Consolidative mediastinal irradiation of malignant lymphoma using active scanning proton beams: clinical outcome and dosimetric comparison.

PURPOSE: Current research approaches in lymphoma focus on reduction of therapy-associated long-term side effects. Especially in mediastinal lymphoma, proton beam radiotherapy (PT) may be a promising approach for reducing the dose to organs at risk (OAR). PATIENTS: In total, 20 patients were irradiated with active scanning PT at Heidelberg Ion Beam Therapy Center (HIT) between September 2014 and February 2017. For comparative analysis, additional photon irradiation plans with helical intensity-modulated radiotherapy (IMRT) were calculated and quantitative and qualitative dose evaluations were made for both treatment modalities. Toxicity and survival outcomes were evaluated. RESULTS: Clinical target volume coverage was comparable in both treatment modalities and did not significantly differ between IMRT and PT. Nevertheless, PT showed superiority regarding the homogeneity index (HIPT = 1.041 vs. HIIMRT = 1.075, p < 0.001). For all OAR, PT showed significantly higher dose reductions compared with IMRT. In particular, the dose to the heart was reduced in PT (absolute dose reduction of Dmean of 3.3 Gy [all patients] and 4.2 Gy [patients with pericardial involvement]). Likewise, the subgroup analysis of female patients, who were expected to receive higher doses to the breast, showed a higher dose reduction in Dmean of 1.2 Gy (right side) and 2.2 Gy (left side). After a median follow-up of 32 months (range 21-48 months), local and distant progression free survival (LPFS and DPFS) were 95.5% and 95.0%, respectively. Radiotherapy was tolerated well with only mild (grade 1-2) radiation-induced acute and chronic side effects. CONCLUSION: A significant reduction in the dose to the surrounding OAR was achieved with PT compared with photon irradiation, without compromising target volume coverage. Dosimetric advantages may have the potential to translate into a reduction of long-term radiation-induced toxicity in young patients with malignant lymphoma of the mediastinum.

Dosimetric comparison of advanced radiotherapy approaches using photon techniques and particle therapy in the postoperative management of thymoma.

BACKGROUND: The purpose of this study was to compare dosimetric differences related to target volume and organs-at-risk (OAR) using 3D-conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), TomoTherapy (Tomo), proton radiotherapy (PRT), and carbon ion radiotherapy (CIRT) as part of postoperative thymoma irradiation. MATERIAL AND METHODS: This single-institutional analysis included 10 consecutive patients treated with adjuvant radiotherapy between December 2013 and September 2016. CT-datasets and respective RT-structures were anonymized and plans for all investigated RT modalities (3DCRT, VMAT, Tomo, PRT, CIRT) were optimized for a total dose of 50 Gy in 25 fractions. Comparisons between target volume and OAR dosimetric parameters were performed using the Wilcoxon rank-sum test. RESULTS: The best target volume coverage (mean PTV V95% for all patients) was observed for Tomo (97.9%), PRT (97.6%), and CIRT (96.6%) followed by VMAT (85.4%) and 3DCRT (74.7%). PRT and CIRT both significantly reduced mean doses to the lungs, breasts, heart, and esophagus, as well as the spinal cord maximum dose compared with photon modalities. Among photon-based techniques, VMAT showed improved OAR sparing over 3DCRT. Tomo was associated with considerable low-dose exposure to the lungs, breasts, and heart. CONCLUSIONS: Particle radiotherapy (PRT, CIRT) showed superior OAR sparing and optimal target volume coverage. The observed dosimetric advantages are expected to reduce toxicity rates. However, their clinical impact must be investigated prospectively.

Carbon ion radiotherapy of hepatocellular carcinoma provides excellent local control: The prospective phase I PROMETHEUS trial.

