Rib fracture after stereotactic radiotherapy on follow-up thin-section computed tomography in 177 primary lung cancer patients

ACR Appropriateness Criteria® Nontraumatic Chest Wall Pain

Chest pain is a common reason that patients may present for evaluation in both ambulatory and emergency department settings, and is often of musculoskeletal origin in the former. Chest wall syndrome collectively describes the various entities that can contribute to chest wall pain of musculoskeletal origin and may affect any chest wall structure. Various imaging modalities may be employed for the diagnosis of nontraumatic chest wall conditions, each with variable utility depending on the clinical scenario. We review the evidence for or against use of various imaging modalities for the diagnosis of nontraumatic chest wall pain. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Relations Between Bone Quantity, Microarchitecture, and Collagen Cross-links on Mechanics Following In Vivo Irradiation in Mice

Humans are exposed to ionizing radiation via spaceflight or cancer radiotherapy, and exposure from radiotherapy is known to increase risk of skeletal fractures. Although irradiation can reduce trabecular bone mass, alter trabecular microarchitecture, and increase collagen cross‐linking, the relative contributions of these effects to any loss of mechanical integrity remain unclear. To provide insight, while addressing both the monotonic strength and cyclic‐loading fatigue life, we conducted total‐body, acute, gamma‐irradiation experiments on skeletally mature (17‐week‐old) C57BL/6J male mice (n = 84). Mice were administered doses of either 0 Gy (sham), 1 Gy (motivated by cumulative exposures from a Mars mission), or 5 Gy (motivated by clinical therapy regimens) with retrieval of the lumbar vertebrae at either a short‐term (11‐day) or long‐term (12‐week) time point after exposure. Micro‐computed tomography was used to assess trabecular and cortical quantity and architecture, biochemical composition assays were used to assess collagen quality, and mechanical testing was performed to evaluate vertebral compressive strength and fatigue life. At 11 days post‐exposure, 5 Gy irradiation significantly reduced trabecular mass (p < 0.001), altered microarchitecture (eg, connectivity density p < 0.001), and increased collagen cross‐links (p < 0.001). Despite these changes, vertebral strength (p = 0.745) and fatigue life (p = 0.332) remained unaltered. At 12 weeks after 5 Gy exposure, the trends in trabecular bone persisted; in addition, regardless of irradiation, cortical thickness (p < 0.01) and fatigue life (p < 0.01) decreased. These results demonstrate that the highly significant effects of 5 Gy total‐body irradiation on the trabecular bone morphology and collagen cross‐links did not translate into detectable effects on vertebral mechanics. The only mechanical deficits observed were associated with aging. Together, these vertebral results suggest that for spaceflight, irradiation alone will likely not alter failure properties, and for radiotherapy, more investigations that include post‐exposure time as a positive control and testing of both failure modalities are needed to determine the cause of increased fracture risk. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Imaging of Novel Oncologic Treatments in Lung Cancer Part 2: Local Ablative Therapies

Conventional approaches to the treatment of early-stage lung cancer have focused on the use of surgical methods to remove the tumor. Recent progress in radiation therapy techniques and in the field of interventional oncology has seen the development of several novel ablative therapies that have gained widespread acceptance as alternatives to conventional surgical options in appropriately selected patients. Local control rates with stereotactic body radiation therapy for early-stage lung cancer now approach those of surgical resection, while percutaneous ablation is in widespread use for the treatment of lung cancer and oligometastatic disease for selected other malignancies. Tumors treated with targeted medical and ablative therapies can respond to treatment differently when compared with conventional therapies. For example, after stereotactic body radiation therapy, radiologic patterns of posttreatment change can mimic disease progression, and, following percutaneous ablation, the expected initial increase in the size of a treated lesion limits the utility of conventional size-based response assessment criteria. In addition, numerous treatment-related side effects have been described that are important to recognize, both to ensure appropriate treatment and to avoid misclassification as worsening tumor. Imaging plays a vital role in the assessment of patients receiving targeted ablative therapy, and it is essential that thoracic radiologists become familiar with these findings.

Chest wall pain following lung stereotactic body radiation therapy using 48Gy in three fractions: A search for predictors

PURPOSE

Chest wall pain is an uncommon but bothersome late complication following lung stereotactic body radiation therapy. Despite numerous studies investigating predictors of chest wall pain, no clear consensus has been established for a chest wall constraint. The aim of our study was to investigate factors related to chest wall pain in a homogeneous group of patients treated at our institution.

