Investigation of the added value of CT-based radiomics in predicting the development of brain metastases in patients with radically treated stage III NSCLC

Introduction:

Despite radical intent therapy for patients with stage III non-small-cell lung cancer (NSCLC), cumulative incidence of brain metastases (BM) reaches 30%. Current risk stratification methods fail to accurately identify these patients. As radiomics features have been shown to have predictive value, this study aims to develop a model combining clinical risk factors with radiomics features for BM development in patients with radically treated stage III NSCLC.

Methods:

Retrospective analysis of two prospective multicentre studies. Inclusion criteria: adequately staged [¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (18-FDG-PET-CT), contrast-enhanced chest CT, contrast-enhanced brain magnetic resonance imaging/CT] and radically treated stage III NSCLC, exclusion criteria: second primary within 2 years of NSCLC diagnosis and prior prophylactic cranial irradiation. Primary endpoint was BM development any time during follow-up (FU). CT-based radiomics features (N = 530) were extracted from the primary lung tumour on 18-FDG-PET-CT images, and a list of clinical features (N = 8) was collected. Univariate feature selection based on the area under the curve (AUC) of the receiver operating characteristic was performed to identify relevant features. Generalized linear models were trained using the selected features, and multivariate predictive performance was assessed through the AUC.

Results:

In total, 219 patients were eligible for analysis. Median FU was 59.4 months for the training cohort and 67.3 months for the validation cohort; 21 (15%) and 17 (22%) patients developed BM in the training and validation cohort, respectively. Two relevant clinical features (age and adenocarcinoma histology) and four relevant radiomics features were identified as predictive. The clinical model yielded the highest AUC value of 0.71 (95% CI: 0.58–0.84), better than radiomics or a combination of clinical parameters and radiomics (both an AUC of 0.62, 95% CIs of 0.47–076 and 0.48–0.76, respectively).

Conclusion:

CT-based radiomics features of primary NSCLC in the current setup could not improve on a model based on clinical predictors (age and adenocarcinoma histology) of BM development in radically treated stage III NSCLC patients.

Optimal delineation of the clinical target volume for thymomas in the post-resection setting: A multi-center study

BACKGROUND

The definition of the clinical target volume (CTV) for post-operative radiotherapy (PORT) for thymoma is largely unexplored. The aim of this study was to analyze the difference in CTV delineation between radiation oncologists (RTO) and surgeons.

METHODS

This retrospective multi-center study enrolled 31 patients who underwent PORT for a thymoma from five hospitals. Three CTVs were delineated per patient: one CTV by the RTO, one CTV by the surgeon (blinded to the results of the RTO) and a joint CTV after collaboration. Volumes (cm³), Hausdorff distances (HD) and Dice similarity coefficients (DSC) were analyzed.

RESULTS

RTO delineated significantly bigger CTVs than surgeons (mean: 93.9 ± 63.1, versus 57.9 ± 61.3 cm³, p = 0.003). Agreement was poor between RO and surgeons, with a low mean DSC (0.34 ± 0.21) and high mean HD of 4.5 (±2.2) cm. Collaborative delineation resulted in significantly smaller volumes compared to RTO (mean 57.1 ± 58.6 cm³, p < 0.001). A mean volume of 18.9 (±38.1) cm³ was included in joint contours, but missed by RTO. Conversely, a mean volume of 55.7 (±39.9) cm³ was included in RTO's delineations, but not in the joint delineations.

CONCLUSIONS

To the best of our knowledge, this is the first study investigating CTV definition in thymoma. We demonstrated a significant variability between RTO and surgeons. Joint delineation prompted revisions in smaller CTV as well as favoring the surgeons' judgement, suggesting that surgeons provided relevant insight into other risk areas than RTO. We recommend a multidisciplinary approach to PORT for thymomas in clinical practice.

Development and external validation of a nomogram to predict overall survival following stereotactic body radiotherapy for early-stage lung cancer

BACKGROUND

Prognostication tools for early-stage non-small cell lung cancer (NSCLC) patients treated with stereotactic body radiotherapy (SBRT) are currently lacking. The purpose of this study was to develop and externally validate a nomogram to predict overall survival in individual patients with peripheral early-stage disease.

METHODS

A total of 587 NSCLC patients treated with biologically effective dose > 100 Gy₁₀ were eligible. A Cox proportional hazards model was used to build a nomogram to predict 6-month, 1-year, 3-year and 5-year overall survival. Internal validation was performed using bootstrap sampling. External validation was performed in a separate cohort of 124 NSCLC patients with central tumors treated with SBRT. Discriminatory ability was measured by the concordance index (C-index) while predictive accuracy was assessed with calibration slope and plots.

