A novel and objective plan evaluation tool for dose escalation in NSCLC within the ADCSCaN trial
Simoes, A. R. L. Mir, R. Lawless, C. Shaw, A. Peedell, C. Pope, T. Lester, J. Landau, D. Matthew, H.
Simoes, A. R. L.
Mir, R.
Lawless, C.
Shaw, A.
Peedell, C.
Pope, T.
Lester, J.
Landau, D.
Matthew, H.
Citations
Altmetric:
Abstract
Purpose or Objective
ADSCaN (Accelerated, Dose-escalated, Sequential Chemo-
Radiotherapy in Non-small cell lung Cancer (NSCLC);
ISRCTN47674500) is a randomised phase II clinical trial
comparing four experimental radiotherapy (RT) regimes
for NSCLC (CHART-ED, IDEAL, I-START and ISOTOXIC IMRT)
to a standard RT regime of 55Gy in 20 fractions. RT
planning for IDEAL, I-START and Isotoxic IMRT includes
novel dose escalation and intensification schemes which
require a change in planning technique. The aim of this
study was to identify and to validate novel metrics to
assess whether an RT plan is optimal.
Material and Methods
A NSCLC benchmark case was sent to ADSCaN
centres. Centres submitted a plan for at least one of the
experimental arms. GTV, CTV and OARs were precontoured.
The PTV was derived at each centre as per the
protocol; 5mm isotropic margin was used by centres
performing per fraction cone-beam CT, and 7mm axially
and 9mm cranio-caudally for those who did not. Table 1
shows the ADSCaN research arm requirements for RT
planning. PTV conformity (V95%isodose /PTV Vtotal) and OAR
compromise (OAR V95%isodose/OAR&PTV VTotal overlap) indices
were calculated and validated for each dose escalation
arm from the 22 submitted plans. This analysis focuses on
the 3 research arms that employ isotoxic dose escalation
methods; therefore CHART-ED arm was not included in this
analysis.
Results
The OAR limiting dose escalation for IDEAL and I-START
plans was the oesophagus, whereas the mediastinal
envelope limits prescription dose for ISOTOXIC IMRT. Table
2 shows the dose achieved to PTV, oesophagus,
mediastinal envelope, PTV conformity and OAR
compromise indices. The remaining OAR doses although
assessed, are not reported in this table as they were easily
achieved for this case. All plans were assessed as per the
requirements described (table 2) and were considered suboptimal
if not achieving the criteria for at least two of the
following: PTV coverage, OAR dose-volume constraints,
PTV conformity and OAR compromise indices. All plans
were also visually assessed in all slices. Conclusion
45.5% of the submitted plans were sub-optimal as plans
had compromised PTV coverage in favour of meeting OAR
dose constraints, overdosed OARs or did not escalated the
prescription dose as high is achievable. We attribute the
high number of sub-optimal plans to the learning curve in
the new individualised planning techniques included in
ADSCaN.
Assessing plans that use novel dose escalation can be
challenging, particularly in determining whether a plan is
optimal. This is a novel and objective evaluation that can
be applicable to any dose escalated lung RT plan.
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Lopes Simões AR, Mir R, Lawless C, Shaw A, Peedell C, Pope T, et al. PO-1879: A novel and objective plan evaluation tool for dose escalation in NSCLC within the ADCSCaN trial. Radiotherapy and Oncology . 2020 Nov;152:S1047–8.