Adaptive Radiotherapy in Patients With Gynecological Tumors

Online-adaptive radiotherapy (ART) makes it possible to adapt the dose distribution to the anatomical changes online immediately before each radiation fraction. Adaptive radiotherapy is a further development of image-guided radiotherapy (IGRT), which is now standard in radiotherapy. Here, a cone-beam CT (CBCT) is also performed at the beginning of each fraction, which is used to position the patients in relation to the radiation field arrangement of the initial radiation plan approved for the series. In contrast to ART, with IGRT the radiation plan cannot be adapted to deformations in the body from radiation fraction to radiation fraction, e.g. due to different rectum and bladder fillings.

In ART mode, the online adaptive treatment plan for the current treatment is then selected and approved by the specialist online onboard in all cases in which the current target volume for the tumor expansion is not sufficiently covered by the initial treatment plan pre-planned for the series with its planned tolerances, or surrounding normal tissue is exposed too much. If the ART plan does not show any clear dosimetric advantages over the reference plan, especially if the initial plan covers the target volume of the day well, there are no dose increases and the normal tissues are spared as intended, the initial radiation plan from the planning CT can also be used as in IGRT. The aim of this study is to treat at least 15 patients with locally advanced gynecological carcinoma (mainly cervical carcinoma, endometrial carcinoma, vaginal carcinoma), who are to receive definitive radiotherapy at the Department for Radiotherapy at the University Hospital Essen, in ART mode on the Ethos therapy device over an initial 10 radiation fractions. The dose distribution is always compared with the adaptive and the initial plan for the radiation series on the anatomy of the day by the specialist and medical physics expert. The aim of this study is to prospectively investigate what percentage of patients benefit from ART when using standard PTV margins and how to recognize the corresponding patients early in the series. Secondarily, it will be investigated in what proportion of patients the risk organ burden and the safety margins around the clinical target volume can be reduced with ART compared to IGRT and how large this reduction can be.

The EORTC and CTC AE toxicitiy scales and further assessment scales will be evaluated in order to quantify objective and subjective side effects.