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Merle Ilona Ronden
OA 01 - The New Aspect of Radiation Therapy (ID 652)
- Event: WCLC 2017
- Type: Oral
- Track: Radiotherapy
- Presentations: 1
OA 01.03 - Patterns of Change in High-Risk Radiological Features in Patients without Local Recurrence after SABR for Early-Stage NSCLC (ID 9185)
11:00 - 12:30 | Presenting Author(s): Merle Ilona Ronden
Five-year local control rates in early-stage NSCLC following stereotactic ablative radiotherapy (SABR) are approximately 90%. However, the resulting focal fibrosis can be difficult to distinguish from tumor recurrences. We investigated the incidence, and patterns of change in previously reported high-risk radiological features (HRF’s), in patients who were known to have no local recurrence.
Patients treated using volumetric modulated arc therapy SABR were eligible if follow-up CT-scans were available for at least 2 years. Five clinicians who were unaware of clinical outcomes scored the following HRF’s on CT-scans: enlarging opacity(EO), sequential enlarging opacity(SE), enlarging opacity after 12 months(EO12), bulging margin(BM), loss of linear margins(LOM), cranio-caudal growth(CCG) and loss of air bronchogram(LOB). CT-scans were reviewed at a workstation using in-house plugin customized for ClearCanvas (Synaptive Medical, Toronto, Canada). After each review, clinicians recommended follow-up procedures based on previously published recommendations.
In 88 patients (747 CT-scans) evaluated, the HRF’s most frequently recorded by ≥3 observers on at least one follow-up CT-scan were EO (64.8%), EO12 (50.0%) and SE (13.6%). Cumulative mean incidence rates of each HRF per category are displayed (figure). Fifty-six patients developed EO in the first year, and 46 of these patients developed subsequent EO12. In 76 patients who developed EO12, 30 had no EO previously. The presence of ≥3 HRF’s have been associated with recurrences, and this was observed in 20 patients. When HRF’s were identified, clinicians indicated that they were either very certain (mean: 37.2%, range: 11.9-70.4%) or moderately certain (mean: 51.2%, range: 26.5-87.1%) about the presence of this feature. In routine care, only 6 patients underwent PET-scans because of a suspected local recurrence, and 4 underwent an attempt at biopsy. Figure 1
Although HRF’s on CT-scan develop in more than 50% of patients without local recurrence after SABR, only 23% had ≥3 HRF’s.
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