ESTRO 2024 Congress report

Two studies that were presented at the ESTRO 2024 annual meeting regarding lung cancer treatment are discussed here.

Re-irradiation in non-small-cell lung cancer: overall survival longer with higher retreatment dose

Robert Rulach from the UK presented findings on the impact of retreatment dose on rates of overall survival (OS) in non-small-cell lung cancer (NSCLC) at the ESTRO 2024 conference. The study aimed to determine the optimal re-irradiation dose, to guide patient selection, and to enhance patient counselling.

A comprehensive MEDLINE search of studies published between January 1970 and October 2018 was conducted. Inclusion criteria were studies with data on OS and re-irradiation dose, along with variables such as inter-treatment interval and planning target volume (PTV) size. Studies with follow-up periods shorter than two years were adjusted for. Logistic regression was used to analyse the dataset, and this led to predicted doses for 30% and 50% two-year OS rates. Model fit was assessed using the Pearson correlation coefficient.

The analysis revealed a significant relationship between higher re-irradiation doses and improved two-year OS rates. Specifically, for a 30% two-year OS rate, a dose of 49.8Gy (95% CI: 40.3-59.4Gy) was predicted, while a 50% two-year OS rate required 76.5Gy (95% CI: 70.7-82.2Gy).

This study underscored the significance of higher retreatment doses in the improvement of survival rates in NSCLC patients who undergo re-irradiation. It may indicate the potential of using stereotactic body radiotherapy (SBRT). Interestingly, tumour size and inter-treatment intervals were not significant predictors of OS rates. These findings may inform clinical practice by aiding in dose optimisation, patient selection, and counselling strategies to improve patient outcomes. Further research is warranted to refine these approaches and to validate the findings in larger, prospective studies.

High survival rates after high-dose re-irradiation of in-field recurrent lung cancer: a prospective trial

Eugenio Cammareri presented this prospective phase II trial, in which the efficacy and safety of high-dose radiotherapy for in-field or marginal recurrences of lung cancer within the thorax had been investigated. The study was designed to evaluate the impact of high-dose re-irradiation on OS rates in patients with recurrent lung cancer that was located within 5cm of the 50Gy isodose line from prior radiotherapy.

Patients received re-irradiation at least nine months after initial treatment, at doses ≥45Gy in equivalent dosage in 2Gy fractions with α/β of 10Gy (EQD2₁₀). Treatment options were chemoradiotherapy or SBRT. Dose summation and recalculations of the EQD2 were performed specific to organs at risk (OARs). The primary targets were a 12-month median OS and minimal high-grade toxicity. The following cumulative dose constraints in EQD2 were used (time between the treatment series):

• Spinal cord: 75Gy (0.75 - five years)
• Oesophagus: 100Gy (≥ nine months)
• Trachea/mainstem bronchus: 110Gy (≥ nine months)
• Plexus brachialis: 90Gy (≥ nine months)

Between 2018 and 2022, 60 patients were treated. The median initial radiotherapy dose was 68Gy EQD2. For re-irradiation, 38 patients received conventional fractionated radiotherapy (median dose: 60Gy EQD2₁₀), and 22 patients received SBRT (median dose: 77Gy EQD2₁₀).

With a median follow-up of 26.5 months, the median OS was 30.1 months, and the median local control was 28.2 months. The median disease-free survival period was 13.6 months. No grade 4 or 5 treatment-related toxicities were observed. Acute grade 3 toxicities occurred in eight patients. Overall, 20% of patients experienced grade 3 toxicities, with pneumonitis being the most common (12%).

The study showed that high-dose re-irradiation for thoracic lung cancer recurrences was feasible, with favourable survival rates and an acceptable toxicity profile. This prospective trial suggests that re-irradiation can be a viable option for patients with recurrent lung cancer, as it offers significant survival benefits while maintaining manageable toxicity levels. Further research is necessary to optimise treatment protocols and to validate these outcomes in larger cohorts.

Jonas Willmann, MD

Radiation oncologist

University Hospital Zurich

Zurich, Switzerland