Practical considerations arising from the implementation of lung stereotactic body radiation therapy (SBRT) at a comprehensive cancer center. J Thorac Oncol. 2008;3:1332-1341. [PMID: 18978570 DOI: 10.1097/jto.0b013e31818b1771]

Harnessing progress in radiotherapy for global cancer control

The pace of technological innovation over the past three decades has transformed the field of radiotherapy into one of the most technologically intense disciplines in medicine. However, the global barriers to access this highly effective treatment are complex and extend beyond technological limitations. Here, we review the technological advancement and current status of radiotherapy and discuss the efforts of the global radiation oncology community to formulate a more integrative 'diagonal approach' in which the agendas of science-driven advances in individual outcomes and the sociotechnological task of global cancer control can be aligned to bring the benefit of this proven therapy to patients with cancer everywhere.

Current Evidence for Stereotactic Body Radiotherapy in Lung Metastases

Lung metastases are the second most common malignant neoplasms of the lung. It is estimated that 20–54% of cancer patients have lung metastases at some point during their disease course, and at least 50% of cancer-related deaths occur at this stage. Lung metastases are widely accepted to be oligometastatic when five lesions or less occur separately in up to three organs. Stereotactic body radiation therapy (SBRT) is a noninvasive, safe, and effective treatment for metastatic lung disease in carefully selected patients. There is no current consensus on the ideal dose and fractionation for SBRT in lung metastases, and it is the subject of study in ongoing clinical trials, which examines different locations in the lung (central and peripheral). This review discusses current indications, fractionations, challenges, and technical requirements for lung SBRT.

Cleaning the dose falloff in lung SBRT plan

PURPOSE

To investigate a planning technique that can possibly reduce low-to-intermediate dose spillage (measured by R50%, D2cm values) in lung SBRT plans.

MATERIALS AND METHODS

Dose falloff outside the target was studied retrospectively in 102 SBRT VMAT plans of lung tumor. Plans having R50% and/or D2cm higher than recommended tolerances in RTOG protocols 0813 and 0915 were replanned with new optimization constraints using novel shell structures and novel constraints. Violations in the RTOG R50% value can be rectified with a dose constraint to a novel shell structure ("OptiForR50"). The construction of structure OptiForR50% and the novel optimization criteria translate the RTOG goals for R50% into direct inputs for the optimizer. Violations in the D2cm can be rectified using constraints on a 0.5 cm thick shell structure with inner surface 2cm from the PTV surface. Wilcoxon signed-rank test was used to compare differences in dose conformity, volume of hot spots, R50%, D2cm of the target in addition to the OAR doses. A two-sided P-value of 0.05 was used to assess statistical significance.

RESULTS

Among 102 lung SBRT plans with PTV sizes ranging from 5 to 179 cc, 32 plans with violations in R50% or D2cm were reoptimized. The mean reduction in R50% (4.68 vs 3.89) and D2cm (56.49 vs 52.51) was statistically significant both having P < 0.01. Target conformity index, volume of 105% isodose contour outside PTV, normal lung V20, and mean dose to heart and aorta were significantly lowered with P < 0.05.

CONCLUSION

The novel planning methodology using multiple shells including the novel OptiForR50 shell with precisely calculated dimensions and optimizer constraints lead to significantly lower values of R50% and D2cm and lower dose spillage in lung SBRT plans. All plans were successfully brought into the zone of no RTOG violations.

Influence of tumor characteristics on correction differences between cone-beam computed tomography-guided patient setup strategies in stereotactic body radiation therapy for lung cancer

BACKGROUND

To evaluate the correction differences between vertebra and tumor matching as cone-beam computed tomography (CBCT)-guided setup strategies in lung stereotactic body radiation therapy (SBRT), and the correlations with tumor characteristics such as size, mobility, and location.

