Assessing Equity of Access to Proton Beam Therapy: A Literature Review

Durable complete response in a patient with leptomeningeal melanoma after treatment with dabrafenib, trametinib, and nivolumab

Leptomeningeal disease (LMD) is a devastating complication of melanoma with a dismal prognosis. We present the case of a young man with stage IV BRAF V600E mutant melanoma with lung, lymph node, and brain metastases initially treated with ipilimumab and nivolumab, who subsequently developed LMD. Upon change to BRAF/MEK targeted therapy with nivolumab, a durable complete response was achieved and remains ongoing, off treatment, 7 years from diagnosis. Management of symptomatic LMD remains a critical unmet clinical challenge, with limited clinical trial data. This exceptional case is instructive, as the first published case of the use of the triplet, and the first durable response with therapy discontinuation, in melanoma LMD. The triple-drug regimen may be considered a viable option in fit patients. This case highlights the potential for long-term disease control and the critical and urgent need to develop clinical trials inclusive of patients with LMD to define the best treatment strategies.

Much ado about nothing? Assessing the actual benefits of proton beam therapy for prostate cancer

We are discussing and commenting on the paper by Yu et al. titled "Updated Analysis of Comparative Toxicity of Proton and Photon Radiation for Prostate Cancer," published in the Journal of Clinical Oncology in June 2024.

Acceptability of a Serious Game About Proton Radiotherapy Designed for Children Aged 5 to 14 Years and Its Potential Impact on Perceived Anxiety: Feasibility and Randomized Controlled Pilot Trial

Background

Children who are going to undergo radiotherapy have displayed fear and anxiety. Therefore, a web-based serious game was developed as a psychological preparation to investigate if it could affect anxiety levels. In an earlier stage, children with experience of radiotherapy had been part of the developmental process.

Objective

The study aimed to investigate the feasibility in terms of reach, usability, and acceptability of a serious game about proton radiotherapy and to pilot that it did not increase anxiety levels in children aged 5 to 14 years undergoing radiotherapy.

Methods

The design was a randomized controlled pilot trial with predefined feasibility criteria. In total, 28 children were assessed for eligibility, and 23 met the inclusion criteria. They were consecutively randomized into 1 of 2 study arms. One child was excluded after randomization. If randomized into arm 1, the children received the intervention before treatment started. Children in arm 2 were treated as controls. Questionnaires with fixed answers were used to assess anxiety levels (an adapted version of the State-Trait Anxiety Inventory for Children) and experiences of gameplay (an adapted version of Player Experience of Need Satisfaction [PENS]). The children were asked to answer questionnaires at 5 different measurement occasions during their radiotherapy treatment.

Results

In arm 1, age ranged from 5 to 13 (mean 8.4, SD 2.4) years. In arm 2, age ranged from 5 to 11 (mean 7.6, SD 2.3) years. The sample consisted of 15 girls and 7 boys. The feasibility criterion that the children should play the game for 20 minutes or more was not met. Mean playtime for children in arm 1 was 32.1 (SD 23.8) minutes, where 18 children had played for at least 15 minutes. The criterion that 70% (n=16) or more of the participants should return all of the questionnaires was not met; however, more than 73% (n=16) returned the PENS questionnaires. The State-Trait Anxiety Inventory for Children was returned by 73% (n=16) on day 0, 77% (n=17) on day 1, 82% (n=18) on day 3, 82% (n=18) on day 6, and 86% (n=19) on day 15.

Conclusions

All feasibility criteria set for the study were not met, suggesting that adaptions need to be made if a future study is to be undertaken. Further, the analysis revealed that there was no indication that playing increased the children's self-reported anxiety. The PENS questionnaire adapted for children showed promising results regarding player satisfaction when using the serious game. When studying children with severe conditions and young age, 5 measurement occasions seemed to be too many. Measuring both player satisfaction or experience and knowledge transfer would be preferable in future studies.

