ESTRO 2021 Abstract Book

S702

ESTRO 2021

index passing rates were near identical using different reference fractions to calculate the DDM, and ranged between 57-89% (PD 20% ) and 60-99% (PD 90% ).

Conclusion The novel δ index quantifies the uncertainty of accumulated dose distributions in MR-guided radiotherapy. For MR-guided lung SBRT, the δ index passing rate increased in the high dose region indicating more reliably accumulated doses. The relatively low dependency of the δ index passing rate on different dose tolerance criteria and DDM distributions show the robustness of this metric to its parameterisation.

Poster discussions: Poster discussion 24: Radiotherapy planning and quality assurance

PD-0866 100% Peer Review in Radiation Oncology. Is it feasible? E. Martin Garcia 1 , F.J. Celada-Álvarez 1 , M.J. Pérez-Calatayud 1 , M. Rodríguez-Plá 1 , O.A. Prato-Carreño 1 , D. Farga-Albiol 1 , O. Pons-Llanas 2 , S. Roldán-Ortega 1 , E. Collado-Ballesteros 1 , Y. Bernisz-Díaz 1 , F.J. Martinez- Arcelus 1 , J. Chimeno 1 , N. Carrasco-Vela 1 , J. Gimeno 1 , F. Lliso 1 , V. Carmona 1 , J.C. Ruiz 1 , J. Pérez-Calatayud 1 , A.J. Conde-Moreno 1 , A. Tormo 1 1 La Fe Polytechnic and University Hospital, Radiation Oncology, Valencia, Spain; 2 La Fe Polytechnic and University Hospital, Radiation Oncology, Valencia, Spain Purpose or Objective Peer review has been proposed as a strategy to ensure patient safety and plan quality in radiation oncology. Our purpose is to analyze peer review process at our institution. Materials and Methods Based on our group peer review process, we quantified the rate of plan changes, time and resources needed for this process. Prospectively, data on cases presented at our daily institutional peer review conference attended by physicians, resident physicians and physicists were collected. Items such as time to present per case, type of patient (adult or pediatric), treatment intent, dose, technique, disease location and receipt of previous radiation were gathered. Cases were then analyzed to determine the rate of major change, minor change and plan rejection after presentation as well as the median time per session. Results Over a period of 4 weeks 148 cases were reviewed (Table 1). Median of attendants was 6 physicians, 3 in- trainning- physicians and 1 physicist. Median time per session was 38 (4-72) minutes. 60.1% of cases were presented in 1-4 minutes, 31.7% in 5-9 minutes and 8.1% in ≥10 minutes. 79.1% of cases were accepted without changes, 11.4% with minor changes, 6% with major changes and 3.4% were rejected with indication of new presentation. Most frequent reason of change was contouring corrections (53.8%)

Type of change

Number of cases (n=148) Time (min)

Age

Adult

144 (97.3%)

5 6

• •

• •

• •

Pediatric

4 (2.7%)

Motive •

Indication Approach

6 (4.1%)

7 5 6

• • •

• • •

140 (94.6%)

• •

Not-expected evolution

2 (1.3%)

Type of tumor •

Primary

98 (66.2%) 48 (32.4%)

4 6

• • •

• • •

Metastasis

• •

Both

2 (1.3%)

15

Treatment intent • Radical •

70 (47.3%) 19 (12.8%) 57 (38.5%)

5 4 4 6

• • • • • • • • • • • •

• • • • • • • • • • • •

Palliative

Neo/Adyuvant No treatment

• •

2 (1.3%)

Technique •

3D-CRT

65 (43.9%) 55 (37.2%) 26 (17.6%)

3 5 6

VMAT SBRT

• • •

SR

2 (1.3%)

10

Receipt of previous radiation • No • In-field • Near • Other location

116 (78.4%)

4 4 9 5

6 (4.1%) 6 (4.1%) 2 /1.3%)

Length of presentation • 1-4 min • 5-9 min • >10 min

88 (60.1%) 48 (31.7%) 12 (8.1%)

- - -

• • •

• • •

Acceptation