Intensity-modulated proton therapy versus helical tomotherapy in nasopharynx cancer: planning comparison and NTCP evaluation

Survival outcomes and toxicity profiles among patients with nonmetastatic nasopharyngeal carcinoma treated with intensity-modulated radiotherapy (IMRT) versus IMRT + carbon-ion radiotherapy: A propensity score-matched analysis

OBJECTIVES

To compare survival outcomes and toxic effects among patients with newly diagnosed nonmetastatic nasopharyngeal carcinoma (NPC) when treated with intensity-modulated radiotherapy (IMRT) versus IMRT + carbon-ion radiotherapy (CIRT).

METHODS

We performed a retrospective propensity score matching analysis (1:1) of patients treated with IMRT and IMRT + CIRT. Descriptive statistics were used to examine the baseline characteristics of the patients. Survival was estimated using the Kaplan-Meier method. Univariate and multivariable logistic regression analysis were used to identify the independent predictors of survival. We examined the association between risk factors and adverse events (AEs) using chi-square tests. Cox model and logistic regression were used to analyze AEs.

RESULTS

Hundred and nine patients who received IMRT + CIRT were included and the median follow-up time was 20.6 months (range: 4.6-82 months). There were no statistically significant differences in locoregional failure-free survival, distant metastasis-free survival, disease-free survival, or overall survival between the two groups, but potentially better in IMRT + CIRT group (p > 0.05, respectively). Nodal boost was the only significant factor associated with LRFS and DFS on multivariable analysis. Thirty-seven patients (34.0%) developed grade 3 acute OMs and no grade 4 acute OMs were observed in IMRT + CIRT group. All patients in IMRT + CIRT group developed grade 1 dermatitis; while in the match group, 76 patients developed grade 1 dermatitis, 27 patients developed grade 2 dermatitis, 5 patients developed grade 3 dermatitis, 1 patient developed grade 4 dermatitis. IMRT + CIRT treatment was associated with a significant trend of lower grades of OM and dermatitis (p < 0.05, respectively). Any severe (i.e., grade 3) chronic AEs, such as xerostomia, skin fibrosis, temporal lobe necrosis, osteoradionecrosis, or radiation-induced optic neuropathy, was not observed.

CONCLUSIONS

In this study, IMRT + CIRT was associated with significantly reduced acute toxicity burden compared with full course of IMRT, with excellent survival outcomes. Patients with persistent disease after treatment and treated with nodal boost had a worse outcome. More accurate assessments of IMRT + CIRT to primary nonmetastatic NPC patients will be imperative.

The top 100 most cited articles in helical tomotherapy: a scoping review

Objective

The purpose of this scoping review was to explore the top 100 most cited articles in helical tomotherapy (HT) through bibliometric analysis and visualization tools, help researchers comprehensively understand the research hotspots of HT, and provide clear and intuitive network visualization.

Methods

The Web of Science Core Collection and the search strategy of "Title (TI)=(tomotherapy)" were used to search for articles related to HT as of 27 May 2023. The top 100 most cited articles were obtained by sorting "citations: highest first". From these top 100 most cited articles, the following information was extracted: journals, years and months, countries, authors, types of tumor treated, and topics. The VOSviewer software was introduced for visualizing all the articles related to HT.

Results

The top 100 most cited articles in HT were published between 1999 and 2019. The citation counts of these articles ranges from 326 to 45, with a total of 8,422 citations at the time of searching. The index of citations per year (CPY) ranges from 22.32 to 2.45. These articles originated from 17 countries, with most publications from the United States (n=50), followed by Canada (n=12), Italy (n=10), Germany (n=7) and Belgium (n=5). The International Journal of Radiation Oncology, Biology, Physics published the highest number of articles (n=31), followed by Radiotherapy and Oncology (n=20), Medical Physics (n=13) and Strahlentherapie und Onkologie (n=12). In terms of specific tumor types, head and neck cancer (n=15) is the most common disease, followed by cancers with complex target structures (n=14), breast cancer (n=12), prostate cancer (n=10) and lung cancer (n=8). The most common research topics also include dosimetric comparison (n = 44), quality assurance (n = 12) and Megavoltage CT (n = 8).

Conclusion

This scoping review provides a comprehensive list of the 100 most cited articles in HT. This analysis offers valuable insights into the current research directions of HT that can be utilized by researchers, clinicians, and policy-makers.

Improving delivery efficiency using spots and energy layers reduction algorithms based on a large momentum acceptance beamline

BACKGROUND

Intensity-modulated proton therapy (IMPT) is a well-known delivery method of proton therapy. Besides higher plan quality, reducing the delivery time is also essential to IMPT plans. It can enhance patient comfort, reduce treatment costs, and improve delivery efficiency. From the perspective of treatment efficacy, it contributes to mitigating the intra-fractional motions and improving the accuracy of radiotherapy, especially for moving tumors.

PURPOSE

However, there is a tradeoff problem between the plan quality and delivery time. We consider the potential of a large momentum acceptance (LMA) beamline and apply the spots and energy layers reduction method to reduce the delivery time.

METHODS

The delivery time for each field consists of the energy layer switching time, spot traveling time, and dose delivery time. The larger momentum spread and higher intensity beam offered by the LMA beamline contribute to reducing the total delivery time compared to the conventional beamline. In addition to the dose fidelity term, an L1 and logarithm items were added to the objective function to increase the sparsity of the low-weighted spots and energy layers. After that, the low-weighted spots and layers were iteratively excluded in the reduced plan, which reduced the energy layer switching time and spot traveling time. We used the standard, reduced, and LMA-reduced plans to validate the proposed method and tested it on prostate and nasopharyngeal cases. Then, we compared and evaluated the plan quality, treatment time, and plan robustness against delivery uncertainty.

RESULTS

Compared with the standard plans, the number of spots in the LMA-reduced plans was on average reduced by 13 400 (95.6%) for prostate cases and by 48 300 (80.7%) for nasopharyngeal cases and the number of energy layers was on average reduced by 49 (61.3%) for prostate cases and by 97 (50.5%) for nasopharyngeal cases. And, the delivery time of the LMA-reduced plans was shortened from 34.5 to 8.6 s for prostate cases and from 163.8 to 53.6 s for nasopharyngeal cases. The LMA-reduced plans had comparable robustness to the spot monitor unit (MU) error compared with the standard plans, but the LMA-reduced plans became more sensitive to spot position uncertainty.

CONCLUSION

The delivery efficiency can be significantly improved using the LMA beamline and spots and energy layers reduction strategies. The method is promising to improve the efficiency of motion mitigation strategies for treating moving tumors.

18F-FMISO PET-guided dose escalation with multifield optimization intensity-modulated proton therapy in nasopharyngeal carcinoma

PURPOSE

The purpose of this study was to evaluate the radiotherapy planning feasibility of dose escalation with intensity-modulated proton therapy (IMPT) to hypoxic tumor regions identified on 18F-Fluoromisonidazole (FMISO) positron emission tomography and computed tomography (PET-CT) in NPC.

MATERIALS AND METHODS

Nine patients with stages T3-4N0-3M0 NPC underwent 18F-FMISO PET-CT before and during week 3 of radiotherapy. The hypoxic volume (GTVhypo) is automatically generated by applying a subthresholding algorithm within the gross tumor volume (GTV) with a tumor to muscle standardized uptake value (SUV) ratio of 1.3 on the 18F-FMISO PET-CT scan. Two proton plans were generated for each patient, a standard plan to 70 Gy and dose escalation plan with upfront boost followed by standard 70GyE plan. The stereotactic boost was planned with single-field uniform dose optimization using two fields to deliver 10 GyE in two fractions to GTVhypo. The standard plan was generated with IMPT with robust optimization to deliver 70GyE, 60GyE in 33 fractions using simultaneous integrated boost technique. A plan sum was generated for assessment.

RESULTS

Eight of nine patients showed tumor hypoxia on the baseline 18F-FMISO PET-CT scan. The mean hypoxic tumor volume was 3.9 cm³ (range .9-11.9cm³ ). The average SUVmax of the hypoxic volume was 2.2 (range 1.44-2.98). All the dose-volume parameters met the planning objectives for target coverage. Dose escalation was not feasible in three of eight patients as the D0.03cc of temporal lobe was greater than 75GyE.

CONCLUSIONS

The utility of boost to the hypoxic volume before standard course of radiotherapy with IMPT is dosimetrically feasible in selected patients. Clinical trials are warranted to determine the clinical outcomes of this approach.

Proton therapy and/or helical tomotherapy for locally advanced sinonasal skull base adenoid cystic carcinoma: Focus on experience of the Institut Curie and review of literature

BACKGROUND

Sinonasal adenoid cystic carcinomas (SNACC) have high propensity for skull base (SB) infiltration. Unresectability or incomplete surgical resection in such cases make radiotherapy treatment paramount. Curative dose escalation is challenging because of adjacent organs at risk, especially in locally advanced cases.

METHODS

Eighteen patients that had locally advanced SB SNACC with unresectable or incomplete surgical resection treated by proton therapy and/or helical tomotherapy at Institut Curie between 3/2010 and 8/2020 were retrospectively included.

