Current status of stereotactic body radiotherapy for lung cancer

Stereotactic Radiosurgery with Volumetric Modulated Arc Radiotherapy: Final Results of a Multi-arm Phase I Trial (DESTROY-2)

AIMS

To present the final results of a phase I trial on stereotactic radiosurgery (SRS) delivered using volumetric modulated arc therapy (VMAT) in patients with primary or metastatic tumors in different extracranial sites.

MATERIALS AND METHODS

The DESTROY-2 trial, planned as a prospective dose escalation study in oligometastatic (one to five lesions) cancer patients relied on the delivery of a single high dose of radiation utilizing high-precision technology. The primary study endpoint was the definition of the maximum tolerated dose (MTD) of SRS-VMAT. The secondary objectives of the study were the evaluation of safety, efficacy, and long-term outcomes. All patients consecutively observed at our radiotherapy unit matching the inclusion criteria were enrolled. Each enrolled subject was included in a different phase I study arm, depending on the tumor site and the disease stage (lung, liver, bone, other), and sequentially assigned to a particular dose level.

RESULTS

Two hundred twenty seven lesions in 164 consecutive patients (male/female: 97/67, median age: 68 years; range: 29-92) were treated. The main primary tumors were: prostate cancer (60 patients), colorectal cancer (47 patients), and breast cancer (39 patients). The maximum planned dose level was achieved in all study arms, and the MTD was not exceeded. 34 Gy, 32 Gy, 24 Gy, and 24 Gy were established as the single-fraction doses for treating lung, liver, bone, and other extracranial lesions, respectively. The prescribed BED 2Gyα/β:10 to the planning target volume ranged from 26.4 Gy to 149.6 Gy. Twenty-seven patients (16.5%) experienced grade 1-2 and only one grade 3 acute toxicity, which was a pulmonary one. In terms of late toxicity, we registered only 5 toxicity>G2: a G3 gastro-intestinal one, three G3 bone toxicity, and a G3 laryngeal toxicity. The overall response was available for 199 lesions: 107 complete response (53.8%), 50 partial response (25.1%), and 31 stable disease (15.6%), leading to an overall response rate of 94.5%. Progression was registered only in 11 cases (5.5%). The overall response rate in each arm ranged from 88.6% to 96.4%. The overall two-year local control, distant metastasis free survival, disease free survival, and overall survival were 81.7%, 33.0%, 25.4%, and 78.7% respectively.

CONCLUSION

In conclusion, the planned doses of 34 Gy, 32 Gy, 24 Gy, and 24 Gy were successfully administered as single-fractions for the treatment of lung, liver, bone, and other extracranial lesions, respectively, in a prospective SRS dose-escalation trial. No dose-limiting toxicities were registered, and minimal acute and late toxicity were reported. New indications for SRS are currently being studied in oligoprogressive patients receiving targeted drugs or in combination with immunotherapy. The DESTROY-2 trial represents, in our opinion, a credible starting point for future modern radiosurgery trials.

Analysis of clinical and physical dosimetric factors that determine the outcome of severe acute radiation pneumonitis in lung cancer patients

OBJECTIVE

We conducted a retrospective statistical analysis of clinical and physical dosimetric factors of lung cancer patients who had previously undergone lung and/or mediastinal radiotherapy and died of or survived severe acute radiation pneumonitis (SARP). Our study was the first to reveal the heterogeneity in clinical factors, physical dosimetric factors, and SARP onset time that determined the clinical outcomes of lung cancer patients who developed SARP.

MATERIALS AND METHODS

The clinical characteristics, physical dosimetry factors, and SARP onset time of deceased and surviving patients were retrospectively analyzed. SPSS 20.0 was used for data analysis. Student's t-test was used for intergroup comparison, and a Mann-Whitney U test was used for data with skewed distribution. Qualitative data were represented using frequencies (%), and Fisher's exact test or χ2 test was used for intergroup comparison of nonparametric data. Binary logistic analysis was used for univariate and multivariate analyses. Differences with a P < 0.05 were considered statistically significant.

RESULTS

Univariate analysis revealed that the potential predictors of SARP death were as follows: ipsilateral lung V5 and V30, contralateral lung V5, V10, and V30, total lung V5, V10, and V30, mean lung dose, mean heart dose, and maximum spinal cord dose. Multivariate analysis showed that ipsilateral lung V5 and total lung V5 were predictors that determined the final outcome of SARP patients. In addition, we analyzed the time from the completion of radiotherapy to SARP onset, and found significant difference between the two groups.

CONCLUSIONS

There was no decisive correlation between clinical characteristics and SARP outcome (i.e., death or survival) in lung radiotherapy patients. Ipsilateral lung V5 and total lung V5 were independent predictors of death in SARP patients.

Stereotactic Body Radiation Therapy (SBRT) for Oligorecurrent/Oligoprogressive Mediastinal and Hilar Lymph Node Metastasis: A Systematic Review

Simple Summary

This paper is a review of the literature on oligorecurrent/oligoprogressive mediastinal and hilar lymph node metastasis treated with SBRT. The use of mediastinal SBRT had historically been not feasible in view of the expected toxicity due to the proximity of critical structures such as the airways and esophagus. Despite the heterogeneity and lack of some data in the studies analyzed, this literature review is the first published and can be a valid guide for the radiotherapist in the management of oligometastatic/oligoprogressive patients, with particular regard to the radiotherapy doses, dose constraints for organs at risk, and clinical outcomes.

