regions were mostly less than 10%, excluding the post-styloid compartment and oropharynx. According to the updated consensus guidelines of the neck node levels for head and neck tumors from 2013, level IIa (77.3%, 256/331), level IIb (75.8%, 251/331), and level VIIa (71.3%, 236/331) were the most frequently involved levels, followed by levels III (42.6%), Va (13.9%), IVa (8.8%), IVb (3.6%), Ib (3.6%), Vb (2.4%), VIIb (2.4%), VIII (1.8%), Vc (0.9%), and Xa (0.3%). Skip lymph node metastasis occurred in only 1.9% of patients.

Conclusions

For NPCs, primary disease and regional lymph node spread follow an orderly pattern, and a skip pattern of lymph node metastasis was unusual. Involved level radiotherapy might be feasible for cervical lymph node levels below the caudal border of cricoid cartilage and level VIIb.