Background & Aims: Inoperable hepatocellular carcinoma (HCC) can be treated by stereotactic body radiotherapy. However, carbon ion radiotherapy (CIRT) is more effective for sparing non-tumorous liver. High linear energy transfer could promote therapy efficacy. Japanese and Chinese studies on hypofractionated CIRT have yielded excellent results. Because of different radiobiological models and the different etiological spectrum of HCC, applicability of these results to European cohorts and centers remains questionable. The aim of this prospective study was to assess safety and efficacy and to determine the optimal dose of CIRT with active raster scanning based on the local effect model (LEM) I. Methods: CIRT was performed every other day in four fractions with relative biological effectiveness (RBE)-weighted fraction doses of 8.1-10.5 Gy (total doses 32.4-42.0 Gy [RBE]). Dose escalation was performed in five dose levels with at least three patients each. The primary endpoint was acute toxicity after 4 weeks. Results: Twenty patients received CIRT (median age 74.7 years, n = 16 with liver cirrhosis, Child-Pugh scores [CP] A5 [n = 10], A6 [n = 4], B8 [n = 1], and B9 [n = 1]). Median follow up was 23 months. No dose-limiting toxicities and no toxicities exceeding grade II occurred, except one grade III gamma-glutamyltransferase elevation 12 months after CIRT, synchronous to out-of-field hepatic progression. During 12 months after CIRT, no CP elevation occurred. The highest dose level could be applied safely. No local recurrence developed during follow up. The objective response rate was 80%. Median overall survival was 30.8 months (1/2/3 years: 75%/64%/22%). Median progression-free survival was 20.9 months (1/2/3 years: 59%/43%/43%). Intrahepatic progression outside of the CIRT target volume was the most frequent pattern of progression. Conclusions: CIRT of HCC yields excellent local control without dose-limiting toxicity. Impact and implications: To date, safety and efficacy of carbon ion radiotherapy for hepatocellular carcinoma have only been evaluated prospectively in Japanese and Chinese studies. The optimal dose and fractionation when using the local effect model for radiotherapy planning are unknown. The results are of particular interest for European and American particle therapy centers, but also of relevance for all specialists involved in the treatment and care of patients with hepatocellular carcinoma, as we present the first prospective data on carbon ion radiotherapy in hepatocellular carcinoma outside of Asia. The excellent local control should encourage further use of carbon ion radiotherapy for hepatocellular carcinoma and design of randomized controlled trials. Clinical Trials Registration: The study is registered at ClinicalTrials.gov (NCT01167374).

Treatment Tolerability and Toxicity of Postoperative Proton Beam Therapy for Gynecologic Malignancies: Results of the Prospective Phase 2 APROVE Trial.

PURPOSE: The APROVE study is a prospective one-arm phase-2 study investigating the safety and treatment tolerability of postoperative proton beam therapy in women with uterine cervical or endometrial cancer. In this analysis, we report the primary study endpoint of safety and treatment tolerability as well as toxicity rates and progression-free survival (PFS). METHODS AND MATERIALS: 25 patients were treated with postoperative proton beam therapy with a total dose of 45 to 50.4 Gy (RBE) in 5 to 6 × 1.8 Gy (RBE) fractions weekly using active raster-scanning intensity modulated proton beam therapy (IMPT). Sequential or simultaneous platinum-based chemotherapy was administered if indicated. The primary endpoint was defined as the lack of any acute ≥grade 3 gastrointestinal (GI) or urogenital (GU) toxicity according to the Common Terminology Criteria for Adverse Events v 4.0 or premature treatment abortion. Secondary endpoints were clinical symptoms and toxicity, quality of life, and PFS. RESULTS: All patients completed IMPT according to the protocol, with a median treatment duration of 43 days (range, 33 to 51 days). No patient developed gastrointestinal or genitourinary toxicity ≥grade 3, and the treatment tolerability rate was 100%. Therefore, the null hypothesis H0: Tolerability Rate ≤80% could be rejected in favor of the alternative hypothesis H1: Tolerability rate >80% using an exact binomial test with a one-sided significance level of α = 10% (one-sided P value P = .0059). The median follow-up time after the end of IMPT was 25.1 months (range, 20.2 to 50.3 months). 18 of 25 (75%) patients completed the study follow-up of 24 months. 7 patients had progressive disease. Kaplan-Meier-estimated mean PFS was 39.9 months (95% confidence interval: 33.37 to 46.5 months). CONCLUSIONS: Postoperative IMPT is a safe treatment option for cervical and endometrial cancer patients, with only low-grade acute and late toxicities. Larger randomized trials are necessary to further assess the potential of IMPT and improve patient selection.

Health-related quality of life and patient-reported symptoms after postoperative proton beam radiotherapy of cervical and endometrial cancer: 2-year results of the prospective phase II APROVE-trial.

