Patients with severe emphysema have a low risk of radiation pneumonitis following stereotactic body radiotherapy

International expert consensus on diagnosis and treatment of lung cancer complicated by chronic obstructive pulmonary disease

Background

Lung cancer combined by chronic obstructive pulmonary disease (LC-COPD) is a common comorbidity and their interaction with each other poses significant clinical challenges. However, there is a lack of well-established consensus on the diagnosis and treatment of LC-COPD.

Methods

A panel of experts, comprising specialists in oncology, respiratory medicine, radiology, interventional medicine, and thoracic surgery, was convened. The panel was presented with a comprehensive review of the current evidence pertaining to LC-COPD. After thorough discussions, the panel reached a consensus on 17 recommendations with over 70% agreement in voting to enhance the management of LC-COPD and optimize the care of these patients.

Results

The 17 statements focused on pathogenic mechanisms (n=2), general strategies (n=4), and clinical application in COPD (n=2) and lung cancer (n=9) were developed and modified. These statements provide guidance on early screening and treatment selection of LC-COPD, the interplay of lung cancer and COPD on treatment, and considerations during treatment. This consensus also emphasizes patient-centered and personalized treatment in the management of LC-COPD.

Conclusions

The consensus highlights the need for concurrent treatment for both lung cancer and COPD in LC-COPD patients, while being mindful of the mutual influence of the two conditions on treatment and monitoring for adverse reactions.

Synergistic combination of a topologically invariant imaging signature and a biomarker for the accurate prediction of symptomatic radiation pneumonitis before stereotactic ablative radiotherapy for lung cancer: A retrospective analysis

Objectives

We aimed to explore the synergistic combination of a topologically invariant Betti number (BN)-based signature and a biomarker for the accurate prediction of symptomatic (grade ≥2) radiation-induced pneumonitis (RP+) before stereotactic ablative radiotherapy (SABR) for lung cancer.

Methods

A total of 272 SABR cases with early-stage non-small cell lung cancer were chosen for this study. The occurrence of RP+ was predicted using a support vector machine (SVM) model trained with the combined features of the BN-based signature extracted from planning computed tomography (pCT) images and a pretreatment biomarker, serum Krebs von den Lungen-6 (BN+KL-6 model). In all, 242 (20 RP+ and 222 RP–(grade 1)) and 30 cases (8 RP+ and 22 RP–) were used for training and testing the model, respectively. The BN-based features were extracted from BN maps that characterize topologically invariant heterogeneous traits of potential RP+ lung regions on pCT images by applying histogram- and texture-based feature calculations to the maps. The SVM models were built to predict RP+ patients with a BN signature that was constructed based on the least absolute shrinkage and selection operator logistic regression model. The evaluation of the prediction models was performed based on the area under the receiver operating characteristic curves (AUCs) and accuracy in the test. The performance of the BN+KL-6 model was compared to the performance based on the BN, conventional original pCT, and wavelet decomposition (WD) models.

Results

The test AUCs obtained for the BN+KL-6, BN, pCT, and WD models were 0.825, 0.807, 0.642, and 0.545, respectively. The accuracies of the BN+KL-6, BN, pCT, and WD models were found to be 0.724, 0.708, 0.591, and 0.534, respectively.

Conclusion

This study demonstrated the comprehensive performance of the BN+KL-6 model for the prediction of potential RP+ patients before SABR for lung cancer.

Lung Function After Stereotactic Body Radiation Therapy for Early-Stage Non-Small Cell Lung Cancer, Changes and Predictive Markers

Introduction

The present study explores changes in pulmonary function, symptoms and radiological signs of pneumonitis after curatively intended stereotactic body radiation therapy (SBRT).

Methods

All inoperable, early-stage non-small cell lung cancer patients treated with stereotactic body radiation therapy (SBRT) from 2014-2017 were included in this single-centre study. They were followed regularly for 12 months after treatment. The patients were classified into three groups based on radiology and symptomatology: no radiation pneumonitis, asymptomatic and symptomatic radiation pneumonitis.

