Dose--volume metrics associated with radiation pneumonitis after stereotactic body radiation therapy for lung cancer. Int J Radiat Oncol Biol Phys. 2012;83:e545-e549. [PMID: 22436782 DOI: 10.1016/j.ijrobp.2012.01.018]

Renin-Angiotensin System Inhibitors Might Help to Reduce the Development of Symptomatic Radiation Pneumonitis After Stereotactic Body Radiotherapy for Lung Cancer

INTRODUCTION

The purpose of the present study was to evaluate the role of renin-angiotensin system (RAS) inhibitors in preventing symptomatic radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT).

MATERIALS AND METHODS

The data from 158 patients with a solitary lung lesion treated with 1 to 3 fractions of SBRT from December 2008 to July 2014 were retrospectively analyzed. The incidence of RP was evaluated according to the Common Toxicity Criteria for Adverse Events, version 4. The use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) was analyzed to assess for possible correlations with the development of grade ≥ 2 RP. The patient and dosimetric variables were also assessed.

RESULTS

After a median follow-up period of 13.8 months (range, 3.2-55.0 months), 22 patients had developed grade ≥ 2 RP. Patients with peripheral lesions, favorable dosimetric data, and ACEI and/or ARB use had a reduced risk of symptomatic RP. In unadjusted and adjusted multivariate analyses, ACEI and/or ARB intake and the dosimetric variables were statistically significant factors. In a secondary analysis, the use of ACEIs and ARBs among patients with a greater planning target volume and higher dosimetric values correlated with a reduced risk of symptomatic RP.

CONCLUSION

The use of a RAS inhibitor was associated with a decreased incidence of symptomatic RP among patients undergoing SBRT for lung lesions. Patients with higher dosimetric values had a reduced risk of grade ≥ 2 RP with ACEI and ARB use.

Stereotactic body radiotherapy for second pulmonary nodules after operation for an initial lung cancer

OBJECTIVE

A second lung cancer is occasionally observed in patients who underwent surgical resection of the index lung cancer. The purpose of this study is to evaluate stereotactic body radiation therapy for second lung cancer.

METHODS

Fifty-one medically inoperable patients who underwent stereotactic body radiation therapy for second lung cancer were the subjects: 31 cases of multiple primary lung cancer and 20 of pulmonary metastasis from the index cancer. Clinical stage was T1a in 27 patients, T1b in 13 patients and T2a in 11 patients, and 70% of subjects had impaired respiratory function. Histology of second lung cancer was adenocarcinoma in 16 patients, squamous cell carcinoma in 9 patients and not assessed in 25 patients. The interval between index cancer operation and stereotactic body radiation therapy was 31 months (range: 4-171). The total stereotactic body radiation therapy doses were 48 Gy in 4 fractions or 60 Gy in 10 fractions.

RESULTS

With the median follow-up of 36 months, 3-year overall survival rates were 62% with the median survival time of 46 months. Cause-specific survival was 73% at 3 years. Overall survival for multiple primary lung cancer and pulmonary metastasis was quite similar: 62 and 61% at 3 years, respectively. Three-year overall survival was 77% for T1a and 43% for T1b or T2a. Grade 2 pulmonary toxicities occurred in five patients and one patient died of Grade 5 pneumonitis.

CONCLUSIONS

Even though the subjects were medically inoperable, the survival outcomes of stereotactic body radiation therapy were favorable. Furthermore, having acceptable toxicity, stereotactic body radiation therapy is feasible and could be an option for multiple primary lung cancer and pulmonary metastasis after surgical resection for the index cancer.

Angiotensin-converting enzyme inhibitors decrease the risk of radiation pneumonitis after stereotactic body radiation therapy

PURPOSE

Although angiotensin-converting enzyme (ACE) inhibitor use during conventionally fractionated radiation therapy has been associated with a decreased risk of radiation pneumonitis (RP), a similar effect has not been demonstrated in stereotactic body radiation therapy (SBRT). The purpose of this study was to examine the impact of ACE inhibitor use during SBRT on the risk of symptomatic (grade ≥2) RP.

METHODS AND MATERIALS

Patients with at least 1 follow-up treated with SBRT for primary lung cancer were included. ACE inhibitors, angiotensin receptor blockers, statins, nonsteroidal anti-inflammatory drugs, and glucocorticoids were examined. RP was determined from all available medical records, including follow-up appointments with radiation oncology, pulmonology, medical oncology, and hospitalizations. It was scored with the Common Terminology Criteria for Adverse Events, version 4.0. Analysis was performed with Kaplan-Meier and Cox proportional hazards modeling.

RESULTS

A total of 257 patients met inclusion criteria. Seventy (27.2%) used an ACE inhibitor during SBRT. The overall rates of grade ≥2 and ≥3 RP were 19.1% (n = 49) and 7.0% (n = 18), respectively. ACE inhibitor users experienced greater freedom from symptomatic RP on univariate (vs nonusers, 89.8% vs 76.3% at 12 months, P = .029) and multivariate analysis (hazard ratio 0.373, 95% confidence interval 0.156-0.891, P =.026). The volume of normal lung tissue receiving ≥5 Gy, %, ≥10 Gy, ≥20 Gy, and mean lung dose were also significantly associated with RP on univariate and multivariate analysis. ACE inhibitor use was not associated with overall survival. Angiotensin receptor blockers, nonsteroidal anti-inflammatory drugs, glucocorticoids, and statin administration were not associated with symptomatic RP or survival.

CONCLUSIONS

ACE inhibitor use during SBRT was associated with significantly greater freedom from grade ≥2 RP, even after adjusting for pulmonary dose. Given the data on their protective effect in human and animal models, a prospective evaluation is warranted.