Abstract

Introduction: Mediastinal or hilar lymph node metastases are a challenging condition in patients affected by solid tumors. Stereotactic body radiation therapy (SBRT) could play a crucial role in the therapeutic management and in the so-called “no-fly zone”, delivering high doses of radiation in relatively few treatment fractions with excellent sparing of healthy surrounding tissues and low toxicity. The aim of this systematic review is to evaluate the feasibility and tolerability of SBRT in the treatment of mediastinal and hilar lesions with particular regard to the radiotherapy doses, dose constraints for organs at risk, and clinical outcomes. Materials and methods: Two blinded investigators performed a critical review of the Medline, Web of Knowledge, Google Scholar, Scopus, and Cochrane databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (PRISMA), starting from a specific question: What is the clinical impact of SBRT for the treatment of oligorecurrent/oligoprogressive mediastinal and hilar metastasis? All retrospective and prospective clinical trials published in English up to February 2022 were analyzed. Results: A total of 552 articles were identified and 12 of them were selected with a total number of 478 patients treated with SBRT for mediastinal or hilar node recurrence. All the studies are retrospective, published between 2015 and 2021 with a median follow-up ranging from 12 to 42.2 months. Studies following SBRT for lung lesions or retreatments after thorax radiotherapy for stage III lung cancer were also included. The studies showed extensive heterogeneity in terms of patient and treatment characteristics. Non-small cell lung cancer was the most frequently reported histology. Different dose schemes were used, with a higher prevalence of 4–8 Gy in 5 or 6 fractions, but dose escalation was also used up to 52 Gy in 4 fractions with dose constraints mainly derived from RTOG 0813 trial. The radiotherapy technique most frequently used was volumetric modulated arc therapy (VMAT) with a median PTV volume ranging from 7 to 25.7 cc. The clinical outcome seems to be very encouraging with 1-year local control (LC), overall survival (OS) and progression-free survival (PFS) rates ranging from 84 to 94%, 53 to 88% and 23 to 53.9%, respectively. Half of the studies did not report toxicity greater than G3 and only five cases of fatal toxicity were reported. CONCLUSIONS: From the present review, it is not possible to draw definitive conclusions because of the heterogeneity of the studies analyzed. However, SBRT appears to be a safe and effective option in the treatment of mediastinal and hilar lymph node recurrence, with a good toxicity profile. Its use in clinical practice is still limited, and there is extensive heterogeneity in patient selection and fractionation schedules. Good performance status, small PTV volume, absence of previous thoracic irradiation, and administration of a high biologically effective dose (BED) seem to be factors that correlate with greater local control and better survival rates. In the presence of symptoms related to the thoracic lymph nodes, SBRT determines a rapid control that lasts over time. We look forward to the prospective studies that are underway for definitive conclusions.

Oligorecurrent nodal prostate cancer: radiotherapy quality assurance of the randomized PEACE V-STORM phase II trial

PURPOSE

Aim of this study is to report the results of the radiotherapy quality assurance program of the PEACE V-STORM randomized phase II trial for pelvic nodal oligorecurrent prostate cancer (PCa).

MATERIAL AND METHODS

A benchmark case (BC) consisting of a postoperative case with 2 nodal recurrences was used for both stereotactic body radiotherapy (SBRT, 30 Gy/3 fx) and whole pelvic radiotherapy (WPRT, 45 Gy/25 fx + SIB boost to 65 Gy).

RESULTS

BC of 24 centers were analyzed. The overall grading for delineation variation of the 1st BC was rated as 'UV' (Unacceptable Variation) or 'AV' (Acceptable Variation) for 1 and 7 centers for SBRT (33%), and 3 and 8 centers for WPRT (46%), respectively. An inadequate upper limit of the WPRT CTV (n=2), a missing delineation of the prostate bed (n=1), and a missing nodal target volume (n=1 for SBRT and WPRT) constituted the observed 'UV'. With the 2nd BC (n=11), the overall delineation review showed 2 and 8 'AV' for SBRT and WPRT, respectively, with no 'UV'. For the plan review of the 2nd BC, all treatment plans were per protocol for WPRT. SBRT plans showed variability in dose normalization (Median D_90% = 30.1 Gy, range 22.9-33.2Gy and 30.6 Gy, range 26.8-34.2Gy for nodes 1 and 2 respectively).

CONCLUSIONS

Up to 46% of protocol deviations were observed in delineation of WPRT for nodal oligorecurrent PCa, while dosimetric results of SBRT showed the greatest disparities between centers. Repeated BC resulted in an improved adherence to the protocol, translating in an overall acceptable contouring and planning compliance rate among participating centers.

Stereobody radiotherapy for nodal recurrences in oligometastatic patients: a pooled analysis from two phase I clinical trials

Stereotactic body radiotherapy (SBRT) has been shown to achieve high local control rates in limited metastatic burden of disease. Few papers reported on the efficacy of SBRT in nodal oligometastases. The primary aim of the present paper was to analyze the treatment outcome in this setting. Data from DESTROY-1 and SRS-DESTROY-2 phase I clinical trials were reviewed and analyzed. These trials were based on a 5 fractions and a single fraction regimens, respectively. End-points of this analysis were toxicity rates, overall response rate (ORR), and local control (LC). Patients treated between December 2003 and January 2018, with any metastatic site, and primary tumor type and histology were included. One hundred-eighty-one patients (M/F: 93/88; median age: 67, range 37-88) treated with SBRT on 253 nodal lesions were analyzed. Initially, the used technique was 3D-CRT (20.9%), while subsequently treatments were delivered by VMAT (79.1%). The total dose to the PTV ranged between 12 Gy/single fraction to 50 Gy/5 fractions. With a median follow-up of 21 months (2-124), no grade 3 acute or late toxicity was recorded. ORR based on functional imaging was 92.5% with a complete response rate of 76%. Two- and three-year actuarial LC were 81.6% and 76.0%, respectively. Our large pooled analysis confirms the efficacy and safety of SBRT/SRS in patients with nodal metastases and identifies clinical and treatment variables able to predict complete response and local control rate.

Stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC): contemporary insights and advances

The standard-of-care treatment for early-stage non-small cell lung cancer (NSCLC) continues to be surgery in the form of lobectomy or pneumonectomy. Stereotactic body radiation therapy (SBRT) has evolved as a viable alternative to surgery for medically inoperable patients, achieving excellent local control (LC) with relatively minimal toxicity in standard-risk patients. Nevertheless, the maturation of SBRT has fostered debate regarding its use, technique, dose, and fractionation, particularly in the context of patient- and disease-specific characteristics such as tumor size and location. This review will cover the recent trends and future directions of SBRT as it becomes an increasingly individualized modality in the treatment of early-stage NSCLC.

Repeated photon and C-ion irradiations in vivo have different impact on alteration of tumor characteristics

Precise characterization of tumor recurrence and regrowth after radiotherapy are important for prognostic understanding of the therapeutic effect. Here, we established a novel in vivo mouse model for evaluating the characteristics of regrown tumor after repeated photon and carbon ion (C-ion) irradiations. The results showed that tumor growth rate, lung metastasis, shortening of the survival of the tumor-bearing mice, and tumor microvessel formation were promoted 2- to 3-fold, and expression of angiogenic and metastatic genes increased 1.5- to 15-fold in regrown tumors after repeated photon irradiations, whereas repeated C-ion irradiations did not alter these characteristics. Interestingly, both repeated photon and C-ion irradiations did not generate radioresistance, which is generally acquired for in vitro treatment. Our results demonstrated that the repetition of photon, and not C-ion, irradiations in vivo alter the characteristics of the regrown tumor, making it more aggressive without acquisition of radioresistance.

Dosimetric evaluation of the feasibility of stereotactic body radiotherapy for primary lung cancer with lobe-specific selective elective nodal irradiation

More than 10% of all patients treated with stereotactic body radiotherapy (SBRT) for primary lung cancer develop regional lymph node recurrence. We evaluated the dosimetric feasibility of SBRT with lobe-specific selective elective nodal irradiation (ENI) on dose-volume histograms. A total of 21 patients were treated with SBRT for Stage I primary lung cancer between January 2010 and June 2012 at our institution. The extents of lobe-specific selective ENI fields were determined with reference to prior surgical reports. The ENI fields included lymph node stations (LNS) 3 + 4 + 11 for the right upper lobe tumors, LNS 7 + 11 for the right middle or lower lobe tumors, LNS 5 + 11 for the left upper lobe tumors, and LNS 7 + 11 for the left lower lobe tumors. A composite plan was generated by combining the ENI plan and the SBRT plan and recalculating for biologically equivalent doses of 2 Gy per fraction, using a linear quadratic model. The V20 of the lung, D(1cm3) of the spinal cord, D(1cm3) and D(10cm3) of the esophagus and D(10cm3) of the tracheobronchial wall were evaluated. Of the 21 patients, nine patients (43%) could not fulfill the dose constraints. In all these patients, the distance between the planning target volume (PTV) of ENI (PTVeni) and the PTV of SBRT (PTVsrt) was ≤2.0 cm. Of the three patients who developed regional metastasis, two patients had isolated lymph node failure, and the lymph node metastasis was included within the ENI field. When the distance between the PTVeni and PTVsrt is >2.0 cm, SBRT with selective ENI may therefore dosimetrically feasible.

Evaluation of dosimetric misrepresentations from 3D conventional planning of liver SBRT using 4D deformable dose integration

The purpose of this study is to evaluate dosimetric errors in 3D conventional planning of stereotactic body radiotherapy (SBRT) by using a 4D deformable image registration (DIR)‐based dose‐warping and integration technique. Respiratory‐correlated 4D CT image sets with 10 phases were acquired for four consecutive patients with five liver tumors. Average intensity projection (AIP) images were used to generate 3D conventional plans of SBRT. Quasi‐4D path‐integrated dose accumulation was performed over all 10 phases using dose‐warping techniques based on DIR. This result was compared to the conventional plan in order to evaluate the appropriateness of 3D (static) dose calculations. In addition, we consider whether organ dose metrics derived from contours defined on the average intensity projection (AIP), or on a reference phase, provide the better approximation of the 4D values. The impact of using fewer (<10) phases was also explored. The AIP‐based 3D planning approach overestimated doses to targets by 1.4% to 8.7% (mean 4.2%) and underestimated dose to normal liver by up to 8% (mean −5.5%; range −2.3% to −8.0%), compared to the 4D methodology. The homogeneity of the dose distribution was overestimated when using conventional 3D calculations by up to 24%. OAR doses estimated by 3D planning were, on average, within 10% of the 4D calculations; however, differences of up to 100% were observed. Four‐dimensional dose calculation using 3 phases gave a reasonable approximation of that calculated from the full 10 phases for all patients, which is potentially useful from a workload perspective. 4D evaluation showed that conventional 3D planning on an AIP can significantly overestimate target dose (ITV and GTV+5mm), underestimate normal liver dose, and overestimate dose homogeneity. Implementing nonadaptive quasi‐4D dose calculation can highlight the potential limitation of 3D conventional SBRT planning and the resultant misrepresentations of dose in some regions affected by motion and deformation. Where the 4D approach is unavailable, contouring on the full expiration phase may yield more accurate dose calculations, most relevant in the case of the healthy liver, but the absolute dose differences are in general small for the other healthy organs. The technique has the potential to quantify under‐ and over‐dosage and improve treatment plan evaluation, retrospective plan analysis, and clinical outcome correlation.