PATIENTS AND METHODS

All 122 patients were treated with the same stereotactic body radiation therapy regimen of 48Gy in three fractions, seen for at least 6 months of follow-up, and planned with heterogeneity correction. Chest wall pain was scored according to the Common Terminology Criteria for Adverse Events classification v3.0. Patient (age, sex, diabetes, osteoporosis), tumour (planning target volume, volume of the overlapping region between planning target volume and chest wall) and chest wall dosimetric parameters (volumes receiving at least 30, 40, and 50Gy, the minimal doses received by the highest irradiated 1, 2, and 5cm³, and maximum dose) were collected. The correlation between chest wall pain (grade 2 or higher) and the different parameters was evaluated using univariate and multivariate logistic regression.

RESULTS

Median follow-up was 18 months (range: 6-56 months). Twelve patients out of 122 developed chest wall pain of any grade (seven with grade 1, three with grade 2 and two with grade 3 pain). In univariate analysis, only the volume receiving 30Gy or more (P=0.034) and the volume of the overlapping region between the planning target volume and chest wall (P=0.038) significantly predicted chest wall pain, but these variables were later proved non-significant in multivariate regression.

CONCLUSION

Our analysis could not find any correlation between the studied parameters and chest wall pain. Considering our present study and the wide range of differing results from the literature, a reasonable conclusion is that a constraint for chest wall pain is yet to be defined.

Chest Wall Toxicity After Stereotactic Body Radiation Therapy: A Pooled Analysis of 57 Studies

PURPOSE

The significance of clinical and dosimetric risk factors in relation to chest wall (CW) injury after stereotactic body radiation therapy (SBRT) for lung tumors were analyzed through a meta-analysis of 57 published studies.

METHODS AND MATERIALS

Studies related to CW injury after lung SBRT were obtained through searching PubMed, Embase, and Cochrane electronic databases. An estimate of the incidence of CW pain (CWP) or rib fracture (RF) was derived using a Bayesian hierarchical model. Linear regression analysis was performed to assess the relationship between CWP or RF and clinical or dosimetric factors.

RESULTS

A total of 57 studies incorporating 5985 cases reporting clinical data on CW injury after SBRT were analyzed. The overall CWP and RF rates by Bayesian hierarchical modeling were 11.0% (95% confidence interval [CI], 8.0-14.4) and 6.3% (95% CI, 3.7-9.7), respectively. The rates of grade ≥2 and grade ≥3 CWP were 6.2% (95% CI, 3.88-8.93) and 1.2% (95% CI, 0.48-2.12), respectively. Sex was significantly correlated with RF (P < .001), with female patients having a greater risk of RF than male patients (hazard ratio = 0.59; 95% CI, 0.46-0.76). No correlation was found between RF, grade ≥2 CWP, or grade ≥3 CWP, with the clinical and dosimetric factors of age, tumor size, origin of lung tumor, gross tumor volume, planning target volume, fractional dose, number of fractions, or biologically effective dose. However, tumor to CW distance (<16-25 mm), body mass index, maximum dose (Dmax) of 0.5 to 5 cm³, and the volume of CW or ribs receiving >30 Gy were significantly associated with CWP and RF.

CONCLUSIONS

The overall rates of RF and grade ≥2 CWP after thoracic SBRT are relatively low. Sex, tumor to CW distance, maximum dose, and the radiation exposure of the CW or ribs are factors associated with the risk of CW toxicity after SBRT.

Exploratory analysis using machine learning to predict for chest wall pain in patients with stage I non-small-cell lung cancer treated with stereotactic body radiation therapy

Background and purpose

Chest wall toxicity is observed after stereotactic body radiation therapy (SBRT) for peripherally located lung tumors. We utilize machine learning algorithms to identify toxicity predictors to develop dose–volume constraints.

Materials and methods

Twenty‐five patient, tumor, and dosimetric features were recorded for 197 consecutive patients with Stage I NSCLC treated with SBRT, 11 of whom (5.6%) developed CTCAEv4 grade ≥2 chest wall pain. Decision tree modeling was used to determine chest wall syndrome (CWS) thresholds for individual features. Significant features were determined using independent multivariate methods. These methods incorporate out‐of‐bag estimation using Random forests (RF) and bootstrapping (100 iterations) using decision trees.