INTRODUCTION: The APROVE-trial investigated the tolerability of postoperative proton beam therapy in women with cervical or endometrial cancer. The present analysis evaluated the secondary endpoints of health-related quality of life (HRQOL) and patient-reported symptoms. METHODS: 25 patients were included in this prospective phase-II-trial and treated with postoperative radiotherapy using protons alone or in combination with chemotherapy. To attain general and gynecologic-specific HRQOL measures, the EORTC-QLQ-C30 questionnaires combined with -QLQ-CX24 for cervical and -QLQ-EN24 for endometrial cancer were assessed at baseline, at the end of RT and up to 2 years after radiotherapy. The results were compared to an age-matched norm reference population. Symptoms were assessed using Common Terminology Criteria for Adverse Events (CTCAE) and institutional patient-reported symptoms grading. RESULTS: Scores regarding global health status were markedly impaired at baseline (mean: 58.0 ± 20.1) compared to reference population data, but significantly (p = 0.036) improved and evened out to comparable norm values 2 years after proton therapy (mean: 69.9 ± 19.3). Treatment caused acute and long-term worsening of pain (p = 0.048) and gastrointestinal symptoms (p = 0.016) for women with endometrial cancer, but no higher-grade CTCAE ≥ 3° toxicity was observed. Dosimetric evaluation of rectum, sigmoid, large and small bowel showed no correlation with the reported gastrointestinal symptoms. After 2 years, fatigue had significantly improved (p = 0.030), whereas patients with cervical cancer experienced more often lymphedema (p = 0.017). Scores for endometrial cancer pertaining to sexual activity (p = 0.048) and body image (p = 0.022) had improved post treatment; in the latter this effect persisted after 2 years. CONCLUSION: Proton beam therapy in the adjuvant setting was well tolerated with only low-grade side effects concerning gastrointestinal symptoms, lymphedema and pain. Overall quality of life was impaired at baseline, but patients were able to recover to values comparable to norm population 2 years after proton therapy. Larger studies are needed to confirm whether the benefit of proton therapy translates into a clinical effect. Sexual dysfunction remains an important issue. TRIAL REGISTRATION: The trial was registered at https://clinicaltrials.gov (ClinicalTrials.gov Identifier: NCT03184350, 09th June 2017).

Results of a prospective randomized trial on long-term effectiveness of protons and carbon ions in prostate cancer: LEM I and α/ß = 2 Gy overestimates the RBE.

AIM: To analyze the long-term effectiveness of carbon ions relative to protons in the prospective randomized controlled ion prostate irradiation (IPI) trial. METHODS: Effectiveness via PSA assessment in a randomized study on prostate irradiation with 20x3.3 Gy(RBE) protons versus carbon ions was analyzed in 92 patients. Proton RBE was based on a fixed RBE of 1.1 while the local effect model (LEM) I and an α/ß = 2 Gy was used for carbon ions. The dose in the prostate was recalculated based on the delivered treatment plan using LEM I and LEM IV and different α/ß values. RESULTS: Five-year overall and progression free survival was 98% and 85% with protons and 91% and 50% with carbon ions, respectively, with the latter being unexpectedly low compared to Japanese carbon ion data and rather corresponding to a photon dose <72 Gy in 2 Gy fractions. According to LEM I and the applied α/ß-value of 2 Gy, the applied carbon ion dose in 2 Gy(RBE) fractions (EQD2) was 87.46 Gy(RBE). Recalculations confirmed a strong dependence of RBE-weighted dose on the α/ß ratio as well as on the RBE-model. CONCLUSION: The data demonstrate a significant lower effectiveness of the calculated RBE-weighted dose in the carbon ion as compared to the proton arm. LEM I and an α/ß = 2 Gy overestimates the RBE for carbon ions in prostate cancer treatment. Adjusting the biological dose calculation by using LEM I with α/ß = 4 Gy could be a pragmatic way to safely escalate dose in carbon ion radiotherapy for prostate cancer.

Secondary Malignancy Risk Following Proton vs. X-ray Radiotherapy of Thymic Epithelial Tumors: A Comparative Modeling Study of Thoracic Organ-Specific Cancer Risk.

BACKGROUND: Proton beam radiotherapy (PBT) offers physical dose advantages that might reduce the risk for secondary malignancies (SM). The aim of the current study is to calculate the risk for SM after X-ray-based 3D conformal (3DCRT) radiotherapy, intensity-modulated radiotherapy (IMRT), and active pencil beam scanned proton therapy (PBS) in patients treated for thymic malignancies. METHODS: Comparative treatment plans for each of the different treatment modalities were generated for 17 patients. The risk for radiation-induced SM was estimated using two distinct prediction models-the Dasu and the Schneider model. RESULTS: The total and fatal SM risks estimated using the Dasu model demonstrated significant reductions with the use of PBS relative to both 3DCRT and IMRT for all independent thoracic organs analyzed with the exception of the thyroid gland (p ≤ 0.001). SM rates per 10,000 patients per year per Gy evaluated using the Schneider model also resulted in significant reductions with the use of PBS relative to 3DCRT and IMRT for the lungs, breasts, and esophagus (p ≤ 0.001). CONCLUSIONS: PBS achieved superior sparing of relevant OARs compared to 3DCRT and IMRT, leading to a lower risk for radiation-induced SM. PBS should therefore be considered in patients diagnosed with thymic malignancies, particularly young female patients.