Evaluating the Effectiveness of Proton Beam Therapy Compared to Conventional Radiotherapy in Non-Metastatic Rectal Cancer: A Systematic Review of Clinical Outcomes

Background and Objectives: Conventional radiotherapies used in the current management of rectal cancer commonly cause iatrogenic radiotoxicity. Proton beam therapy has emerged as an alternative to conventional radiotherapy with the aim of improving tumour control and reducing off-set radiation exposure to surrounding tissue. However, the real-world treatment and oncological outcomes associated with the use of proton beam therapy in rectal cancer remain poorly characterised. This systematic review seeks to evaluate the radiation dosages and safety of proton beam therapy compared to conventional radiotherapy in patients with non-metastatic rectal cancer. Materials and Methods: A computer-assisted search was performed on the Medline, Embase and Cochrane Central databases. Studies that evaluated the adverse effects and oncological outcomes of proton beam therapy and conventional radiotherapy in adult patients with non-metastatic rectal cancer were included. Results: Eight studies were included in this review. There was insufficient evidence to determine the adverse treatment outcomes of proton beam therapy versus conventional radiotherapy. No current studies assessed radiotoxicities nor oncological outcomes. Pooled dosimetric comparisons between proton beam therapy and various conventional radiotherapies were associated with reduced radiation exposure to the pelvis, bowel and bladder. Conclusions: This systematic review demonstrates a significant paucity of evidence in the current literature surrounding adverse effects and oncological outcomes related to proton beam therapy compared to conventional radiotherapy for non-metastatic rectal cancer. Pooled analyses of dosimetric studies highlight greater predicted radiation-sparing effects with proton beam therapy in this setting. This evidence, however, is based on evidence at a moderate risk of bias and clinical heterogeneity. Overall, more robust, prospective clinical trials are required.

Temporal Evolution and Diagnostic Diversification of Patients Receiving Proton Therapy in the United States: A Ten-Year Trend Analysis (2012 to 2021) From the National Association for Proton Therapy

PURPOSE

The National Association for Proton Therapy conducted 8 surveys of all operational United States proton centers (2012-2021) and analyzed the patients treated, diagnoses, and treatment complexity to evaluate trends and diversification of patients receiving proton therapy.

METHODS AND MATERIALS

Detailed surveys were sent in 2015, which requested data from 2012 to 2014, and then annually thereafter to active proton centers in the United States. The numbers of patient treated at each center for the preceding calendar year(s) were collated for tumors in the following categories: central nervous system, intraocular, pituitary, skull base/skeleton, head/neck, lung, retroperitoneal/soft tissue sarcoma, pediatric (solid tumors in children of age ≤18), gastrointestinal tract, urinary tract, female pelvic, prostate, breast, and "other." Complexity levels were assessed using Current Procedural Terminology codes 77520-77525.

RESULTS

Survey response rates were excellent (100% in 2015 to 94.9% in 2021); additional publicly available information provided near-complete information on all centers. Trend comparisons between 2012 and 2021 showed that the total annual number of patients treated with protons gradually increased from 5377 to 15,829. The largest numeric increases were for head/neck (316 to 2303; 7.3-fold), breast (93 to 1452; 15.6-fold), and gastrointestinal tumors (170 to 1259; 7.4-fold). Patient numbers also increased significantly for central nervous system (598 to 1743; 2.9-fold), pediatric (685 to 1870; 2.7-fold), and skull base tumors (179 to 514; 2.9-fold). For prostate cancer, the percentage of proton-treated patients decreased from 43.4% to 25.0% of the total. Simple compensated treatments decreased from 43% in 2012 to 7% in 2021, whereas intermediate complexity treatments increased from 45% to 73%.

CONCLUSIONS

The number of patients treated with protons is gradually increasing, with a substantial proportionate decline in patients with prostate cancer receiving proton therapy. The number of patients treated for "commonly accepted" indications for protons (eg, pediatric, central nervous system, and skull base tumors) is gradually increasing. Greater proportional increases were observed for breast, lung, head/neck, and gastrointestinal tumors. Treatment complexity is gradually increasing over time.

Photon vs proton hypofractionation in prostate cancer: A systematic review and meta-analysis

BACKGROUND

High-level evidence on hypofractionated proton therapy (PT) for localized and locally advanced prostate cancer (PCa) patients is currently missing. The aim of this study is to provide a systematic literature review to compare the toxicity and effectiveness of curative radiotherapy with photon therapy (XRT) or PT in PCa.

METHODS

PubMed, Embase, and the Cochrane Library databases were systematically searched up to April 2022. Men with a diagnosis of PCa who underwent curative hypofractionated RT treatment (PT or XRT) were included. Risk of grade (G) ≥ 2 acute and late genitourinary (GU) OR gastrointestinal (GI) toxicity were the primary outcomes of interest. Secondary outcomes were five-year biochemical relapse-free survival (b-RFS), clinical relapse-free, distant metastasis-free, and prostate cancer-specific survival. Heterogeneity between study-specific estimates was assessed using Chi-square statistics and measured with the I2 index (heterogeneity measure across studies).