Results

Forty-four patients with stage IA-IIB disease were treated with 45–56 Gy in 3–8 fractions. The median age was 75 years, 43% of the patients were female; 60% of the patients had a COPD in GOLD grade of 2-4, and 95.5% were active or former smokers. Symptomatic radiation pneumonitis occurred in 18% of the patients and asymptomatic pneumonitis as defined by radiology, in 39%. The mean of forced expiratory volume in 1 second (FEV1) and diffusion capacity for carbon monoxide (DLCO) decreases for all patients during the first years were higher than one would expect from physiologic ageing. FEV1 and DLCO in percent decrease 7-8% at 1-1.5 months in the symptomatic radiation pneumonitis group. CT scan findings consistent with radiation pneumonitis occurred after a median of 2.9 months in the symptomatic and 5.4 months in the asymptomatic radiation pneumonitis groups. In the group with symptomatic radiation pneumonitis, symptoms, as measured by the Clinical COPD questionnaire score, significantly increased at 3 and 6 months. Significant higher maximum doses to the critical lung volumes DC1000cm³ (1000 cm³ of lung receiving a given dose or less) and DC 1500cm³ (1500 cm³ of lung receiving a given dose or less) were observed in patients who developed radiation pneumonitis.

Conclusion

Early decrease in measured FEV1 and DLCO occurred before imaging changes and symptoms and might indicate the development of symptomatic radiation pneumonitis. The dose to critical lung volumes of DC1000 cm³ and DC1500 cm³ may predict the risk for the development of symptomatic radiation pneumonitis.

Risk of radiation pneumonitis in patients with emphysema after stereotactic body radiotherapy for non-small cell lung cancer assessed by quantitative CT

Quantitative CT assessment of patients with pulmonary emphysema is used to measure pulmonary function. The present study evaluated whether the quantitative CT value can accurately estimate the risk of radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT) for non-small cell lung cancer (NSCLC) in patients with and without emphysema. A total of 80 patients with stage I NSCLC receiving SBRT at a dose of 50 or 60 Gy in five fractions at our hospital between November 2003 and October 2015 were included in the analysis. A total of 33 (41%) patients were diagnosed with emphysema on CT examination. Dosimetric parameters, quantitative CT percentage value of low attenuation area (LAA%) in the whole lung, and average whole lung CT density values were used to examine the risk of RP. Among the 80 patients, 26 (33%) and 3 (4%) experienced Grade 1 and Grade 2 RP, respectively, during the median observation period of 18.8 (1.8-106.8) months. The RP rate for patients with a LAA% (<-910 HU) of ≤25% was significantly higher than that of subjects with LAA% (<-910 HU) >25% (P=0.037). The RP rate in subjects with an average HU value of >-790 HU was significantly higher compared with that of patients with ≤-790 HU (P=0.036). Age (hazard ratio [HR]=2.46; P=0.03) and average HU (HR=3.39; P=0.02) were significantly associated with RP, whereas mean lung dose was not identified to be significant in multivariate analysis. The quantitative CT value was associated with RP after SBRT.

Prognosis of patients with acute exacerbation of combined pulmonary fibrosis and emphysema: a retrospective single-centre study

BACKGROUND

Previous analyses of combined pulmonary fibrosis and emphysema (CPFE) cohorts have provided conflicting data on the survival of patients with CPFE. Therefore, the aim of this study was to investigate the clinical prognosis of acute exacerbations (AE) of CPFE.

METHODS

We retrospectively reviewed the medical records of patients who had been treated at the Shinshu University Hospital (Matsumoto, Japan) between 2003 and 2017. We identified 21 patients with AE of CPFE and 41 patients with AE of idiopathic pulmonary fibrosis (IPF) and estimated their prognoses using the Kaplan-Meier method.