Complications from Stereotactic Body Radiotherapy for Lung Cancer

Stereotactic body radiotherapy (SBRT) has become a standard treatment option for early stage, node negative non-small cell lung cancer (NSCLC) in patients who are either medically inoperable or refuse surgical resection. SBRT has high local control rates and a favorable toxicity profile relative to other surgical and non-surgical approaches. Given the excellent tumor control rates and increasing utilization of SBRT, recent efforts have focused on limiting toxicity while expanding treatment to increasingly complex patients. We review toxicities from SBRT for lung cancer, including central airway, esophageal, vascular (e.g., aorta), lung parenchyma (e.g., radiation pneumonitis), and chest wall toxicities, as well as radiation-induced neuropathies (e.g., brachial plexus, vagus nerve and recurrent laryngeal nerve). We summarize patient-related, tumor-related, dosimetric characteristics of these toxicities, review published dose constraints, and propose strategies to reduce such complications.

Effect of stereotactic dosimetric end points on overall survival for Stage I non-small cell lung cancer: a critical review

Stereotactic body radiation therapy (SBRT) delivers a high biologically effective dose while minimizing toxicities to surrounding tissues. Within the scope of clinical trials and local practice, there are inconsistencies in dosimetrics used to evaluate plan quality. The purpose of this critical review was to determine if dosimetric parameters used in SBRT plans have an effect on local control (LC), overall survival (OS), and toxicities. A database of relevant trials investigating SBRT for patients with early-stage non-small cell lung cancer was compiled, and a table of dosimetric variables used was created. These parameters were compared and contrasted for LC, OS, and toxicities. Dosimetric end points appear to have no effect on OS or LC. Incidences of rib fractures correlate with a lack of dose-volume constraints (DVCs) reported. This review highlights the great disparity present in clinical trials reporting dosimetrics, DVCs, and toxicities for lung SBRT. Further evidence is required before standard DVCs guidelines can be introduced. Dosimetric end points specific to stereotactic treatment planning have been proposed but require further investigation before clinical implementation.

Salvage stereotactic body radiotherapy for locally recurrent non-small cell lung cancer after sublobar resection and i(125) vicryl mesh brachytherapy

Purpose

Locally recurrent non-small cell lung cancer (LR-NSCLC) remains challenging to treat, particularly in patients having received prior radiotherapy. Heterogeneous populations and varied treatment intent in existing literature result in significant limitations in evaluating efficacy of lung re-irradiation. In order to better establish the impact of re-irradiation in patients with LR-NSCLC following high-dose radiotherapy, we report outcomes for patients treated with prior sublobar resection and brachytherapy that subsequently underwent stereotactic body radiotherapy (SBRT).

Methods

A retrospective review of patients initially treated with sublobar resection and I¹²⁵ vicryl mesh brachytherapy, who later developed LR-NSCLC along the suture line, was performed. Patients received salvage SBRT with curative intent. Dose and fractionation were based on tumor location and size, with a median prescription dose of 48 Gy in 4 fractions (range 20–60 Gy in 1–4 fractions).

Results

Thirteen consecutive patients were identified with median follow-up of 2.1 years (range 0.7–5.6 years). Two in-field local failures occurred at 7.5 and 11.1 months, resulting in 2-year local control of 83.9% (95% CI, 63.5–100.0%). Two-year disease-free survival and overall survival estimates were 38.5% (95% CI, 0.0–65.0%) and 65.8% (95% CI, 38.2–93.4%). Four patients (31%) remained disease-free at last follow-up. All but one patient who experienced disease recurrence developed isolated or synchronous distant metastases. Only one patient (7.7%) developed grade ≥3 toxicity, consisting of grade 3 esophageal stricture following a centrally located recurrence previously treated with radiofrequency ablation.

Conclusion

Despite high-local radiation doses delivered to lung parenchyma previously with I¹²⁵ brachytherapy, re-irradiation with SBRT for LR-NSCLC results in excellent local control with limited morbidity, allowing for potential disease cure in a subset of patients.

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.

Patterns of CT lung injury and toxicity after stereotactic radiotherapy delivered with helical tomotherapy in early stage medically inoperable NSCLC

OBJECTIVE

To evaluate toxicity and patterns of radiologic lung injury on CT images after hypofractionated image-guided stereotactic body radiotherapy (SBRT) delivered with helical tomotherapy (HT) in medically early stage inoperable non-small-cell lung cancer (NSCLC).

METHODS

28 elderly patients (31 lesions) with compromised pulmonary reserve were deemed inoperable and enrolled to undergo SBRT. Patterns of lung injury based on CT appearance were assessed at baseline and during follow up. Acute (6 months or less) and late (more than 6 months) events were classified as radiation pneumonitis and radiation fibrosis (RF), respectively.

RESULTS

After a median follow-up of 12 months (range, 4-20 months), 31 and 25 lesions were examined for acute and late injuries, respectively. Among the former group, 25 (80.6%) patients showed no radiological changes. The CT appearance of RF revealed modified conventional, mass-like and scar-like patterns in three, four and three lesions, respectively. No evidence of late lung injury was demonstrated in 15 lesions. Five patients developed clinical pneumonitis (four patients, grade 2 and one patient, grade 3, respectively), and none of whom had CT findings at 3 months post-treatment. No instance of symptomatic RF was detected. The tumour response rate was 84% (complete response + partial response). Local control was 83% at 1 year.

CONCLUSION

Our findings show that HT-SBRT can be considered an effective treatment with a mild toxicity profile in medically inoperable patients with early stage NSCLC. No specific pattern of lung injury was demonstrated.

ADVANCES IN KNOWLEDGE

Our study is among the few showing that HT-SBRT represents a safe and effective option in patients with early stage medically inoperable NSCLC, and that it is not associated with a specific pattern of lung injury.