RESULTS

A total of 230 studies matched inclusion criteria and, due to overlapped populations, 160 were included in the present analysis. Significant lower rates of G ≥ 2 acute GI incidence (2 % vs 7 %) and improved 5-year biochemical relapse-free survival (95 % vs 91 %) were observed in the PT arm compared to XRT. PT benefits in 5-year biochemical relapse-free survival were maintained for the moderate hypofractionated arm (p-value 0.0122) and among patients in intermediate and low-risk classes (p-values < 0.0001 and 0.0368, respectively). No statistically relevant differences were found for the other considered outcomes.

CONCLUSION

The present study supports that PT is safe and effective for localized PCa treatment, however, more data from RCTs are needed to draw solid evidence in this setting and further effort must be made to identify the patient subgroups that could benefit the most from PT.

Travel-Time Disparities in Access to Proton Beam Therapy for Cancer Treatment

Importance

Proton beam therapy is an emerging radiotherapy treatment for patients with cancer that may produce similar outcomes as traditional photon-based therapy for many cancers while delivering lower amounts of toxic radiation to surrounding tissue. Geographic proximity to a proton facility is a critical component of ensuring equitable access both for indicated diagnoses and ongoing clinical trials.

Objective

To characterize the distribution of proton facilities in the US, quantify drive-time access for the population, and investigate the likelihood of long commutes for certain population subgroups.

Design, Setting, and Participants

This population-based cross-sectional study analyzed travel times to proton facilities in the US. Census tract variables in the contiguous US were measured between January 1, 2017, and December 31, 2021. Statistical analysis was performed from September to November 2023.

Exposures

Drive time in minutes to nearest proton facility. Population totals and prevalence of specific factors measured from the American Community Survey: age; race and ethnicity; insurance, disability, and income status; vehicle availability; broadband access; and urbanicity.

Main Outcomes and Measures

Poor access to proton facilities was defined as having a drive-time commute of at least 4 hours to the nearest location. Median drive time and percentage of population with poor access were calculated for the entire population and by population subgroups. Univariable and multivariable odds of poor access were also calculated for certain population subgroups.

Results

Geographic access was considered for 327 536 032 residents of the contiguous US (60 594 624 [18.5%] Hispanic, 17 974 186 [5.5%] non-Hispanic Asian, 40 146 994 [12.3%] non-Hispanic Black, and 195 265 639 [59.6%] non-Hispanic White; 282 031 819 [86.1%] resided in urban counties). The median (IQR) drive time to the nearest proton facility was 96.1 (39.6-195.3) minutes; 119.8 million US residents (36.6%) lived within a 1-hour drive of the nearest proton facility, and 53.6 million (16.4%) required a commute of at least 4 hours. Persons identifying as non-Hispanic White had the longest median (IQR) commute time at 109.8 (48.0-197.6) minutes. Multivariable analysis identified rurality (odds ratio [OR], 2.45 [95% CI, 2.27-2.64]), age 65 years or older (OR, 1.09 [95% CI, 1.06-1.11]), and living below the federal poverty line (OR, 1.22 [1.20-1.25]) as factors associated with commute times of at least 4 hours.

Conclusions and Relevance

This cross-sectional study of drive-time access to proton beam therapy found that disparities in access existed among certain populations in the US. These results suggest that such disparities present a barrier to an emerging technology in cancer treatment and inhibit equitable access to ongoing clinical trials.

Proton therapy (PT) combined with concurrent chemotherapy for locally advanced non-small cell lung cancer with negative driver genes

PURPOSE

To discuss the optimal treatment modality for inoperable locally advanced Non-Small Cell Lung Cancer patients with poor physical status, impaired cardio-pulmonary function, and negative driver genes, and provide clinical evidence.

MATERIALS AND METHODS

Retrospective analysis of 62 cases of locally advanced non-small cell lung cancer patients with negative driver genes treated at Tsukuba University Hospital(Japan) and Qingdao University Affiliated Hospital(China).The former received proton therapy with concurrent chemotherapy, referred to as the proton group, with 25 cases included; while the latter underwent X-ray therapy with concurrent chemoradiotherapy followed by 1 year of sequential immunomodulatory maintenance therapy, referred to as the X-ray group, with 37 cases included.The treatment response and adverse reactions were assessed using RECIST v1.1 criteria and CTCAE v3.0, and radiotherapy planning and evaluation of organs at risk were performed using the CB-CHOP method.All data were subjected to statistical analysis using GraphPad Prism v9.0, with a T-test using P < 0.05 considered statistically significant.