RESULTS

After median follow-up of 52 months, 5-year OS, LRRFS, DMFS, DFS rates were, respectively, 47% (95%CI: 26-83), 50% (95%CI: 36-88), 39% (95%CI: 26-81), 33% (95%CI: 22-73). One patient had grade 4 late optic nerve disorder. Eight patients had grade 3 late toxicity including mainly hearing impairments.

CONCLUSION

Proton therapy and helical tomotherapy are effective and safe methods for curative dose escalation of locally advanced SB SNACC, which are a poor prognosis subgroup. Available literature suggests carbon-ion therapy could be an efficient alternative.

External validation of an 18F-FDG-PET radiomic model predicting survival after radiotherapy for oropharyngeal cancer

PURPOSE/OBJECTIVE

The purpose of the study is to externally validate published ¹⁸F-FDG-PET radiomic models for outcome prediction in patients with oropharyngeal cancer treated with chemoradiotherapy.

MATERIAL/METHODS

Outcome data and pre-radiotherapy PET images of 100 oropharyngeal cancer patients (stage IV:78) treated with concomitant chemotherapy to 66-69 Gy/30 fr were available. Tumors were segmented using a previously validated semi-automatic method; 450 radiomic features (RF) were extracted according to IBSI (Image Biomarker Standardization Initiative) guidelines. Only one model for cancer-specific survival (CSS) prediction was suitable to be independently tested, according to our criteria. This model, in addition to HPV status, SUVmean and SUVmax, included two independent meta-factors (F_i), resulting from combining selected RF clusters. In a subgroup of 66 patients with complete HPV information, the global risk score R was computed considering the original coefficients and was tested by Cox regression as predictive of CSS. Independently, only the radiomic risk score R_F derived from F_i was tested on the same subgroup to learn about the radiomics contribution to the model. The metabolic tumor volume (MTV) was also tested as a single predictor and its prediction performances were compared to the global and radiomic models. Finally, the validation of MTV and the radiomic score R_F were also tested on the entire dataset.

RESULTS

Regarding the analysis of the subgroup with HPV information, with a median follow-up of 41.6 months, seven patients died due to cancer. R was confirmed to be associated to CSS (p value = 0.05) with a C-index equal 0.75 (95% CI=0.62-0.85). The best cut-off value (equal to 0.15) showed high ability in patient stratification (p=0.01, HR=7.4, 95% CI=1.6-11.4). The 5-year CSS for R were 97% (95% CI: 93-100%) vs 74% (56-92%) for low- and high-risk groups, respectively. R_F and MTV alone were also significantly associated to CSS for the subgroup with an almost identical C-index. According to best cut-off value (R_F>0.12 and MTV>15.5cc), the 5-year CSS were 96% (95% CI: 89-100%) vs 65% (36-94%) and 97% (95% CI: 88-100%) vs 77% (58-93%) for RF and MTV, respectively. Results regarding RF and MTV were confirmed in the overall group.

CONCLUSION

A previously published PET radiomic model for CSS prediction was independently validated. Performances of the model were similar to the ones of using only the MTV, without improvement of prediction accuracy.

Interobserver Variability Prediction of Primary Gross Tumor in a Patient with Non-Small Cell Lung Cancer

This research addresses the problem of interobserver variability (IOV), in which different oncologists manually delineate varying primary gross tumor volume (pGTV) contours, adding risk to targeted radiation treatments. Thus, a method of IOV reduction is urgently needed. Hypothesizing that the radiation oncologist’s IOV may shrink with the aid of IOV maps, we propose IOV prediction network (IOV-Net), a deep-learning model that uses the fuzzy membership function to produce high-quality maps based on computed tomography (CT) images. To test the prediction accuracy, a ground-truth pGTV IOV map was created using the manual contour delineations of radiation therapy structures provided by five expert oncologists. Then, we tasked IOV-Net with producing a map of its own. The mean squared error (prediction vs. ground truth) and its standard deviation were 0.0038 and 0.0005, respectively. To test the clinical feasibility of our method, CT images were divided into two groups, and oncologists from our institution created manual contours with and without IOV map guidance. The Dice similarity coefficient and Jaccard index increased by ~6 and 7%, respectively, and the Hausdorff distance decreased by 2.5 mm, indicating a statistically significant IOV reduction (p < 0.05). Hence, IOV-net and its resultant IOV maps have the potential to improve radiation therapy efficacy worldwide.

Acute toxicity in patients treated with concurrent chemoradiotherapy with proton versus intensity-modulated radiation therapy for nonmetastatic head and neck cancers

BACKGROUND

We evaluated if proton therapy is associated with decreased acute toxicities compared to intensity-modulated radiation therapy (IMRT) in patients receiving concurrent chemoradiotherapy for head and neck cancers.

METHODS

We analyzed 580 patients with nonmetastatic head and neck cancers. Primary endpoint was any 90-day grade ≥3 toxicity, prospectively collected and graded per CTCAEv4. Modified Poisson regression models were used.

RESULTS

Ninety-five patients received proton and 485 IMRT. The proton group had more HPV-positive tumors (65.6 vs. 58.0%, p = 0.049), postoperative treatment (76.8 vs. 62.1%, p = 0.008), unilateral neck treatment (18.9 vs. 6.6%, p < 0.001) and significantly lower doses to organs-at-risk compared to IMRT group. Adjusted for patient and treatment characteristics, the proton group had decreased grade 2 dysgeusia (RR0.67, 95%CI 0.53-0.84, p = 0.004) and a trend toward lower grade ≥3 toxicities (RR0.60, 95%CI 0.41-0.88, p = 0.06).

CONCLUSIONS

Proton therapy was associated with significantly reduced grade 2 dysgeusia and nonstatistically significant decrease in acute grade ≥3 toxicities compared to IMRT.

Proton Therapy for Squamous Cell Carcinoma of the Head and Neck: Early Clinical Experience and Current Challenges

Simple Summary

Proton therapy is a promising type of radiation therapy used to destroy tumor cells. It has the potential to further improve the outcomes for patients with head and neck cancer since it allows to minimize the radiation dose to vital structures around the tumor, leading to less toxicity. This paper describes the current experience worldwide with proton therapy in head and neck cancer.

Abstract

Proton therapy (PT) is a promising development in radiation oncology, with the potential to further improve outcomes for patients with squamous cell carcinoma of the head and neck (HNSCC). By utilizing the finite range of protons, healthy tissue can be spared from beam exit doses that would otherwise be irradiated with photon-based treatments. Current evidence on PT for HNSCC is limited to comparative dosimetric analyses and retrospective single-institution series. As a consequence, the recognized indications for the reimbursement of PT remain scarce in most countries. Nevertheless, approximately 100 PT centers are in operation worldwide, and initial experiences for HNSCC are being reported. This review aims to summarize the results of the early clinical experience with PT for HNSCC and the challenges that are currently faced.

Proton Radiation Therapy for Nasopharyngeal Cancer Patients: Dosimetric and NTCP Evaluation Supporting Clinical Decision

(1) Background: we proposed an integrated strategy to support clinical allocation of nasopharyngeal patients between proton and photon radiotherapy. (2) Methods: intensity-modulated proton therapy (IMPT) plans were optimized for 50 consecutive nasopharyngeal carcinoma (NPC) patients treated with volumetric modulated arc therapy (VMAT), and differences in dose and normal tissue complication probability (ΔNTCPx-p) for 16 models were calculated. Patient eligibility for IMPT was assessed using a model-based selection (MBS) strategy following the results for 7/16 models describing the most clinically relevant endpoints, applying a model-specific ΔNTCPx-p threshold (15% to 5% depending on the severity of the complication) and a composite threshold (35%). In addition, a comprehensive toxicity score (CTS) was defined as the weighted sum of all 16 ΔNTCPx-p, where weights follow a clinical rationale. (3) Results: Dose deviations were in favor of IMPT (ΔD_mean ≥ 14% for cord, esophagus, brainstem, and glottic larynx). The risk of toxicity significantly decreased for xerostomia (-12.5%), brain necrosis (-2.3%), mucositis (-3.2%), tinnitus (-8.6%), hypothyroidism (-9.3%), and trismus (-5.4%). There were 40% of the patients that resulted as eligible for IMPT, with a greater advantage for T3-T4 staging. Significantly different CTS were observed in patients qualifying for IMPT. (4) Conclusions: The MBS strategy successfully drives the clinical identification of NPC patients, who are most likely to benefit from IMPT. CTS summarizes well the expected global gain.

Intensity-modulated proton radiation therapy as a radical treatment modality for nasopharyngeal carcinoma in China: A cost-effectiveness analysis

BACKGROUND

Compared to conventional intensity-modulated photon radiation therapy (IMRT), intensity-modulated proton radiation therapy (IMPT) has potential to reduce irradiation-induced late toxicities while maintaining excellent tumor control in patients with nasopharyngeal carcinoma (NPC). However, the relevant cost-effectiveness remains controversial.

METHODS

A Markov decision tree analysis was performed under the assumption that IMPT offered normal tissue complication probability reduction (NTCP reduction) in long-term dysphagia, xerostomia, and hearing loss, compared to IMRT. Base-case evaluation was performed on T2N2M0 NPC of median age (43 years old). A Chinese societal willingness-to-pay threshold (33558 US dollars [$])/quality-adjusted life-year [QALY]) was adopted.