METHODS

The manual registrations for 33 lung tumors treated with SBRT were retrospectively performed by matching thoracic vertebrae for vertebra matching and then by matching CBCT-visualized tumors within the internal target volume obtained from a four-dimensional CT dataset for tumor matching.

RESULTS

The mean correction difference between the two matching methods during the SBRT fractions was larger in the anterior-posterior direction (2.7 mm) than in the superior-inferior (2.1 mm) and left-right (1.4 mm) directions, with differences of less than 5 mm in 90% of the total 134 CBCT fractions. The X-axis and direct distances from the central axis to the tumor had significant correlations with the correction differences in all three directions, while the mobility-related parameters were correlated only in the superior-inferior direction. The absolute differences in lung-dose parameters after applying the margins (3.4-6.5 mm) required for the setup errors from vertebra matching relative to tumor matching were mild, with values of 1.95 Gy for the mean lung dose and 3.9% for V20.

CONCLUSION

The setup differences between vertebra and tumor matching in the CBCT-guided setup without rotation correction were increased in tumors located long distances from the central axis. The additional safety margins of 3.4-6.5 mm were required for the setup errors from vertebra matching.

KEY POINTS

Significant findings of the study The correction difference between the vertebra and tumor matching as CBCT-guided setup strategies was the largest in the anterior-posterior direction and significantly correlated with the X-axis and direct distances from the central axis to the tumor. What this study adds Setup differences between vertebra and tumor matching in the CBCT-guided setup were increased in tumors located long distances from the central axis. The additional safety margins of 3.4-6.5 mm were required for the setup errors from vertebra matching.

Stereotactic body radiotherapy for centrally located stage I non-small cell lung cancer

Stereotactic body radiotherapy (SBRT) has become the standard of care for the treatment of early stage non-small cell lung cancer in high risk or medically inoperable patients. It is very well tolerated when given to peripherally located tumors and is associated with high rates of local control. Centrally located tumors represent a bigger challenge as they are closer to a number of critical structures, namely the major bronchi, esophagus, large vessels and brachial plexus, that can be damaged by the high ablative doses of SBRT needed for optimal tumor control. Thus, the fractionation schedule for centrally located tumors needs to balance the need for tumor control while minimizing the risk of significant radiotherapy toxicity. In this article, we review the current evidence, summarize the prospective and retrospective studies of SBRT for centrally located tumors, and highlight several practical considerations.

Target migration from re-inflation of adjacent atelectasis during lung stereotactic body radiotherapy

Stereotactic body radiotherapy (SBRT) is a widely accepted option for the treatment of medically inoperable early-stage non-small cell lung cancer (NSCLC). Herein, we highlight the importance of interfraction image guidance during SBRT. We describe a case of early-stage NSCLC associated with segmental atelectasis that translocated 15 mm anteroinferiorly due to re-expansion of the adjacent segmental atelectasis following the first fraction. The case exemplifies the importance of cross-sectional image-guided radiotherapy that shows the intended target, as opposed to aligning based on rigid anatomy alone, especially in cases associated with potentially “volatile” anatomic areas.

Salvage pulmonary resection after stereotactic body radiotherapy: A feasible and safe option for local failure in selected patients

OBJECTIVE

For inoperable patients with pulmonary malignancy, stereotactic body radiotherapy is a reasonable therapeutic option. Despite good early tumor control, local failure occurs in up to 10% of patients by 3 years. Because management of local recurrence after stereotactic body radiotherapy is unclear, we evaluated use of surgery as a salvage option.

METHODS

A retrospective review was conducted of consecutive patients from a single institution who underwent salvage resection of primary and metastatic pulmonary malignancies previously treated with stereotactic body radiotherapy. In addition, a literature search was conducted to identify previous reports of pulmonary resection for local stereotactic body radiotherapy failures, to allow cumulative analyses with previously published cases.