SBRT in operable early stage lung cancer patients

Since decades the gold standard for treatment of early stage non-small cell lung cancer (NSCLC) is surgical lobectomy plus mediastinal lymph node dissection. Patients in worse health status are treated with sublobar resection or radiation treatment. With development of stereotactic-body-radiotherapy (SBRT), outcome of patients treated with radiation was substantially improved. Comparison of SBRT and surgical techniques is difficult due to the lack of randomized trials. However, all available evidence in form of case control studies of population based studies show equivalence between sublobar resection and SBRT indicating that SBRT-when performed by a trained and experienced team-should be offered to all high-risk surgical patients. For patients not willing to take the risk of lobectomy and therefore refusing surgery, SBRT is an excellent treatment option.

Baseline correction of a correlation model for improving the prediction accuracy of infrared marker-based dynamic tumor tracking

We previously found that the baseline drift of external and internal respiratory motion reduced the prediction accuracy of infrared (IR) marker‐based dynamic tumor tracking irradiation (IR Tracking) using the Vero4DRT system. Here, we proposed a baseline correction method, applied immediately before beam delivery, to improve the prediction accuracy of IR Tracking. To perform IR Tracking, a four‐dimensional (4D) model was constructed at the beginning of treatment to correlate the internal and external respiratory signals, and the model was expressed using a quadratic function involving the IR marker position (x) and its velocity (v), namely function F(x,v). First, the first 4D model, F1st(x,v), was adjusted by the baseline drift of IR markers (BDIR) along the x‐axis, as function F′(x,v). Next, BDdetect, that defined as the difference between the target positions indicated by the implanted fiducial markers (Pdetect) and the predicted target positions with F′(x,v) (Ppredict) was determined using orthogonal kV X‐ray images at the peaks of the Pdetect of the end‐inhale and end‐exhale phases for 10 s just before irradiation. F′(x,v) was corrected with BDdetect to compensate for the residual error. The final corrected 4D model was expressed as Fcor(x,v)=F1st{(x−BDIR),v}−BDdetect. We retrospectively applied this function to 53 paired log files of the 4D model for 12 lung cancer patients who underwent IR Tracking. The 95th percentile of the absolute differences between Pdetect and Ppredict (|Ep|) was compared between F1st(x,v) and Fcor(x,v). The median 95th percentile of |Ep| (units: mm) was 1.0, 1.7, and 3.5 for F1st(x,v), and 0.6, 1.1, and 2.1 for Fcor(x,v) in the left–right, anterior–posterior, and superior–inferior directions, respectively. Over all treatment sessions, the 95th percentile of |Ep| peaked at 3.2 mm using Fcor(x,v) compared with 8.4 mm using F1st(x,v). Our proposed method improved the prediction accuracy of IR Tracking by correcting the baseline drift immediately before irradiation.

PACS number: 87.19.rs, 87.19.Wx, 87.56.‐v, 87.59.‐e, 88.10.gc

Stereotactic body radiotherapy with helical TomoTherapy for medically inoperable early stage primary and second-primary non-small-cell lung neoplasm: 1-year outcome and toxicity analysis

OBJECTIVE

This study investigated the effectiveness of stereotactic body radiotherapy with helical TomoTherapy (T-SBRT) for treating medically inoperable primary and second-primary early stage non-small-cell lung neoplasm (SPLN) and evaluated whether the movement of organizing pneumonia (OP) within the irradiation field (IF) can be detected via analysis of radiological changes.

METHODS

Patients (n = 16) treated for 1 year (2011-12) at our hospital by T-SBRT at a total dose of 60 Gy in five fractions were examined retrospectively. Outcome and toxicity were recorded and were separately described for SPLN. CT scans were reviewed by a single radiologist.

RESULTS

Of the 16 patients, 5 (31.3%) had primary lung malignancies, 10 (62.5%) had SPLN, and 1 case (6.3%) had isolated mediastinal metastasis of lung neoplasm. Pathological evidence was obtained for 72.2% of all lesions. The median radiological follow-up was 11 months (10.5 months for SPLN). For all cases, the 6- and 12-month survival rates were 100% and 77.7% (100% and 71.4%, respectively, for SPLN), and the 6- and 12-month locoregional control rates were 100% in all cases. 2 (12.5%) of 16 patients developed grade 3 late transient radiation pneumonitis following steroid therapy and 1 (6.3%) presented asymptomatic infiltrates comparable to OP opacities.

CONCLUSION

T-SBRT seems to be safe and effective.

ADVANCES IN KNOWLEDGE

Mild OP is likely associated with radiation-induced anomalies in the IF, identification of migrating opacities can help discern relapse of radiation-induced opacities.

Outcomes of stereotactic body radiotherapy (SBRT) treatment of multiple synchronous and recurrent lung nodules

Background

Stereotactic body radiotherapy (SBRT) is evolving into a standard of care for unresectable lung nodules. Local control has been shown to be in excess of 90% at 3 years. However, some patients present with synchronous lung nodules in the ipsilateral or contralateral lobe or metasynchronous disease. In these cases, patients may receive multiple courses of lung SBRT or a single course for synchronous nodules. The toxicity of such treatment is currently unknown.

Methods

Between 2006 and 2012, 63 subjects with 128 metasynchronous and synchronous lung nodules were treated at the Mayo Clinic with SBRT. Demographic patient data and dosimetric data regarding SBRT treatments were collected. Acute toxicity (defined as toxicity < 90 days) and late toxicity (defined as toxicity > = 90 days) were reported and graded as per standardized CTCAE 4.0 criteria. Local control, progression free survival and overall survival were also described.