RESULTS

Treatment content and respiratory management were not significantly different between the two groups before and after exacerbation. At the time of AE, the median serum Krebs von den Lungen-6 level was significantly lower in the CPFE group (Krebs von den Lungen-6: 966 U/μL; white blood cell count: 8810 /μL) than that in the IPF group (Krebs von den Lungen-6: 2130 U/μL, p < 0.001; white blood cells: 10809/μL, p = 0.0096). The baseline Gender-Age-Physiology scores were not significantly different between the two groups (CPFE, 4.5 points; IPF, 4.7 points; p = 0.58). Kaplan-Meier curves revealed that the survival time after AE for patients with CPFE was longer than that for patients with IPF (p < 0.001, log-rank test).

CONCLUSIONS

Survival prognoses after AE were significantly better for patients with CPFE than that for those with IPF. Our findings may improve the medical treatment and respiratory management of patients with AE-CPFE.

Emphysema quantification on computed tomography and its value in predicting radiation pneumonitis in lung cancer treated by stereotactic body radiotherapy

A large portion of patients with early-stage non-small-cell lung cancer (NSCLC) who are receiving stereotactic body radiation therapy (SBRT) are medically inoperable due to compromised pulmonary function, and among these patients pulmonary emphysema (PE) is common. However, the relationship between PE and radiation-induced lung injuries remains unclear. In this study, we aimed to describe the full spectrum of computed tomography (CT) features after SBRT for NSCLC, and to explore their relationship with variables, including PE and dosimetric factors. In all, 71 patients were enrolled. PE was quantified as the percentage of low attenuation area [attenuation values of <-860 Hounsfield units (HU)] within the radiation field (%LAA-860). Spearman's correlation and logistic regression were used to explore factors related to radiological features and radiation pneumonitis (RP). At the 1-year follow-up, acute radiological changes included: (i) diffuse consolidation, 11.3%; (ii) patchy consolidation and ground-glass opacities, 42.3%; and (iii) patchy ground-glass opacity, 14.1%. Late morphological changes occurred in 61.9% of patients (50.7% with a modified conventional pattern, 5.6% with a mass-like pattern and 5.6% with a scar-like pattern). Lower %LAA-860 was the only factor that was significantly associated with consolidation changes at 6 months after SBRT [odds ratio (OR), 0.008; P = 0.009], and it was also a significant predictor for Grade ≥ 2 RP (OR, 0.003; P = 0.04). Our study showed that patients with PE can benefit from SBRT on the condition that good control of dose-volume constraints is achieved.

Stereotactic body radiotherapy in patients with chronic obstructive pulmonary disease and interstitial pneumonia: a review

Stereotactic body radiation therapy (SBRT) can yield excellent local tumor control, as well as survival benefit comparable to that of surgery for early-stage lung cancer. However, in terms of toxicity, SBRT might lead to fatal radiation pneumonitis. Lung diseases, such as chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD), are major risk factors for lung cancer. However, these patients are typically not candidates for the gold-standard treatment option, lobectomy, because of the perioperative risks. In addition, patients with poor respiratory function can be excluded in prospective clinical trials. Thus, SBRT for patients with pulmonary diseases is still challenging, but there appears to be a clinical role for this modality as an alternative treatment. However, there are few well-documented review articles on SBRT for patients with pulmonary diseases. Therefore, we aimed to review SBRT in the context of important patient-related factors, including COPD and ILD. SBRT is an acceptable alternative treatment option for patients with lung cancer who also have COPD with an equivalent risk of radiation pneumonitis to normal lung. However, latent ILD should be detected prior to treatment. The indication for SBRT should be decided by carefully considering the risks and benefit for patients with ILD.

Does the presence of emphysema increase the risk of radiation pneumonitis in lung cancer patients?

Introduction

Radiotherapy (rt) plays an important role in the treatment of lung cancer. One of the most common comorbidities in patients with lung cancer is pulmonary emphysema. The literature offers conflicting data about whether emphysema increases the occurrence and severity of radiation pneumonitis (rp). As a result, whether high doses of rt (with curative intent) should be avoided in patients with emphysema is still unclear.