RESULTS

For patients at median age and having NTCP reduction of 10%, 20%, 30%, 40%, 50%, and 60%, their incremental cost-effectiveness ratios were $102684.0/QALY, $43161.2/QALY, $24134.7/QALY, $13991.6/QALY, $8259.8/QALY, and $4436.1/QALY, respectively; IMPT should provide an NTCP reduction of ≥24% to be considered cost-effective.

CONCLUSIONS

IMPT has potential to be cost-effective for average Chinese NPC patients and should be validated clinically.

Intensity-Modulated Proton Therapy for Nasopharynx Cancer: 2-year Outcomes from a Single Institution

Purpose

Advances in radiotherapy have improved tumor control and reduced toxicity in the management of nasopharyngeal carcinoma (NPC). Local failure remains a problem for some patients with advanced primary tumors, and toxicities are significant given the large treatment volume and tumor proximity to critical structures, even with modern photon-based radiotherapy. Proton therapy has unique dosimetric advantages, and recent technological advances now allow delivery of intensity-modulated proton therapy (IMPT), which can potentially improve the therapeutic ratio in NPC. We report our 2-year clinical outcomes with IMPT for NPC.

Materials and Methods

We retrospectively reviewed treatment records of patients with NPC treated with IMPT at our center. Demographics, dosimetry, tumor response, local regional control (LRC), distant metastasis, overall survival, and acute and late toxicity outcomes were reviewed. Analyses were performed with descriptive statistics and Kaplan-Meier method. Toxicity was graded per Common Terminology Criteria for Adverse Events (version 4.0).

Results

Twenty-six patients were treated from 2015 to 2020. Median age was 48 years (range, 19–73 years), 62% (n = 16) had T3-T4 disease, 92% (n = 24) were node positive, 92% (n = 24) had stage III-IV disease, and 69% (n = 18) had positive results for Epstein-Barr virus. Dose-painted pencil-beam IMPT was used. Most patients (85%; 22 of 26) were treated with 70 Gy(RBE) in 33 fractions once daily; 4 (15%) underwent hyperfractionated accelerated treatment twice daily. All received concurrent cisplatin chemotherapy; 7 (27%) also received induction chemotherapy. All patients (100%) completed the planned radiotherapy, and no acute or late grade 4 or 5 toxicities were observed. At median follow-up of 25 months (range, 4-60), there were 2 local regional failures (8%) and 3 distant metastases (12%). The Kaplan-Meier 2-year LRC, freedom from distant metastasis, and overall survival were 92%, 87%, and 85% respectively.

Conclusion

IMPT is feasible in locally advanced NPC with early outcomes demonstrating excellent LRC and favorable toxicity profile. Our data add to the growing body of evidence supporting the clinical use of IMPT for NPC.

Pediatric Craniospinal Irradiation - The implementation and Use of Normal Tissue Complication Probability in Comparing Photon versus Proton Planning

Purpose:

The preferred radiotherapy treatment for medulloblastoma is craniospinal irradiation (CSI). With the aim of developing the potential to reduce normal tissue dose and associated post-treatment complications with photon and proton radiotherapy techniques for CSI. This report aims to carefully compare and rank treatment planning and dosimetric outcomes for pediatric medulloblastoma patients using normal tissue complication probability (NTCP) formalism between photon (three-dimensional conformal radiotherapy, intensity-modulated radiotherapy [IMRT], volumetric-modulated arc therapy [VMAT], and HT) and proton CSI.

Methods and Materials:

The treatment data of eight pediatric patients who typically received CSI treatment were used in this study. The patients were 7 years of age on average, with ages ranging from 3 to 11 years. A prescription dose of 3600 cGy was delivered in 20 fractions by the established planning methods. The Niemierko's and Lyman–Kutcher–Burman models were followed to carefully estimate NTCP and compare different treatment plans.

Results:

The NTCP of VMAT plans in upper and middle thoracic volumes was relatively high compared to helical tomotherapy (HT) and pencil beam scanning (PBS) (all P < 0.05). PBS rather than IMRT and VMAT in the middle thoracic region (P < 0.06) could significantly reduce the NTCP of the heart. PBS significantly reduced NTCP of the lungs and liver (all P < 0.05).

Conclusion:

The NTCP and tumor control probability (TCP) model-based plan ranking along with dosimetric indices will help the clinical practitioner or medical physicists to choose the best treatment plan for each patient based on their anatomical or clinical challenges.

Dosimetric comparison of intensity modulated radiotherapy and intensity modulated proton therapy in the treatment of recurrent nasopharyngeal carcinoma

BACKGROUND AND PURPOSE

To compare the dosimetric performance of Intensity Modulated Proton Therapy (IMPT) and Intensity Modulated Radiotherapy (IMRT) in terms of target volume coverage and sparing of neurological organs-at-risk (OARs) in salvaging recurrent nasopharyngeal carcinoma (rNPC). The maximum dose to the internal carotid artery (ICA) and nasopharyngeal (NP) mucosa, which are associated with potential carotid blowout and massive epistaxis, were also evaluated.

MATERIALS AND METHODS

IMRT and IMPT treatment plans were created for twenty patients with locally advanced rNPC. Planning Target Volume (PTV) was used to account for the setup and spatial error/uncertainty in the IMRT planning. Robust optimization on Clinical Target Volume (CTV) coverage with consideration of range and setup uncertainty was employed to produce two IMPT plans with 3-field and 4-field arrangements. The planning objective was to deliver 60 Gy to the PTV (IMRT) and CTV (IMPT) without exceeding the maximum lifetime cumulative Biologically Effective Dose (BED) of the neurological OARs (applied to the Planning organs-at-risk volume). The target dose coverage as well as the maximum dose to the neurological OARs, ICA, and NP mucosa were compared.

RESULTS

Compared with IMRT, 3-field IMPT achieved better coverage to GTV V100% (83.3% vs. 73.2%, P <0.01) and CTV V100% (80.5% vs. 72.4%, P <0.01), and lower maximum dose to the critical OARs including the spinal cord (19.2 Gy vs. 22.3 Gy, P <0.01), brainstem (30.0 Gy vs. 32.3 Gy, P <0.01) and optic chiasm (6.6 Gy vs. 9.8 Gy, P <0.01). The additional beam with the 4-fields IMPT plans further improved the target coverage from the 3-field IMPT (CTV V98%: 85.3% vs. 82.4%, P <0.01) with similar OAR sparing. However, the target dose was highly non-uniform with both IMPT plans, leading to a significantly higher maximum dose to the ICA (∼68 Gy vs. 62.6 Gy, P <0.01) and NP mucosa (∼72 Gy vs. 62.8 Gy, P <0.01) than IMRT.

CONCLUSION

IMPT demonstrated some dosimetric advantage over IMRT in treating rNPC. However, IMPT could also result in very high dose hot spots in the target volume. Careful consideration of the ICA and NP mucosal complications is recommended when applying IMPT on rNPC patients.

Intensity Modulated Proton Beam Therapy versus Volumetric Modulated Arc Therapy for Patients with Nasopharyngeal Cancer: A Propensity Score-Matched Study

(1) Background: We compared the outcomes of patients with nasopharyngeal carcinoma treated with IMPT and VMAT. (2) Methods: We performed a retrospective propensity score matching analysis (1:1) of patients treated with IMPT (years: 2016-2018) and VMAT (2014-2018). Survival was estimated using the Kaplan-Meier method. Multivariate Cox proportional hazards regression analysis was used to identify the independent predictors of survival. Binary toxicity endpoint analyses were performed using a Cox model and logistic regression. (3) Results: Eighty patients who received IMPT and VMAT were included. The median follow-up time was 24.1 months in the IMPT group. Progression-free survival (PFS) and overall survival (OS) were not statistically different between the two groups but potentially better in IMPT group. In multivariate analysis, advanced N-stage and body weight loss (BWL; >7%) during radiotherapy were associated with decreased PFS. The IMPT group had significantly less requirement for nasogastric (NG) tube placement and BWL during treatment. The mean oral cavity dose was the only predictive factor in stepwise regression analysis, and IMPT required a significantly lower mean dose. However, IMPT increased the grade 3 radiation dermatitis. (4) Conclusions: IMPT is associated with reduced rates of NG tube insertion and BWL through reducing oral mean dose, potentially producing better oncologic outcomes.

PTCOG Head and Neck Subcommittee Consensus Guidelines on Particle Therapy for the Management of Head and Neck Tumors

Purpose

Radiation therapy is a standard modality in the treatment for cancers of the head and neck, but is associated with significant short- and long-term side effects. Proton therapy, with its unique physical characteristics, can deliver less dose to normal tissues, resulting in fewer side effects. Proton therapy is currently being used for the treatment of head and neck cancer, with increasing clinical evidence supporting its use. However, barriers to wider adoption include access, cost, and the need for higher-level evidence.

Methods

The clinical evidence for the use of proton therapy in the treatment of head and neck cancer are reviewed here, including indications, advantages, and challenges.

Results

The Particle Therapy Cooperative Group Head and Neck Subcommittee task group provides consensus guidelines for the use of proton therapy for head and neck cancer.

Conclusion

This report can be used as a guide for clinical use, to understand clinical trials, and to inform future research efforts.