Results

The median age of patients treated was 73 years. Sixty five percent were primary or recurrent lung cancers with the remainder metastatic lung nodules of varying histologies. Of 63 patients, 18 had prior high dose external beam radiation to the mediastinum or chest. Dose and fractionation varied but the most common prescriptions were 48 Gy/4 fractions, 54 Gy/3 fractions, and 50 Gy/5 fractions. Only 6 patients demonstrated local recurrence. With a median follow up of 12.6 months, median SBRT specific overall survival and progression free survival were 35.7 months and 10.7 months respectively. Fifty one percent (32/63 patients) experienced acute toxicity, predominantly grade 1 and 2 fatigue. One patient developed acute grade 3 radiation pneumonitis at 75 days. Forty six percent (29/63 patients) developed late effects. Most were grade 1 dyspnea. There was one patient with grade 5 pneumonitis.

Conclusion

Multiple courses of SBRT and SBRT delivery after external beam radiotherapy appear to be feasible and safe. Most toxicity was grade 1 and 2 but the risk was approximately 50% for both acute and late effects.

Risk of Pneumonitis After Stereotactic Body Radiation Therapy in Patients With Previous Anatomic Lung Resection

BACKGROUND

Stereotactic body radiation therapy (SBRT) has emerged as a standard treatment of early-stage, medically inoperable lung cancer. Limited data have evaluated the radiation pneumonitis (RP) risk with SBRT after previous anatomic lung resection (ALR). We assessed the incidence of RP and all pulmonary toxicity (PT) in patients who underwent lung SBRT after ALR and compared them with those of patients without previous ALR.

MATERIALS AND METHODS

We reviewed the medical records of 84 consecutively treated patients with stage T1-T2b non-small-cell lung cancer (NSCLC) treated with 88 courses of SBRT for 94 lung tumors from January 2007 to December 2014, including 17 patients with previous ALR. The rates of RP and all PT were compared between the patients with and without previous ALR.

RESULTS

At a median follow-up duration of 18.3 months (range, 1.8-85.6 months), the crude grade 2+ RP rate was 5.9% and 2.8% for patients with and without previous ALR, respectively (P = .51). The corresponding 2-year estimates of freedom from RP were 89% and 97% (P = .51). The crude rate of all grade 2+ PT was 11.8% and 2.8% for those with and without previous ALR (P = .11), with 2-year estimates of freedom from PT of 97% and 84% (P = .11), respectively. The 2 cohorts were well matched by the mean lung dose, percentage of lung volume receiving 20 Gy (P = .86), and prescribed dose (P = .75). The 2-year estimates of local control, cause-specific survival, and overall survival were similar between the 2 cohorts.

CONCLUSION

The observed rates of PT were low among all patients, with a trend toward increased grade 2 and 3 lung toxicity among patients with previous ALR. Previous ALR did not increase the risk of grade 4 and 5 RP, and SBRT appears safe and effective in this population.

Influence of the correlation modeling period on the prediction accuracy of infrared marker-based dynamic tumor tracking using a gimbaled X-ray head

PURPOSE

To assess the utility of 10 s and 20 s modeling periods, rather than the 40 s currently used, in the clinical construction of practical correlation models (CMs) in dynamic tumor tracking irradiation using the Vero4DRT.

METHODS

The CMs with five independent parameters (CM parameters) were analyzed retrospectively for 10 consecutive lung cancer patients. CM remodeling was performed two or three times per treatment session. Three different CMs trained over modeling periods of 10, 20, and 40 s were built from a single, original CM log file. The predicted target positions were calculated from the CM parameters and the vertical displacement of infrared markers on the abdomen (PIR) during the modeling. We assessed how the CM parameters obtained over modeling periods of T s (T = 10, 20, and 40 s) were robust to changes in respiratory patterns after several minutes. The mimic-predicted target positions after several minutes were computed based on the previous CM parameters and PIR during the next modeling. The 95th percentiles of the differences between mimic-predicted and detected target positions over 40 s (E95robust,T: T = 10, 20, and 40 s) were then calculated.

RESULTS

Strong correlations greater than 0.92 were observed between the E95robust,20 and E95robust,40 values. Meanwhile, irregular respiratory patterns with inconsistent amplitudes of motion created differences between the E95robust,10 and E95robust,40 values of ≥10 mm.

CONCLUSIONS

The accuracies of CMs derived using 20 s were almost identical to those obtained over 40 s, and superior to those obtained over 10 s.

Correlations Between Serum IL-6 Levels and Radiation Pneumonitis in Lung Cancer Patients: A Meta-Analysis

OBJECTIVE

Diagnostic significance of interleukin 6 (IL-6) for lung cancer patients with radiation pneumonitis (RP) was examined within various studies, but yielded conflicting results. Thus, this meta-analysis was performed to demonstrate correlations between serum IL-6 levels and RP in lung cancer patients.

METHOD

Electronic databases updated to March 2014 were searched to find relevant studies. Relevant literatures were searched under the PubMed, Embase, Web of Science, Cochrane Library, CISCOM, CINAHL, Google Scholar, CBM and CNKI databases. STATA statistical software (Version 12.0, Stata Corporation, and College Station, TX) Standardized mean difference (SMD), and its corresponding 95% confidence intervals (CIs) were used for this meta-analysis. In addition, nine cohort studies met the inclusion criteria and involved a total of 137 RP patients and 295 non-RP patients.

RESULTS

The results of combined SMD suggested that serum IL-6 levels in RP patients was significantly higher than in non-RP patients before radiotherapy. While, there was a significant difference in serum IL-6 levels of RP patients between before and after radiotherapy, we observed no difference in serum IL-6 levels between RP patients and non-RP patients after radiotherapy. Ethnicity-stratified analyses indicated that increased serum IL-6 levels were related to the risk of RP in lung cancer patients among Caucasians, but not detected among Asians (all P > 0.05).

CONCLUSION

The main finding of our meta-analysis reveals that increased serum IL-6 levels may contribute to the incidence of RP in lung cancer patients, especially among Caucasians.

