Late Toxicity and Long-Term Local Control in Patients With Ultra-Central Lung Tumours Treated by Intensity-Modulated Radiotherapy-Based Stereotactic Ablative Body Radiotherapy With Homogenous Dose Prescription.

AIMS: To report late toxicity and long-term outcomes of intensity-modulated radiotherapy (IMRT)-based stereotactic ablative body radiotherapy (SABR) in patients with ultra-central lung tumours. MATERIALS AND METHODS: This is a single-institution retrospective analysis of patients treated with SABR for ultra-central tumours between May 2008 and April 2016. Ultra-central location was defined as tumour (GTV) abutting or involving trachea, main or lobar bronchi. Respiratory motion management and static-field dynamic-IMRT were used, with dose prescribed homogeneously (maximum <120%). Descriptive analysis, Kaplan-Meier method, log-rank test and Cox regression were used to assess outcomes. RESULTS: Sixty-five per cent of patients had inoperable primary non-small cell lung cancer and 35% had lung oligometastases. The median age was 72 (range 34-85) years. The median gross tumour volume and planning target volume (PTV) were 19.6 (range 1.7-203.3) cm3 and 57.4 (range 7.7-426.6) cm3, respectively. The most commonly used dose fractionation was 60 Gy in eight fractions (n = 51, 87.8%). Median BED10 for D98%PTV and D2%PTV were 102.6 Gy and 115.06 Gy, respectively. With a median follow-up of 26.5 (range 3.2-100.5) months, fatal haemoptysis occurred in five patients (8.7%), of which two were directly attributable to SABR. A statistically significant difference was identified between median BED3 for 4 cm3 of airway, for patients who developed haemoptysis versus those who did not (147.4 versus 47.2 Gy, P = 0.005). At the last known follow-up, 50 patients (87.7%) were without local recurrence. Freedom from local progression at 2 and 4 years was 92 and 79.8%, respectively. The median overall survival was 34.3 (95% confidence interval 6.1-61.6) months. Overall survival at 2 and 4 years was 55.1 and 41.2%, respectively. CONCLUSION: In patients with high-risk ultra-central lung tumours, IMRT-based SABR with homogenous dose prescription achieves high local control, similar to that reported for peripheral tumours. Although fatal haemoptysis occurred in 8.7% of patients, a direct causality with SABR was evident in only 3%. Larger studies are warranted to ascertain factors associated with outcomes, especially toxicity, and identify patients who would probably benefit from this treatment.

Stereotactic Ablative Radiation Therapy for Large (≥5 cm) Non-small Cell Lung Carcinoma.

AIMS: Stereotactic ablative radiation therapy (SABR) is a standard of care for medically inoperable early stage non-small cell lung carcinoma. Tumours greater than 5 cm have been excluded from randomised trials using SABR and, hence, it is not used as a standard for larger lung tumours. However, improvements in radiation therapy techniques and the success of SABR in treatment of early stage disease may allow safe delivery of ablative doses to larger tumours. We analysed our experience with tumours ≥5 cm to determine the efficacy and toxicity profile of SABR in this setting. MATERIALS AND METHODS: We evaluated survival, control rates, patterns of failure and toxicity in patients with a tumour diameter larger than 5 cm that had no nodal or distant metastases treated with SABR technology. Patients had been treated in two centres since 2009 and were retrospectively analysed. All patients had positron emission tomography staging, were discussed at a tumour board and were documented to have no nodal or distant metastatic disease. Treatment outcomes were analysed using Kaplan-Meier estimates and compared using the Log-rank test. Cox regression was used to investigate the association between the survival outcomes and predictor variables. RESULTS: In total, 86 patients were identified. Six patients had no follow-up imaging. Therefore, 80 patients were available for analysis. All patients were reclassified according to the updated AJCC eighth edition. The median follow-up was 19.6 months. No patients received neoadjuvant or concurrent systemic therapy. One patient received adjuvant systemic therapy. The median age at treatment was 77 years (range 58-91). Eighty-four per cent were stage T3N0M0 and 16% were staged T4N0M0. The median tumour diameter was 5.8 cm (range 5.0-9.3 cm). The median gross tumour volume, measured on a single phase of the respiratory cycle, was 45.7 cm3 (range 12.1-203.3 cm3). The median overall survival was 20.9 months (95% confidence interval 12.6-29.1 months). One-, 2- and 3-year overall survival was 71%, 48% and 32%, respectively. The median local failure-free survival was 19.5 months (95% confidence interval 14.4-24.6). The median disease-free survival was 15.1 months (95% confidence interval 9.9-20.4 months). Local control at 1, 2 and 3 years was 85% (95% confidence interval 76-94%), 71% (95% confidence interval 58-84%) and 57% (95% confidence interval 40-74%), respectively. Forty-four patients (55%) had any treatment failure (local, mediastinal, intrapulmonary or distant metastases). Out-of-field intrapulmonary disease progression was the most common mode of failure, occurring in 21 patients (26%). Local failure occurred in 19 patients (24%) - alone or in combination with other progression. Distant metastases occurred in 20 patients (25%). Neither histological subtype, tumour size nor gross tumour volume had a statistically significant effect on local failure-free survival. Two patients experienced grade 3 late dyspnoea. There were no other reported grade 3 or higher acute or late toxicities. CONCLUSION: SABR for larger lung tumours ≥5 cm results in high local control and acceptable survival in patients with medically inoperable large non-small cell lung carcinoma treated with radiation alone. Such patients should be considered for SABR owing to fewer treatment fractions and acceptable toxicity. Local control analysis reveals a sustained pattern of local failure emphasising the need for long-term follow-up. Improvements in technical strategies are required to further improve local control.