ESTRO 2024 - Abstract Book

S1800

Clinical - Lung

ESTRO 2024

1 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom. 2 Christie NHS Foundation Trust, Department of Clinical Oncology, Manchester, United Kingdom. 3 The Hashemite University, Department of Anatomy, Physiology and Biochemistry, Zarqa, Jordan

Purpose/Objective:

The standard treatment for extensive-stage small-cell lung cancer (SCLC) is chemo-immunotherapy as per the IMpower133 (1) and CASPIAN (2) trials. We compared the outcomes of extensive-stage SCLC patients treated with chemotherapy and chemoimmunotherapy, investigated the effects of these treatments on subsequent brain metastasis incidence and quantified the impact of prophylactic cranial irradiation (PCI) and thoracic radiotherapy in these patients.

Material/Methods:

Patients with extensive-stage SCLC treated at The Christie NHS Foundation Trust (Manchester, UK) between 01/07/2020 and 01/05/2022 were retrospectively reviewed. This project was approved by the Quality Improvement & Clinical Audit Committee (reference number: 3583). We included fit patients (Eastern Cooperative Oncology Group Performance status (ECOG PS) ≤ 2) with newly diagnosed extensive -stage SCLC who received at least 2 cycles of chemotherapy or chemoimmunotherapy with complete records to the date of death or the most recent outpatient follow-up. The following variables were extracted from the structured electronic patient record: age, gender, diagnosis date, ECOG PS, clinical frailty score, TNM stage, sites of metastases at diagnosis/ follow-up, treatment details, date of death/ last follow-up and patient-reported outcomes (PRO). The primary endpoint was overall survival (OS). Secondary endpoints included the development of brain metastasis after starting treatment and PRO, a measurement of the patient’s health state on a scale of 0– 100, with 0 classed as the worst possible health and 100 as the best possible health. We used Cox regression to analyze factors associated with survival (clinical frailty score, ECOG PS, age, gender, metastasis sub-stage and additional treatments (PCI alone, thoracic radiotherapy alone or both PCI and thoracic radiotherapy). Analyses were performed using IBM SPSS and GraphPad Prism. Ninety-six patients with extensive-stage SCLC underwent either chemotherapy (N=52; median age: 72 years (range, 47-88 years)) or chemoimmunotherapy (N=44; median age: 64.5 years (range, 45-78 years)). Patients treated with chemoimmunotherapy were younger, had better ECOG PS and clinical frailty scores, were more likely to receive combination chemotherapy and less likely to harbour brain or liver metastases at the time of diagnosis (all p<0.01). More patients in the chemoimmunotherapy group received second- or third-line treatments compared to the chemotherapy group, but this difference was not statistically significant; table 1. Across both groups, 78 patients (81%) received 4 cycles of chemotherapy (followed by maintenance atezolizumab in the chemoimmunotherapy group). Patients in the chemoimmunotherapy group had improved OS (HR 0.62, 95% CI 0.40-0.97; p=0.0318) with a median OS of 10.8 months vs. 8.3 months in the chemotherapy group (Figure 1A). The 12-month OS rates for the chemotherapy and the chemoimmunotherapy groups were 28.8% and 45.1%, respectively. Cox regression showed that reduced clinical frailty scores and treatment with PCI alone (but not with thoracic radiotherapy alone or both PCI and thoracic radiotherapy) were associated with improved survival in both groups (p<0.05); Figure 1B. There was no difference in the incidence of new brain metastasis diagnosed after starting treatment between the chemotherapy (N=15, 28%) and chemoimmunotherapy (N=15, 34%) groups, respectively (p=0.581). At least one PRO measure was completed by N=27 (51.9%) in the chemotherapy group and by N=37 (84.1%) in the chemo immunotherapy group. The highest reported score (but not the lowest score) was significantly higher in the chemoimmunotherapy group compared to the chemotherapy group (p<0.001). Results: