Comparison of outcomes for patients with medically inoperable Stage I non–small-cell lung cancer treated with two-dimensional vs. three-dimensional radiotherapy

Patient-specific finite element modeling of respiratory lung motion using 4D CT image data

Development and optimization of methods for adequately accounting for respiratory motion in radiation therapy of thoracic tumors require detailed knowledge of respiratory dynamics and its impact on corresponding dose distributions. Thus, computer aided modeling and simulation of respiratory motion have become increasingly important. In this article a biophysical approach for modeling respiratory lung motion is described: Major aspects of the process of lung ventilation are formulated as a contact problem of elasticity theory which is solved by finite element methods; lung tissue is assumed to be isotropic, homogeneous, and linearly elastic. A main focus of the article is to assess the impact of biomechanical parameters (values of elastic constants) on the modeling process and to evaluate modeling accuracy. Patient-specific models are generated based on 4D CT data of 12 lung tumor patients. Simulated motion patterns of inner lung landmarks are compared with corresponding motion patterns observed in the 4D CT data. Mean absolute differences between model-based predicted landmark motion and corresponding breathing-induced landmark displacements as observed in the CT data sets are in the order of 3 mm (end expiration to end inspiration) and 2 mm (end expiration to midrespiration). Modeling accuracy decreases with increasing tumor size both locally (landmarks close to tumor) and globally (landmarks in other parts of the lung). The impact of the values of the elastic constants appears to be small. Outcomes show that the modeling approach is an adequate strategy in predicting lung dynamics due to lung ventilation. Nevertheless, the decreased prediction quality in cases of large tumors demands further study of the influence of lung tumors on global and local lung elasticity properties.

Accelerated radical radiotherapy for non-small cell lung cancer using two common regimens: a single-centre retrospective study of outcome

AIMS

A variety of radical radiotherapy regimens are in use for non-small cell lung cancer. Continuous hyperfractionated accelerated radiotherapy (CHART: 54 Gy in 36 fractions over 12 days) and accelerated hypofractionated radiotherapy using 55 Gy in 20 fractions over 4 weeks are standard fractionations in our centre. The primary aim of this retrospective study was to evaluate survival outcome seen in routine clinical practice.

MATERIALS AND METHODS

All case notes and radiotherapy records of radically treated patients between 1999 and 2004 were retrospectively reviewed. Basic patient demographics, tumours, characteristics, radiotherapy and survival data were collected.

RESULTS

In total, 277 patients received radical radiotherapy: 137 and 140 patients received CHART and hypofractionated radiotherapy, respectively. There were differences noted in the demographics between the two treatment schedules: median age 65 years (range 41-83) vs 73 years (range 33-87); histological confirmation rates 90% vs 76%; prior chemotherapy 34% vs 19% for CHART and hypofractionated treatment, respectively. For CHART patients, stages I, II, III and unclassified were 12, 8, 68 and 12% and the staging for the hypofractionated regimen was 54, 11, 34 and 2%, respectively. The median overall survival from the time of diagnosis was 20.4 months with a 40% 2-year survival rate. For the two fractionations the median survival was 16.6 months vs 21.4 months and 34% vs 45% of patients were alive at 2 years in the CHART and hypofractionated groups, respectively. On multivariate analysis, stage was the only factor affecting overall survival - no difference was seen according to radiotherapy regimen.

CONCLUSION

This single-centre study reflects the outcome of unselected consecutively treated non-small cell lung cancer patients. Adjusting for stage, there was no significant difference in survival seen according to regimen. Encouragingly, CHART outcome shows reproducibility with the original CHART paper. Our hypofractionated outcome is similar to that previously reported, but despite this being the UK's most common regimen, 55 Gy in 20 daily fractions remains unvalidated by phase III trial data.