RESULTS

(1)Target dose distribution: compared to the X-ray group, the proton group exhibited smaller CTV and field sizes, with a more pronounced bragg peak.(2)Organs at risk dose: When comparing the proton group to the X-ray group, lung doses (V5, V20, MLD) and heart doses (V40, Dmax) were lower, with statistical significance (P < 0.05), while spinal cord and esophagus doses showed no significant differences between the two groups (P > 0.05).(3)Treatment-related toxicities: The incidence of grade 3 or higher adverse events in the proton group and X-ray group was 28.6% and 4.2%, respectively, with a statistically significant difference (P < 0.05). In terms of the types of adverse events, the proton group primarily experienced esophagitis and pneumonia, while the X-ray group primarily experienced pneumonia, esophagitis, and myocarditis. Both groups did not experience radiation myelitis or esophagotracheal fistula.(4)Efficacy evaluation: The RR in the proton group and X-ray group was 68.1% and 70.2%, respectively (P > 0.05), and the DCR was 92.2% and 86.4%, respectively (P > 0.05), indicating no significant difference in short-term efficacy between the two treatment modalities.(5)Survival status: The PFS in the proton group and X-ray group was 31.6 ± 3.5 months (95% CI: 24.7 ~ 38.5) and 24.9 ± 1.55 months (95% CI: 21.9 ~ 27.9), respectively (P > 0.05), while the OS was 51.6 ± 4.62 months (95% CI: 42.5 ~ 60.7) and 33.1 ± 1.99 months (95% CI: 29.2 ~ 37.1), respectively (P < 0.05).According to the annual-specific analysis, the PFS rates for the first to third years in both groups were as follows: 100%, 56.1% and 32.5% for the proton group vs. 100%, 54.3% and 26.3% for the X-ray group. No statistical differences were observed at each time point (P > 0.05).The OS rates for the first to third years in both groups were as follows: 100%, 88.2%, 76.4% for the proton group vs. 100%, 91.4%, 46.3% for the X-ray group. There was no significant difference in the first to second years (P > 0.05), but the third year showed a significant difference (P < 0.05). Survival curve graphs also depicted a similar trend.

CONCLUSION

There were no significant statistical differences observed between the two groups in terms of PFS and OS within the first two years. However, the proton group demonstrated a clear advantage over the X-ray group in terms of adverse reactions and OS in the third year. This suggests a more suitable treatment modality and clinical evidence for populations with frail health, compromised cardio-pulmonary function, post-COVID-19 sequelae, and underlying comorbidities.

Failure patterns of locoregional recurrence after reducing target volumes in patients with nasopharyngeal carcinoma receiving adaptive replanning during intensity-modulated radiotherapy: a single-center experience in China

BACKGROUND

Previous researches have demonstrated that adaptive replanning during intensity-modulated radiation therapy (IMRT) could enhance the prognosis of patients with nasopharyngeal carcinoma (NPC). However, the delineation of replanning target volumes remains unclear. This study aimed to evaluate the feasibility of reducing target volumes through adaptive replanning during IMRT by analyzing long-term survival outcomes and failure patterns of locoregional recurrence in NPC.

METHODS

This study enrolled consecutive NPC patients who received IMRT at our hospital between August 2011 and April 2018. Patients with initially diagnosed, histologically verified, non-metastatic nasopharyngeal cancer were eligible for participation in this study. The location and extent of locoregional recurrences were transferred to pretreatment planning computed tomography for dosimetry analysis.

RESULTS

Among 274 patients, 100 (36.5%) received IMRT without replanning and 174 (63.5%) received IMRT with replanning. Five-year rates of locoregional recurrence-free survival (LRFS) were 90.1% (95%CI, 84.8% to 95.4%) and 80.8% (95%CI, 72.0% to 89.6%) for patients with and without replanning, P = 0.045. There were 17 locoregional recurrences in 15 patients among patients with replanning, of which 1 (5.9%) was out-field and 16 (94.1%) were in-field. Among patients without replanning, 19 patients developed locoregional recurrences, of which 1 (5.3%) was out-field, 2 (10.5%) were marginal, and 16 (84.2%) were in-field.

CONCLUSIONS

In-field failure inside the high dose area was the most common locoregional recurrent pattern for non-metastatic NPC. Adapting the target volumes and modifying the radiation dose prescribed to the area of tumor reduction during IMRT was feasible and would not cause additional recurrence in the shrunken area.