Objective

We measured the documented incidence of rp in patients with and without emphysema who received curative radiation treatment.

Methods

This retrospective cohort study considered patients in the lung cancer clinical database of the Peter Brojde Lung Cancer Centre. Data from the database has been used previously for research studies, including a recent publication about emphysema grading, based on the percentage of lung occupied by emphysema on computed tomography (ct) imaging.

Results

Using previously published methods, chest ct imaging for 498 patients with lung cancer was scored for the presence of emphysema. The analysis considered 114 patients who received at least 30 Gy radiation. Of those 114 patients, 64 (56%) had emphysema, with approximately 23% having severe or very severe disease. The incidence of rp was 34.4% in patients with emphysema (n = 22) and 32.0% in patients with no emphysema (n = 16, p = 0.48). No difference in the incidence of rp was evident between patients with various grades of emphysema (p = 0.96). Similarly, no difference in the incidence of rp was evident between the two treatment protocols-that is, definitive rt 17 (37%) and combined chemotherapy-rt 21 (31%, p = 0.5).

Conclusions

In our cohort, the presence of emphysema on chest ct imaging was not associated with an increased risk of rp. That finding suggests that patients with lung cancer and emphysema should be offered rt when clinically indicated. However, further prospective studies will be needed for confirmation.

Diabetes mellitus and radiation induced lung injury after thoracic stereotactic body radiotherapy

BACKGROUND

Radiographic radiation induced lung injury (RILI) is frequently observed after stereotactic body radiotherapy (SBRT). Models of radiographic change can identify patient risk factors that predict clinical toxicity. We examined the association between radiographic lung changes and lung tissue dose-density response over time with clinical risk factors for RILI, such as diabetes.

METHODS

424 baseline and follow up CT scans at 3, 6, and 12 months post-treatment were analyzed in 116 patients (27 with diabetes) undergoing thoracic SBRT. Volumes of dense/hazy regions and lung parenchyma dose-density response curves were evaluated with respect to follow up time, diabetes, and other factors.

RESULTS

Dense and hazy tissue regions were larger in the diabetic population, with the effect most pronounced at 3 months. Similarly, dose-density response curves showed greater density change versus dose in the diabetic group (all p < 0.05). Diabetes, time, the interaction of diabetes and time, smoking status, African American race, baseline lung density, and tumor location were significantly associated with radiographic changes on mixed effect analyses. PTV size, pulmonary function, and medication exposure did not significantly impact RILI. Clinical grade 1-2 pneumonitis was more prevalent in diabetic patients (p = 0.02). However, radiographic change did not correlate with clinical pneumonitis.

CONCLUSIONS

The presence of diabetes and other clinical factors is associated with increased volume and density of radiographic RILI after lung SBRT, most prominently early after treatment. This is the first report demonstrating the increased severity of RILI after SBRT in diabetic patients. Increased caution treating diabetic patients may be warranted.

Improved postoperative lung function after sublobar resection of non-small-cell lung cancer combined with lung volume reduction surgery in patients with advanced emphysema

Background

Radiotherapy is recommended as primary local therapy for inoperable patients with non-small cell lung cancer (NSCLC). We hypothesized that selected patients with advanced emphysema could be candidates for surgery and improved functional outcome might result in addition to low mortality and morbidity and successful cancer control when sublobar resection in a lung volume reduction surgery (LVRS) concept is applied.

Methods

All patients with NSCLC and severe emphysema who underwent cancer resection in a LVRS concept between 2003 and 2015 were included for analysis. Postoperative 90-day mortality, complications, survival and lung function with forced expiratory volume in one second pre-operatively and three months postoperatively served as endpoints.

Results

Fourteen patients were included. Three procedures were bilateral and eleven unilateral, eight have been performed with thoracoscopy and six with conversion to an open procedure due to adhesions. In ten patients, tumor resection was atypical and in four patients an anatomic segmentectomy was performed. All patients had lung volume reduction. Prolonged air leak occurred in three patients. Perioperative 90-mortality was zero. Median pre-operative forced expiratory volume in one second was 32.5% and increased to 37% (P=0.002) 3 months following surgery. Three and 5-year survival rates were 50% and 35%, respectively.