RESULTS

A total of 21 patients met inclusion criteria. The median time between stereotactic body radiotherapy and salvage surgery was 16.2 months (range, 6.4-71.5). Postoperative complications occurred in 7 patients (18.9%), in whom atrial arrhythmias and prolonged air leaks (>5 days) were most frequent (n = 2 each, 5.4%). There was no local recurrence after salvage surgery. Distant failure occurred in 5 of 21 patients (23.8%) at a median of 36.2 months, and median disease-free survival was 19.2 months. The 30- and 90-day mortality was 4.8% (1 patient). Cumulative analysis included 37 patients from 4 institutions and comprised 26 (78.8%) primary non-small cell lung cancers and 11 (29.7%) lung metastases. Median overall survival after salvage surgery was 46.9 months, and 3-year survival was 71.8%.

CONCLUSIONS

After local failure of stereotactic body radiotherapy, salvage resection remains a viable option for operable patients, with acceptable morbidity and survival. As use of stereotactic body radiotherapy continues to expand, further studies to evaluate the optimal management for local failure are needed.

Advances in radiotherapy techniques and delivery for non-small cell lung cancer: benefits of intensity-modulated radiation therapy, proton therapy, and stereotactic body radiation therapy

The 21st century has seen several paradigm shifts in the treatment of non-small cell lung cancer (NSCLC) in early-stage inoperable disease, definitive locally advanced disease, and the postoperative setting. A key driver in improvement of local disease control has been the significant evolution of radiation therapy techniques in the last three decades, allowing for delivery of definitive radiation doses while limiting exposure of normal tissues. For patients with locally-advanced NSCLC, the advent of volumetric imaging techniques has allowed a shift from 2-dimensional approaches to 3-dimensional conformal radiation therapy (3DCRT). The next generation of 3DCRT, intensity-modulated radiation therapy and volumetric-modulated arc therapy (VMAT), have enabled even more conformal radiation delivery. Clinical evidence has shown that this can improve the quality of life for patients undergoing definitive management of lung cancer. In the early-stage setting, conventional fractionation led to poor outcomes. Evaluation of altered dose fractionation with the previously noted technology advances led to advent of stereotactic body radiation therapy (SBRT). This technique has dramatically improved local control and expanded treatment options for inoperable, early-stage patients. The recent development of proton therapy has opened new avenues for improving conformity and the therapeutic ratio. Evolution of newer proton therapy techniques, such as pencil-beam scanning (PBS), could improve tolerability and possibly allow reexamination of dose escalation. These new progresses, along with significant advances in systemic therapies, have improved survival for lung cancer patients across the spectrum of non-metastatic disease. They have also brought to light new challenges and avenues for further research and improvement.

Development and Evaluation of Patient Education Materials for Elderly Lung Cancer Patients

Patients treated for lung cancer are often elderly presenting a unique challenge for developing patient education materials. This study developed and evaluated a patient education pamphlet on lung stereotactic body radiotherapy (SBRT) designed specifically for an elderly population. The SBRT pamphlet was developed using a participatory design involving a convenience sample of patients. This prospective study assessed patient's opinions of pamphlet effectiveness through self-report questionnaires. The pamphlet was deemed "effective" if patients rated 16/18 evaluation statements as "strongly agree" or "agree." Demographic data and health literacy (Rapid Estimate of Adult Literacy in Medicine short-form (REALM-SF)) were also assessed. Patient opinion of pamphlet "effectiveness" was compared between patients with REALM-SF scores of 7 versus <7 using Fisher's exact test. The overall EQ-5D-5L score was compared for patients who did and did not find the pamphlet effective using the Wilcoxon-Mann-Whitney test. Thirty-seven patients participated. The median age was 76 years (range 56-93) and 22 patients (59 %) had ≤high school education. Most patients preferred to have verbal (65 %) or written (78 %) educational materials as opposed to online information or educational classes. Thirty-two patients (86 %) rated the pamphlet as effective. The proportion of patients who found the pamphlet effective was 85.7 versus 86.7 % (p = 1.00) in those with REALM 7 versus <7. The mean EQ-5D score was 67.5 (SD 19.1) versus 71.8 (SD 8.7) (p = 0.84) in those who found the pamphlet effective versus not. Participatory design is an effective method for developing education materials for challenging patient groups such as elderly patients. Despite advanced age and comorbidity, this patient group had adequate health literacy.

