Femke O.B. Spoelstra

High-risk CT features for detection of local recurrence after stereotactic ablative radiotherapy for lung cancer

BACKGROUND AND PURPOSE Early detection of local recurrences following stereotactic ablative radiotherapy (SABR) for lung cancer may allow for curative salvage treatment, but recurrence can be difficult to distinguish from fibrosis. We studied the clinical performance of CT imaging high-risk features (HRFs) for detecting local recurrence. MATERIALS AND METHODS Patients treated with SABR for early stage lung cancer between 2003 and 2012 who developed pathology-proven local recurrence (n=12) were matched 1:2 to patients without recurrences (n=24), based on baseline factors. Serial CT images were assessed by blinded radiation oncologists. Previously reported HRFs were (1) enlarging opacity at primary site; (2) sequential enlarging opacity; (3) enlarging opacity after 12-months; (4) bulging margin; (5) loss of linear margin and (6) air bronchogram loss. RESULTS All HRFs were significantly associated with local recurrence (p<0.01), and one new HRF was identified: cranio-caudal growth (p<0.001). The best individual predictor of local recurrence was opacity enlargement after 12-months (100% sensitivity, 83% specificity, p<0.001). The odds of recurrence increased 4-fold for each additional HRF detected. The presence of ≥3 HRFs was highly sensitive and specific for recurrence (both >90%). CONCLUSION The systematic assessment of post-SABR CT images for HRFs enables the accurate prediction of local recurrence.

Variations in Target Volume Definition for Postoperative Radiotherapy in Stage III Non–Small-Cell Lung Cancer: Analysis of an International Contouring Study

PURPOSE Postoperative radiotherapy (PORT) in patients with completely resected non-small-cell lung cancer with mediastinal involvement is controversial because of the failure of earlier trials to demonstrate a survival benefit. Improved techniques may reduce toxicity, but the treatment fields used in routine practice have not been well studied. We studied routine target volumes used by international experts and evaluated the impact of a contouring protocol developed for a new prospective study, the Lung Adjuvant Radiotherapy Trial (Lung ART). METHODS AND MATERIALS Seventeen thoracic radiation oncologists were invited to contour their routine clinical target volumes (CTV) for 2 representative patients using a validated CD-ROM-based contouring program. Subsequently, the Lung ART study protocol was provided, and both cases were contoured again. Variations in target volumes and their dosimetric impact were analyzed. RESULTS Routine CTVs were received for each case from 10 clinicians, whereas six provided both routine and protocol CTVs for each case. Routine CTVs varied up to threefold between clinicians, but use of the Lung ART protocol significantly decreased variations. Routine CTVs in a postlobectomy patient resulted in V(20) values ranging from 12.7% to 54.0%, and Lung ART protocol CTVs resulted in values of 20.6% to 29.2%. Similar results were seen for other toxicity parameters and in the postpneumectomy patient. With the exception of upper paratracheal nodes, protocol contouring improved coverage of the required nodal stations. CONCLUSION Even among experts, significant interclinician variations are observed in PORT fields. Inasmuch as contouring variations can confound the interpretation of PORT results, mandatory quality assurance procedures have been incorporated into the current Lung ART study.

Impact of Audio-Coaching on the Position of Lung Tumors

PURPOSE Respiration-induced organ motion is a major source of positional, or geometric, uncertainty in thoracic radiotherapy. Interventions to mitigate the impact of motion include audio-coached respiration-gated radiotherapy (RGRT). To assess the impact of coaching on average tumor position during gating, we analyzed four-dimensional computed tomography (4DCT) scans performed both with and without audio-coaching. METHODS AND MATERIALS Our RGRT protocol requires that an audio-coached 4DCT scan is performed when the initial free-breathing 4DCT indicates a potential benefit with gating. We retrospectively analyzed 22 such paired scans in patients with well-circumscribed tumors. Changes in lung volume and position of internal target volumes (ITV) generated in three consecutive respiratory phases at both end-inspiration and end-expiration were analyzed. RESULTS Audio-coaching increased end-inspiration lung volumes by a mean of 10.2% (range, -13% to +43%) when compared with free breathing (p = 0.001). The mean three-dimensional displacement of the center of ITV was 3.6 mm (SD, 2.5; range, 0.3-9.6mm), mainly caused by displacement in the craniocaudal direction. Displacement of ITV caused by coaching was more than 5 mm in 5 patients, all of whom were in the subgroup of 9 patients showing total tumor motion of 10 mm or more during both coached and uncoached breathing. Comparable ITV displacements were observed at end-expiration phases of the 4DCT. CONCLUSIONS Differences in ITV position exceeding 5 mm between coached and uncoached 4DCT scans were detected in up to 56% of mobile tumors. Both end-inspiration and end-expiration RGRT were susceptible to displacements. This indicates that the method of audio-coaching should remain unchanged throughout the course of treatment.