A Systematic Review of Proton Therapy for the Management of Nasopharyngeal Cancer

Purpose

With improved technology, more patients with nasopharyngeal cancer (NPC) are receiving definitive treatment with proton therapy, which allows greater sparing of dose to normal tissues without compromising efficacy. As there is no randomized data, the purpose of this study was to systematically review the available literature on proton therapy in this setting, focusing on the toxicity endpoints.

Materials and Methods

A systematic search using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines was conducted in 5 databases: PubMed, Embase, SCOPUS, Web of Science, and the Cochrane Central Register of Controlled Trials. A total of 491 studies were found on the topic of NPC and proton therapy. Following independent study selection by 2 investigators, 9 studies were found to have sufficient focus and relevance to be incorporated into the systematic review.

Results

All 9 studies were retrospective and examined only NPC patients except for one that also included paranasal sinus cancer. One study was a reirradiation study. Four studies used 3D or double scatter technique, while all others used intensity-modulated proton therapy. Oncologic outcomes were similar to intensity-modulated radiation therapy (IMRT) rates, with 2-year local and regional progression-free survival (LRFS) ranging from 84% to 100%, 2-year progression-free survival (PFS) ranging from 75% to 88.9%, and 2-year overall survival (OS) ranging from 88% to 95% in the up-front setting. Four comparison studies with IMRT found significantly lower feeding tube rates (20% versus 65%, P = .015; and 14% versus 85%, P < .001) with proton therapy as well as lower mucositis (G2 46% versus 70%, P = .019; and G3 11% versus 76%, P = .0002). All other acute and late effects were largely improved with proton therapy but not statistically significant.

Conclusions

NPC patients receiving proton therapy maintain good outcomes with improved toxicity profile, likely due to sparing of dose to normal structures. Prospective studies are ongoing to better quantify the magnitude.

Nasopharyngeal carcinoma in children and adolescents: The EXPeRT/PARTNER diagnostic and therapeutic recommendations

Nasopharyngeal carcinoma (NPC) is a rare pediatric tumor. Collaborative studies performed over the last decades showed improved results compared to historical data, but standardized guidelines for diagnosis and management of pediatric NPC are still unavailable. This study presents a European consensus guideline for the diagnosis and treatment of pediatric NPC developed by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT). Main recommendations include induction chemotherapy with cisplatin and 5-flurouracil, concomitant chemoradiotherapy in advanced disease, and to consider maintenance treatment with interferon beta (IFN-β) for selected high-risk patients. Dose adjustments of radiotherapy based on response to induction chemotherapy may decrease the rates of long-term treatment-related complications that affect most of the survivors.

Intensity-modulated proton therapy for oropharyngeal cancer reduces rates of late xerostomia

BACKGROUND AND PURPOSE

To determine rates of xerostomia after intensity-modulated radiotherapy (IMRT) or intensity-modulated proton therapy (IMPT) for oropharyngeal cancer (OPC) and identify dosimetric factors associated with xerostomia risk.

MATERIALS AND METHODS

Patients with OPC who received IMRT (n = 429) or IMPT (n = 103) from January 2011 through June 2015 at a single institution were studied retrospectively. Every 3 months after treatment, each patient completed an eight-item self-reported xerostomia-specific questionnaire (XQ; summary XQ score, 0-100). An XQ score of 50 was selected as the demarcation value for moderate-severe (XQs ≥ 50) and no-mild (XQs < 50) xerostomia. The mean doses and percent volumes of organs at risk receiving various doses (V5-V70) were extracted from the initial treatment plans. The dosimetric variables and xerostomia risk were compared using an independent-sample t-test or chi-square test.

RESULTS

The median follow-up time was 36.2 months. The proportions of patients with moderate-severe xerostomia were similar in the two treatment groups up to 18 months after treatment. However, moderate-severe xerostomia was less common in the IMPT group than in the IMRT group at 18-24 months (6% vs. 20%; p = 0.025) and 24-36 months (6% vs. 20%; p = 0.01). During the late xerostomia period (24-36 months), high dose/volume exposures (V25-V70) in the oral cavity were associated with high proportions of patients with moderate-severe xerostomia (all p < 0.05), but dosimetric variables regarding the salivary glands were not associated with late xerostomia.

CONCLUSION

IMPT was associated with less late xerostomia than was IMRT in OPC patients. Oral cavity dosimetric variables were related to the occurrence of late xerostomia.

Patient-Derived Nasopharyngeal Cancer Organoids for Disease Modeling and Radiation Dose Optimization

Effective radiation treatment (RT) for recurrent nasopharyngeal cancers (NPC), featuring an intrinsic hypoxic sub-volume, remains a clinical challenge. Lack of disease‐specific in-vitro models of NPC, together with difficulties in establishing patient derived xenograft (PDX) models, have further hindered development of personalized therapeutic options. Herein, we established two NPC organoid lines from recurrent NPC PDX models and further characterized and compared these models with original patient tumors using RNA sequencing analysis. Organoids were cultured in hypoxic conditions to examine the effects of hypoxia and radioresistance. These models were then utilized to determine the radiobiological parameters, such as α/β ratio and oxygen enhancement ratio (OER), characteristic to radiosensitive normoxic and radioresistant hypoxic NPC, using simple dose-survival data analytic tools. The results were further validated in-vitro and in-vivo, to determine the optimal boost dose and fractionation regimen required to achieve effective NPC tumor regression. Despite the differences in tumor microenvironment due to the lack of human stroma, RNA sequencing analysis revealed good correlation of NPC PDX and organoid models with patient tumors. Additionally, the established models also mimicked inter-tumoral heterogeneity. Hypoxic NPC organoids were highly radioresistant and had high α/β ratio compared to its normoxic counterparts. In-vitro and in-vivo fractionation studies showed that hypoxic NPC was less sensitive to RT fractionation scheme and required a large bolus dose or 1.4 times of the fractionated dose that was effective against normoxic cells in order to compensate for oxygen deficiency. This study is the first direct experimental evidence to predict optimal RT boost dose required to cause sufficient damage to recurrent hypoxic NPC tumor cells, which can be further used to develop dose-painting algorithms in clinical practice.

Potential benefits of adaptive intensity-modulated proton therapy in nasopharyngeal carcinomas

Purpose

To investigate potential advantages of adaptive intensity‐modulated proton beam therapy (A‐IMPT) by comparing it to adaptive intensity‐modulated X‐ray therapy (A‐IMXT) for nasopharyngeal carcinomas (NPC).

Methods

Ten patients with NPC treated with A‐IMXT (step and shoot approach) and concomitant chemotherapy between 2014 and 2016 were selected. In the actual treatment, 46 Gy in 23 fractions (46Gy/23Fx.) was prescribed using the initial plan and 24Gy/12Fx was prescribed using an adapted plan thereafter. New treatment planning of A‐IMPT was made for the same patients using equivalent dose fractionation schedule and dose constraints. The dose volume statistics based on deformable images and dose accumulation was used in the comparison of A‐IMXT with A‐IMPT.

Results

The means of the D_mean of the right parotid gland (P < 0.001), right TM joint (P < 0.001), left TM joint (P < 0.001), oral cavity (P < 0.001), supraglottic larynx (P = 0.001), glottic larynx (P < 0.001), , middle PCM (P = 0.0371), interior PCM (P < 0.001), cricopharyngeal muscle (P = 0.03643), and thyroid gland (P = 0.00216), in A‐IMPT are lower than those of A‐IMXT, with statistical significance. The means of, D_0.03cc, and D_mean of each sub portion of auditory apparatus and D_30% for Eustachian tube and D_0.5cc for mastoid volume in A‐IMPT are significantly lower than those of A‐IMXT. The mean doses to the oral cavity, supraglottic larynx, and glottic larynx were all reduced by more than 20 Gy (RBE = 1.1).

Conclusions

An adaptive approach is suggested to enhance the potential benefit of IMPT compared to IMXT to reduce adverse effects for patients with NPC.

Comparative evaluation of treatment plan quality for a prototype biology-guided radiotherapy system in the treatment of nasopharyngeal carcinoma

We aimed to compare prototype treatment plans for a new biology-guided radiotherapy (BgRT) machine in its intensity-modulated radiation therapy (IMRT) mode with those using existing IMRT delivery techniques in treatment of nasopharyngeal carcinoma (NPC). We retrospectively selected ten previous NPC patients treated in 33 fractions according to the NRG-HN001 treatment protocol. Three treatment plans were generated for each patient: a helical tomotherapy (HT) plan with a 2.5-cm jaw, a volumetric modulated arc therapy (VMAT) plan using 2 to 4 6-MV arc fields, and a prototype IMRT plan for a new BgRT system which uses a 6-MV photon beam on a ring gantry that rotates at 60 rotations per minute with a couch that moves in small incremental steps. Treatment plans were compared using dosimetric parameters to planning target volumes (PTVs) and organs at risk (OARs) as specified by the NRG-HN001 protocol. Plans for the three modalities had comparable dose coverage, mean dose, and dose heterogeneity to the primary PTV, while the prototype IMRT plans had greater dose heterogeneity to the non-primary PTVs, with the average homogeneity index ranging from 1.28 to 1.50 in the prototype plans. Six of all the 7 OAR mean dose parameters were lower with statistical significance in the prototype plans compared to the HT and VMAT plans with the other mean dose parameter being comparable, and all the 18 OAR maximum dose parameters were comparable or lower with statistical significance in the prototype plans. The average left and right parotid mean doses in the prototype plans were 10.5 Gy and 10.4 Gy lower than those in the HT plans, respectively, and were 5.1 Gy and 5.2 Gy lower than those in the VMAT plans, respectively. Compared to that with the HT and VMAT plans, the treatment time was longer with statistical significance with the prototype IMRT plans. Based on dosimetric comparison of ten NPC cases, the prototype IMRT plans achieved comparable or better critical organ sparing compared to the HT and VMAT plans for definitive NPC radiotherapy. However, there was higher dose heterogeneity to non-primary targets and longer estimated treatment time with the prototype plans.