Results

Univariate analysis identified rib dose to 1 cc < 4000 cGy (P = 0.01), chest wall dose to 30 cc < 1900 cGy (P = 0.035), rib Dmax < 5100 cGy (P = 0.05) and lung dose to 1000 cc < 70 cGy (P = 0.039) to be statistically significant thresholds for avoiding CWS. Subsequent multivariate analysis confirmed the importance of rib dose to 1 cc, chest wall dose to 30 cc, and rib Dmax. Using learning‐curve experiments, the dataset proved to be self‐consistent and provides a realistic model for CWS analysis.

Conclusions

Using machine learning algorithms in this first of its kind study, we identify robust features and cutoffs predictive for the rare clinical event of CWS. Additional data in planned subsequent multicenter studies will help increase the accuracy of multivariate analysis.

Possibility of chest wall dose reduction using volumetric-modulated arc therapy (VMAT) in radiation-induced rib fracture cases: comparison with stereotactic body radiation therapy (SBRT)

The present study compares dosimetric parameters between volumetric-modulated arc therapy (VMAT) and 3D conformal radiation therapy (3D-CRT) in lung tumors adjacent to the chest wall treated with stereotactic body radiation therapy (SBRT). The study focused on the radiation dose to the chest wall of 16 patients who had developed radiation-induced rib fractures (RIRF) after SBRT using 3D-CRT. The targets in all patients were partially overlapping with the fractured ribs, and the median overlapping rib-PTV distance was 0.4 cm. Stereotactic body radiation therapy was re-planned for all patients. The prescribed dose was 48 Gy in four fractions to cover at least 95% of the planning target volume (PTV). Evaluated dosimetric factors included D98% and the conformation number (CN) of the PTV, the D2cm3, V40 and V30 of the fractured ribs, the V30 of the chest wall, and the Dmean, V20 and V5 of the lung. A comparison of 3D-CRT with the VMAT plan for PTV revealed that CN was significantly improved in the VMAT plan, whereas D98% did not significantly differ between the two plans. Regarding organs at risk (OARs), the D2cm3, V40 and V30 of fractured ribs, the V30 of the chest wall, and the Dmean, V20 and V5 of the lung, were significantly decreased in the VMAT plan. We concluded that the dose to OARs such as ribs and chest wall could be reduced with improved target conformity using VMAT instead of 3D-CRT for SBRT to treat peripheral lung tumors.

Lung stereotactic ablative radiotherapy (SABR): dosimetric considerations for chest wall toxicity

OBJECTIVE

To investigate chest wall pain in patients with peripheral early stage lung cancer treated with stereotactic ablative radiotherapy (SABR), and to identify factors predictive of Common Terminology Criteria of Adverse Events Grade 2 + chest wall pain.

METHODS

Patients who received 55 Gy in five fractions were included. A chest wall structure was retrospectively defined on planning scans, and chest wall dosimetry and tumour-related factors recorded. Logistic regression was performed to identify factors predictive of ≥Grade 2 chest wall pain.

RESULTS

182 patients and 187 tumours were included. There were 20 (10.9%) episodes of ≥Grade 2 chest wall pain. Multivariate logistic regression demonstrated that the maximum dose received by 1 cm(3) of chest wall (Dmax1 cm(3)) and tumour size were significant predictors of ≥Grade 2 chest wall pain [Dmax1 cm(3) odds ratio : 1.104, 95% confidence interval : 1.012-1.204, p = 0.025; tumour size (mm) odds ratio : 1.080, 95% confidence interval : 1.026-1.136, p = 0.003]. This model was an adequate fit to the data (Hosmer and Lemeshow test non-significant) and a fair discriminator for chest wall pain (area under receiver-operating characteristic curve: 0.74). Using the multivariate logistic regression model, parameters for Dmax1 cm(3) are provided, which predict <10% and <20% risks of ≥Grade 2 chest wall pain for different tumour sizes.

CONCLUSION

Grade 2+ chest wall pain is an uncommon side effect of lung SABR. Larger tumour size and increasing Dmax1 cm(3) are significant predictors of ≥Grade 2 chest wall pain. When planning lung SABR, it is prudent to try to avoid hot volumes in the chest wall, particularly for larger tumours.