Outcomes of concurrent chemoradiotherapy in patients with stage III non-small-cell lung cancer and significant comorbidity

BACKGROUND published trials of concurrent chemoradiotherapy (CCRT) in stage III non-small-cell lung cancer (NSCLC) generally excluded patients with significant comorbidity. We evaluated outcomes in patients who were selected by using radiation planning parameters and were considered, despite comorbidity, fit enough to receive cisplatin-based chemotherapy. PATIENTS AND METHODS from 2003 to 2008, 89 patients with stage III NSCLC fit to receive cisplatin-based chemotherapy and a V(20) <42% underwent CCRT at one center outside clinical trials. Most received one cycle of cisplatin-gemcitabine, followed by two to three cycles of cisplatin-etoposide concurrent with involved-field thoracic radiotherapy between 46 and 66 Gy. RESULTS median age was 64 years; performance status (PS) of zero, one or two in 20/64/5 patients; one or more comorbidities in 41.6%; 14% were treated previously for NSCLC. Median V(20) was 26.6% (range 4%-39.4%). Grade III esophagitis and pneumonitis occurred in 28.1% and 7.9% of patients, respectively, while 4.5% died during treatment. Median overall survival was 18.2 months [95% confidence interval (CI) 13.1-23.3 months]. Independent prognostic factors for overall survival were PS (0 versus ≥ 1, P = 0.041) and planning target volume (P = 0.022). CONCLUSIONS patients with significant comorbidity who are fit to undergo cisplatin-based CCRT achieve median survivals similar to that reported in phase III trials and with relatively few late toxic effects.

Outcomes of Hypofractionated High-Dose Radiotherapy in Poor-Risk Patients with “Ultracentral” Non–Small Cell Lung Cancer

Introduction: We defined “ultracentral” lung tumors as centrally located non–small cell lung cancers with planning target volumes overlapping the trachea or main bronchi. Increased toxicity has been reported after both conventional and stereotactic radiotherapy for such lesions. We studied outcomes after 12 fractions of 5 Gy (BED10 = 90 Gy, heterogeneous dose distribution) to ultracentral tumors in patients unfit for surgery or conventional chemoradiotherapy. Methods: Clinical outcomes and dosimetric details were analyzed in 47 consecutive patients with single primary or recurrent ultracentral non–small cell lung cancer treated between 2010 and 2015. Those irradiated previously or with metastasis to sites other than the brain and adrenal glands were excluded. Treatments were delivered using volumetric modulated arc therapy. Results: The median age was 77.5 years, 49% of patients had a World Health Organization performance score of 2 or higher, and the median planning target volume was 104.5cm3 (range 17.7–508.5). At a median follow‐up of 29.3 months, median overall survival was 15.9 months, and 3‐year survival was 20.1%. No isolated local recurrences were observed. Grade 3 or higher toxicity was recorded in 38% of patients, with 21% scored as having a “possible” (n = 2) or “likely” (n = 8) treatment‐related death between 5.2 and 18.2 months after treatment. Fatal pulmonary hemorrhage was observed in 15% of patients. Conclusions: Unfit patients with ultracentral tumors who were treated using this scheme had a high local control and a median survival of 15.9 months. Despite manifestation of rates of a fatal lung bleeding comparable to those seen with conventional radiotherapy for endobronchial tumors, the overall rate of G5 toxicity is of potential concern. Additional work is needed to identify tumor and treatment factors related to hemorrhage.

Role of Adaptive Radiotherapy During Concomitant Chemoradiotherapy for Lung Cancer: Analysis of Data From a Prospective Clinical Trial

PURPOSE Respiratory-gated radiotherapy allows for the reduction of the toxicity associated with concomitant chemoradiotherapy, but the smaller fields used could increase the risk of missing the target. A prospective study was performed to evaluate the dosimetric consequences of time-trend changes in patients with lung cancer who were treated with concomitant chemoradiotherapy. METHODS AND MATERIALS A total of 24 lung cancer patients eligible for chemoradiotherapy and gated delivery underwent four-dimensional computed tomography (4D-CT) after 15 fractions. This scan was co-registered with the initial planning 4D-CT and a new planning target volume (PTV) was generated on the basis of the tumor visualized after 15 fractions. Coverage of the repeat PTV was evaluated by applying the original plan to the second scan and recalculating the dose. Plan modification was triggered by a 5% reduction in the PTV included within the 95% isodose volume or an unacceptable increase in the critical organ dose. RESULTS Of the 21 evaluable patients, 15 had an average reduction in the PTV of 8% after 30 Gy. The PTV increased in the remaining 6 patients, but the increase was >20% in only 1 patient. In the latter patient, disease progression was observed, and repeat planning was required. The plans created using the new PTV were acceptable in all the other patients. CONCLUSION The role of adaptive radiotherapy appears limited when respiratory-gated radiotherapy is used to reduce the toxicity related to concomitant chemoradiotherapy. The use of more conformal treatment techniques might provide the rationale for repeat imaging as a method to identify patients at risk of dosimetric miss.