Salivary Gland Hypofunction and Xerostomia in Head and Neck Radiation Patients

BACKGROUND

The most manifest long-term consequences of radiation therapy in the head and neck cancer patient are salivary gland hypofunction and a sensation of oral dryness (xerostomia).

METHODS

This critical review addresses the consequences of radiation injury to salivary gland tissue, the clinical management of salivary gland hypofunction and xerostomia, and current and potential strategies to prevent or reduce radiation injury to salivary gland tissue or restore the function of radiation-injured salivary gland tissue.

RESULTS

Salivary gland hypofunction and xerostomia have severe implications for oral functioning, maintenance of oral and general health, and quality of life. Significant progress has been made to spare salivary gland function chiefly due to advances in radiation techniques. Other strategies have also been developed, e.g., radioprotectors, identification and preservation/expansion of salivary stem cells by stimulation with cholinergic muscarinic agonists, and application of new lubricating or stimulatory agents, surgical transfer of submandibular glands, and acupuncture.

CONCLUSION

Many advances to manage salivary gland hypofunction and xerostomia induced by radiation therapy still only offer partial protection since they are often of short duration, lack the protective effects of saliva, or potentially have significant adverse effects. Intensity-modulated radiation therapy (IMRT), and its next step, proton therapy, have the greatest potential as a management strategy for permanently preserving salivary gland function in head and neck cancer patients.Presently, gene transfer to supplement fluid formation and stem cell transfer to increase the regenerative potential in radiation-damaged salivary glands are promising approaches for regaining function and/or regeneration of radiation-damaged salivary gland tissue.

Proton pencil-beam scanning radiotherapy in the treatment of nasopharyngeal cancer: dosimetric parameters and 2-year results

OBJECTIVES

 Patients with nasopharyngeal cancer are candidates for proton radiotherapy due to large and comprehensive target volumes, and the necessity for sparing of healthy tissues. The aim of this work is to evaluate treatment outcome and toxicity profile of patients treated with proton pencil-beam scanning radiotherapy.

MATERIALS AND METHODS

 Between Jan 2013 and June 2018, 40 patients were treated for nasopharyngeal cancer (NPC) with IMPT (proton radiotherapy with modulated intensity). Median age was 47 years and the majority of patients had locally advanced tumors (stage 2-8 patients. (20%); stage 3-18 patients (45%); stage 4A-10 patients. (25%); stage 4B-4 patients. (10%). Median of total dose was 74 GyE (70-76 GyE) in 37 fractions (35-38). Bilateral neck irradiation was used in all cases. Concomitant chemotherapy was applied in 34 cases. (85%). Median follow-up time was 24 (1.5-62) months.

RESULTS

Two-year overall survival (OS), disease-free survival (DFS), and local control (LC) were 80%, 75%, and 84%, respectively. Acute toxicity was generally mild despite large target volumes and concurrent application of chemotherapy with skin toxicity and dysphagia reported as the most frequent acute side effects. The insertion of a percutaneous endoscopic gastrectomy (PEG) was necessary in four cases (10%). Serious late toxicity (G > 3. RTOG) was observed in two patients (5%) (dysphagia and brain necrosis).

CONCLUSION

 IMPT for nasopharyngeal cancer patients is feasible with mild acute toxicity. Treatment outcomes are promising despite the high percentage of advanced disease in this group.

Role of Proton Beam Therapy in Current Day Radiation Oncology Practice

Proton beam therapy (PBT), because of its unique physics of no–exit dose deposition in the tissue, is an exciting prospect. The phenomenon of Bragg peak allows protons to deposit their almost entire energy towards the end of the path of the proton and stops any further dose delivery. Braggs peak equips PBT with superior dosimetric advantage over photons or electrons because PBT doesn’t traverse the target/body but is stopped sharply at an energy dependent depth in the target/body. It also has no exit dose. Because of no exit dose and normal tissue sparing, PBT is hailed for its potential to bring superior outcomes. Pediatric malignancies is the most common malignancy where PBT have found utmost application. Nowadays, PBT is also being used in the treatment of other malignancies such as carcinoma prostate, carcinoma breast, head and neck malignancies, and gastrointestinal (GI) malignancies. Despite advantages of PBT, there is not only a high cost of setting up of PBT centers but also a lack of definitive phase-III data. Therefore, we review the role of PBT in current day practice of oncology to bring out the nuances that must guide the practice to choose suitable patients for PBT.

Quality of Life, Toxicity and Unmet Needs in Nasopharyngeal Cancer Survivors

Concerted research efforts over the last three decades have resulted in improved survival and outcomes for patients diagnosed with nasopharyngeal carcinoma (NPC). The evolution of radiotherapy techniques has facilitated improved dose delivery to target volumes while reducing dose to the surrounding normal tissue, improving both disease control and quality of life (QoL). In parallel, clinical trials focusing on determining the optimal systemic therapy to use in conjunction with radiotherapy have been largely successful, resulting in improved locoregional, and distant control. As a consequence, neoadjuvant chemotherapy (NACT) prior to definitive chemoradiotherapy has recently emerged as the preferred standard for patients with locally advanced NPC. Two of the major challenges in interpreting toxicity and QoL data from the published literature have been the reliance on: (1) clinician rather than patient reported outcomes; and (2) reporting statistical rather than clinical meaningful differences in measures. Despite the lower rates of toxicity that have been achieved with highly conformal radiotherapy techniques, survivors remain at moderate risk of persistent and long-lasting treatment effects, and the development of late radiation toxicities such as hearing loss, cranial neuropathies and cognitive impairment many years after successful treatment can herald a significant decline in QoL. Future approaches to reduce long-term toxicity will rely on: (1) identifying individual patients most likely to benefit from NACT; (2) development of response-adapted radiation strategies following NACT; and (3) anticipated further dose reductions to organs at risk with proton and particle therapy. With increasing numbers of survivors, many in the prime of their adult life, research to identify, and strategies to address the unmet needs of NPC survivors are required. This contemporary review will summarize our current knowledge of long-term toxicity, QoL and unmet needs of this survivorship group.

Mixed-beam approach in locally advanced nasopharyngeal carcinoma: IMRT followed by proton therapy boost versus IMRT-only. Evaluation of toxicity and efficacy

Objective: To compare radiation-induced toxicity and dosimetry parameters in patients with locally advanced nasopharyngeal cancer (LANPC) treated with a mixed-beam (MB) approach (IMRT followed by proton therapy boost) with an historic cohort of patients treated with a full course of IMRT-only.Material and methods: Twenty-seven patients with LANPC treated with the MB approach were compared to a similar cohort of 17 patients treated with IMRT-only. The MB approach consisted in a first phase of IMRT up to 54-60 Gy followed by a second phase delivered with a proton therapy boost up to 70-74 Gy (RBE). The total dose for patients treated with IMRT-only was 69.96 Gy. Induction chemotherapy was administrated to 59 and 88% and concurrent chemoradiotherapy to 88 and 100% of the MB and IMRT-only patients, respectively. The worst toxicity occurring during the entire course of treatment (acute toxicity) and early-late toxicity were registered according to the Common Terminology Criteria Adverse Events V4.03.Results: The two cohorts were comparable. Patients treated with MB received a significantly higher median total dose to target volumes (p = .02). Acute grade 3 mucositis was found in 11 and 76% (p = .0002) of patients treated with MB and IMRT-only approach, respectively, while grade 2 xerostomia was found in 7 and 35% (p = .02) of patients treated with MB and IMRT-only, respectively. There was no statistical difference in late toxicity. Local progression-free survival (PFS) and progression-free survival curves were similar between the two cohorts of patients (p = .17 and p = .40, respectively). Local control rate was 96% and 81% for patients treated with MB approach and IMRT-only, respectively.Conclusions: Sequential MB approach for LANPC patients provides a significantly lower acute toxicity profile compared to full course of IMRT. There were no differences in early-late morbidities and disease-related outcomes (censored at two-years) but a longer follow-up is required to achieve conclusive results.