A Randomized Phase 2 Study Comparing 2 Stereotactic Body Radiation Therapy Schedules for Medically Inoperable Patients With Stage I Peripheral Non-Small Cell Lung Cancer: NRG Oncology RTOG 0915 (NCCTG N0927)

PURPOSE

To compare 2 stereotactic body radiation therapy (SBRT) schedules for medically inoperable early-stage lung cancer to determine which produces the lowest rate of grade ≥3 protocol-specified adverse events (psAEs) at 1 year.

METHODS AND MATERIALS

Patients with biopsy-proven peripheral (≥2 cm from the central bronchial tree) T1 or T2, N0 (clinically node negative by positron emission tomography), M0 tumors were eligible. Patients were randomized to receive either 34 Gy in 1 fraction (arm 1) or 48 Gy in 4 consecutive daily fractions (arm 2). Rigorous central accreditation and quality assurance confirmed treatment per protocol guidelines. This study was designed to detect a psAEs rate >17% at a 10% significance level (1-sided) and 90% power. Secondary endpoints included rates of primary tumor control (PC), overall survival (OS), and disease-free survival (DFS) at 1 year. Designating the better of the 2 regimens was based on prespecified rules of psAEs and PC for each arm.

RESULTS

Ninety-four patients were accrued between September 2009 and March 2011. The median follow-up time was 30.2 months. Of 84 analyzable patients, 39 were in arm 1 and 45 in arm 2. Patient and tumor characteristics were balanced between arms. Four (10.3%) patients on arm 1 (95% confidence interval [CI] 2.9%-24.2%) and 6 (13.3%) patients on arm 2 (95% CI 5.1%-26.8%) experienced psAEs. The 2-year OS rate was 61.3% (95% CI 44.2%-74.6%) for arm 1 patients and 77.7% (95% CI 62.5%-87.3%) for arm 2. The 2-year DFS was 56.4% (95% CI 39.6%-70.2%) for arm 1 and 71.1% (95% CI 55.5%-82.1%) for arm 2. The 1-year PC rate was 97.0% (95% CI 84.2%-99.9%) for arm 1 and 92.7% (95% CI 80.1%-98.5%) for arm 2.

CONCLUSIONS

34 Gy in 1 fraction met the prespecified criteria and, of the 2 schedules, warrants further clinical research.

Usefulness of target delineation based on the two extreme phases of a four-dimensional computed tomography scan in stereotactic body radiation therapy for lung cancer

Background

An evaluation of the usefulness of target delineation based only on the two extreme phases of a four-dimensional computed tomography (4D CT) scan in lung stereotactic body radiation therapy (SBRT).

Methods

Seventeen patients treated with SBRT via 4D CT scans for lung cancer were retrospectively enrolled. Volumetric and geometric analyses were performed for the internal target volumes (ITVs) and planning target volumes (PTVs) generated using different respiratory phases (all phases and 2 extreme phases) and setup margins (3 mm and 5 mm).

Results

As the setup margins were added to the ITVs, the overlap percentage between the PTVs based on all phases and the two extreme phases increased (85.1% for ITVs, 89.8% for PTVs_3 mm, and 91.3% for PTVs_5 mm), and there were no differences according to the tumor parameters, such as the gross tumor volume and 3D mobility. The missing-volume differences for ITVs derived from cone-beam CT images also decreased, with values of 5.3% between ITVs, 0.5% between PTVs_3 mm, and 0.2% between PTVs_5 mm. Compared with the plan based on all phases and a 3 mm margin, the average lung-dose differences found for the PTV based on the two extreme phases and a 5 mm margin were 0.41 Gy for the mean lung dose and 0.93% for V20.

