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S. Bowles
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P1.14 - Radiotherapy (ID 700)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Radiotherapy
- Presentations: 1
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P1.14-009 - Comparison of Dosimetric Parameters and Outcome in Non-Small Cell Lung Cancer Patients Having 3D Conformal or VMAT Plans (ID 7535)
09:30 - 09:30 | Author(s): S. Bowles
- Abstract
Background:
Advances in lung cancer radiotherapy now permits increased accuracy of tumour targeting through image guided radiotherapy (IGRT) and advanced forms of intensity modulated radiotherapy (IMRT) such as volumetric modulated arc radiotherapy (VMAT), which helps minimise toxicity to normal tissues. We conducted a retrospective analysis to assess the impact of these new technologies on our patients.
Method:
We compared 2 radical (chemo)radiotherapy patient cohorts treated in our institution; Group A treated from February 2013 - February 2014 and Group B from September 2015 - September 2016. We analysed radiotherapy planning techniques, dose delivered, normal tissue doses and outcomes.
Result:
In Group B, we treated double the number of patients (26) with radical radiotherapy (64Gy/32# or 55Gy/20#) compared to Group A (13). Baseline characteristics were similar; median age 65yrs (A) and 70yrs (B). Most patients had stage III disease (69%-A, 81%-B). 77% of patients in both groups had concurrent cisplatin and vinorelbine chemotherapy. All patients in Group A had conventional CT planning scans and 3D-conformal planning. In Group B, all had 4D-CT planning scans and 85% (22/26) had VMAT plans. Patients treated with 55Gy/20# increased from 23% (3/13-A) to 46% (12/26-B). The median CTV increased from 64cm[3] (range 45cm[3 ]– 99cm[3] Group A) to 142cm[3] (range 15cm[3] – 656cm[3] Group B), (p-value 0.00005). Despite the increase in CTV, the median PTV remained similar (312cm[3]- A vs 364cm[3]- B). With VMAT plans, the lung doses remained low despite the increase in CTV; lung V20 (22%-A vs 20%-B), lung V5 (49% vs 49%) and mean lung dose (15Gy vs 12Gy). We selected the 5 largest CTVs from group B (CTV range 294 cm[3] – 656 cm[3]) and compared 3D conformal plans with the respective VMAT plans. We found VMAT allowed optimal dose coverage without compromising the PTV. VMAT benefited large midline tumours most where constraints of cord, heart and brachial plexus were met without PTV compromise. All Group A and 25/26 Group B patients completed their planned treatment. Median overall survival in Group A was 20.1 months but not yet reached in Group B.
Conclusion:
Adoption of 4D-CT scanning and VMAT treatment delivery has enabled us to treat larger tumours which seems to be particularly advantageous for large midline tumours. We hypothesise that radiotherapeutic advancements can increase the number of patients treatable to a radical radiotherapy dose without PTV compromise and further work is underway to confirm this and the possible impact it might have on our workload and resources.