Timing and characteristics of radiation pneumonitis after stereotactic body radiotherapy for peripherally located stage I lung cancer

BACKGROUND

This study was conducted to determine the timing and characteristics of radiation pneumonitis (RP) associated with stereotactic body radiotherapy (SBRT) for stage I lung cancer.

METHODS

Two hundred thirty-one patients treated with SBRT using 52 Gy in 4 fractions were identified. Control rate, RP incidence rate, and predictive factors and timing of RP were evaluated retrospectively.

RESULTS

The 3-year overall survival and local control rates were 80.7 and 92.0 %, respectively. The grade ≥2 RP rate was 13.0 %; no grade 4-5 RP occurred. The most statistically significant predictive factor of grade ≥2 RP was V10. The median intervals to first graphical appearance were 4.2 and 2.5 months for grade 1 and grade 2-3 RP, respectively. Median intervals to maximum radiological density change were 6.0 and 4.6 months for grade 1 and grade 2-3 RP, respectively. A significantly different interval to first graphical appearance between grade 1 and grade 2-3 RP was observed; no significantly different interval to maximum radiological density change was noted.

CONCLUSIONS

The first graphical appearance of grade ≥2 RP was earlier than that of grade 1 RP, although the timing of maximum radiological density change was not significantly different.

Radiation pneumonitis after stereotactic radiation therapy for lung cancer

Stereotactic body radiation therapy (SBRT) has a local control rate of 95% at 2 years for non-small cell lung cancer (NSCLC) and should improve the prognosis of inoperable patients, elderly patients, and patients with significant comorbidities who have early-stage NSCLC. The safety of SBRT is being confirmed in international, multi-institutional Phase II trials for peripheral lung cancer in both inoperable and operable patients, but reports so far have found that SBRT is a safe and effective treatment for early-stage NSCLC and early metastatic lung cancer. Radiation pneumonitis (RP) is one of the most common toxicities of SBRT. Although most post-treatment RP is Grade 1 or 2 and either asymptomatic or manageable, a few cases are severe, symptomatic, and there is a risk for mortality. The reported rates of symptomatic RP after SBRT range from 9% to 28%. Being able to predict the risk of RP after SBRT is extremely useful in treatment planning. A dose-effect relationship has been demonstrated, but suggested dose-volume factors like mean lung dose, lung V20, and/or lung V2.5 differed among the reports. We found that patients who present with an interstitial pneumonitis shadow on computed tomography scan and high levels of serum Krebs von den Lungen-6 and surfactant protein D have a high rate of severe radiation pneumonitis after SBRT. At our institution, lung cancer patients with these risk factors have not received SBRT since 2006, and our rate of severe RP after SBRT has decreased significantly since then.

Stereotactic body radiation therapy for post-pulmonary lobectomy isolated lung metastasis of thoracic tumor: survival and side effects

BACKGROUND

Stereotactic body radiation therapy (SBRT) has emerged as an alternative treatment for patients with early stage non-small cell lung cancer (NSCLC) or metastatic pulmonary tumors. However, for isolated lung metastasis (ILM) of thoracic malignances after pulmonary lobectomy, reported outcomes of SBRT have been limited. This study evaluates the role of SBRT in the treatment of such patients.

METHODS

A retrospective search of the SBRT database was conducted in three hospitals. The parameters analyzed in the treated patients were local control, progression-free survival (PFS), overall survival (OS), and the treatment-related side-effects.

RESULTS

In total, 23 patients with single ILM after pulmonary lobectomy treated with SBRT were identified and the median follow-up time was 14 months (range: 6.0-47.0 months). Local recurrences were observed in two patients during follow-up and the 1-year local control rate was 91.3%. Median PFS and OS for the studied cohort were 10.0 months [95% confidence interval (CI) 5.1-14.9 months] and 21.0 months (95% CI 11.4-30.6 months), respectively. Acute radiation pneumonitis (RP) of grade 2 or worse was observed in five (21.7%) and three (13.0%) patients, respectively. Other treatment-related toxicities included chest wall pain in one patient (4.3%) and acute esophagitis in two patients (8.7%). By Pearson correlation analysis, the planning target volume (PTV) volume and the volume of the ipsilateral lung exposed to a minimum dose of 5 Gy (IpV5) were significantly related to the acute RP of grade 2 or worse in present study (p < 0.05). The optimal thresholds of the PTV and IpV5 to predict RP of acute grade 2 or worse RP were 59 cm3 and 51% respectively, according to the receiver-operating characteristics curve analysis, with sensitivity/specificity of 75.0%/80.0% and 62.5%/80.0%.

CONCLUSIONS

SBRT for post-lobectomy ILM was effective and well tolerated. The major reason for disease progression was distant failure but not local recurrence. The PTV and IpV5 are potential predictors of acute RP of grade 2 or higher and should be considered in treatment planning for such patients.

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 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.

Safety and efficacy of intensity-modulated stereotactic body radiotherapy using helical tomotherapy for lung cancer and lung metastasis

Stereotactic body radiotherapy (SBRT) proved to be an effective treatment with acceptable toxicity for lung tumors. However, the use of helical intensity-modulated (IM) SBRT is controversial. We investigated the outcome of lung tumor patients treated by IMSBRT using helical tomotherapy with a Japanese standard fractionation schedule of 48 Gy in 4 fractions (n = 37) or modified protocols of 50-60 Gy in 5-8 fractions (n = 35). Median patient's age was 76 years and median follow-up period for living patients was 20 months (range, 6-46). The median PTV was 6.9 cc in the 4-fraction group and 14 cc in the 5- to 8-fraction group (P = 0.001). Grade 2 radiation pneumonitis was seen in 2 of 37 patients in the 4-fraction group and in 2 of 35 patients in the 5- to 8-fraction group (log-rank P = 0.92). Other major complications were not observed. The LC rates at 2 years were 87% in the 4-fraction group and 83% in the 5- to 8-fraction group. Helical IMSBRT for lung tumors is safe and effective. Patients with a high risk of developing severe complications may also be safely treated using 5-8 fractions. The results of the current study warrant further studies of helical IMSBRT.