PACS numbers: 87.55.‐x, 87.55.D‐, 87.55.de, 87.55.dk, 87.55.Qr, 87.57.nj

Hypofractionated stereotactic body radiation therapy for elderly patients with stage IIB-IV nonsmall cell lung cancer who are ineligible for or refuse other treatment modalities

Objective

In elderly patients with stage IIB–IV nonsmall cell lung cancer who cannot tolerate chemotherapy, conventionally fractionated radiotherapy is the treatment of choice. We present our experience with hypofractionated stereotactic body radiation therapy (SBRT) in the treatment of this patient population.

Methods

Thirty-three patients with a median age of 80 years treated with fractionated SBRT were retrospectively analyzed. Most patients were smokers and had preexisting lung disease and either refused treatment or were ineligible. A median prescribed dose of 40 Gy was delivered to the prescription isodose line over a median of five treatments. The majority of patients (70%) did not receive chemotherapy.

Results

With a median follow-up of 9 months (range: 4–40 months), the actuarial median overall survival (OS) and progression-free survival were 12 months for both. One year actuarial survival outcomes were 75%, 58%, 44%, and 48% for local control, regional control, progression-free survival, and OS, respectively. Increased volume of disease was a statistically significant predictor of worse OS. Three patients developed a grade 1 cough that peaked 3 weeks after treatment and resolved within 1 month. One patient developed grade 1 tracheal mucositis and three patients developed grade 1 pneumonitis. Both resolved 6 weeks after treatment. Three patients died within the first month of treatment, but the cause of death did not appear to be related to the treatment.

Conclusion

Hypofractionated SBRT is a relatively safe and convenient treatment option for elderly patients with inoperable stage IIB–IV nonsmall cell lung cancer. However, given the small sample size and the heterogeneity of the patient population, larger studies are needed before adopting this treatment option into clinical practice.

Feasibility study of stereotactic body radiotherapy for peripheral lung tumors with a maximum dose of 100 Gy in five fractions and a heterogeneous dose distribution in the planning target volume

We evaluated toxicity and outcomes for patients with peripheral lung tumors treated with stereotactic body radiation therapy (SBRT) in a dose-escalation and dose-convergence study. A total of 15 patients were enrolled. SBRT was performed with 60 Gy in 5 fractions (fr.) prescribed to the 60% isodose line of maximum dose, which was 100 Gy in 5 fr., covering the planning target volume (PTV) surface (60 Gy/5 fr. - (60%-isodose)) using dynamic conformal multiple arc therapy (DCMAT). The primary endpoint was radiation pneumonitis (RP) ≥ Grade 2 within 6 months. Toxicities were graded according to the Common Terminology Criteria for Adverse Events, version 4.0. Using dose-volumetric analysis, the trial regimen of 60 Gy/5 fr. - (60%-isodose) was compared with our institutional conventional regimen of 50 Gy/5 fr. - (80%-isodose). The enrolled consecutive patients had either a solitary peripheral tumor or two ipsilateral tumors. The median follow-up duration was 22.0 (12.0-27.0) months. After 6 months post-SBRT, the respective number of RP Grade 0, 1 and 2 cases was 5, 9 and 1. In the Grade 2 RP patient, the image showed an organizing pneumonia pattern at 6.0 months post-SBRT. No other toxicity was found. At last follow-up, there was no evidence of recurrence of the treated tumors. The target volumes of 60 Gy/ 5 fr. - (60%-isodose) were irradiated with a significantly higher dose than those of 50 Gy/5 fr. - (80%-isodose), while the former dosimetric parameters of normal lung were almost equivalent to the latter. SBRT with 60 Gy/5 fr. - (60%-isodose) using DCMAT allowed the delivery of very high and convergent doses to peripheral lung tumors with feasibility in the acute and subacute phases. Further follow-up is required to assess for late toxicity.

Stereotactic radiosurgery (SRS) with volumetric modulated arc therapy (VMAT): interim results of a multi-arm phase I trial (DESTROY-2)

AIMS

To present the interim results of a phase I trial on stereotactic radiosurgery (SRS) delivered using volumetric modulated arc therapy (VMAT) in patients with primary or metastatic tumours in different extracranial sites.

MATERIALS AND METHODS

Patients were enrolled in different arms according to tumour site and clinical stage, and sequentially assigned to a given dose level. Acute toxicity, tumour response and early local control were investigated and reported.

RESULTS

One hundred lesions in 65 consecutive patients (male/female: 30/35, median age: 66 years; range: 40-89) were treated. Of these 100 lesions, 21 were primary or metastatic lung tumours, 24 were liver metastases, 30 were bone metastases, 24 were nodal metastases and one was a primary vulvar melanoma. The prescribed dose ranged from 12 (BED(2Gy,α/β:10) = 26.4 Gy) to 28 Gy (BED(2Gy,α/β:10) = 106.4 Gy) to the planning target volume. Twenty-one patients (32.3%) experienced grade 1-2 acute toxicity, which was grade 2 in only two cases. The overall response rate based on computed tomography/magnetic resonance imaging was 52% (95% confidence interval 40.1-63.2%) and based on positron emission tomography scan was 90% (95% confidence interval 76.2-96.4%). As of November 2013, the median duration of follow-up was 11 months (range = 1-38). Recurrence/progression within the SRS-VMAT treated field was observed in nine patients (total lesions = 18): the inside SRS-VMAT field local control expressed on a per lesion basis was 87.8% at 12 months and 71.9% at 24 months.

CONCLUSIONS

The maximum tolerable dose has not yet been reached in any study arm. SRS-VMAT resulted in positive early clinical results in terms of tumour response, local control rate and acute toxicity.