Clinical implementation in proton therapy of multi-field optimization by a hybrid method combining conventional PTV with robust optimization

To implement a robust multi-field optimization (MFO) technique compatible with the application of a Monte Carlo (MC) algorithm and to evaluate its robustness. Nine patients (three brain, five head-and-neck, one spine) underwent proton treatment generated by a novel robust MFO technique. A hybrid (hMFO) approach was implemented, planning dose coverage on isotropic PTV compensating for setup errors, whereas range calibration uncertainties are incorporated into PTV robust optimization process. hMFO was compared with single-field optimization (SFO) and full robust multi-field optimization (fMFO), both on the nominal plan and the worst-case scenarios assessed by robustness analysis. The SFO and the fMFO plans were normalized to hMFO on CTV to obtain iso-D95 coverage, and then the organs at risk (OARs) doses were compared. On the same OARs, in the normalized nominal plans the potential impact of variable relative biological effectiveness (RBE) was investigated. hMFO reduces the number of scenarios computed for robust optimization (from twenty-one in fMFO to three), making it practicable with the application of a MC algorithm. After normalizing on D95 CTV coverage, nominal hMFO plans were superior compared to SFO in terms of OARs sparing (p   <  0.01), without significant differences compared to fMFO. The improvement in OAR sparing with hMFO with respect to SFO was preserved in worst-case scenarios (p   <  0.01), confirming that hMFO is as robust as SFO to physical uncertainties, with no significant differences when compared to the worst case scenarios obtained by fMFO. The dose increase on OARs due to variable RBE was comparable to the increase due to physical uncertainties (i.e. 4-5 Gy(RBE)), but without significant differences between these techniques. hMFO allows improving plan quality with respect to SFO, with no significant differences with fMFO and without affecting robustness to setup, range and RBE uncertainties, making clinically feasible the application of MC-based robust optimization.

Radiation induced optic neuropathy: Does treatment modality influence the risk?

Radiation induced optic neuropathy (RION) is a rare but disastrous complication of radiation therapy in treatment of periorbital tumors. The objective of this study is to investigate the incidence of RION in series of patients treated from peri orbital tumors by recent photon and proton irradiation modalities. We searched the Pub Med database for studies in periorbital tumors including base of skull, sinonasal, pituitary, nasopharyngeal tumors and craniopharyngioma treated with Intensity modulated radiotherapy (IMRT) and with proton beam therapy (PBT) between 1992 and 2017 excluding metastatic tumors, lymphomas, pediatric series, those treated mainly with chemotherapy, target therapy and those written in languages other than English and French. The result retrieved 421 articles that were revised by the panel. Fourteen articles with IMRT and 27 with PBT reported usable data for the review from which 31studies that had pointed to the doses to the optic nerve (ON) and/or optic chiasm (OC) and incidence of RION have been analyzed. We have found that the incidence of RION had been reported fairly in both modalities and many other factors related to the patient, tumor, and irradiation process interplay in its development. We have concluded that proper treatment planning, good selection of treatment modality, adherence to dose constraints applied to critical structures all along with regular oncological and ophthalmological follow up, control of co-morbidities and early intervention, could help reducing its magnitude.

New frontiers in proton therapy: applications in cancers

Proton therapy offers dominant advantages over photon therapy due to the unique depth-dose characteristics of proton, which can cause a dramatic reduction in normal tissue doses both distal and proximal to the tumor target volume. In turn, this feature may allow dose escalation to the tumor target volume while sparing the tumor-neighboring susceptible organs at risk, which has the potential to reduce treatment toxicity and improve local control rate, quality of life and survival. Some dosimetric studies in various cancers have demonstrated the advantages over photon therapy in dose distributions. Further, it has been observed that proton therapy confers to substantial clinical advantage over photon therapy in head and neck, breast, hepatocellular, and non-small cell lung cancers. As such, proton therapy is regarded as the standard modality of radiotherapy in many pediatric cancers from the technical point of view. However, due to the limited clinical evidence, there have been concerns about the high cost of proton therapy from an economic point of view. Considering the treatment expenses for late radiation-induced toxicities, cost-effective analysis in many studies have shown that proton therapy is the most cost-effective option for brain, head and neck and selected breast cancers. Additional studies are warranted to better unveil the cost-effective values of proton therapy and to develop newer ways for better protection of normal tissues. This review aims at reviewing the recent studies on proton therapy to explore its benefits and cost-effectiveness in cancers. We strongly believe that proton therapy will be a common radiotherapy modality for most types of solid cancers in the future.

Monitoring skin dose changes during image-guided helical tomotherapy for head and neck cancer patients

PURPOSE

An increase of skin dose during head and neck cancer (HNC) radiotherapy is potentially dangerous. Aim of this study was to quantify skin dose variation and to assess the need of planning adaptation (ART) to counteract it.

METHODS

Planning CTs of 32 patients treated with helical tomotherapy (HT) according to a Simultaneous Integrated Boost (SIB) technique delivering 54/66 Gy in 30 fractions were deformably co-registered to MVCTs taken at fractions 15 and 30; in addition, the first fraction was also considered. The delivered dose-of-the-day was calculated on the corresponding deformed images. Superficial body layers (SL) were considered as a surrogate for skin, considering a layer thickness of 2 mm. Variations of SL DVH (∆SL) during therapy were quantified, focusing on ∆SL95% (i.e., 62.7 Gy).

RESULTS

Small changes (within ± 1 cc for ∆SL95%) were seen in 15/32 patients. Only 2 patients experienced ∆SL95% > 1 cc in at least one of the two monitored fractions. Negative ∆SL95% > 1 cc (up to 17 cc) were much more common (15/32 patients). The trend of skin dose changes was mostly detected at the first fraction. Negative changes were correlated with the presence of any overlap between PTV and SL at planning and were explained in terms of how the planning system optimizes the PTV dose coverage near the skin. Acute toxicity was associated with planning DVH and this association was not improved if considering DVHs referring to fractions 15/30.

CONCLUSION

About half of the patients treated with SIB with HT for HNC experienced a skin-sparing effect during therapy; only 6% experienced an increase. Our findings do not support skin-sparing ART, while suggesting the introduction of improved skin-sparing planning techniques.

Management of locally recurrent nasopharyngeal carcinoma

As a consequence of the current excellent loco-regional control rates attained using the generally accepted treatment paradigms involving intensity-modulated radiotherapy for nasopharyngeal carcinoma (NPC), only 10-20% of patients will suffer from local and/or nodal recurrence after primary treatment. Early detection of recurrence is important as localized recurrent disease is still potentially salvageable, but this treatment often incurs a high risk of major toxicities. Due to the possibility of radio-resistance of tumors which persist or recur despite adequate prior irradiation and the limited tolerance of adjacent normal tissues to sustain further additional treatment, the management of local failures remains one of the greatest challenges in this disease. Both surgical approaches for radical resection and specialized re-irradiation modalities have been explored. Unfortunately, available data are based on retrospective studies, and the majority of them are based on a small number of patients or relatively short follow-up. In this article, we will review the different salvage treatment options and associated prognostic factors for each of them. We will also propose a treatment algorithm based on the latest available evidence and discuss the future directions of treatment for locally recurrent NPC.

Update in pediatric nasopharyngeal undifferentiated carcinoma

Many of the principles established in adults with undifferentiated nasopharyngeal carcinoma (NPC) apply to children, adolescents and young adults. However, NPC in young patients should be distinguished from the adult form by several points. This review focuses mainly on differences between adult and pediatric NPC. The role of biology and genetics in pediatric NPC is discussed. Systemic treatment modalities including type of chemotherapy induction, timing of treatment, role of immunotherapy as adjuvant treatment, or in relapsing/ metastatic diseases are reported. Radiation modalities (doses, techniques…) in children are also reviewed. Long-term effects including secondary cancers are finally be discussed in this young NPC population.

Modern radiotherapy for head and neck cancer

Radiation therapy (RT) plays a key role in curative-intent treatments for head and neck cancers. Its use is indicated as a sole therapy in early stage tumors or in combination with surgery or concurrent chemotherapy in advanced stages. Recent technologic advances have resulted in both improved oncologic results and expansion of the indications for RT in clinical practice. Despite this, RT administered to the head and neck region is still burdened by a high rate of acute and late side effects. Moreover, about 50% of patients with high-risk disease experience loco-regional recurrence within 3 years of follow-up. Therefore, in recent decades, efforts have been dedicated to optimize the cost/benefit ratio of RT in this subset of patients. The aim of the present review was to highlight modern concepts of RT for head and neck cancers considering both the technological advances that have been achieved and recent knowledge that has informed the biological interaction between radiation and both tumor and healthy tissues.

Early clinical outcomes of helical tomotherapy/intensity-modulated proton therapy combination in nasopharynx cancer

This study aimed to evaluate the feasibility of combining helical tomotherapy (HT) and intensity‐modulated proton therapy (IMPT) in treating patients with nasopharynx cancer (NPC). From January 2016 to March 2018, 98 patients received definitive radiation therapy (RT) with concurrent chemotherapy (CCRT). Using simultaneous integrated boost and adaptive re‐plan, 3 different dose levels were prescribed: 68.4 Gy in 30 parts to gross tumor volume (GTV), 60 Gy in 30 parts to high‐risk clinical target volume (CTV), and 36 Gy in 18 parts to low‐risk CTV. In all patients, the initial 18 fractions were delivered by HT, and, after rival plan evaluation on the adaptive re‐plan, the later 12 fractions were delivered either by HT in 63 patients (64.3%, HT only) or IMPT in 35 patients (35.7%, HT/IMPT combination), respectively. Propensity‐score matching was conducted to control differences in patient characteristics. In all patients, grade ≥ 2 mucositis (69.8% vs 45.7%, P = .019) and grade ≥ 2 analgesic usage (54% vs 37.1%, P = .110) were found to be less frequent in HT/IMPT group. In matched patients, grade ≥ 2 mucositis were still less frequent numerically in HT/IMPT group (62.9% vs 45.7%, P = .150). In univariate analysis, stage IV disease and larger GTV volume were associated with increased grade ≥ 2 mucositis. There was no significant factor in multivariate analysis. With the median 14 month follow‐up, locoregional and distant failures occurred in 9 (9.2%) and 12 (12.2%) patients without difference by RT modality. In conclusion, comparable early oncologic outcomes with more favorable acute toxicity profiles were achievable by HT/IMPT combination in treating NPC patients.