RESULTS

The resulting nomogram was based on six prognostic factors: age, sex, Karnofsky Performance Status, operability, Charlson Comorbidity Index, and tumor diameter. The slope of the calibration curve for nomogram-predicted versus Kaplan-Meier-estimated overall survival was 0.77. The C-index of the nomogram (corrected for optimism) was moderate at 0.64. In the external validation cohort, the model yielded a C-index of 0.62.

CONCLUSIONS

We established and validated a nomogram which can provide individual survival predictions for patients with early stage lung cancer treated with SBRT. The nomogram may assist patients and clinicians with treatment decision-making.

Prophylactic Cranial Irradiation Versus Observation in Radically Treated Stage III Non-Small-Cell Lung Cancer: A Randomized Phase III NVALT-11/DLCRG-02 Study

Purpose The purpose of the current study was to investigate whether prophylactic cranial irradiation (PCI) reduces the incidence of symptomatic brain metastases in patients with stage III non-small-cell lung cancer (NSCLC) treated with curative intention. Patients and Methods Patients with stage III NSCLC-staged with a contrast-enhanced brain computed tomography or magnetic resonance imaging-were randomly assigned to either observation or PCI after concurrent/sequential chemoradiotherapy with or without surgery. The primary end point-development of symptomatic brain metastases at 24 months-was defined as one or a combination of key symptoms that suggest brain metastases-signs of increased intracranial pressure, headache, nausea and vomiting, cognitive or affective disturbances, seizures, and focal neurologic symptoms-and magnetic resonance imaging or computed tomography demonstrating the existence of brain metastasis. Adverse effects, survival, quality of life, quality-adjusted survival, and health care costs were secondary end points. Results Between 2009 and 2015, 175 patients were randomly assigned: 87 received PCI and 88 underwent observation only. Median follow-up was 48.5 months (95% CI, 39 to 54 months). Six (7.0%) of 86 patients in the PCI group and 24 (27.2%) of 88 patients in the control group had symptomatic brain metastases ( P = .001). PCI significantly increased the time to develop symptomatic brain metastases (hazard ratio, 0.23; [95% CI, 0.09 to 0.56]; P = .0012). Median time to develop brain metastases was not reached in either arm. Overall survival was not significantly different between both arms. Grade 1 and 2 memory impairment (26 of 86 v seven of 88 patients) and cognitive disturbance (16 of 86 v three of 88 patients) were significantly increased in the PCI arm. Quality of life was only decreased 3 months post-PCI and was similar to the observation arm thereafter. Conclusion PCI significantly decreased the proportion of patients who developed symptomatic brain metastases with an increase of low-grade toxicity.

Which patients with ES-SCLC are most likely to benefit from more aggressive radiotherapy: A secondary analysis of the Phase III CREST trial

INTRODUCTION

In ES-SCLC patients with residual intrathoracic disease after first-line chemotherapy, the addition of thoracic radiotherapy reduces the risk of intrathoracic recurrence, and improves 2-year survival. To identify patient subgroups for future trials investigating higher dose (extra)thoracic radiotherapy, we investigated the prognostic importance of number and sites of metastases in patients included in the CREST trial.

MATERIALS/ METHODS

Additional data on sites and numbers of metastases were collected from individual records of 260 patients from the top 9 recruiting centers in the randomized CREST trial (53% of 495 study patients), which compared thoracic radiotherapy (TRT) to no TRT in ES-SCLC patients after any response to chemotherapy. All patients received prophylactic cranial irradiation.

RESULTS

The clinical characteristics and outcomes of the 260 patients analyzed here did not differ significantly from that of the other 235 patients included in the CREST trial, except that fewer patients had a WHO=0 performance status (24% vs 45%), and a higher proportion had WHO=2 (15% vs 5%; p<0.0001). No distant metastases were recorded in 5%, 39% had metastases confined to one organ, 34% to two, and 22% to three or more organ sites. Metastases were present in the liver (47%), bone (40%), lung (28%), extrathoracic (non-supraclavicular) lymph nodes (19%), supraclavicular nodes (18%), adrenals (17%) and other sites (12%). The OS (p=0.02) and PFS (p=0.04) were significantly better in patients with 2 or fewer metastases, with OS significantly worse if liver (p=0.03) and/or bone metastases (p=0.04) were present.