ADVANCES IN KNOWLEDGE

This article demonstrates that Grade 2 or greater chest wall pain following lung SABR is more common when the tumour is larger in size and the Dmax1 cm(3) of the chest wall is higher. When planning lung SABR, the risk of chest wall pain may be reduced if maximum doses are minimized, particularly for larger tumours.

Incidence, risk factors, and dose-volume relationship of radiation-induced rib fracture after carbon ion radiotherapy for lung cancer

BACKGROUND

The purpose of this study was to assess the incidence, risk factors, and dose-volume relationship of radiation-induced rib fracture (RIRF) after carbon ion radiotherapy for lung cancer.

MATERIAL AND METHODS

Fifty-seven ribs of 18 patients with peripheral stage I non-small cell lung cancer treated with carbon ion radiotherapy were analyzed on rib fracture. The patients were treated at a total dose of 52.8 Gy [relative biologic effectiveness (RBE)] or 60.0 Gy (RBE) in 4 fractions and were followed at least six months. Patient characteristics and dosimetric parameters were analyzed for associations with RIRF.

RESULTS

Eighteen patients and 57 ribs were included in this study. The median length of follow-up was 36.5 months. RIRF was observed in seven (39%) of the 18 patients, and in 11 (19%) of 57 ribs. Only one patient developed symptomatic fracture. The distance from the ribs to the tumor site was significantly shorter in fractured ribs than in non-fractured ribs (1.4 ± 0.3 cm vs. 2.5 ± 0.3 cm). Receiver operating characteristic curve analysis showed that [Formula: see text] as a cut-off value for discriminating RIRF had the largest area under the curve (AUC =0.78). Comparison of the two-year cumulative incidence of RIRF among two groups as determined by cut-off values, yielded the following result: 53% vs. 4% [[Formula: see text], ≥ 38.2 Gy (RBE) or less]. Results from the two groups were significantly different (p < 0.05).

CONCLUSION

The crude incidence of RIRF after carbon ion radiotherapy was 39% but incidence of symptomatic fracture was low. The [Formula: see text] as cut-off values may be helpful for discriminating the risk of RIRF.

Radiation-induced rib fracture after stereotactic body radiotherapy with a total dose of 54-56 Gy given in 9-7 fractions for patients with peripheral lung tumor: impact of maximum dose and fraction size

BACKGROUND

Radiation-induced rib fracture after stereotactic body radiotherapy (SBRT) for lung cancer has been recently reported. However, incidence of radiation-induced rib fracture after SBRT using moderate fraction sizes with a long-term follow-up time are not clarified. We examined incidence and risk factors of radiation-induced rib fracture after SBRT using moderate fraction sizes for the patients with peripherally located lung tumor.

METHODS

During 2003-2008, 41 patients with 42 lung tumors were treated with SBRT to 54-56 Gy in 9-7 fractions. The endpoint in the study was radiation-induced rib fracture detected by CT scan after the treatment. All ribs where the irradiated doses were more than 80% of prescribed dose were selected and contoured to build the dose-volume histograms (DVHs). Comparisons of the several factors obtained from the DVHs and the probabilities of rib fracture calculated by Kaplan-Meier method were performed in the study.

RESULTS

Median follow-up time was 68 months. Among 75 contoured ribs, 23 rib fractures were observed in 34% of the patients during 16-48 months after SBRT, however, no patients complained of chest wall pain. The 4-year probabilities of rib fracture for maximum dose of ribs (Dmax) more than and less than 54 Gy were 47.7% and 12.9% (p = 0.0184), and for fraction size of 6, 7 and 8 Gy were 19.5%, 31.2% and 55.7% (p = 0.0458), respectively. Other factors, such as D2cc, mean dose of ribs, V10-55, age, sex, and planning target volume were not significantly different.

CONCLUSIONS

The doses and fractionations used in this study resulted in no clinically significant rib fractures for this population, but that higher Dmax and dose per fraction treatments resulted in an increase in asymptomatic grade 1 rib fractures.

Role of stereotactic body radiotherapy in spinal metastasis and subsequent fracture risk: identifying and treating the at-risk patient

The treatment of spinal metastasis has considerably improved with the advent of stereotactic body radiotherapy. Technological advances have enabled the precise delivery of high-dose radiation that may supplant surgery and standard fractionation postoperative radiation as a treatment for spinal metastasis without cord compression. Unfortunately, the higher biologically equivalent doses conferred by stereotactic body radiotherapy can also result in radiation toxicity, notably myelitis and vertebral body fracture. These are toxicities that the radiation oncologist must be able to anticipate, mitigate and manage. Although myelitis can be prevented largely by instituting dose constraints, it is less clear what the fracture risk of a structurally compromised vertebra is, and what should be done in terms of stabilization and dosimetry to mitigate this risk. This review answers these questions by defining the appropriate patient for stereotactic body radiotherapy, and what dose, fractionation and spinal stabilization should be used for potentially unstable spines.