Conclusions

Regardless of tumor characteristics, PTV construction based only on the two extreme phases and a 5 mm setup margin may be a useful tool for reducing the clinical workload involved in target delineation in SBRT for lung cancer.

Recent advances in radiotherapy for thoracic tumours

Radiation Oncology technology has continued to advance at a rapid rate and is bringing significant benefits to patients. This review outlines some of the advances in technology and radiotherapy treatment of thoracic cancers including brachytherapy, stereotactic radiotherapy, tomotherapy and intensity modulated radiotherapy. The importance of functional imaging with PET and management of movement are highlighted. Most of the discussion relates to non-small cell lung cancer but management of mesothelioma and small cell lung cancer are also covered. This technology has substantial benefits to patients in terms of decreasing toxicity both in the short and longer term.

Cost-Effectiveness Analysis Comparing Conventional Versus Stereotactic Body Radiotherapy for Surgically Ineligible Stage I Non–Small-Cell Lung Cancer

The authors show that based on a threshold of $50,000 per life-year gained, stereotactic body radiotherapy seems cost effective compared with conventionally fractionated radiotherapy.

The impact of tumor size on outcomes after stereotactic body radiation therapy for medically inoperable early-stage non-small cell lung cancer

PURPOSE

Stereotactic body radiation therapy for medically inoperable early-stage non-small cell lung cancer (NSCLC) offers excellent control rates. Most published series deal mainly with small (usually <4 cm), peripheral, solitary tumors. Larger tumors are associated with poorer outcomes (ie, lower control rates, higher toxicity) when treated with conventional RT. It is unclear whether SBRT is sufficiently potent to control these larger tumors. We therefore evaluated and examined the influence of tumor size on treatment outcomes after SBRT.

METHODS AND MATERIALS

Between October 2004 and October 2010, 185 medically inoperable patients with early (T1-T2N0M0) NSCLC were treated on a prospective research ethics board-approved single-institution protocol. Prescription doses were risk-adapted based on tumor size and location. Follow-up included prospective assessment of toxicity (as per Common Terminology Criteria for Adverse Events, version 3.0) and serial computed tomography scans. Patterns of failure, toxicity, and survival outcomes were calculated using Kaplan-Meier method, and the significance of tumor size (diameter, volume) with respect to patient, treatment, and tumor factors was tested.

RESULTS

Median follow-up was 15.2 months. Tumor size was not associated with local failure but was associated with regional failure (P=.011) and distant failure (P=.021). Poorer overall survival (P=.001), disease-free survival (P=.001), and cause-specific survival (P=.005) were also significantly associated with tumor size (with tumor volume more significant than diameter). Gross tumor volume and planning target volume were significantly associated with grade 2 or worse radiation pneumonitis. However, overall rates of grade ≥3 pneumonitis were low and not significantly affected by tumor or target size.

CONCLUSIONS

Currently employed stereotactic body radiation therapy dose regimens can provide safe effective local therapy even for larger solitary NSCLC tumors (up to 5.7 cm in tumor diameter or 100 cm(3) in tumor volume) but are associated with more nonlocal failures as well as poorer survival. These observations suggest these patients may benefit from more extensive staging or consideration of adjuvant therapy.

Alternatives to surgery in early stage disease-stereotactic body radiotherapy

The management of early stage non-small cell lung carcinoma (NSCLC) has been revolutionized by the introduction of stereotactic body radiotherapy (SBRT). SBRT is now the standard of care for medically inoperable patients with early stage NSCLC. However, the role of SBRT in medically operable patients remains controversial. This article will review the indications, the technical considerations, image guidance principles, potential toxicities and special circumstances in lung SBRT.

