IBS19.02 Novel Radiotherapy Approaches in Small Cell Lung Carcinoma – Has SABR and Radionuclide Therapy Got a Role to Play?

Abstract

Thoracic radiotherapy has been shown in to increase overall survival when added to systemic therapy in patients with small cell lung carcinoma (SCLC) and M0 stage. The dose, fractionation, treatment time and timing issues have not been fully resolved. A recent study did not show the superiority of 66Gy in 33 daily fractions over 6.5 weeks over twice-daily radiotherapy to a dose of 45 Gy in 30 fractions over 3 weeks twice daily [1]. For stage I non-small cell lung carcinoma (NSCLC), stereotactic ablative body radiotherapy (SABR) has been clearly shown to be superior to conventional fractionation [2]. Given the clear benefit seen in early stage NSCLC, it is postulated that SABR may have a role to play in early stage SCLC. A recent multi-institutional cohort study has reported favourable outcomes in this setting [3]. However, randomised data of equivalence or indeed superiority are lacking. Furthermore, questions remain as the timing and role of systemic therapy and prophylactic cranial irradiation when SABR is used in this setting. In advanced SCLC, many tumors display neuroendocrine clinical and cytological features and many SCLC tumors express somatostatin receptor and this can be imaged using radiolabeled somatostatin analogs such as 68Ga-DOTATATE [4]. Given the uptake by some SCLC tumors of 68Ga-DOTATATE, higher doses of the tracer have been used in an attempt to provide radiolabelled radiotherapy treatment in metastatic disease in what has been described as peptide receptor radionuclide therapy (PRRT) [5]. This molecularly target radiotherapy is a potentially exciting therapeutic approach, but the ideal positioning of such therapy in tumors which are suitable for treatment with PRRT and the safety of PRRT with systemic therapy have yet to be determined. 1. Faivre-Finn C, Snee M, Ashcroft L, et al. Concurrent once-daily versus twice-daily chemoradiotherapy in patients with limited-stage small-cell lung cancer (CONVERT): an open-label, phase 3, randomised, superiority trial. Lancet Oncol. 2017;18(8):1116–1125. https://doi.org/10.1016/S1470-2045(1730318-2) 2. Ball D, Mai GT, Vinod S, et al. Stereotactic ablative radiotherapy versus standard radiotherapy in stage 1 non-small cell lung cancer (TROG 09.02. CHISEL): a phase 3, open-label, randomised controlled trial. The Lancet. 2019; 20: 494-503 3. Verma V, Simone CB, 2nd, Allen PK, et al. Multi-Institutional Experience of Stereotactic Ablative Radiation Therapy for Stage I Small Cell Lung Cancer. Int J Radiat Oncol Biol Phys 2017;97:362-71 4. Sollini M, Farioli D, Froio A, et al. Brief Report on the Use of Radiolabeled Somatostatin Analogs for the Diagnosis and Treatment of Metastatic Small-Cell Lung Cancer Patients. J Thor Oncol 2013;8(8):1095-1101. 5. Lapa C, Hänscheid H, Wild V, et al. Somatostatin receptor expression in small cell lung cancer as a prognostic marker and a target for peptide receptor radionuclide therapy. Oncotarget. 2016 Apr 12;7(15):20033-40. SCLC, SABR, radiotherapy