Dosimetric benefit to organs at risk following margin reductions in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy

Genome-Wide Association Study of Susceptibility Loci for Radiation-Induced Brain Injury

BACKGROUND

Radiation-induced brain injury is a nonnegligible issue in the management of cancer patients treated by partial or whole brain irradiation. In particular, temporal lobe injury (TLI), a deleterious late complication in nasopharyngeal carcinoma, greatly affects the long-term life quality of these patients. Although genome-wide association studies (GWASs) have successfully identified single nucleotide polymorphisms (SNPs) associated with radiation toxicity, genetic variants contributing to the radiation-induced brain injury have not yet been assessed.

METHODS

We recruited and performed follow-up for a prospective observational cohort, Genetic Architecture of Radiotherapy Toxicity and Prognosis, using magnetic resonance imaging for TLI diagnosis. We conducted genome-wide association analysis in 1082 patients and validated the top associations in two independent cohorts of 1119 and 741 patients, respectively. All statistical tests were two-sided.

RESULTS

We identified a promoter variant rs17111237 (A > G, minor allele frequency [MAF] = 0.14) in CEP128 associated with TLI risk (hazard ratio = 1.45, 95% confidence interval = 1.26 to 1.66, Pcombined=3.18 × 10-7) which is in moderate linkage disequilibrium (LD) with rs162171 (MAF = 0.18, R2 = 0.69), the top signal in CEP128 (hazard ratio = 1.46, 95% confidence interval = 1.29-1.66, Pcombined= 6.17 × 10-9). Combining the clinical variables with the top SNP, we divided the patients into different subgroups with varying risk with 5-year TLI-free rates ranging from 33.7% to 95.5%. CEP128, a key component of mother centriole, tightly interacts with multiple radiation-resistant genes and plays an important role in maintaining the functional cilia, which otherwise will lead to a malfunction of the neural network. We found that A > G alteration at rs17111237 impaired the promoter activity of CEP128 and knockdown of CEP128 decreased the clonogenic cell survival of U87 cells under radiation. Noteworthy, 12.7% (27/212) of the GWAS-based associated genes (P < .001) were enriched in the neurogenesis pathway.

CONCLUSIONS

This three-stage study is the first GWAS of radiation-induced brain injury that implicates the genetic susceptibility gene CEP128 involved in TLI development and provides the novel insight into the underlying mechanisms of radiation-induced brain injury.

Evaluation of mixed energy partial arcs for volumetric modulated arc therapy for prostate cancer

PURPOSE

The purpose of this work was to investigate the dosimetric impact of mixed energy (6-MV, 15-MV) partial arcs (MEPAs) technique on prostate cancer VMAT plans.

METHODS

This work involved prostate only patients, planned with 79.2 Gy in 44 fractions to the planning target volume (PTV). Femoral heads, bladder, and rectum were considered organs at risk. This study was performed in two parts. For each of the 25 patients in Part 1, two single-energy single-arc plans, a 6 MV-SA plan and a 15 MV-SA plan, and a third MEPA plan involving composite of 6-MV anterior-posterior partial arcs and a 15-MV lateral partial arc weighted 1:2 were created. The dosimetric difference between MEPA(6/15 MV 1:2 weighted) and 6 MV-SA plans, and MEPA(6/15 MV 1:2 weighted) and 15 MV-SA plans were measured. In the Part 2 of this study, a second MEPAs plan (6 MV anterior-posterior arcs and 15 MV lateral arcs weighted 1:1), (MEPA 6/15 MV 1:1 weighted), was generated for 15 patients and compared only with two single-energy partial arcs plans, a 6 and a 15 MV-PA, to investigate the influence of the energy only. Dosimetric parameters of each structure, total monitor-units (MUs), homogeneity index (HI), and conformity number (CN) were analyzed.

RESULTS

In Part 1, no statistically significant differences were observed for mean dose to PTV and CN for MEPAs (6/15 MV 1:2 weighted) vs 6 and 15 MV-SA. MEPAs (6/15 MV 1:2 weighted) increased HI compared to 6 and 15 MV-SA (P < 0.0005; P < 0.0005). MEPAs (6/15 MV 1:2 weighted) produced significantly lower mean doses to rectum, bladder, and MUs/fraction, but higher mean doses to femoral heads, compared to 6 MV-SA (P < 0.0005) and 15 MV-SA (P < 0.0005). The results of Part 2 of this study showed that, in comparison to 6 and 15 MV-PA, MEPAs (6/15 MV 1:1 weighted) plans significantly improved CNs (P < 0.0005; P < 0.0005) and produced significantly lower mean doses to the rectum and bladder (P < 0.0005; P < 0.0005). While mean doses to the PTV and femoral heads of MEPAs (6/15 MV 1:1 weighted) plans were statistically comparable to 6 MV-PA (P > 0.05), MEPAs (6/15 MV 1:1 weighted) increased mean doses to left (P = 0.04) and right (P = 0.04) femoral heads compared to 15 MV-PA. MEPAs (6/15 MV 1:1 weighted) resulted in significantly lower total MUs compared to 6 MV-PA (P < 0.0005) and 15 MV-PA (P = 0.04).

CONCLUSION

The study for prostate radiotherapy demonstrated that a choice of MEPAs for VMAT has the potential to minimize doses to OARs and improve dose conformity to PTV, at the expense of a moderate increase in mean dose to the femoral heads.

Immobilization versus no immobilization for pelvic external beam radiotherapy

Aim

To identify the most reproducible technique of patient positioning and immobilization during pelvic radiotherapy.

Background

Radiotherapy plays an important role in the treatment of pelvic malignancies. Errors in positioning of patient are an integral component of treatment. The present study compares two methods of immobilization with no immobilization with an aim of identifying the most reproducible method.

Materials and methods

65 consecutive patients receiving pelvic external beam radiotherapy were retrospectively analyzed. 30, 21 and 14 patients were treated with no-immobilization with a leg separator, whole body vacuum bag cushion (VBC) and six point aquaplast immobilization system, respectively. The systematic error, random error and the planning target volume (PTV) margins were calculated for all the three techniques and statistically analyzed.

Results

The systematic errors were the highest in the VBC and random errors were the highest in the aquaplast group. Both systematic and random errors were the lowest in patients treated with no-immobilization. 3D Systematic error (mm, mean ± 1SD) was 4.31 ± 3.84, 3.39 ± 1.71 and 2.42 ± 0.97 for VBC, aquaplast and no-immobilization, respectively. 3D random error (mm, 1SD) was 2.96, 3.59 and 1.39 for VBC, aquaplast and no-immobilization, respectively. The differences were statistically significant between all the three groups. The calculated PTV margins were the smallest for the no-immobilization technique with 4.56, 4.69 and 4.59 mm, respectively, in x, y and z axes, respectively.

Conclusions

Among the three techniques, no-immobilization technique with leg separator was the most reproducible technique with the smallest PTV margins. For obvious reasons, this technique is the least time consuming and most economically viable in developing countries.

Lower limb immobilization device induced small setup errors in the radiotherapy

The aim of this study was to design a lower limb immobilization device and investigate its clinical application in the radiotherapy of the lower limbs.Around 38 patients who underwent lower limb radiotherapy using the designed immobilization device were included in this study. The setup errors were calculated by comparison of the portal images and the simulator films or digital reconstructed radiographs (DRRs).From all 38 patients accomplished the radiotherapy using this device, 178 anteroposterior portal images and 178 lateral portal images were used for the analysis of the positional accuracy. Significant differences were observed in the setup error of the head-foot direction compared with the left-right direction (t = 3.404, P = .002) and the anterior-posterior directions (t = 3.188, P = .003). No statistical differences were identified in the setup error in the left-right direction and anterior-posterior direction (t = 0.497, P = .622).The use of the in-house designed lower limb immobilization device allowed for relatively small setup errors. Furthermore, it showed satisfactory accuracy and repeatability.

Treatment Outcomes of 257 Patients with Locoregionally Advanced Nasopharyngeal Carcinoma Treated with Nimotuzumab Plus Intensity-Modulated Radiotherapy with or without Chemotherapy: A Single-Institution Experience

OBJECTIVES: To report the long-term outcome and toxicity of locoregionally advanced nasopharyngeal carcinoma (LA NPC) treated with nimotuzumab (h-R3) plus intensity-modulated radiotherapy (IMRT) with or without chemotherapy. METHODS: From May 2008 to March 2014, 3022 newly histology-proven, nonmetastatic NPC patients were retrospectively reviewed; among them, 257 patients treated with h-R3 were enrolled in this study. The patients' age range was between 10 and 76 years. The distribution of patients by disease stage was 150 (58.4%) in stage III, 88 (34.2%) in stage IV A, and 19 (7.4%) in stage IV B. All the patients received the treatment of h-R3 plus IMRT, and from them, 239 cases were also treated with cisplatin-based chemotherapy. Acute and late radiation-related toxicities were graded according to the Acute and Late Radiation Morbidity Scoring Criteria of Radiation Therapy Oncology Group. The accumulated survival was calculated according to the Kaplan-Meier method. Log-rank test was used to compare the survival difference. Multivariate analysis was performed using Cox's proportional-hazard model. RESULTS: All 257 patients had completed combined treatment; 231 patients received h-R3 plus IMRT with induction chemotherapy (IC), while 26 patients received only h-R3 plus IMRT. With a median follow-up of 48 months (range, 13-75 months), the estimated 5-year local recurrence-free survival, regional recurrence-free survival, distant metastases-free survival, progression-free survival, and overall survival (OS) rates were 94.3%, 94.8%, 91.9%, 83.4%, and 86.2%, respectively. Univariate analysis showed that age, T stage, clinical stage, and IC were related with OS. Multivariate analysis indicated that T stage and IC were independent prognostic factors for OS. The incidence of grade 3 to 4 acute mucositis and leukocytopenia was 10.9% and 19.8%, respectively, with no cases of skin rash and infusion reaction. Xerostomia was the most common late complication, and the degree of dry mouth in most survivors was mild to moderate at the last follow-up time. CONCLUSION: h-R3 plus IMRT with or without chemotherapy showed promising outcomes in terms of locoregional control and survival without increasing the incidence of radiation-related toxicities for patients.