Future of Radiotherapy in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy with unique clinical biological profiles such as associated Epstein-Barr virus infection and high radiosensitivity. Radiotherapy has long been recognized as the mainstay for the treatment of NPC. However, the further efficacy brought by radical radiotherapy has reached the bottleneck in advanced patients, who are prone to develop recurrence and distant metastasis after treatment. The application of photon therapy makes it possible for radiation dose escalation in refractory cases and may provide second chance for recurrent patients with less unrecoverable tissue damage. The concept of adaptive radiotherapy is put forward in consideration of target volume shrinkage during treatment. The replanning procedure offers better protection for the organ at risk. However, the best timing and candidates for adaptive radiotherapy is still under debate. The current tendency of artificial intelligence in NPC mainly focuses on image recognition, auto-segmentation and dose prediction. Although artificial intelligence is still in developmental stage, the future of it is promising.To further improve the efficacy of NPC, multimodality treatment is encouraged. In-depth studies on genetic and epigenetic variations help to explain the great heterogeneity among patients, and could further be applied to precise screening and prediction, personalized radiotherapy and the evolution of targeted drugs. Given the clinical benefit of immunotherapy in other cancers, the application of immunotherapy, especially immune checkpoint inhibitor, in NPC is also of great potential. Results from ongoing clinical trials combining immunotherapy with radiotherapy in NPC are expected.

Adapted strategy to tumor response in childhood nasopharyngeal carcinoma: the French experience

PURPOSE

The aim of this study was to retrospectively study survival and long-term morbidities of children with nasopharyngeal carcinoma (NPC) treated by induction chemotherapy and concurrent chemoradiation (CRT). The total dose of radiation was adapted to the response following neoadjuvant chemotherapy.

METHODS

Children with non-metastatic NPC treated in France between 1999 and 2015 were retrospectively included in the study. The strategy combined neoadjuvant platinum-based chemotherapy, followed by adapted CRT to tumor response.

RESULTS

In total, 95 patients (median age 15 years [range, 7-23 years], male-to-female ratio 1.8) with undifferentiated NPC were included; 59% of patients had TNM stage IV. Intensity-modulated radiotherapy (IMRT) was delivered to 57 patients (60%), while the other patients were treated with conformal RT (3D-RT). After a median follow-up of 4.5 years [range, 3.6-5.5 years], 13 relapses and seven deaths had occurred. The 3‑year overall and relapse-free survival (RFS) were 94% [95% CI, 85-97%] and 86% [77-92%], respectively. The locoregional failure rate was 6% [95% CI, 2-14]. Long-term treatment-related sequelae of grade 2+ were reported by 37 (50%) patients; odynophagia was significantly reduced treated by IMRT vs. conventional 3D-RT (7% vs. 55%, p = 0.015). Using a reduction dose of 59.4 Gy, 54 Gy, and 45 Gy, respectively, to the primary, involved, and uninvolved neck nodes, after a favorable tumor response, was not associated with an increased locoregional failure rate.

CONCLUSIONS

The survival rates for NPC have been considerably improved by means of multimodal therapy, but long-term locoregional morbidity remains common. Use of IMRT may induce less residual odynophagia. Radiation dose reduction adapted to chemotherapy response does not have a negative impact on outcome. These findings support the use of an RT protocol adapted to the tumor response to neoadjuvant chemotherapy for a long-lasting improvement in the patient's quality of life.

Bimodal Radiotherapy with Active Raster-Scanning Carbon Ion Radiotherapy and Intensity-Modulated Radiotherapy in High-Risk Nasopharyngeal Carcinoma Results in Excellent Local Control

Background: In this analysis, we aimed to present the first results of carbon ion radiotherapy (CIRT), which is known for its conformal dose distribution and increased biological effectiveness in the treatment of high-risk nasopharyngeal carcinoma (NPC). Methods: We retrospectively analyzed twenty-six consecutive patients who had been treated at our center with CIRT for high-risk NPC between 2009 and 2018. Carbon ion (C12) boost was applied in a bimodal setting combined with intensity-modulated radiotherapy (IMRT) base plan. The median cumulative total dose was 74 Gy (RBE), and patients with inoperable (n = 17, 65%) or incompletely resected (n = 7, 27%) tumors were included in the analysis. Overall, 81% received concomitant chemotherapy (n = 21). Results: The median follow-up time was 40 months (range 10–97 months) for all patients. At the last follow-up, 92% of the patients were still alive. We could identify excellent tumor response with complete tumor remission (CR) in 60% (n = 15/25), partial tumor remission (PR) in 20% (n = 5/25), and stable disease (SD) in 12% (n = 3/25) of the patients according to the RECIST (Response Evaluation Criteria in Solid Tumors) criteria. Despite unfavorable tumor characteristics, only one patient showed a locally in-field recurrence after 56 months (4%) and another patient a locoregional recurrence in the unilateral cervical lymph nodes after 21 months (4%). The 2-year local control (LC), distant progression-free survival (DPFS), and overall survival (OS) were 95%, 93%, and 100% and the estimated 5-year LC, DPFS, and OS were 90%, 86%, and 86%, respectively. Overall, treatment was tolerated well with 20% acute and 16% chronic grade 3 side effects. No toxicity greater than grade 3 occurred. Conclusion: Bimodal radiotherapy including IMRT and active raster-scanning CIRT for high-risk nasopharyngeal cancer is a safe treatment method resulting in moderate toxicity and excellent local control. A larger patient number and longer follow-up time would be necessary to strengthen the current findings.

Skin DVHs predict cutaneous toxicity in Head and Neck Cancer patients treated with Tomotherapy

PURPOSE

To explore the association between planning skin dose-volume data and acute cutaneous toxicity after Radio-chemotherapy for Head and Neck (HN) cancer patients.

METHODS

Seventy HN patients were treated with Helical Tomotherapy (HT) with radical intent (SIB technique: 54/66 Gy to PTV1/PTV2 in 30fr) ± chemotherapy superficial body layer 2 mm thick (SL2) was delineated on planning CT. CTCAE v4.0 acute skin toxicity data were available. Absolute average Dose-Volume Histograms (DVH) of SL2 were calculated for patients with severe (G3) and severe/moderate (G3/G2) skin acute toxicities. Differences against patients with none/mild toxicity (G0/G1) were analyzed to define the most discriminative regions of SL2 DVH; univariable and multivariable logistic analyses were performed on DVH values, CTV volume, age, sex, chemotherapy.

RESULTS

Sixty-one % of patients experienced G2/G3 toxicity (rate of G3 = 19%). Differences in skin DVHs were significant in the range 53-68Gy (p-values: 0.005-0.01). V56/V64 were the most predictive parameters for G2/G3 (OR = 1.12, 95%CI = 1.03-1.21, p = 0.001) and G3 (OR = 1.13, 95%CI = 1.01-1.26, p = 0.027) with best cut-off of 7.7cc and 2.7cc respectively. The logistic model for V56 was well calibrated being both, slope and R2, close to 1. Average V64 were 2.2cc and 6cc for the two groups (G3 vs G0-G2 toxicity); the logistic model for V64 was quite well calibrated, with a slope close to 1 and R2 equal to 0.60.

CONCLUSION

SL2 DVH is associated with the risk of acute skin toxicity. Constraining V64 < 3cc (equivalent to a 4x4cm2 skin surface) should keep the risk of G3 toxicity below or around 10%.

Results of a combination treatment with intensity modulated radiotherapy and active raster-scanning carbon ion boost for adenoid cystic carcinoma of the minor salivary glands of the nasopharynx

OBJECTIVES

We aimed to present the first clinical results for adenoid cystic carcinoma (ACC) of the nasopharynx after primary radiotherapy (RT) with the focus on local control (LC) and patterns of recurrence.

MATERIALS AND METHODS

We retrospectively analyzed 59 patients with ACC of the nasopharynx, who were treated with bimodal radiotherapy (RT) consisting of intensity modulated radiotherapy and carbon ion boost at the Heidelberg Ion-Beam Therapy Center between 2009 and 2018. The patients had predominantly inoperable (n = 42, 72%) or incompletely resected (n = 17, 29%) tumors. Kaplan-Meier estimates and the log-rank (Mantel-Cox) test were used for univariate and multivariate analyses.