Conclusions

Sublobar resection of NSCLC combined with LVRS in patients with severely impaired lung function due to emphysema can be performed with low mortality and morbidity making it an alternative treatment modality to radiotherapy. This approach allows cancer resection in marginal patients and improves emphysema symptoms simultaneously.

Is severe emphysema, as defined by quantitative CT measurement, a negative risk factor of radiation fibrosis?

OBJECTIVE

To investigate whether patients with emphysema, as evaluated by quantitative CT image measurement, are at risk of developing radiation pneumonitis (RP) after radiotherapy (RT) for non-small cell lung cancer (NSCLC).

METHODS

Between March 2011 and June 2015, 68 consecutive patients with Stage I NSCLC treated with a RT dose of 75 Gy given in 30 fractions were enrolled. The median age was 79 years and there were 45 males and 23 females. The number of patients with T₁ and T₂ were 49 and 19, respectively. The severity of emphysema was evaluated by the percentages of the low attenuation area (LAA) of ≤-860 or -950 Hounsfield unit (HU) and average HU in the whole lung.

RESULTS

The mean difference percentages of LAA of ≤-860 (p = 0.0004) or -950 HU (p = 0.005) and average HU (p = 0.001) in patients with RP were significantly lower than those in patients without RP. The area under curve (AUC) of average HU was significantly higher than AUC of LAA of ≤-860 (p < 0.0001) or -950 HU (p < 0.0001). The RP rate after RT was significantly lower when the average HU values were ≤-850 HU (p = 0.0003).

CONCLUSION

Patients with emphysema evaluated by average HU (≤-850 HU) in the whole lung were found to be at low risk of RP after RT. Advances in Knowledge: Quantitative measurement of average HU from CT images was predicted of RP after RT.

Risk factors for radiation pneumonitis after stereotactic radiation therapy for lung tumours: clinical usefulness of the planning target volume to total lung volume ratio

OBJECTIVE

To identify risk factors for symptomatic radiation pneumonitis (RP) after stereotactic radiation therapy (SRT) for lung tumours.

METHODS

We retrospectively evaluated 68 lung tumours in 63 patients treated with SRT between 2011 and 2015. RP was graded according to the National Cancer Institute-Common Terminology Criteria for Adverse Events version 4.0. SRT was delivered at 7.0-12.0 Gy per each fraction, once daily, to a total of 48-64 Gy (median, 50 Gy). Univariate analysis was performed to assess patient- and treatment-related factors, including age, sex, smoking index (SI), pulmonary function, tumour location, serum Krebs von den Lungen-6 value (KL-6), dose-volume metrics (V5, V10, V20, V30, V40 and VS5), homogeneity index of the planning target volume (PTV), PTV dose, mean lung dose (MLD), contralateral MLD and V2, PTV volume, lung volume and the PTV/lung volume ratio (PTV/Lung). Performance of PTV/Lung in predicting symptomatic RP was also analysed using receiver operating characteristic (ROC) analysis.

RESULTS

The median follow-up period was 21 months. 10 of 63 patients (15.9%) developed symptomatic RP after SRT. On univariate analysis, V10, V20, PTV volume and PTV/Lung were significantly associated with occurrence of RP  ≥Grade 2. ROC curves indicated that symptomatic RP could be predicted using PTV/Lung [area under curve (AUC): 0.88, confidence interval (CI: 0.78-0.95), cut-off value: 1.09, sensitivity: 90.0% and specificity: 72.4%].

CONCLUSION

PTV/Lung is a good predictor of symptomatic RP after SRT. Advances in knowledge: The cases with high PTV/Lung should be carefully monitored with caution for the occurrence of RP after SRT.

Prognostic Value of Radiation Pneumonitis After Stereotactic Body Radiotherapy: Effect of Pulmonary Emphysema Quantitated Using CT Images

BACKGROUND

The aim of this study was to determine the prognostic factors of radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT).