Differences in rates of radiation-induced true and false rib fractures after stereotactic body radiation therapy for Stage I primary lung cancer

The purpose of this study was to analyze the dosimetry and investigate the clinical outcomes of radiation-induced rib fractures (RIRFs) after stereotactic body radiotherapy (SBRT). A total of 126 patients with Stage I primary lung cancer treated with SBRT, who had undergone follow-up computed tomography (CT) at least 12 months after SBRT and who had no previous overlapping radiation exposure were included in the study. We used the Mantel-Haenszel method and multiple logistic regression analysis to compare risk factors. We analyzed D(0.5 cm(3)) (minimum absolute dose received by a 0.5-cm(3) volume) and identified each rib that received a biologically effective dose (BED) (BED3, using the linear-quadratic (LQ) formulation assuming an α/β = 3) of at least 50 Gy. Of the 126 patients, 46 (37%) suffered a total of 77 RIRFs. The median interval from SBRT to RIRF detection was 15 months (range, 3-56 months). The 3-year cumulative probabilities were 45% (95% CI, 34-56%) and 3% (95% CI, 0-6%), for Grades 1 and 2 RIRFs, respectively. Multivariate analysis showed that tumor location was a statistically significant risk factor for the development of Grade 1 RIRFs. Of the 77 RIRFs, 71 (92%) developed in the true ribs (ribs 1-7), and the remaining six developed in the false ribs (ribs 8-12). The BED3 associated with 10% and 50% probabilities of RIRF were 55 and 210 Gy to the true ribs and 240 and 260 Gy to the false ribs. We conclude that RIRFs develop more frequently in true ribs than in false ribs.

Stereotactic body radiotherapy for very elderly patients (age, greater than or equal to 85 years) with stage I non-small cell lung cancer

BACKGROUND

Stereotactic body radiotherapy (SBRT) for non-small cell lung cancer (NSCLC) is primarily a treatment option for medically inoperable patients, who are often elderly. However, few studies report the effects of SBRT in elderly patients. Thus, we retrospectively analyzed clinical outcomes and feasibility following treatment of very elderly patients (age ≥ 85 years) with stage Ι NSCLC and younger patients (age < 85 years) with SBRT in our institution.

METHODS

From January 2006 to December 2012, 81 patients (20 very elderly; median age, 80 years; age range 64-93 years) with stage Ι NSCLC received SBRT. Prescription doses of 48 Gy were delivered in 4 fractions over 2 weeks or doses of 60 Gy were delivered in 10 fractions over 3 weeks.

RESULTS

Local control was achieved in 91.8% of all patients at 3 years (83.1% and 93.8% of very elderly and younger patients, respectively), and the 3-year overall survival (OS) rate was 69.4% (40.7% and 75.0% of very elderly and younger patients, respectively). OS rates were significantly shorter for the very elderly group than for the younger group, with a 3-year cause-specific survival (CSS) rate of 77.9% (50.4% and 81.6% of very elderly and younger patients, respectively) and a 3-year progression-free survival (PFS) rate of 59.5% (44.7% and 63.5% in very elderly and younger groups, respectively). Multivariate analysis revealed a significant correlation between T stage and OS. Grades 2 and 3 radiation pneumonitis (RP) occurred in 7 (8.6%) and 2 (2.5%) patients, respectively. Among patients of very elderly and younger groups, grade 2 RP occurred in 4 (20%) and 3 (4.9%) patients, and grade 3 occurred in 2 (10%) and 0 (0%) patients, respectively. No grade 4 or 5 toxicity was observed, RP was significantly more severe among very elderly patients.

CONCLUSIONS

SBRT for stage Ι NSCLC was well tolerated and feasible in very elderly patients. The efficacy of SBRT was comparable to that achieved in younger patients, although very elderly patients experienced significantly more severe RP. Although this study cohort included only 20 very elderly patients, the present data suggest that decreasing volumes of normal lung tissues exposed to ≥ 20 Gy and mean lung doses reduces the risk of RP in very elderly patients. The present data warrant studies of larger very elderly cohorts.