RESULTS

The median follow-up was 32 months. At last follow-up, 67% of the patients were still alive (n = 39/58), of whom 74% were free of progression (n = 29/39). The 2-year LC, distant progression-free survival (DPFS) and overall survival (OS) were 83%, 81%, 87% and the estimated 5-year LC, DPFS and OS were 49%, 54%, 69%, respectively. LC was significantly inferior in patients with large tumor volumes (gross tumor volume, GTV > 100 cc, p = 0.020) and T4 tumors (p = 0.021). The majority of the recurrences occurred at the margin, where critical structures were spared (n = 11/19, 58%). Overall, grade 3 toxicity was moderate with 12% acute and 8% late side effects.

CONCLUSION

Bimodal RT including active raster-scanning carbon ion boost for nasopharyngeal ACC resulted in adequate LC and OS rates with moderate toxicity. T4 stage, large tumor volume and the necessary dose sparing in critical structures, i.e. optic nerves, brain stem and orbit, negatively affected LC.

Intensity modulated proton therapy (IMPT) - The future of IMRT for head and neck cancer

Radiation therapy plays an integral role in the management of head and neck cancers (HNCs). While most HNC patients have historically been treated with photon-based radiation techniques such as intensity modulated radiation therapy (IMRT), there is a growing awareness of the potential clinical benefits of proton therapy over IMRT in the definitive, postoperative and reirradiation settings given the unique physical properties of protons. Intensity modulated proton therapy (IMPT), also known as "pencil beam proton therapy," is a sophisticated mode of proton therapy that is analogous to IMRT and an active area of investigation in cancer care. Multifield optimization IMPT allows for high quality plans that can target superficially located HNCs as well as large neck volumes while significantly reducing integral doses. Several dosimetric studies have demonstrated the superiority of IMPT over IMRT to improve dose sparing of nearby organs such as the larynx, salivary glands, and esophagus. Evidence of the clinical translation of these dosimetric advantages has been demonstrated with documented toxicity reductions (such as decreased feeding tube dependency) after IMPT for patients with HNCs. While there are relative challenges to IMPT planning that exist today such as particle range uncertainties and high sensitivity to anatomical changes, ongoing investigations in image-guidance techniques and robust optimization methods are promising. A systematic approach towards utilizing IMPT and additional prospective studies are necessary in order to more accurately estimate the clinical benefit of IMPT over IMRT and passive proton therapy on a case-by-case basis for patients with sub-site specific HNCs.

Three-year results after radiotherapy for locally advanced sinonasal adenoid cystic carcinoma, using highly conformational radiotherapy techniques proton therapy and/or Tomotherapy

PURPOSE

We report the patient outcomes of a treatment combining proton therapy and Tomotherapy in sinonasal adenoid cystic carcinoma involving skull base.

MATERIALS AND METHODS

We included patients treated at Curie Institute, Paris, France, between March 2010 and February 2014 for an advanced adenoid cystic carcinoma involving skull base. Patients received Tomotherapy, proton therapy or both. We evaluated treatment toxicity (according to CTCAE V4), local control, distant metastasis-free survival and overall survival.

RESULTS

Thirteen patients were included, with a median follow-up of 34 months. Radiation therapy followed surgery for 77% of the patients and margins were positive in all those cases. Median dose was 73.8Gy. Local control, distant metastasis-free survival and overall survival at 3 years were respectively 60%, 48% and 60%. One-sided grade 3 hearing impairment occurred in 46% of the patients.

CONCLUSION

Combining high-dose proton therapy and Tomotherapy is effective and has moderate toxicity in the treatment of T4 sinonasal adenoid cystic carcinoma involving skull base.

Radiotherapy-induced anti-tumor immune response and immune-related adverse events in a case of recurrent nasopharyngeal carcinoma undergoing anti-PD-1 immunotherapy

BACKGROUND

Treatment of recurrent nasopharyngeal carcinoma is a challenging clinical problem. We report the case of a 46 year old male showing excellent response and signs of immunostimulation following re-re-irradiation for recurrent nasopharyngeal carcinoma under systemic treatment with pembrolizumab.

CASE PRESENTATION

Patient was first diagnosed with locoregionally advanced, non-keratinizing nasopharyngeal carcinoma in 2010. After achieving complete remission following induction chemotherapy and concurrent curative chemoradiation, the patient subsequently developed distant and locoregionally recurrent disease. He received various treatments (neck dissection, radiotherapy to a bony metastasis, palliative chemotherapy, stereotactic re-irradiation of local recurrence) before initiation of anti- PD-1 immunotherapy with pembrolizumab in January of 2016. Following marked local progression 6 months thereafter, we performed re-re-irradiation of the recurrent tumor after careful evaluation and treatment planning. While treatment was well tolerated, the patient subsequently developed marked clinical and radiological signs of immunostimulation with mucosal irritation and swelling of lacrimal and salivary glands as described in the report. Immunotherapy with pembrolizumab was reinitiated, with re- staging showing excellent response with regression of all tumorous lesions. At the time of this report, following near complete recovery of inflammatory symptoms, the patient remains in excellent condition and free from recurrence under treatment with pembrolizumab.

CONCLUSIONS

To our knowledge, we report the first observation of a combined effect of immunotherapy and radiotherapy in a patient with recurrent nasopharyngeal carcinoma. Demonstrating distinct signs of immunostimulation as well as excellent tumor response in a heavily pretreated patient progressing under anti-PD-1 immunotherapy, the case adds to the rising paradigm of an immunostimulatory effect of radiotherapy in patients undergoing treatment with immune checkpoint inhibitors.

Technical Note: A treatment plan comparison between dynamic collimation and a fixed aperture during spot scanning proton therapy for brain treatment

PURPOSE

To quantitatively assess the advantages of energy-layer specific dynamic collimation system (DCS) versus a per-field fixed aperture for spot scanning proton therapy (SSPT).

METHODS

Five brain cancer patients previously planned and treated with SSPT were replanned using an in-house treatment planning system capable of modeling collimated and uncollimated proton beamlets. The uncollimated plans, which served as a baseline for comparison, reproduced the target coverage and organ-at-risk sparing of the clinically delivered plans. The collimator opening for the fixed aperture-based plans was determined from the combined cross sections of the target in the beam's eye view over all energy layers which included an additional margin equivalent to the maximum beamlet displacement for the respective energy of that energy layer. The DCS-based plans were created by selecting appropriate collimator positions for each row of beam spots during a Raster-style scanning pattern which were optimized to maximize the dose contributions to the target and limited the dose delivered to adjacent normal tissue.

RESULTS

The reduction of mean dose to normal tissue adjacent to the target, as defined by a 10 mm ring surrounding the target, averaged 13.65% (range: 11.8%-16.9%) and 5.18% (2.9%-7.1%) for the DCS and fixed aperture plans, respectively. The conformity index, as defined by the ratio of the volume of the 50% isodose line to the target volume, yielded an average improvement of 21.35% (19.4%-22.6%) and 8.38% (4.7%-12.0%) for the DCS and fixed aperture plans, respectively.

CONCLUSIONS

The ability of the DCS to provide collimation to each energy layer yielded better conformity in comparison to fixed aperture plans.

Contour scanning for penumbra improvement in pencil beam scanned proton therapy

Proton therapy, especially in the form of pencil beam scanning (PBS), allows for the delivery of highly conformal dose distributions for complex tumor geometries. However, due to scattering of protons inside the patient, lateral dose gradients cannot be arbitrarily steep, which is of importance in cases with organs at risk (OARs) in close proximity to, or overlapping with, planning target volumes (PTVs). In the PBS approach, physical pencil beams are planned using a regular grid orthogonal to the beam direction. In this work, we propose an alternative to this commonly used approach where pencil beams are placed on an irregular grid along concentric paths based on the target contour. Contour driven pencil beam placement is expected to improve dose confirmation by allowing the optimizer to best enhance the penumbra of irregularly shaped targets using edge enhancement. Its effectiveness has been shown to improve dose confirmation to the target volume and reduce doses to OARs in head-and-neck planning studies. Furthermore, the deliverability of such plans, as well as the dosimetric improvements over conventional grid-based plans, have been confirmed in first phantom based verifications.

The price of robustness; impact of worst-case optimization on organ-at-risk dose and complication probability in intensity-modulated proton therapy for oropharyngeal cancer patients

PURPOSE

To quantify the impact of the degree of robustness against setup errors and range errors on organ-at-risk (OAR) dose and normal tissue complication probabilities (NTCPs) in intensity-modulated proton therapy for oropharyngeal cancer patients.

MATERIAL AND METHODS

For 20 oropharyngeal cases (10 unilateral and 10 bilateral), robust treatment plans were generated using 'minimax' worst-case optimization. We varied the robustness against setup errors ('setup robustness') from 1 to 7mm and the robustness against range errors ('range robustness') from 1% to 7% (+1mm). We evaluated OAR doses and NTCP-values for xerostomia, dysphagia and larynx edema.

RESULTS

Varying the degree of setup robustness was found to have a considerably larger impact than varying the range robustness. Increasing setup robustness from 1mm to 3, 5, and 7mm resulted in average NTCP-values to increase by 1.9, 4.4 and 7.5 percentage point, whereas they increased by only 0.4, 0.8 and 1.2 percentage point when increasing range robustness from 1% to 3%, 5% and 7%. The degree of setup robustness was observed to have a clinically significant impact in bilateral cases in particular.

CONCLUSIONS

For oropharyngeal cancer patients, minimizing setup errors should be given a higher priority than minimizing range errors.