PATIENTS AND METHODS

A total of 50 patients (36 male and 14 female) were treated with SBRT for 42 primary lung cancers and 8 metastatic lung cancers. SBRT was performed with 48 Gy in 4 fractions to the isocenter or with 40 Gy in 4 fractions covering 95% of the planning target volume. Percentage of low attenuation area (%LAA) was defined as percentage of the lung area with attenuation of -860 Hounsfield units (HU) or lower (%LAA-860) or of -960 HU or lower (%LAA-960). The dosimetric parameter of V_{20 Gy}, which means percentage volume of the lung receiving 20 Gy or more, was recalculated. RP was assessed using Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

The median follow-up period was 39.0 months (range, 7.2-94.5 months). RP of Grade 0, Grade 1, and Grade 2 to 3 was diagnosed in 11, 29, and 10 patients, respectively. Multivariate analyses (MVA) for Grade 1 showed that higher %LAA-860 and higher %LAA-960 were significantly associated with a lower rate of Grade 1 RP. MVA for Grade 2 to 3 showed that lower Brinkman index and lower lung V_{20 Gy} were significantly associated with a lower rate of Grade 2 to 3 RP, and, in contrast, %LAA-860 and %LAA-960 had no association with Grade 2 to 3 RP.

CONCLUSION

This result suggests that high %LAA is associated with radiological changes (Grade 1) but that %LAA has no correlation with Grade 2 to 3 RP because symptomatic RP might also be affected by other factors.

Pulmonary emphysema is a risk factor for radiation pneumonitis in NSCLC patients with squamous cell carcinoma after thoracic radiation therapy

Pulmonary emphysema (PE) has been demonstrated to have a high prevalence in patients with locally advanced non-small cell lung cancer (NSCLC). A total of 153 patients with locally advanced NSCLC were enrolled in this study to investigate the association between PE and radiation pneumonitis (RP) after definitive thoracic radiation therapy (TRT). The incidence of RP in Grade 2, 3 and 5 were 11.1%, 9.8% and 0.7%, respectively. Univariate analysis revealed that age, PE, forced vital capacity (FVC), arterial partial pressure of oxygen (PO₂) and mean lung dose (MLD) were significantly associated with the risk of Grade ≥2 or Grade ≥3 RP in patients with squamous cell carcinoma (SCC, P < 0.05). Logistic analysis demonstrated that PE was an independent risk factor of RP in SCC (P < 0.05). Receiver operating characteristics (ROC) analysis revealed that the combination of age, PE, FVC, PO₂ and MLD had a higher value to predict RP in SCC (AUC = 0.856 in Grade ≥2 RP and 0.882 in Grade ≥3 RP, respectively). Kaplan-Meier analysis revealed that the more severe the PE, the higher the incidence of RP in SCC. Our results revealed that PE was a high risk factor for locally advanced NSCLC patients followed definitive TRT, especially for SCC patients.

Predicting risk factors for radiation pneumonitis after stereotactic body radiation therapy for primary or metastatic lung tumours

OBJECTIVE

To investigate risk factors for radiation-induced pneumonitis (RP) after hypofractionated stereotactic body radiotherapy (SBRT) in patients with lung tumours.

METHODS

From May 2004 to January 2016, 66 patients with 71 primary or metastatic lung tumours were treated with SBRT; these 71 cases were retrospectively analyzed for RP. To explore the risk factors for RP, the following factors were investigated: age, sex, performance status, operability, number of treatments, respiratory gating, pulmonary emphysema, tumour location and subclinical interstitial lung disease (ILD). Irradiated underlying lung volumes of more than 5 Gy, 10 Gy, 20 Gy and 30 Gy (Lung V5, V10, V20 and V30), mean lung dose and volumes of gross tumour volume (in cubic centimetre) and planning target volume were calculated for possible risk factors of RP.

