Patterns of relapse following thoracic radiotherapy in patients with limited-stage small cell lung cancer as part of the CONVERT trial
AffiliationClinical Oncology Department, The Christie NHS Foundation Trust, Manchester,
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AbstractBackground: Small-cell lung cancer (SCLC) is an aggressive disease associated with poor prognosis despite curative-intent treatment. Recurrences within high-dose radiotherapy field can indicate radioresistance. We aim to identify areas of relapse and whether they occurred within high-dose areas. Methods: Patients with limited-stage SCLC treated at The Christie as part of the phase III CONVERT trial from 2008 were included in the analysis. Patients received either 45 Gy in 30 twice-daily (BD) fractions or 66 Gy in 33 daily (OD) fractions with concurrent chemotherapy. Elective nodal irradiation was not given. All follow-up CT scans were retrospectively reviewed for evidence of relapse. Patients were classified as thoracic-only relapses (i.e. within radiotherapy field), distant metastases or relapse in both areas. For thoracic relapses all lesions that progressed were contoured on the relapse CT by a radiation oncologist. We estimated the planned mean dose over each relapse lesions by mapping the planning dose from the planning CT onto the relapse CT using non-rigid registrations (Elastix). As extreme anatomical changes existed for some patients, registration was repeated using NiftyReg. Lesions that resulted in disagreement of 2 Gy were visually checked and manually tuned. Results: 49 of 90 patients had evidence of relapse. 20 patients had thoracic-only relapses, 19 had only distant metastases and 10 patients relapsed in both areas. Of the 30 thoracic relapses 25 sets of scans were available for mapping analysis. We identified 67 lesions in total, a mean of 2.7 lesions per patient (range 1–9). Mean size of lesions was 18.8 cm3 (range 0.01 cm3–549 cm3). 16 of 25 patients relapsed within 95% isodose region (11/25 received BD radiotherapy) and 6 also had distant metastases. The remaining 9 of 25 thoracic relapses progressed within 20% to 95% isodoses (6/9 received OD radiotherapy). Conclusions: 3 out of 4 patients who relapsed had thoracic progression. The mapping analysis showed that the majority of thoracic relapses (64.0%) occurred within the high-dose radiotherapy region. This suggest that there is scope for further local treatment intensification
CitationPortner R, Osorio EV, Iype R, Faivre-Finn C. 49MO Patterns of relapse following thoracic radiotherapy in patients with limited-stage small cell lung cancer as part of the CONVERT trial. Journal of Thoracic Oncology. 2021 Apr;16(4):S722.
JournalJournal of Thoracic Oncology
TypeMeetings and Proceedings