ESTRO 2022

Session Item

Brachytherapy: Gynaecology

Session Code: 7014

Session Type: Poster (digital)

Track: Brachytherapy

Adjuvant HDR brachytherapy for endometrial cancer: to replan or not to replan?

Stefano Durante, Italy

Presentation Number: PO-1794

Abstract

Abstract Title:

Adjuvant HDR brachytherapy for endometrial cancer: to replan or not to replan?

Authors:

Stefano Durante¹, Andrea Vavassori¹, Francesca Colombo^1,2, Jessica Franzetti^1,2, Stefania Comi³, Raffaella Cambria^4,4, Roberto Orecchia⁵, Barbara Alicja Jereczeck Fossa^6,2

¹European Institute of Oncology, Division of Radiation Oncology, Milan, Italy; ²University of Milan, Department of Oncology and Hemato-Oncology, Milan, Italy; ³European Institute of Oncology , Unit of Medical Physics, Milan, Italy; ⁴European Institute of Oncology, Unit of Medical Physics, Milan, Italy; ⁵European Institute of Oncology, Scientific Direction, Milan, Italy; ⁶European Institute of Oncology , Division of Radiation Oncology, Milan, Italy

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Purpose or Objective

To retrospectively compare the differences between plans obtained prior to each fraction for adjuvant high-dose-rate (HDR) vaginal brachytherapy (BT) with dedicated Multichannel (MCH) cylinders in endometrial cancer (EC) patients and to evaluate the dosimetric advantages of fractional re-planning.

Material and Methods

For our study, two distinct planning modalities were used retrospectively to compare dosimetric differences to vaginal cuff and to organ at risk (OAR):

1) Fractional re-planning (RP): a CT scan was obtained and a 3D-optimized plan was generated for each fraction;

2) First fraction planning only (FP): the plan values of the first fraction were applied to the imaging data set and structures to subsequent fractions without repeat CT planning.

Dose-volume-histogram (DVH) analysis was mainly focused on the dose received by the 90% of the clinical target volume (CTV-D90) and the dose received by 2cm³ of bladder (BD2cc), rectum (RD2cc) and bowel (BoD2cc).

Dosimetric differences from the first and the second re-planned fraction (RP1 vs RP2) and from the RP1 and the third re-planned fraction (RP1 vs RP3) were examined. In additions, dosimetric indices of FP plans (FP2 and FP3) were compared to the RP1, and the dosimetric variations compared with RP2 and RP3.

Results

Between September 2016 and January 2019, 24 consecutive patients with early stage EC underwent adjuvant HDR-BT to the vaginal cuff with the MCH cylinder.

A total number of 72 plans were retrospectively reviewed.

The median percentage dose difference between RP1 and RP2 and between RP1 and RP3 were 0,81% and 0,4% for CTV-D90, 4.19% and 1.63% for BD2cc, 0.06% and 1.87% for RD2cc, 3.48% and 4,60% for BoD2cc, respectively.

The median percentage dose difference in terms of CTV-D90, BD2cc, RD2cc and BoD2cc were 4.95%, 5.73%, 0.65% and 2.16% between RP1 and FP2 and 3.95%, 4.06%, 0.41% and 9.11%between RP1 and FP3, respectively.

The absolute differences in individual doses for the investigated DVH parameters for a given fraction between the two methods were small for nearly all the 72 plans. Qualitatively, the isodose distributions and DVHs were similar.

Conclusion

A small benefit was found for the customized fractional re-planning used to compensate for inter-fraction difference. The interfractional RP could ensure a higher target coverage and a better bladder and bowel sparing.