Nicole Nesvacil

Recommendations from gynaecological (GYN) GEC-ESTRO working group – ACROP: Target concept for image guided adaptive brachytherapy in primary vaginal cancer

External beam radiotherapy (EBRT) combined with brachytherapy has an essential role in the curative treatment of primary vaginal cancer. EBRT is associated with significant tumour shrinkage, making primary vaginal cancer suitable for image guided adaptive brachytherapy (IGABT). The aim of these recommendations is to introduce an adaptive target volume concept for IGABT of primary vaginal cancer. In December 2013, a task group was initiated within GYN GEC-ESTRO with the purpose to introduce an IGABT target concept for primary vaginal cancer. All participants have broad experience in IGABT and vaginal cancer brachytherapy. The target concept was elaborated as consensus agreement based on an iterative process including target delineation and dose planning comparison, retrospective analysis of clinical data and expert opinions. Gynaecological examination and MR imaging are the modalities of choice for local tumour assessment. A specific template for standardised documentation with clinical drawings for vaginal cancer was developed. The adaptive target volume concept comprises different response-related target volumes. For EBRT these are related to the primary tumour and the lymph nodes, while for IGABT these are related to the primary tumour and are consisting of the residual gross tumour volume (GTV-T This target concept for IGABT of primary vaginal cancer defines adaptive target volumes for volumetric dose prescription and should improve comparability of different radiotherapy schedules of this rare disease. A prospective evaluation of the target volume concept within a multicentre study is planned.

Diffusion weighted imaging for gross tumor volume delineation in primary radiochemotherapy and image guided adaptive brachytherapy for cervical cancer

Accurate gross tumor volume (GTV) delineation is critical for successful radiochemotherapy and image-guided adaptive brachytherapy (BT) in cervical cancer. This study investigated whether diffusion-weighted imaging (DWI) improves GTV delineation accuracy compared to T2-weighted (T2w) MRI alone, across different physician experience levels. Twenty-seven patients with locally advanced cervical carcinoma undergoing primary radiochemotherapy were analyzed. Six physicians (three experts, three residents) delineated GTVs at three time points: diagnosis (init), pre-brachytherapy (preBT), and pre-brachytherapy with applicator in situ (BT). Segmentations were performed using T2w images alone and T2w plus DWI (b=800smm DWI guidance significantly improved inter-observer agreement among experts at init (conformity index: 0.62→ 0.70, p<0.05) and BT (0.33→ 0.39, p<0.05) time points. For residents, DWI guidance enhanced agreement with expert consensus, particularly during BT, with significant improvements in Dice coefficient (median increase 9%, p<0.05) and reduced Hausdorff distance (median decrease 1.3 mm, p<0.05). Tumor volume correlation between preBT and BT time points improved with DWI guidance for both groups. Incorporating DWI into the segmentation workflow reduces inter-observer variability for both expert and resident radiation oncologists. DWI guidance particularly benefits less experienced physicians, enabling them to achieve contours closer to expert consensus standards through additional functional information.