Extracranial radiosurgery with volumetric modulated arc therapy: Feasibility evaluation of a phase I trial

The aim of this study was to report early clinical experience in stereotactic body radiosurgery (SBRS) delivered using volumetric intensity modulated arc therapy (VMAT) in patients with primary or metastatic tumors in various extra-cranial body sites. Each enrolled subject was included in a different phase I study arm, depending on the tumor site and the disease stage (lung, liver, bone, metastatic), and sequentially assigned to a particular dose level. Technical feasibility and dosimetric results were investigated. The acute toxicity, tumor response and early local control were also studied. In total, 25 lesions in 20 consecutive patients (male/female, 11/9; median age, 67 years; age range, 47-86 years) were treated. Of these 25 lesions, 4 were primary or metastatic lung tumors, 6 were liver metastases, 8 were bone metastases and 7 were nodal metastases. The dose-volume constraints for organs at risk (OARs) were observed in 19 patients using a single-arc technique. Only in one patient were two arcs required. The treatment was performed without interruption or any other technical issues. The prescribed dose ranged from 12-26 Gy to the planning target volume (PTV). Delivery time ranged from 4 min to 9 min and 13 sec (median, 6 min and 6 sec). No incidence of grade 2-4 acute toxicity was recorded. The overall response rate was 48% (95% confidence interval (CI), 24.2-70.2) based on computed tomography (CT)/magnetic resonance imaging (MRI) and 89% (95% CI, 58.6-98.7) based on the positron emission tomography (PET) scan. SBRS delivered by means of VMAT allowed the required target coverage to be achieved while remaining within the normal tissue dose-volume constraints in the 20 consecutive patients. VMAT-SBRS resulted in adequate technical feasibility; the maximum tolerable dose has not yet been reached in any study arm.

Multi-institutional comparison of treatment planning using stereotactic ablative body radiotherapy for hepatocellular carcinoma - benchmark for a prospective multi-institutional study

Introduction

Several single institution phase I and phase II trials of stereotactic ablative body radiotherapy (SABR) for liver tumors have reported promising results and high local control rates of over 90%. However, there are wide variations in dose and fractionation due to different prescription policies and treatment methods across SABR series that have been published to date.

This study aims to assess and minimize inter-institutional variations in treatment planning using SABR for hepatocellular carcinoma (HCC) in preparation for a prospective multi-institutional study.

Methods

Four institutions (A-D) participated in this study. Each institution was provided with data from four cases, including planning and diagnostic CT images and clinical information, and asked to implement three plans (a practice plan and protocol plans 1 and 2). Practice plans were established based on the current treatment protocols at each institution. In protocol plan 1, each institution was instructed to prescribe 40 Gy in five fractions within 95% of the planning target volume (PTV). After protocol plan 1 was evaluated, we made protocol plan 2, The additional regulation to protocol plan 1 was that 40 Gy in five fractions was prescribed to a 70% isodose line of the global maximum dose within the PTV. Planning methods and dose volume histograms (DVHs) including the median PTV D50 (D_m50) and the median normal liver volume that received 20 Gy or higher (V_m20) were compared.

Results

In the practice plan, D_m50 was 48.4 Gy (range, 43.6-51.2 Gy). V_m20 was 15.9% (range, 12.2-18.9%). In protocol plan 1, the D_m50 at institution A was higher (51.2 Gy) than the other institutions (42.0-42.2 Gy) due to differences in dose specifications. In protocol plan 2, variations in DVHs were reduced. The D_m50 was 51.9 Gy (range, 51.0-53.1 Gy), and the V_m20 was 12.3% (range, 10.4-13.2%). The homogeneity index was nearly equivalent at all institutions.

Conclusions

There were notable inter-institutional differences in practice planning using SABR to treat HCC. The range of PTV and normal liver DVH values was reduced when the dose was prescribed to an isodose line within the PTV. In multi-institutional studies, detailed dose specifications based on collaboration are necessary.

Quality of life and toxicity of stereotactic radiotherapy in pancreatic tumors: a case series

AIM

To analyze the results of extracranial stereotactic radiotherapy (ESRT) experience in pancreatic cancer patients.

METHODS

Four noncoplanar fixed beams were used in all patients.

RESULTS

Analysis of 16 patients was carried out. Overall response rate was 56.2%. Fifteen patients experienced local and/or distant progression of disease (median follow-up: 24 months). Two-year local progression-free, distant progression-free, and overall survivals were 85.7%, 58.7%, and 50.0%, respectively. Toxicity was less than grade 2 in all, although 1 patient had severe duodenal bleeding. Quality of life scores were unchanged.

CONCLUSIONS

ESRT was associated with low complication rate, and not worsening the patients' quality of life.

Short-term outcomes of CyberKnife therapy for advanced high-risk tumors: A report of 160 cases

The objective of the present study was to evaluate short-term outcomes of CyberKnife therapy in patients with advanced high-risk tumors. A total of 201 target areas from 341 advanced high-risk tumor lesions in 160 patients were treated with CyberKnife. A prescribed dose of 18-60 Gy to the gross tumor volume was delivered in 1-6 fractions to complete the entire treatment in 1 week. Radiographic studies and clinical examinations were performed at 1- to 3-month follow-up intervals, and the results were compared to outcomes of 160 similar advanced high-risk tumor patients who were treated by conformal radiotherapy (CRT). After CyberKnife therapy, the short-term improvement in the quality of life was significant according to radiographic study, radioimmunoassay and ZPS scores of these patients. The total rates of objective efficacy and alleviation of ascities were as high as 66.88 and 67.90%. The short-term outcomes in our series of patients with advanced high-risk tumors treated with CyberKnife appeared to be better compared to conventional CRT. CyberKnife may be an option for patients with incurable advanced high-risk tumors, although further studies of the long-term outcomes are required to confirm the validity.