Carbon Ion Radiotherapy: An Evidence-Based Review and Summary Recommendations of Clinical Outcomes for Skull-Base Chordomas and Chondrosarcomas

Skull-base chordoma and chondrosarcoma are rare radioresistant tumors treated with surgical resection and/or radiotherapy. Because of the established dosimetric and biological benefits of heavy particle therapy, we performed a systematic and evidence-based review of the clinical outcomes of patients with skull-base chordoma and chondrosarcoma treated with carbon ion radiotherapy (CIRT). A literature review was performed using a MEDLINE search of all articles to date. We identified 227 studies as appropriate for review, and 24 were ultimately included. The published data illustrate that CIRT provides benchmark disease control outcomes for skull-base chordoma and chondrosarcoma, respectively, with acceptable toxicity. CIRT is an advanced treatment technique that may provide not only dosimetric benefits over conventional photon therapy but also biologic intensification to overcome mechanisms of radioresistance. Ongoing research is needed to define the magnitude of benefit, patient selection, and cost-effectiveness of CIRT compared to other forms of radiotherapy.

Risk of temporal lobe necrosis between proton beam and volumetric modulated arc therapies in patients with different head and neck cancers

BACKGROUND

To investigate the frequency of temporal lobe necrosis (TLN) soon after radiotherapy (RT) and identify differences among patients with various types of head and neck cancer (HNC) and between different RT methods.

METHODS

We retrospectively reviewed 483 patients with HNC who had completed RT in our hospital after January, 2015. These patients were followed-up at the radio-oncology department and received contrast-enhanced magnetic resonance imaging (MRI) or computed tomography (CT) to identify metastases or recurrence of cancer at regular intervals. Meanwhile, the occurrence of TLN, graded according to the Common Terminology Criteria for Adverse Events V5.0, was recorded. We categorized the patients into nasopharyngeal carcinoma (NPC) and non-NPC groups and compared the cumulative occurrence of TLN between the groups using Kaplan-Meier and Cox regression analyses. We further compared the cumulative occurrence of TLN between proton beam therapy (PBT) and volumetric modulated arc therapy (VMAT) in patients with any HNC, NPC, and non-NPC HNC.

RESULTS

Compared with the non-NPC group, the NPC group had a higher frequency of TLN (5.6% vs. 0.4%,  p < 0.01) and were more commonly associated with TLN in the Kaplan-Meier analysis (p < 0.01) and the Cox regression model after covariates were adjusted for (adjusted hazard ratio: 13.35, 95% confidence interval: 1.37-130.61) during the follow-up period. Furthermore, the frequency of TLN was similar between patients receiving PBT and those receiving VMAT (PBT vs. VMAT: 4.7% vs. 6.3%, p = 0.76). Kaplan-Meier analysis revealed that the accumulated risks of TLN were similar between PBT and VMAT in patients with any HNC (p = 0.44), NPC (p = 0.84), and non-NPC HNC (p = 0.70).

CONCLUSION

Our study demonstrated that patients with NPC are susceptible to TLN during the early period after RT. In addition, PBT may be associated with an equivalent risk of TLN when compared with VMAT in patients with NPC or other HNCs.

Neurocognition and mean radiotherapy dose to vulnerable brain structures: new organs at risk?

BACKGROUND

Children with brain tumors are at high risk of neurocognitive decline after radiotherapy (RT). However, there is a lack of studies on how RT doses to organs at risk (OARs) impacts neurocognition. The aim of this study was to examine dose-risk relationships for mean RT dose to different brain structures important for neurocognitive networks. We explored previously established OARs and potentially new OARs.

METHODS

A sample of 44 pediatric brain tumor survivors who had received proton and/or photon RT were included. Correlations between mean RT doses to OARs and IQ were analyzed. Previously established OARs were cochleae, optic chiasm, optic nerve, pituitary gland, hypothalamus, hippocampus and pons. Potential new OARs for RT-induced neurocognitive decline were cerebellum, vermis and thalamus.

RESULTS

Mean RT dose to different OARs correlated with several IQ subtests. Higher mean RT dose to cochleae, optic nerve, cerebellum, vermis and pons was correlated with lower performance on particularly full-scale IQ (FIQ), Perceptual Reasoning (PRI), Working Memory (WMI) and Processing Speed Index (PSI). Higher mean RT dose to hippocampus correlated with lower performance on processing speed and working memory. For those receiving whole brain RT (WBRT), higher mean RT dose to the pituitary gland correlated with lower performance on working memory.

CONCLUSION

A high dose-risk correlation was found between IQ subtests and mean RT dose in established and potential new OARs. Thus, in the lack of validated dose constraints for vulnerable brain structures, a parsimonious approach in RT planning should be considered to preserve neurocognitive networks.