Long-term outcome of proton therapy and carbon-ion therapy for large (T2a-T2bN0M0) non-small-cell lung cancer

INTRODUCTION

: Although many reports have shown the safety and efficacy of stereotactic body radiotherapy (SBRT) for T1N0M0 non-small-cell lung cancer (NSCLC), it is rather difficult to treat T2N0M0 NSCLC, especially T2b (>5 cm) tumor, with SBRT. Our hypothesis was that particle therapy might be superior to SBRT in T2 patients. We evaluated the clinical outcome of particle therapy for T2a/bN0M0 NSCLC staged according to the 7th edition of the International Union Against Cancer (UICC) tumor, node, metastasis classification.

METHODS

: From April 2003 to December 2009, 70 histologically confirmed patients were treated with proton (n = 43) or carbon-ion (n = 27) therapy according to institutional protocols. Forty-seven patients had a T2a tumor and 23 had a T2b tumor. The total dose and fraction (fr) number were 60 (Gray equivalent) GyE/10 fr in 20 patients, 52.8 GyE/4 fr in 16, 66 GyE/10 fr in 16, 80 GyE/20 fr in 14, and other in four patients, respectively. Toxicities were scored according to the Common Terminology Criteria for Adverse Events, Version 4.0.

RESULTS

: The median follow-up period for living patients was 51 months (range, 24-103). For all 70 patients, the 4-year overall survival, local control, and progression-free survival rates were 58% (T2a, 53%; T2b, 67%), 75% (T2a, 70%; T2b, 84%), and 46% (T2a, 43%; T2b, 52%), respectively, with no significant differences between the two groups. The 4-year regional recurrence rate was 17%. Grade 3 pulmonary toxicity was observed in only two patients.

CONCLUSION

: Particle therapy is well tolerated and effective for T2a/bN0M0 NSCLC. To further improve treatment outcome, adjuvant chemotherapy seems a reasonable option, whenever possible.

Volume Modulated Arc Therapy (VMAT) for pulmonary Stereotactic Body Radiotherapy (SBRT) in patients with lesions in close approximation to the chest wall

Purpose: Chest wall pain and discomfort has been recognized as a significant late effect of radiation therapy in historical and modern treatment models. Stereotactic Body Radiotherapy (SBRT) is becoming an important treatment tool in oncology care for patients with intrathoracic lesions. For lesions in close approximation to the chest wall with motion management, SBRT techniques can deliver high dose to the chest wall. As an unintended target of consequence, there is possibility of imposing significant chest wall pain and discomfort as a late effect of therapy. The purpose of this paper is to evaluate the potential role of Volume Modulated Arc Therapy (VMAT) technologies in decreasing chest wall dose in SBRT treatment of pulmonary lesions in close approximation to the chest wall.

Materials and Methods: Ten patients with pulmonary lesions of various sizes and tomography in close approximation to the chest wall were selected for retrospective review. All volumes including tumor target, chest wall, ribs, and lung were contoured with maximal intensity projection maps and four-dimensional computer tomography planning. Radiation therapy planning consisted of static techniques including Intensity Modulated Radiation Therapy compared to VMAT therapy to a dose of 60 Gy in 12 Gy fraction dose. Dose volume histogram to rib, chest wall, and lung were compared between plans with statistical analysis.

Results: In all patients, dose and volume were improved to ribs and chest wall using VMAT technologies compared to static field techniques. On average, volume receiving 30 Gy to the chest wall was improved by 74%; the ribs by 60%. In only one patient did the VMAT treatment technique increase pulmonary volume receiving 20 Gy (V20).

Conclusions: VMAT technology has potential of limiting radiation dose to sensitive chest wall regions in patients with lesions in close approximation to this structure. This would also have potential value to lesions treated with SBRT in other body regions where targets abut critical structures.

Rib fractures after percutaneous radiofrequency and microwave ablation of lung tumors: incidence and relevance

PURPOSE

To retrospectively identify the incidence and probable risk factors for rib fractures after percutaneous radiofrequency ablation (RFA) and microwave ablation (MWA) of neoplasms in the lung and to identify complications related to these fractures.

