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Patterns of relapse following thoracic radiotherapy in patients with limited-stage small cell lung cancer as part of the CONVERT trial
Portner, R Vasquez Osorio, Eliana Iype, Rohan
Portner, R
Vasquez Osorio, Eliana
Iype, Rohan
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Abstract
Background: 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
Description
Date
2021
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Portner 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.