Image-guided radiation therapy for non-small cell lung cancer

Recent developments in image-guided radiotherapy are ushering in a new era of radiotherapy for lung cancer. Positron emission tomography/computed tomography (PET/CT) has been shown to improve targeting accuracy in 25 to 50% of cases, and four-dimensional CT scanning helps to individualize radiotherapy by accounting for tumor motion. Daily on-board imaging reduces treatment set-up uncertainty and provides information about daily organ motion and variations in anatomy. Image-guided intensity-modulated radiotherapy may allow for the escalation of radiotherapy dose with no increase in toxicity. More importantly, treatment adaptations based on anatomic changes during the course of radiotherapy and dose painting within involved lesions using functional imaging such as PET may further improve clinical outcomes of lung cancer patients and potentially lead to new clinical trials. Image-guided stereotactic radiotherapy can achieve local control rates exceeding 90% through the use of focused, hypofractionated, highly biologically effective doses. These novel approaches were considered experimental just a few years ago, but accumulating evidence of their potential for significantly improving clinical outcomes is leading to their inclusion in standard treatments for lung cancer at major cancer centers. In this review article, we focus on novel image-guided radiotherapy approaches, particularly PET/CT and four-dimensional CT-based radiotherapy planning and on-board image-guided delivery, stereotactic radiotherapy, and intensity-modulated radiotherapy for mobile nonsmall cell lung cancer.

Proton therapy in lung cancer: clinical outcomes and technical issues. A systematic review

BACKGROUND AND PURPOSE

To determine whether, according to the currently available literature, proton therapy (PT) has a role in the treatment of non-small-cell lung cancer (NSCLC), to assess its safety and efficacy and to evaluate the main technical issues specifically related to this treatment technique.

MATERIALS AND METHODS

During March 2007, two independent researchers conducted a systematic review of the current data on the treatment of NSCLC with PT.

RESULTS

In total, 113 reports were retrieved, 17 of which were included in the analysis. There were no prospective trials (randomized or non-randomized). Nine uncontrolled single-arm studies were available from three PT centers, providing clinical outcomes for 214 patients in total. These reports were mainly related to stage I-II tumors, with results comparable to those obtained with surgery, without significant toxicity. In addition, two papers were found that compared photon and proton dose distributions, which showed a potential for dose escalation and/or a sparing of the organ at risk with PT. Finally, six studies analyzed dosimetric and technical issues related with PT, mainly underlining the difficulties in designing dose distributions that are representative of the dose actually delivered during treatment.

CONCLUSIONS

Although from a physical point of view PT is a good option for the treatment of NSCLC, limited data are available on its application in the clinical practice. Furthermore, the application of PT to lung cancer does present technical challenges. Because of the small number of institutions involved in the treatment of this disease, number of patients, and methodological weaknesses of the trials it is therefore not possible to draw definitive conclusions about the superiority of PT with respect to the photon techniques currently available for the treatment of NSCLC.

Comparison of limited surgery and three-dimensional conformal radiation in high-risk patients with stage I non-small cell lung cancer

INTRODUCTION

Anatomic resection is currently the standard of care for patients with stage I non-small cell lung cancer (NSCLC). Some stage I patients are unable to tolerate lobectomy because of limited lung function or prohibitive comorbidities. In this study, we retrospectively compared the outcome of patients treated with wedge resection or three-dimensional (3-D) conformal radiation therapy, the most common treatment modalities used for such high-risk patients.

METHODS

All patients with stage I NSCLC from 1988 to 2005 who were not considered candidates for anatomic surgical resection were reviewed. Univariate and multivariate analyses were performed to assess the influence of 3-D conformal radiation and surgery on overall survival and recurrence-free survival. Propensity score-matched analysis and cost assessments were performed to compare outcomes with both modalities. Propensity matching was performed for gender, histology, tumor size, performance status, and age.