[Stereotactic ablative irradiation for lung cancer]

Stereotactic radiotherapy for lung cancer is a technique that is now well established in the therapeutic arsenal. Protocols are effective, with very high local control rate and an acceptable rate of survival if one takes into account the patient's age and comorbidities. Complications are rare. This review of the literature analyses the whole process of the therapeutic indications and future prospects.

Reconstitution of internal target volumes by combining four-dimensional computed tomography and a modified slow computed tomography scan in stereotactic body radiotherapy planning for lung cancer

Background

To evaluate the volumetric and geometric differences in the ITVs generated by four-dimensional (4D) computed tomography (CT), a modified slow CT scan, and a combination of these CT methods in lung cancer patients treated with stereotactic body radiotherapy (SBRT).

Methods

Both 4D CT and modified slow CT using a multi-slice CT scanner were performed for SBRT planning in 14 patients with 15 pulmonary targets. Volumetric and geometric analyses were performed for (1) ITVall, generated by combining the gross tumor volumes (GTVs) from all 8 phases of the 4D CT; (2) ITV2, generated by combining the GTVs from 2 extreme phases of the 4D CT; (3) ITVslow, derived from the GTV on the modified slow CT scan; (4) ITVall+slow, generated by combining ITVall and ITVslow; and (5) ITV2+slow, generated by combining ITV2 and ITVslow. Three SBRT plans were performed using 3 ITVs to assess the dosimetric effects on normal lung caused by the various target volumes.

Results

ITVall (11.8 ± 8.3 cm³) was significantly smaller than ITVall+slow (12.5 ± 8.9 cm³), with mean values of 5.8% for the percentage volume difference, and a mean of 7.5% of ITVslow was not encompassed in ITVall. The geometric coverages of ITV2 and ITVslow for ITVall were 84.7 ± 6.6% and 76.2 ± 9.3%, respectively, but the coverage for ITVall increased to 90.9 ± 5.9% by using the composite of these two ITVs. There were statistically significant increases in the lung-dose parameters of the plans based on ITVall+slow compared to the plans based on ITVall or ITV2+slow. However, the magnitudes of these differences were relatively small, with a value of less than 3% in all dosimetric parameters.

Conclusions

Due to its ability to provides additional motion information, the combination of 4D CT and a modified slow CT scan in SBRT planning for lung cancer can be used to reduce possible errors in true target delineation caused by breathing pattern variations.

The effect of arm position on the dosimetry of thoracic stereotactic ablative radiation therapy using volumetric modulated arc therapy

PURPOSE

Patient comfort and positioning stability may be improved in the arms down (AD) compared with the typical arms up (AU) position in thoracic stereotactic ablative radiation therapy (SABR). We compared plan quality for AD vs AU when using volumetric modulated arc therapy (VMAT), and evaluated the sensitivity of AD plans to arm positioning variability.

METHODS AND MATERIALS

We took plans of 14 patients with 17 lung tumors treated with thoracic SABR using VMAT in the AD position and simulated the same treatments in the AU position by re-optimizing after digitally removing the ipsilateral arm. To evaluate the sensitivity of AD plans to arm positioning variability, all plans were recalculated without re-optimization after assigning water density to the ipsilateral arm (AD-W) and then digitally shifting the arm 2.5 cm anterolaterally (AD-WS).

RESULTS

Between AD and AU plans, statistically significant but clinically insignificant (all original planning constraints met) differences were found for the following parameters: mean planning target volume maximum dose, difference of 2.3% of prescription dose (P = .049); mean intermediate dose conformity index, difference of 0.27 (P = .012); median percent lung volume receiving a minimum of 10, 20, and 30 Gy (V10, V20, and V30), differences of 0.5%, 0.2%, and 0.1%, respectively (P = .040, .007, and .001); and median spinal cord maximum dose, difference of 33.5 cGy (P = .017). Similarly, between AD-W and AD-WS plans, statistically significant but clinically insignificant differences were found for median lung V20 and V30, difference of 0.0% for both (P = .034 and .016, by matched pair analysis).

CONCLUSIONS

Our exploratory planning study suggests that when using VMAT for lung tumor SABR, AD and AU positioning achieve clinically equivalent plan quality, and AD plans are insensitive to relatively large variability in arm position.

The green tea extract epigallocatechin-3-gallate inhibits irradiation-induced pulmonary fibrosis in adult rats

The present study evaluated the effect of epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea, on irradiation-induced pulmonary fibrosis and elucidated its mechanism of action. A rat model of irradiation-induced pulmonary fibrosis was generated using a ⁶⁰Co irradiator and a dose of 22 Gy. Rats were intraperitoneally injected with EGCG (25 mg/kg) or dexamethasone (DEX; 5 mg/kg) daily for 30 days. Mortality rates and lung index values were calculated. The severity of fibrosis was evaluated by assaying the hydroxyproline (Hyp) contents of pulmonary and lung tissue sections post-irradiation. Alveolitis and fibrosis scores were obtained from semi-quantitative analyses of hematoxylin and eosin (H&E) and Masson’s trichrome lung section staining, respectively. The serum levels of transforming growth factor β1 (TGF-β1), interleukin (IL)-6, IL-10, and tumor necrosis factor-α (TNF-α) were also measured. Surfactant protein-B (SPB) and α-SMA expression patterns were evaluated using immunohistochemistry, and the protein levels of nuclear transcription factor NF-E2-related factor 2 (Nrf-2) and its associated antioxidant enzymes heme oxygenase-1 enzyme (HO-1) and NAD(P)H:quinone oxidoreductase-1 (NQO-1) were examined via western blot analysis. Treatment with EGCG, but not DEX, reduced mortality rates and lung index scores, improved histological changes in the lung, reduced collagen depositions, reduced MDA content, enhanced SOD activity, inhibited (myo)fibroblast proliferation, protected alveolar epithelial type II (AE2) cells, and regulated serum levels of TGF-β1, IL-6, IL-10, and TNF-α. Treatment with EGCG, but not DEX, activated Nrf-2 and its downstream antioxidant enzymes HO-1 and NQO-1. Taken together, these results showed that EGCG treatment significantly inhibits irradiation-induced pulmonary fibrosis. Furthermore, the results suggested promising clinical EGCG therapies to treat this disorder.