An evaluation of two internal surrogates for determining the three-dimensional position of peripheral lung tumors.

PURPOSE Both carina and diaphragm positions have been used as surrogates during respiratory-gated radiotherapy. We studied the correlation of both surrogates with three-dimensional (3D) tumor position. METHODS AND MATERIALS A total of 59 repeat artifact-free four-dimensional (4D) computed tomography (CT) scans, acquired during uncoached breathing, were identified in 23 patients with Stage I lung cancer. Repeat scans were co-registered to the initial 4D CT scan, and tumor, carina, and ipsilateral diaphragm were manually contoured in all phases of each 4D CT data set. Correlation between positions of carina and diaphragm with 3D tumor position was studied by use of log-likelihood ratio statistics. Models to predict 3D tumor position from internal surrogates at end inspiration (EI) and end expiration (EE) were developed, and model accuracy was tested by calculating SDs of differences between predicted and actual tumor positions. RESULTS Motion of both the carina and diaphragm significantly correlated with tumor motion, but log-likelihood ratios indicated that the carina was more predictive for tumor position. When craniocaudal tumor position was predicted by use of craniocaudal carina positions, the SDs of the differences between the predicted and observed positions were 2.2 mm and 2.4 mm at EI and EE, respectively. The corresponding SDs derived with the diaphragm positions were 3.7 mm and 3.9 mm at EI and EE, respectively. Prediction errors in the other directions were comparable. Prediction accuracy was similar at EI and EE. CONCLUSIONS The carina is a better surrogate of 3D tumor position than diaphragm position. Because residual prediction errors were observed in this analysis, additional studies will be performed using audio-coached scans.

Feasibility of using anatomical surrogates for predicting the position of lung tumours

We studied the use of internal anatomical surrogates (carina and diaphragm) for the purpose of predicting the 3D position of lung tumours in 41 patients, in whom repeat 4DCT scans were available. Despite using two surrogates, significant prediction errors were observed, which varied depending on tumour position, baseline tumour motion and respiratory phase.

Optimizing SABR delivery for synchronous multiple lung tumors using volumetric-modulated arc therapy

Abstract Background: Volumetric-modulated arc therapy (VMAT) delivery for stereotactic ablative radiotherapy (SABR) of multiple lung tumors allows for faster treatments. We report on clinical outcomes and describe a general approach for treatment planning. Material and methods: Patients undergoing multi iso-center VMAT-based SABR for ≥2 lung lesions between 2009 and 2014 were identified from the VU University Medical Center and London Health Sciences Centre. Patients were eligible if the start date of the SABR treatment for the different lesions was within a time range of 30 days. SABR was delivered using separate iso-centers for lesions at a substantial distance from each other. Tumors were either treated with a single fraction of 34 Gy, or using three risk-adapted dose-fractionation schemes, namely three fractions of 18 Gy, five fractions of 11 Gy, or eight fractions of 7.5 Gy, depending on the tumor size and the location. Multivariable analysis was performed to assess factors predictive of clinical outcomes. Results: Of 84 patients (188 lesions) identified, 46% were treated for multiple metastases and 54% for multiple primary NSCLC. About 97% were treated for two or three lesions, and 56% had bilateral disease. After a median follow-up of 28 months, median overall survival (OS) for primary tumors was 27.6 months, and not reached for metastatic lesions (p = .028). Grade ≥3 toxicity was observed in 2% of patients. Multivariable analysis showed that grade 2 or higher radiation pneumonitis (n = 9) was best predicted by a total lung V35Gy of ≥6.5% (in 2Gy/fraction equivalent) (p = .007). Conclusion: Severe toxicity was uncommon following SABR using VMAT for up to three lung tumors. Further investigations of planning parameters are needed in patients presenting with more lesions.

Diagnostic challenges in survivors of early stage lung cancer

OBJECTIVES Survivors of early stage non-small cell lung cancer (NSCLC) are at risk of developing disease recurrence, as well as new lung tumors. Distinguishing metastatic disease from a second primary lung tumor (SPLC) is important, but can pose diagnostic challenges in what are often frail patients. MATERIALS AND METHODS We highlight three long-term survivors of early stage NSCLC who developed multiple new lung lesions on long-term follow-up after undergoing an initial stereotactic ablative radiotherapy procedure. RESULTS New radiological lesions were always evaluated by a multidisciplinary tumor board in order to determine the optimal diagnostic procedure and treatment. When identical histological types were identified, array comparative genomic hybridization (CGH) was used to differentiate between metastases and a second primary tumor. When a tissue diagnosis is not possible, a validated calculator of tumor probability can be used to calculate the likelihood of malignancy. All patients underwent multiple episodes of curative radiotherapy. CONCLUSION These long-term survivors of early stage NSCLC highlight the importance of radiological follow-up, and describe approaches for guiding diagnostic and therapeutic management.