RESULTS

Of 160 patients studied, 68 patients received limited resection and 92 patients received 3-D conformal radiation. Univariate and multivariate analyses suggested a trend toward improved outcome in limited resection. Propensity matching was performed with 34 matched pairs and demonstrated no statistically significant difference in overall survival or recurrence-free survival. The mean cost of radiation therapy ($32,735) was not statistically significantly different from surgery ($30,411).

CONCLUSION

In high-risk patients with NSCLC, limited resection has a tendency towards improved outcome. A propensity matched analysis did not show a clear benefit for limited resection, which may be due in part to an inadequate number of patients for analysis and/or increased comorbidities of patients treated with 3-D conformal radiation.

Stereotactic Body Radiation Therapy for Stage I Non–Small Cell Lung Cancer

Image-guided SBRT with the delivery of a BED greater than 100 Gy is feasible and safe in the treatment of peripherally located inoperable stage I NSCLC. The 3- to 5-year local control and overall survival rates for SBRT seem to be much better than the rates for conventional radiotherapy, and the toxicity rate is minimal. Particularly for stage Ia (T1N0M0) disease, survival rates with SBRT were comparable with rates seen with surgical resection. SBRT is becoming the standard treatment for inoperable stage I NSCLC. Its role in operable stage I NSCLC. however. is not clear. To balance improved targeting accuracy with minimized treatment-related toxicity. a reliable immobilization device and consideration of image-guided tumor motion are crucial. The optimal dose regimen remains unclear, but a BED greater than 100 Gy seems warranted.

A potential to reduce pulmonary toxicity: The use of perfusion SPECT with IMRT for functional lung avoidance in radiotherapy of non-small cell lung cancer

BACKGROUND AND PURPOSE

The study aimed to examine specific avoidance of functional lung (FL) defined by a single photon emission computerized tomography (SPECT) lung perfusion scan, using intensity modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3-DCRT) in patients with non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Patients with NSCLC underwent planning computerized tomography (CT) and lung perfusion SPECT scan in the treatment position using fiducial markers to allow co-registration in the treatment planning system. Radiotherapy (RT) volumes were delineated on the CT scan. FL was defined using co-registered SPECT images. Two inverse coplanar RT plans were generated for each patient: 4-field 3-DCRT and 5-field step-and-shoot IMRT. 3-DCRT plans were created using automated AutoPlan optimisation software, and IMRT plans were generated employing Pinnacle(3) treatment planning system (Philips Radiation Oncology Systems). All plans were prescribed to 64 Gy in 32 fractions using data for the 6 MV beam from an Elekta linear accelerator. The objectives for both plans were to minimize the volume of FL irradiated to 20 Gy (fV(20)) and dose variation within the planning target volume (PTV). A spinal cord dose was constrained to 46 Gy. Volume of PTV receiving 90% of the prescribed dose (PTV(90)), fV(20), and functional mean lung dose (fMLD) were recorded. The PTV(90)/fV(20) ratio was used to account for variations in both measures, where a higher value represented a better plan.

RESULTS

Thirty-four RT plans of 17 patients with stage I-IIIB NSCLC suitable for radical RT were analysed. In 6 patients with stage I-II disease there was no improvement in PTV(90), fV(20), PTV/fV(20) ratio and fMLD using IMRT compared to 3-DCRT. In 11 patients with stage IIIA-B disease, the PTV was equally well covered with IMRT and 3-DCRT plans, with IMRT producing better PTV(90)/fV(20) ratio (mean ratio - 7.2 vs. 5.3, respectively, p=0.001) and reduced fMLD figures compared to 3-DCRT (mean value - 11.5 vs. 14.3 Gy, p=0.001). This was due to reduction in fV(20) while maintaining PTV coverage.

CONCLUSION

The use of IMRT compared to 3-DCRT improves the avoidance of FL defined by perfusion SPECT scan in selected patients with locally advanced NSCLC. If the dose to FL is shown to be the primary determinant of lung toxicity, IMRT would allow for effective dose escalation by specific avoidance of FL.