A prospective study on radiation doses to organs at risk (OARs) during intensity-modulated radiotherapy for nasopharyngeal carcinoma patients

This study is to investigate the dose distribution of organs at risk (OARs) in cases of nasopharyngeal carcinoma (NPC). From July 2013 to October 2014, a prospective cohort study involving 148 patients was carried out at our center. OARs surrounding the nasopharynx were contoured on axial CT planning images in all patients. Dose-volume histograms of OARs and gross tumor volumes (GTV) were calculated. Multivariate analysis showed that radiation dose to OARs was associated with T stage and, especially, GTV. Seven OARs, including the spinal cord, eye and mandible, easily tolerated radiation doses in all patients; six OARs including the brain stem, chiasm and temporal lobe easily tolerated radiation doses in patients with a small GTV, but with difficulty when GTV was large; and other nine OARs including the parotid gland, cochlea and tympanic cavity met tolerance doses with difficulty in all patients. According to the patterns of radiation doses to OARs, it may help us to further reduce subsequent complications by improving the efficiency of plan optimization and evaluation.

Induction chemotherapy followed by intensity-modulated radiotherapy with reduced gross tumor volume delineation for stage T3-4 nasopharyngeal carcinoma

Purpose

A common problem in stage T3–4 nasopharyngeal carcinoma (NPC) is the narrow gap between the primary tumor and neurological structures, which makes dose optimization difficult. Considering that significant tumor shrinkage may occur during induction chemotherapy (IC), this study explored the efficacy of intensity-modulated radiotherapy (IMRT) using reduced gross tumor volume (GTV) in the treatment of T3–4 NPC.

Patients and methods

Between January 2009 and April 2014, 103 patients with non-metastatic stage T3–4 NPC were prospectively recruited. They were assigned to accept IC, followed by reduced-volume IMRT and adjuvant chemotherapy. GTV was based on the post-IC volume of intracavity tumors and lymph nodes, and the pre-IC volume of the remaining involved structures.

Results

For all treated patients, the 3-year local failure-free survival (LFFS) was 91.9%. After IC, 91 (88.3%) patients achieved local objective response (OR), and their 3-year LFFS rates were significantly better than in patients who failed to achieve local OR (94.1% vs 75.0%, P=0.023). A multivariate analysis demonstrated the prognostic value of tumor response to IC for LFFS. Dosimetric analysis showed good homogeneity, and the dose constraints were stringent. Asymptomatic temporal lobe necrosis in the ipsilateral side of tumor occurred in one patient.

Conclusion

IMRT using a reduced GTV delineation delivered satisfactory doses to the target volumes and avoided overdosing of critical neurological structures. Results showed satisfactory survival outcomes with few treatment-related toxicities. Tumor response to IC could facilitate selection of patients with stage T3–4 NPC eligible for treatment with this method.

A retrospective study comparing the outcomes and toxicities of intensity-modulated radiotherapy versus two-dimensional conventional radiotherapy for the treatment of children and adolescent nasopharyngeal carcinoma

Purpose

To compare the clinical outcomes and toxicities of two-dimensional conventional radiotherapy (2D-CRT) and intensity-modulated radiotherapy (IMRT) for the treatment of children and adolescent nasopharyngeal carcinoma (NPC).

Methods

A total of 176 children with non-metastatic NPC treated at Sun Yat-sen University Cancer Center between October 2003 and September 2013 were included in this study. Of the 176 patients, 74 received 2D-CRT and 102 were treated with IMRT. The clinical outcomes and acute and late toxicities were determined and compared.