Quantification of incidental mediastinal and hilar irradiation delivered during definitive stereotactic body radiation therapy for peripheral non-small cell lung cancer

To determine the amount of incidental radiation dose received by the mediastinal and hilar nodes for patients with non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT). Fifty consecutive patients with NSCLC, treated using an SBRT technique, were identified. Of these patients, 38 had a prescription dose of 60 Gy in 20-Gy fractions and were eligible for analysis. For each patient, ipsilateral upper (level 2) and lower (level 4) paratracheal, and hilar (level 10) nodal regions were contoured on the planning computed tomography (CT) images. Using the clinical treatment plan, dose and volume calculations were performed retrospectively for each nodal region. SBRT to upper lobe tumors resulted in an average total ipsilateral mean dose of between 5.2 and 7.8 Gy for the most proximal paratracheal nodal stations (2R and 4R for right upper lobe lesions, 2L and 4L for left upper lobe lesions). SBRT to lower lobe tumors resulted in an average total ipsilateral mean dose of between 15.6 and 21.5 Gy for the most proximal hilar nodal stations (10R for right lower lobe lesions, 10 l for left lower lobe lesions). Doses to more distal nodes were substantially lower than 5 Gy. The often substantial incidental irradiation, delivered during SBRT for peripheral NSCLC of the lower lobes to the most proximal hilar lymph nodes may be therapeutic for low-volume, subclinical nodal disease. Treatment of peripheral upper lobe lung tumors delivers less incidental irradiation to the paratracheal lymph nodes with lower likelihood of therapeutic benefit.

Analysis of suitable prescribed isodose line fitting to planning target volume in stereotactic body radiotherapy using dynamic conformal multiple arc therapy

PURPOSE

To assess the most suitable value of a relative prescribed dose in clinical treatment plans of stereotactic body radiotherapy (SBRT) using dynamic conformal multiple arc therapy to treat lung tumors.

METHODS AND MATERIALS

We retrospectively generated alternative SBRT plans for typical examples of 8 patients who had been treated with SBRT for a lung tumor with a prescribed dose of 50 Gy in 5 fractions. The prescribed dose had been defined as 80% of the maximal dose in the planning target volume (PTV) ("the 80% isodose plan"). Alternative 20%-90% isodose plans at 10% intervals were generated (64 plans; 8 plans for each of the 8 patients), and factors related to leaf margins, target volume, normal lung volume, and monitor units were compared using dose-volume histogram analysis.

RESULTS

We could generate all the 64 plans. Compared with the 80% isodose plan, the V20 and mean lung dose (MLD) were both lower in the 60% plan; the V20 was approximately 19% lower (4.72% vs 3.84%) and the MLD was 13% lower (4.0 Gy vs 3.5 Gy). Mean PTV and ITV doses were higher in the lower percentage isodose plans. Compared with the 80% isodose plan, in the 60% isodose plan the mean PTV was 19% higher (56.1 Gy vs 66.8 Gy) and the mean ITV was 30% higher (59.6 Gy vs 77.4 Gy). The mean total monitor units increased more steeply than did the mean homogeneity index. The mean conformity index values in the 60% and 70% isodose plans were less than 1.15.

CONCLUSIONS

The 60% isodose plan was considered the best plan in this analysis because of the lower comparative dosimetric factors in normal lung tissue (including V20 and MLD) and the higher comparative mean PTV and internal target volume doses achieved, along with good conformity index values. In clinical use, accurate estimation and commissioning should be performed for the dose distribution prior to selecting a plan. Further investigation is warranted to determine whether the calculated dosimetric advantages result in improved outcomes.

A contemporary review of stereotactic radiotherapy: inherent dosimetric complexities and the potential for detriment

OBJECTIVE

The advantages of highly localised, conformal treatments achievable with stereotactic radiotherapy (SRT) are increasingly being extended to extracranial sites as stereotactic body radiotherapy with advancements in imaging and beam collimation. One of the challenges in stereotactic treatment lies in the significant complexities associated with small field dosimetry and dose calculation. This review provides a comprehensive overview of the complexities associated with stereotactic radiotherapy and the potential for detriment.

METHODS

This study is based on a comprehensive review of literature accessible via PubMed and other sources, covering stereotactic radiotherapy, small-field dosimetry and dose calculation.

FINDINGS

Several key issues were identified in the literature. They pertain to dose prescription, dose measurement and dose calculation within and beyond the treatment field. Field-edge regions and penumbrae occupy a significant portion of the total field size. Spectral and dosimetric characteristics are difficult to determine and are compounded by effects of tissue inhomogeneity. Measurement of small-fields is made difficult by detector volume averaging and energy response. Available dosimeters are compared, and emphasis is given to gel dosimetry which offers the greatest potential for three-dimensional small-field dosimetry. The limitations of treatment planning system algorithms as applied to small-fields (particularly in the presence of heterogeneities) is explained, and a review of Monte Carlo dose calculation is provided, including simplified treatment planning implementations. Not incorporated into treatment planning, there is evidence that far from the primary field, doses to patients (and corresponding risks of radiocarcinogenesis) from leakage/scatter in SRT are similar to large fields.

CONCLUSIONS

Improved knowledge of dosimetric issues is essential to the accurate measurement and calculation of dose as well as the interpretation and assessment of planned and delivered treatments. This review highlights such issues and the potential benefit that may be gained from Monte Carlo dose calculation and verification via three-dimensional dosimetric methods (such as gel dosimetry) being introduced into routine clinical practice.

Extra-cranial Stereotactic Radiation Therapy (ESRT) in the treatment of inoperable stage 1 & 2 non-small-cell lung cancer patients with highly mobile tumours: a literature review

Objective: Extra-cranial Stereotactic Radiation Therapy (ESRT) techniques and equipment utilised in the treatment of Stage 1 or 2 inoperable non-small-cell lung cancer (NSCLC); accounting for Respiratory Induced Tumour Motion (RITM).