MATERIALS AND METHODS

Institutional review board approval was obtained for this HIPAA-compliant retrospective study. Study population was 163 patients treated with MWA and/or RFA for 195 lung neoplasms between February 2004 and April 2010. Follow-up computed tomographic images of at least 3 months were retrospectively reviewed by board-certified radiologists to determine the presence of rib fractures. Generalized estimating equations were performed to assess the effect that patient demographics, tumor characteristics, treatment parameters, and ablation zone characteristics had on development of rib fractures. Kaplan-Meier curve was used to estimate patients' probability of rib fracture after ablation as a function of time. Clinical parameters (ie, pain in ribs or chest, organ damage caused by fractured rib) were evaluated for patients with confirmed fracture.

RESULTS

Rib fractures in proximity to the ablation zone were found in 13.5% (22 of 163) of patients. Estimated probability of fracture was 9% at 1 year and 22% at 3 years. Women were more likely than were men to develop fracture after ablation (P = .041). Patients with tumors closer to the chest wall were more likely to develop fracture (P = .0009), as were patients with ablation zones that involved visceral pleura (P = .039). No patients with rib fractures that were apparently induced by RFA and MWA had organ injury or damage related to fracture, and 9.1% (2 of 22) of patients reported mild pain.

CONCLUSION

Rib fractures were present in 13.5% of patients after percutaneous RFA and MWA of lung neoplasms. Patients who had ablations performed close to the chest wall should be monitored for rib fractures.

CyberKnife with Tumor Tracking: An Effective Treatment for High-Risk Surgical Patients with Single Peripheral Lung Metastases

Standard treatment for operable patients with single peripheral lung metastases is metastasectomy. We report mature CyberKnife outcomes for high-risk surgical patients with biopsy proven single peripheral lung metastases. Twenty-four patients (median age 73 years) with a mean maximum tumor diameter of 2.5 cm (range, 0.8–4.5 cm) were treated over a 6-year period extending from September 2004 to September 2010 and followed for a minimum of 1 year or until death. A mean dose of 52 Gy (range, 45–60 Gy) was delivered to the prescription isodose line in three fractions over a 3–11 day period (mean, 7 days). At a median follow-up of 20 months, the 2-year Kaplan–Meier local control and overall survival rates were 87 and 50%, respectively. CyberKnife with fiducial tracking is an effective treatment for high-risk surgical patients with single small peripheral lung metastases. Trials comparing CyberKnife with metastasectomy for operable patients are necessary to confirm equivalence.

Stereotactic body radiation therapy for patients with heavily pretreated liver metastases and liver tumors

We present our initial experience with CyberKnife stereotactic body radiation therapy (SBRT) in a heavily pretreated group of patients with liver metastases and primary liver tumors. From October 2007 to June 2009, 48 patients were treated at the Philadelphia CyberKnife Center for liver metastases or primary liver tumors. We report on 30 patients with 41 discrete lesions (1–4 tumors per patient) who received an ablative radiation dose (BED ≥ 79.2 Gy10 = 66 Gy EQD2). The treatment goal was to achieve a high SBRT dose to the liver tumor while sparing at least 700 cc of liver from radiation doses above 15 Gy. Twenty-three patients were treated with SBRT for metastatic cancer to the liver; the remainder (n = 7) were primary liver tumors. Eighty-seven percent of patients had prior systemic chemotherapy with a median 24 months from diagnosis to SBRT; 37% had prior liver directed therapy. Local control was assessed for 28 patients (39 tumors) with 4 months or more follow-up. At a median follow-up of 22 months (range, 10–40 months), 14/39 (36%) tumors had documented local failure. A decrease in local failure was found with higher doses of SBRT (p = 0.0237); 55% of tumors receiving a BED ≤ 100 Gy10 (10/18) had local failure compared with 19% receiving a BED > 100 Gy10 (4/21). The 2-year actuarial rate of local control for tumors treated with BED > 100 Gy10 was 75% compared to 38% for those patients treated with BED ≤ 100 Gy10 (p = 0.04). At last follow-up, 22/30 patients (73%) had distant progression of disease. Overall, seven patients remain alive with a median survival of 20 months from treatment and 57 months from diagnosis. To date, no patient experienced persistent or severe adverse effects. Despite the heavy pretreatment of these patients, SBRT was well tolerated with excellent local control rates when adequate doses (BED > 100 Gy10) were used. Median survival was limited secondary to development of further metastatic disease in the majority of patients.