Results

The IMRT group achieved significantly higher overall survival (OS) (90.4% vs. 76.1% at 5 year, P = 0.007) and disease-free survival (DFS) (85.7% vs. 71.2%, P = 0.029) mainly due to an improvement in locoregional relapse-free survival (LRRFS) (97.9 vs. 88.3%, P = 0.049). After stratification by disease stage, IMRT provided significant benefits for patients with stage III–IV disease in terms of OS, LRRFS and DFS. Multivariate analyses indicated that the treatment group (2D-CRT vs. IMRT) was a prognostic factor for OS, LRRFS and DFS. A significant reduction in Grade 2–4 xerostomia (52.7 vs. 34.3%, P = 0.015) and hearing loss (40.5 vs. 22.5%, P = 0.010) was observed in patients treated by IMRT.

Conclusion

IMRT provides better locoregional relapse-free survival and overall survival, especially in late-stage children and adolescent NPC patients, and is associated with a lower incidence of Grade 2–4 xerostomia as well as hearing loss compared with 2D-CRT. Distant metastasis remains a challenge in the treatment of children and adolescent NPC.

Reducing radiation-related morbidity in the treatment of nasopharyngeal carcinoma

While radiation therapy is the mainstay of treatment for nasopharyngeal carcinoma, the anatomic location of the nasopharynx in close proximity to radiation-sensitive organs such as the salivary glands, optic nerves and chiasm, cochlea, brainstem and temporal lobes presents a special challenge. Technological approaches to reducing the morbidity of nasopharyngeal cancer irradiation have been historically successful with the evolution from 2D techniques to increasingly conformal forms of radiation therapy. This report reviews normal tissue dose constraints and major considerations in target delineation for patients with nasopharyngeal cancer in the intensity-modulated radiation therapy era. Furthermore, this report discusses more contemporary approaches to toxicity reduction such as the judicious reduction or omission of radiation to low-risk regions and the potential role of particle beam therapy.

Recommendations for Updating T and N Staging Systems for Nasopharyngeal Carcinoma in the Era of Intensity-Modulated Radiotherapy

Objective

The aim of this study was to compare the 2008 Chinese and the 7^th edition of the American Joint Committee on Cancer (AJCC) staging systems for nasopharyngeal carcinoma and to provide proposals for updating T and N staging systems of the present staging system.

Methods

Between January 2007 and December 2012, a cohort of 752 patients with biopsy-proven, newly diagnosed, non-metastatic nasopharyngeal carcinoma who were treated with intensity-modulated radiotherapy were retrospectively analysed. Prognoses were compared by T stage, N stage, and clinical stage according to the two staging systems for overall survival (OS), local relapse-free survival (LRFS), and distant metastasis-free survival (DMFS).

Results

In terms of both the T and N staging systems, the two current staging systems were comparable in predicting OS. The T classification of the 2008 Chinese staging system was better in predicting LRFS, while the N classification of the 7th edition AJCC staging system was superior in predicting DMFS. In the modern era of intensity-modulated radiotherapy, the staging system should be updated by down-staging the current stage T2 to T1, and it might be rational to merge subcategories N1 and N2.

Conclusions

The two current staging systems each had advantages in predicting prognosis. It seems reasonable to downstage T2 to T1 and to merge N1 and N2.

Forty-six cases of nasopharyngeal carcinoma treated with 50 Gy radiotherapy plus hematoporphyrin derivative: 20 years of follow-up and outcomes from the Sun Yat-sen University Cancer Center

BACKGROUND

With the improved overall survival (OS) of nasopharyngeal carcinoma (NPC) patients, the importance of quality of life (QoL) is increasingly being recognized. For some radiosensitive NPC patients, whether low-dose radiotherapy can improve the QoL without affecting clinical efficacy is unknown. This study aimed to assess the survival rates and QoL of NPC patients treated with 50 Gy radiotherapy plus hematoporphyrin derivative (HPD).

METHODS

Forty-six newly diagnosed NPC patients treated with 50 Gy radiotherapy plus HPD between June 1988 and July 1992 were analyzed. All patients were restaged according to the 7th edition of the American Joint Committee on Cancer staging system. The radiotherapy plan was designed on the basis of pretreatment computed tomography. The OS, local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) rates were estimated using the Kaplan-Meier method. QoL was assessed using the Late Radiation Morbidity Scoring Criteria of the Radiation Therapy Oncology Group.

RESULTS

The 5-year OS, LRFS, DMFS, and DFS rates were 74.3%, 72.6%, 82.1%, and 61.2%, respectively. The corresponding 10-year rates were 38.4%, 62.9%, 78.5%, and 49.8%, respectively, and the 20-year rates were 27.7%, 51.4%, 78.5%, and 40.7%, respectively. None of the patients developed severe radiation-related complications, such as radiation-induced temporal lobe necrosis, hearing loss, trismus, and dysphagia.

CONCLUSION

Some NPC patients were sensitive to 50 Gy radiotherapy plus HPD, and this sensitivity was characterized by long-term survival without significant late treatment morbidities.