Outcomes of accelerated hypofractionated radiotherapy in stage i non-small-cell lung cancer

PURPOSE

Outcomes after treatment with accelerated hypofractionated radiotherapy in stage i medically inoperable non-small-cell lung cancer (nsclc) patients were determined.

METHODS

Our single-institution retrospective review looked at medically inoperable patients with T1-2N0M0 nsclc treated with accelerated hypofractionated curative-intent radiotherapy between 1999 and 2009. Patients were staged mainly by computed tomography imaging of chest and abdomen, bone scan, and computed tomography/magnetic resonance imaging of brain. Positron-emission tomography (pet) staging was performed in 6 patients. Medical charts were reviewed to determine demographics, radiotherapy details, sites of failure, toxicity (as defined by the Common Terminology Criteria for Adverse Events, version 3.0) and vital status. The cumulative incidence of local and distant failure was calculated. Overall (os) and cause-specific (css) survival were estimated by the Kaplan-Meier method.

RESULT

In the 60 patients treated during the study period, the dose regimens were 50 Gy in 20 fractions (n = 6), 55 Gy in 20 fractions (n = 8), 60 Gy in 20 fractions (n = 42), and 60 Gy in 25 fractions (n = 4). All patients were treated once daily. The median follow-up was 27 months (range: 4-94 months). The os rates at 2 and 5 years were 61% [95% confidence interval (ci): 50% to 75%] and 19% (95% ci: 10% to 34%) respectively. The css rates at 2 and 5 years were 79% (95% ci: 68% to 91%) and 39% (95% ci: 24% to 63%) respectively. The cumulative incidence of local failure was 20% at 5 years. The cumulative incidence of distant failure was 28% at 5 years. No patients experienced grade 3 or greater pneumonitis or esophagitis.

CONCLUSIONS

Accelerated hypofractionated regimens are well tolerated and provide good local control in medically inoperable patients with stage i nsclc. Such regimens may be a reasonable treatment alternative when stereotactic body radiation therapy is not feasible.

Stereotactic body radiotherapy for medically inoperable lung cancer: prospective, single-center study of 108 consecutive patients

PURPOSE

To present the results of stereotactic body radiotherapy (SBRT) for medically inoperable patients with Stage I non-small-cell lung cancer (NSCLC) and contrast outcomes in patients with and without a pathologic diagnosis.

METHODS AND MATERIALS

Between December 2004 and October 2008, 108 patients (114 tumors) underwent treatment according to the prospective research ethics board-approved SBRT protocols at our cancer center. Of the 108 patients, 88 (81.5%) had undergone pretreatment whole-body [18F]-fluorodeoxyglucose positron emission tomography/computed tomography. A pathologic diagnosis was unavailable for 33 (28.9%) of the 114 lesions. The SBRT schedules included 48 Gy in 4 fractions or 54-60 Gy in 3 fractions for peripheral lesions and 50-60 Gy in 8-10 fractions for central lesions. Toxicity and radiologic response were assessed at the 3-6-month follow-up visits using conventional criteria.

RESULTS

The mean tumor diameter was 2.4-cm (range, 0.9-5.7). The median follow-up was 19.1 months (range, 1-55.7). The estimated local control rate at 1 and 4 years was 92% (95% confidence interval [CI], 86-97%) and 89% (95% CI, 81-96%). The cause-specific survival rate at 1 and 4 years was 92% (95% CI, 87-98%) and 77% (95% CI, 64-89%), respectively. No statistically significant difference was found in the local, regional, and distant control between patients with and without pathologically confirmed NSCLC. The most common acute toxicity was Grade 1 or 2 fatigue (53 of 108 patients). No toxicities of Grade 4 or greater were identified.

CONCLUSIONS

Lung SBRT for early-stage NSCLC resulted in excellent local control and cause-specific survival with minimal toxicity. The disease-specific outcomes were comparable for patients with and without a pathologic diagnosis. SBRT can be considered an option for selected patients with proven or presumed early-stage NSCLC.