Methods: A narrative review of current world literature.

Results: Four main strategies are employed to address RITM: (1) tumour movement minimisation/immobilisation; (2) integration of respiratory movements into planning; (3) respiratory-gating techniques; and (iv) tumour-tracking techniques.

Discussion: Analysis of data gathered suggests that due to inherent difficulties with respiratory function, combined with co-morbidities and the level of dose escalation facilitated by ESRT: techniques that do not require patient ability to comply are more likely to be effective with a wider range of patients. Similarly, treatment planning must incorporate accurate four-dimensional (4D) data to ensure target coverage, although setup and verification should be controlled to smaller margins for error.

Conclusion: The disparate nature of reporting methods restricts statistical comparison. However, this paper suggests that the ESRT technique using abdominal compression (AC), free-breathing respiratory-gating (FBRG), 4D computed tomography (4DCT) planning, combined with daily on board kV cone beam computed tomography (CBCT) imaging for setup and target verification, is a possible candidate for further treatment regime assessments in large multi-centre trials.

High dose-per-fraction irradiation of limited lung volumes using an image-guided, highly focused irradiator: simulating stereotactic body radiotherapy regimens in a small-animal model

PURPOSE

To investigate the underlying biology associated with stereotactic body radiotherapy (SBRT), both in vivo models and image-guided, highly focal irradiation systems are necessary. Here, we describe such an irradiation system and use it to examine normal tissue toxicity in a small-animal model at lung volumes similar to those associated with human therapy.

METHODS AND MATERIALS

High-dose radiation was delivered to a small volume of the left lung of C3H/HeJCr mice using a small-animal stereotactic irradiator. The irradiator has a collimation mechanism to produce focal radiation beams, an imaging subsystem consisting of a fluorescent screen coupled to a charge-coupled device camera, and a manual positioning stage. Histopathologic examination and micro-CT were used to evaluate the radiation response.

RESULTS

Focal obliteration of the alveoli by fibrous connective tissue, hyperplasia of the bronchiolar epithelium, and presence of a small number of inflammatory cells are the main reactions to low-volume/high-dose irradiation of the mouse lung. The tissue response suggested a radiation dose threshold for early phase fibrosis lying between 40 and 100 Gy. The irradiation system satisfied our requirements of high-dose-rate, small beam diameter, and precise localization and verification.

CONCLUSIONS

We have established an experimental model and image-guided animal irradiation system for the study of high dose per fraction irradiations such as those used with SBRT at volumes analogous to those used in human beings. It will also allow the targeting of specific anatomical structures of the thorax or ultimately, orthotopic tumors of the lung.

Systemic review of the patterns of failure following stereotactic body radiation therapy in early-stage non-small-cell lung cancer: clinical implications

PURPOSE

To analyze the patterns of failure, the toxicity profile, and the factors influencing efficacy of stereotactic body radiation (SBRT) for early-stage non-small-cell lung cancer (NSCLC).

METHODS AND MATERIALS

A search was based on PubMed electronic databases. All searches were conducted in May, 2009.

RESULTS

The local control ranged from 80% to 100% in most studies with adequate isocentric or peripheral biologically effective dose (BED). Recurrences were associated with increased tumor size. The main pattern of failure after SBRT was distant metastasis. Grades 3-5 toxicity occurred mostly in centrally located tumors, and adjuvant chemotherapy may further decrease all recurrences; possibly translating to a survival benefit in large or centrally located tumors where high BED cannot be safely reached.

CONCLUSION

SBRT is an excellent treatment option for early-stage, and mostly medically inoperable, NSCLC. BED at both the isocenter and the tumor periphery is very important for optimal tumor control; higher doses are required for large (T2) lesions; SBRT for centrally located tumors can be feasible with a much less aggressive dose regimen than 60-66Gy/3 fractions and adjacent critical structures excluded from the target volume; chemotherapy may optimize the clinical outcome in large or centrally located lesions.

Gamma knife-treated hepatoma: case of obstructive jaundice and management

Gamma knife therapy is becoming more frequently applied in solid tumor treatment. This article reports a unique case of severe obstructive jaundice arising as a complication of treatment of hepatoma at the hepatic hilum using a gamma knife.While planning an intervention, some images seem to promise success but actually lead to failure. Radiation damage to specific organs is difficult to predict because of several variables. Radiation-induced fibrosis and necrosis are the most common long-term adverse effects of radiotherapy; they are usually considered irreversible and result in induration and firmness of the tissue.To minimize radiation fibrosis, accurate patient positioning and tumor relocalization are essential for gamma knife use in the liver and other extracranial sites. Even when practiced frequently, any intervention must be delivered with caution if the liver has been treated with radiation. Otherwise, even with much experience, the unwary doctor can be trapped by deceptive images.

Dose distribution analysis in stereotactic body radiotherapy using dynamic conformal multiple arc therapy

PURPOSE

We have used dynamic conformal multiple arc therapy (DCMAT) for stereotactic body radiotherapy (SBRT) since 2001. We investigated the consistency of DCMAT for SBRT using dose-volume histogram analysis.

METHODS AND MATERIALS

A total of 50 patients with peripheral lung tumors underwent SBRT. The median tumor diameter was 2.4 cm (range, 0.9-5.9). Treatment planning was performed using a superposition algorithm. The prescribed 50 Gy dose was divided into five fractions. The prescribed dose was defined as 80% of the maximal dose in the planning target volume (PTV), and the leaf margins were modified to ensure the PTV was included in the 80% isodose surface. The dose-volume histogram analysis was used to assess the PTV and normal lung volume.