[Radiation pneumonitis after stereotactic body radiation therapy for early stage non-small cell lung cancer]

With the development of radiation technology, stereotactic body radiation therapy (SBRT) has been widely used in early stage non-small cell lung cancer (NSCLC). It is not only the standard therapy for medically inoperable early-stage NSCLC, but also one of the therapies for operable early-stage NSCLC. Radiation pneumonitis (RP) is one of the most common adverse effects after SBRT, it may reduce the patients' quality of life, even cause treatment failure. Therefore, in order to improve the patients' quality of life and enhance local control rate of tumor, it is important to reduce the risk of RP. The unique fractionation schemes and the dose distribution of SBRT make it not only different from conventional fraction radiation therapy in treatment outcomes, but also in the incidence of radiation pneumonitis. This article reviews the applying of SBRT for early stage NSCLC, the incidence of radiation pneumonitis, radiological appearance after SBRT and predictive factors.

Investigating strategies to reduce toxicity in stereotactic ablative radiotherapy for central lung tumors

BACKGROUND

[corrected] Stereotactic radiotherapy for central lung tumors has a narrower therapeutic index than that for peripheral tumors. Tumor tracking strategies have been proposed to reduce treatment volumes and toxicity, however they need to consider uncertainties in tumor size and shape change throughout respiration to ensure optimal local control. We quantified these uncertainties and explored strategies to account for them.

MATERIAL AND METHODS

Ten patients with central tumors, PTV > 100 cm(3), motion > 5 mm and a 10-phase 4DCT without significant artifact in the tumor region were evaluated. Uncertainties were quantified using GTV size in different phases, and the Hausdorff distance (HD) between the phase 50% GTV and other phases after soft-tissue rigid registration. An individualized internal target volume for tracking (ITV(T)) was generated from the union of the GTVs in all phases after rigid registration. This was compared to ITVs generated for tracking based on the phase 50% GTV alone or with isotropic margins of 3 or 5 mm for size and volume overlap.

RESULTS

Median free-breathing PTV size and motion were 162.1 cm(3) (110-210) and 8.9 mm (6.1-14.1). Overall, median GTV size variation and HD were 4.7% (0.2-22.3) and 6.3 mm (3.9-17.6). Tracking using GTV 50% alone resulted in median volume overlap with ITV(T) of 71.7% (range 56.8-85.1). Isotropic margins of 3 or 5mm always resulted in a volume overlap less than 95% or a volume larger than the ITV(T).

CONCLUSIONS

Changes in size and shape of central lung tumors are substantial during respiration. These limit the ability to reduce treatment volumes with tracking, especially if isotropic margins are used. An individualized ITV for tracking, such as the ITV(T) is preferred.

Complications of thoracic radiotherapy

The issue of toxicity is a primary concern for chest irradiation, because it is a dose-limiting toxicity and because in some circumstances it can alleviate the survival benefit of radiation therapy. Potential acute and delayed side effects can compromise the patients' prognosis and generate significant morbidity. Here we review on chest complications of radiation therapy, with focus on cardiac and pulmonary radio-induced side effects. Most radiographic changes associated with thoracic irradiation are asymptomatic. However, chest irradiation generated by treatment of breast cancer, bronchopulmonary malignancies, or mediastinal lymphoma has been associated with a risk of acute radiation pneumonitis and late lung fibrosis. An increasing number of clinical studies suggest that some dosimetric factors (e.g. V20, V30, mean lung dose) should be considered for limiting the risk of lung toxicity. Improvements in radiation techniques as well as changes in indications, volumes and prescribed doses of radiation therapy should help to better spare lungs from irradiation and thus decreasing the risk of subsequent toxicity. Numerous other contributing factors should also be considered, such as chemotherapeutic agents, smoking, tumor topography, or intrinsic sensitivity. Cardiac toxicity is another clinically relevant issue in patients receiving radiation therapy for breast cancer or for lymphoma. This life threatening toxicity should be analyzed in the light of dosimetric factors (including low doses) but also associated systemic agents which almost carry a potential for additive toxicity toward myocardium or coronaries. A long-term follow-up of patients as well as an increasing knowledge of the underlying biological pathways involved in cardiac toxicity should help designing effective preventing strategies.

Markerless EPID image guided dynamic multi-leaf collimator tracking for lung tumors