DISCUSSION

This analysis of patients recruited from the top 9 accruing centers in the CREST trial suggests that future studies evaluating more intensive thoracic and extra-thoracic radiotherapy in ES-SCLC should focus on patients with fewer than 3 distant metastases.

Stereotactic radiotherapy with real-time tumor tracking for non-small cell lung cancer: clinical outcome

PURPOSE

To report the clinical outcome of treatment using real-time tumor tracking for 70 patients with inoperable stage I non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Seventy inoperable patients with peripherally located early-stage NSCLC were treated with 45 or 60 Gy in three fractions using CyberKnife. Pathology was available in 51% of patients. Thirty-nine patients had a T1-tumor and 31 had a T2-tumor. Markers were placed using the vascular, percutaneous intra-, or extra-pulmonary approach, depending on the risk of pneumothorax.

RESULTS

The actuarial 2-year local control rate for patients treated with 60 Gy was 96%, compared to 78% for patients treated with a total dose of 45 Gy (p=0.197). All local recurrences (n=4) occurred in patients with T2-tumors. Overall survival for the whole group at two years was 62% and the cause specific survival was 85%. The median follow-up was 15 months. Grade 3 toxicity occurred in two patients (3%) after marker placement. Treatment-related late grade 3 toxicity occurred in 7 patients (10%). No grade > or = 4 toxicity occurred.

CONCLUSION

Excellent local control of 96% at 1- and 2-years was achieved using 60 Gy in three fractions for NSCLC patients treated with the real-time tumor tracking. Toxicity was low.

Four-dimensional Stereotactic Radiotherapy for Early Stage Non-Small Cell Lung Cancer: A Comparative Planning Study

In this study we sought to assess the potential of the respiratory tumor tracking system of the CyberKnife to administer 3 fractions of 15 Gy in the treatment of early stage non-small cell lung cancer (NSCLC). The CyberKnife plans were compared to those developed for 3-D conformal radiotherapy (3-D CRT) administering 20 fractions of 3 Gy based on a slow CT. Ten patients with stage I NSCLC, who were previously treated with 3-D CRT, were re-planned with the CyberKnife treatment planning system. In the 3-D CRT plan, the planning target volume (PTV) included the gross tumor volume (GTV)slow and a 15-mm margin, whereas in the CyberKnife plan the margin was 8 mm. The physical doses from both treatment plans were converted to normalized total doses (NTD) using the linear quadratic model with an α/βtumor of 10 Gy and α/βorgansatrisk(OAR) of 3 Gy. The average minimal and mean doses administered to the PTV with the CyberKnife and 3-D CRT were 93 and 115.8 Gy and 61 and 66 Gy, respectively (p<0.0001). The mean V20 of the CyberKnife and 3-D CRT plans were 8.2% and 6.8%, respectively (p=0.124). Both plans complied with the OAR constraints. In conclusion, 4-dimensional stereotactic radiotherapy can increase the minimal and mean biological dose with 51% and 75%, in comparison with 3-D CRT without significantly increasing the V20, respectively.

Lung tumor tracking during stereotactic radiotherapy treatment with the CyberKnife: Marker placement and early results

Lung tumor tracking during stereotactic radiotherapy with the CyberKnife requires the insertion of markers in or close to the tumor. To reduce the risk of pneumothorax, three methods of marker placement were used: 1) intravascular coil placement, 2) percutaneous intrathoracal, and 3) percutaneous extrathoracal placement. We investigated the toxicity of marker placement and the tumor response of the lung tumor tracking treatment. Markers were placed in 20 patients with 22 tumors: 13 patients received a curative treatment, seven a palliative. The median Charlson Comorbidity Score was 4 (range: 1-8). Platinum fiducials and intravascular embolisation coils were used as markers. In total, 78 markers were placed: 34 intrathoracal, 23 intravascular and 21 extrathoracal. The PTV equaled the GTV + 5 mm. A median dose of 45 Gy (range: 30-60 Gy, in 3 fractions) was prescribed to the 70-85% isodose. The response was evaluated with a CTscan performed 6-8 weeks after the last treatment and routinely thereafter. The median follow-up was 4 months (range: 2-11). No severe toxicity due to the marker placement was seen. Pneumothorax was not seen. The local control was 100%. Four tumors in four patients showed a complete response, 15 tumors in 14 patients a partial response, and three tumors in two patients with metastatic disease had stable disease. No severe toxicity of marker placement was seen due to the appropriate choice of one of the three methods. CyberKnife tumor tracking with markers is feasible and resulted in excellent tumor response. Longer follow-up is needed to validate the local control.