RESULTS

The median dose covering 95% of the PTV was 50.27 Gy (range, 46.14-52.67), essentially consistent with the prescribed dose. The median homogeneity and conformity index was 1.41 (range, 1.31-1.53) and 1.73 (range, 1.41-2.21), respectively. The median volume of lung receiving > or =20 Gy (V(20)) was 4.2% (range, 1.4-10.2%). A linear correlation was found between the tumor diameter and V(20), and an even stronger correlation was found between the PTV/(normal lung volume) and V(20). The estimated V(20) was 7.1% (range, 3.9-10.4%) for a 5-cm-diameter tumor, assumed to be the maximal size limitation for SBRT.

CONCLUSION

SBRT with DCMAT achieved high conformity and delivered adequate doses within the PTV. The median dose covering 95% of the PTV was consistent with the prescribed dose. V(20) can be estimated using the tumor diameter and normal lung volume. DCMAT was thus both a feasible and a reproducible method of SBRT delivery.

Radiation-induced rib fractures after hypofractionated stereotactic body radiation therapy of non-small cell lung cancer: a dose- and volume-response analysis

BACKGROUND AND PURPOSE

The aim of this study is to analyse the dose-response and the volume-response of radiation-induced rib fractures after hypofractionated stereotactic body radiation therapy (SBRT).

MATERIALS AND METHODS

During the period 1998-2005, 68 patients with medically inoperable stage I non-small cell lung cancer (NSCLC) were treated with hypofractionated SBRT to 45 Gy in 3 fractions. Among the 33 patients with complete treatment records and radiographic follow-up exceeding 15 months (median: 29 months), 13 fractures were found in seven patients. Identifying all ribs receiving at least 21 Gy, 81 ribs (13 with and 68 without fracture) in 26 patients were separately contoured and their dose-volume histograms (DVHs) were obtained. The DVHs were assessed with the mean dose and cut-off models. Maximum likelihood estimation was used to fit dose-response and volume-response curves to each model.

RESULTS

It was possible to quantify the risk of radiation-induced rib fracture using response curves and information contained in the DVHs. Absolute volumes provided better fits than relative volumes and dose-response curves were more suitable than volume-response curves. For the dose given by the 2 cm(3) cut-off volume, D(2 cm(3)), the logistic dose-response curve for three fractions was parameterised by D(50)=49.8 Gy and gamma(50)=2.05. Consequently, for a median follow-up of 29 months, if D(2 cm(3))<3 x 7.0 Gy the risk is close to 0, and the 5% and 50% risks are given by D(2 cm(3))=3 x 9.1 Gy and 3 x 16.6 Gy, respectively.

CONCLUSIONS

In this group of patients, the risk for radiation-induced rib fracture following hypofractionated SBRT was related to the dose to 2 cm(3) of the rib.

Accuracy of 3D volumetric image registration based on CT, MR and PET/CT phantom experiments

Registration is critical for image‐based treatment planning and image‐guided treatment delivery. Although automatic registration is available, manual, visual‐based image fusion using three orthogonal planar views (3P) is always employed clinically to verify and adjust an automatic registration result. However, the 3P fusion can be time consuming, observer dependent, as well as prone to errors, owing to the incomplete 3‐dimensional (3D) volumetric image representations. It is also limited to single‐pixel precision (the screen resolution). The 3D volumetric image registration (3DVIR) technique was developed to overcome these shortcomings. This technique introduces a 4th dimension in the registration criteria beyond the image volume, offering both visual and quantitative correlation of corresponding anatomic landmarks within the two registration images, facilitating a volumetric image alignment, and minimizing potential registration errors. The 3DVIR combines image classification in real‐time to select and visualize a reliable anatomic landmark, rather than using all voxels for alignment. To determine the detection limit of the visual and quantitative 3DVIR criteria, slightly misaligned images were simulated and presented to eight clinical personnel for interpretation. Both of the criteria produce a detection limit of 0.1 mm and 0.1°. To determine the accuracy of the 3DVIR method, three imaging modalities (CT, MR and PET/CT) were used to acquire multiple phantom images with known spatial shifts. Lateral shifts were applied to these phantoms with displacement intervals of 5.0±0.1mm. The accuracy of the 3DVIR technique was determined by comparing the image shifts determined through registration to the physical shifts made experimentally. The registration accuracy, together with precision, was found to be: 0.02±0.09mm for CT/CT images, 0.03±0.07mm for MR/MR images, and 0.03±0.35mm for PET/CT images. This accuracy is consistent with the detection limit, suggesting an absence of detectable systematic error. This 3DVIR technique provides a superior alternative to the 3P fusion method for clinical applications.

PACS numbers: 87.57.nj, 87.57.nm, 87.57.‐N, 87.57.‐s

Charged particle radiotherapy at the Hyogo Ion Beam Medical Center: Characteristics, technology and clinical results

The Hyogo Ion Beam Medical Center was constructed in 2001 as the world's first charged particle radiotherapy center where both proton and carbon-ion radiotherapy can be performed. From April 2001 to February 2007, more than 1,400 patients with a variety of cancers were treated. Most of the tumors except for prostate cancer were considered hard to cure with standard treatments such as surgery or conventional x-ray radiotherapy. The clinical results obtained so far are very encouraging, mainly due to the excellent dose localization to the tumor and strong cell killing effects of protons and carbon-ions. The good indications are localized tumors including skull base tumors, head and neck tumors, cancers of the lung, the liver, and the prostate, and bone and soft tissue sarcomas. Charged particle radiotherapy will significantly improve the quality of life of cancer patients and promote their speedy return to normal lives or work if it is used for early stage cancer.