Compensation of target motion during the delivery of radiotherapy has the potential to improve treatment accuracy, dose conformity and sparing of healthy tissue. We implement an online image guided therapy system based on soft tissue localization (STiL) of the target from electronic portal images and treatment aperture adaptation with a dynamic multi-leaf collimator (DMLC). The treatment aperture is moved synchronously and in real time with the tumor during the entire breathing cycle. The system is implemented and tested on a Varian TX clinical linear accelerator featuring an AS-1000 electronic portal imaging device (EPID) acquiring images at a frame rate of 12.86 Hz throughout the treatment. A position update cycle for the treatment aperture consists of four steps: in the first step at time t = t0 a frame is grabbed, in the second step the frame is processed with the STiL algorithm to get the tumor position at t = t0, in a third step the tumor position at t = ti + δt is predicted to overcome system latencies and in the fourth step, the DMLC control software calculates the required leaf motions and applies them at time t = ti + δt. The prediction model is trained before the start of the treatment with data representing the tumor motion. We analyze the system latency with a dynamic chest phantom (4D motion phantom, Washington University). We estimate the average planar position deviation between target and treatment aperture in a clinical setting by driving the phantom with several lung tumor trajectories (recorded from fiducial tracking during radiotherapy delivery to the lung). DMLC tracking for lung stereotactic body radiation therapy without fiducial markers was successfully demonstrated. The inherent system latency is found to be δt = (230 ± 11) ms for a MV portal image acquisition frame rate of 12.86 Hz. The root mean square deviation between tumor and aperture position is smaller than 1 mm. We demonstrate the feasibility of real-time markerless DMLC tracking with a standard LINAC-mounted (EPID).

Developments in stereotactic ablative radiotherapy for the treatment of early-stage lung cancer

SUMMARY Stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiation therapy, has emerged as an effective treatment for inoperable early-stage non-small-cell lung cancer. SABR differs from conventional radiotherapy by virtue of its tight spatial tolerances and use of oligofractionated radiation. The modern technique is characterized by management of tumor motion, image guidance before each fraction and specialized radiation delivery techniques. The result is a highly conformal target dose with a sharp gradient that spares normal tissues with great accuracy. This enables delivery of very potent (ablative) doses, causing more rapid and durable responses than traditional radiation therapy treatment regimens can achieve. The established techniques, new developments and ongoing questions related to SABR for early-stage non-small-cell lung cancer are reviewed herein.

Positional accuracy of novel x-ray-image-based dynamic tumor-tracking irradiation using a gimbaled MV x-ray head of a Vero4DRT (MHI-TM2000)

PURPOSE

To verify the positional accuracy of a novel x-ray-image-based dynamic tumor-tracking (DTT) irradiation technique using the gimbaled MV x-ray head of a Vero4DRT (MHI-TM2000).

METHODS

Verification of the x-ray-image-based DTT was performed using three components: a three-dimensional moving phantom with a steel ball target, a laser displacement gauge, and an orthogonal kV x-ray imaging subsystem with a gimbaled MV x-ray head and the system controller of the Vero4DRT. The moving phantom was driven based on seven periodic patterns [peak-to-peak amplitude (A): 20-40 mm, breathing period (T): 2-5 s] and 15 patients' aperiodic respiratory patterns (A: 6.5-22.9 mm, T: 1.9-5.8 s). The target position was detected in real time with the orthogonal kV x-ray imaging subsystem using the stereo vision technique. Subsequently, the Vero4DRT predicted the next position of the target, and then the gimbaled MV x-ray head tracked the corresponding orientation of the target. The displacements of the target were measured synchronously using the laser displacement gauge. The difference between the target positions predicted by the Vero4DRT and those measured by the laser displacement gauge was computed as the prediction error (E(P)), and the difference between the target positions tracked by the gimbaled MV x-ray head and predicted target positions was computed as the mechanical error (E(M)). Total tracking system error (E(T)) was defined as the difference between the tracked and measured target positions.

RESULTS

The root mean squares (RMSs) of E(P), E(M), and E(T) were up to 0.8, 0.3, and 0.7 mm, respectively, for the periodic patterns. Regarding the aperiodic patterns, the median RMSs of E(P), E(M), and E(T) were 1.2 (range, 0.9-1.8) mm, 0.1 (range, 0.1-0.5) mm, and 1.2 (range, 0.9-1.8) mm, respectively. From the results of principal component analysis, tracking efficiency, defined as the ratio of twice the RMS of E(T) to A, was improved for patients with high respiratory function (R = 0.91; p < 0.01).

CONCLUSIONS

The present study demonstrated that the Vero4DRT is capable of high-accuracy x-ray-image-based DTT. E(T) was caused primarily by E(P), and E(M) was negligible. Furthermore, principal component analysis showed that tracking efficiency could be improved with this system, especially for patients with high respiratory function.

Clinical outcome and predictors of survival and pneumonitis after stereotactic ablative radiotherapy for stage I non-small cell lung cancer

Background

Stereotactic ablative radiotherapy (SABR) can achieve excellent local control rates in early-stage non-small cell lung cancer (NSCLC) and has emerged as a standard treatment option for patients who cannot undergo surgery or those with isolated recurrences. However, factors that may predict toxicity or survival are largely unknown. We sought here to identify predictors of survival and pneumonitis after SABR for NSCLC in a relatively large single-institution series.

Methods

Subjects were 130 patients with stage I NSCLC treated with four-dimensional computed tomography (4D CT) –planned, on-board volumetric image–guided SABR to 50 Gy in 4 fractions. Disease was staged by positron emission tomography/computed tomography (PET/CT) and scans were obtained again at the second follow-up after SABR.

Results

At a median follow-up time of 26 months, the 2-year local control rate was 98.5%. The median overall survival (OS) time was 60 months, and OS rates were 93.0% at 1 year, 78.2% at 2 years, and 65.3% at 3 years. No patient experienced grade 4–5 toxicity; 15 had radiation pneumonitis (12 [9.3%] grade 2 and 3 [2.3%] grade 3). Performance status, standardized uptake value (SUV)_max on staging PET/CT, tumor histology, and disease operability were associated with OS on univariate analysis, but only staging SUV_max was independently predictive on multivariate analysis (P = 0.034). Dosimetric factors were associated with radiation pneumonitis on univariate analysis, but only mean ipsilateral lung dose ≥9.14 Gy was significant on multivariate analysis (P = 0.005).

Conclusions

OS and radiation pneumonitis after SABR for stage I NSCLC can be predicted by staging PET SUV_max and ipsilateral mean lung dose, respectively.