RESULTS

The median follow-up period was 32 months. RP of Grade 2 or more, according to the Common Terminology Criteria for Adverse Events v. 4.0, was detected in 6 (8.4%) of the 71 cases. Grade 5 RP was identified in two cases. Of the risk factors of RP, subclinical ILD was the only factor significantly associated with the occurrence of RP of Grade 2 or more (p < 0.001). Both cases with Grade 5 RP had ILD with a honeycombing image.

CONCLUSION

Subclinical ILD was the only significant factor for Grade 2-5 RP. In addition, the cases with honeycombing had a high potential for fatality related to severe RP. Patients with subclinical ILD should be carefully monitored for the occurrence of severe RP after SBRT. Advances in knowledge: Hypofractionated SBRT for primary or metastatic lung tumours provides a high local control rate and safe treatment.

Time course and predictive factors for lung volume reduction following stereotactic ablative radiotherapy (SABR) of lung tumors

Background

Stereotactic ablative volume reduction (SAVR) is a potential alternative to lung-volume reduction surgery in patients with severe emphysema and excessive surgical risk. Having previously observed a dose-volume response for localized lobar volume reduction after stereotactic ablative radiotherapy (SABR) for lung tumors, we investigated the time course and factors associated with volume reduction.

Methods

We retrospectively identified 70 eligible patients receiving lung tumor SABR during 2007-2013. We correlated lobar volume reduction (relative to total, bilateral lung volume [TLV]) with volume receiving high biologically effective doses (V_XXBED3) and other pre-treatment factors in all patients, and measured the time course of volume changes on 3-month interval CT scans in patients with large V_60BED3 (n = 21, V_60BED3 ≥4.1 % TLV).

Results

Median CT follow-up was 15 months. Median volume reduction of treated lobes was 4.5 % of TLV (range 0.01–13.0 %), or ~9 % of ipsilateral lung volume (ILV); median expansion of non-target adjacent lobes was 2.2 % TLV (−4.6–9.9 %; ~4 % ILV). Treated lobe volume reduction was significantly greater with larger V_XXBED3 (XX = 20–100 Gy, R² = 0.52–0.55, p < 0.0001) and smaller with lower pre-treatment FEV1% (R² = 0.11, p = 0.005) in a multivariable linear model. Maximum volume reduction was reached by ~12 months and persisted.

Conclusions

We identified a multivariable model for lobar volume reduction after SABR incorporating dose-volume and pre-treatment FEV1% and characterized its time course.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-016-0616-8) contains supplementary material, which is available to authorized users.

The Fate of Residual Tumor Masses That Persist After Stereotactic Body Radiotherapy for Solitary Lung Nodules: Will They Recur?

BACKGROUND

After stereotactic body radiotherapy (SBRT) to the lung, radiation pneumonitis and fibrotic changes often develop, and the tumor shadow usually becomes indistinguishable from the fibrotic shadow. Occasionally, however, a residual mass in patients with no or mild radiation pneumonitis will be observed on serial computed tomography (CT) scans. The purpose of the present study was to evaluate the fate of such residual masses and, if possible, to determine the types of tumor at increased risk of local recurrence.

PATIENTS AND METHODS

A total of 50 patients (underlying disease: primary lung cancer in 45, local recurrence in 2, and metastasis in 3) were selected because they had been followed up for > 2 years or until death and had observable CT changes and measurable tumor size for > 1 year, regardless of the influence of radiation pneumonitis. The patients' outcomes were compared according to various patient and tumor characteristics, including the presence and absence of emphysema, tumor size, and tumor shrinkage rate. The median follow-up period was 52 months.

RESULTS

Of the 50 patients, only 8 developed local recurrence. The local control rate was 81% at 3 years and 73% at 5 years. The local control rates were similar between patients with a high tumor shrinkage rate and those with a low rate. The patients with emphysema exhibited a lower local control rate.

CONCLUSION

The persistence of lung masses for > 1 year after SBRT is not necessarily indicative of an increased risk of local recurrence. A low tumor shrinkage rate also was not predictive of recurrence.