James William Anderson PhD, Presenter: Nothing to Disclose

Krystyna Danuta Kiel MD, Abstract Co-Author: Nothing to Disclose

Yixiang Liao, Abstract Co-Author: Nothing to Disclose

Rui Yao PhD, Abstract Co-Author: Nothing to Disclose

Damian Bernard PhD, Abstract Co-Author: Nothing to Disclose

Julius Turian, Abstract Co-Author: Nothing to Disclose

James C.H. Chu PhD, Abstract Co-Author: Research Grant, Varian Medical Systems, Inc

To study the feasibility and benefit of boosting dose to active regions of cervical cancer identified by positron emission tomography (PET) imaging during brachytherapy.

5 patients imaged with both MRI and PET/CT were retrospectively studied. An experienced physician contoured the GTV and HR-CTV using the MRI scan alone, and then contoured the region of PET-hot activity using a PET/CT image. The MRI and PET/CT images where then fused, and a PET-HR-CTV volume was constructed from the union of the HR-CTV and PET-GTV. Each patient had been treated using a Syed or T&R applicator with 4-20 interstitial needles. Two new plans were optimized using Oncentra’s IPSA package with the following objectives: 1) a plan using only the MRI contours in which the HR-CTV-D90 received the prescription dose (Rx), and 2) a plan where the HR-CTV D90 received Rx and the PET-GTV D90 was boosted to 1.5Rx. In both cases the EQD2 D2cc dose to the bladder and rectum were kept below the GEC-ESTRO guidelines of 90 and 75 Gy, including the contribution from external beam therapy. Dose-volume parameters calculated for the all volumes.  

Significant differences were seen between the MRI-GTV and PET-GTV coutours (average size difference 21.8cc, average overlap 50%, see Figure 2). The PET-GTV boost to 150% was possible in four out of five cases, with the last case reaching 127% before reaching the rectal D2cc limit (Table 1). In 3 of the test cases, the PET-GTV also received about 150% of the Rx dose in the MRI-only plans—the two other cases were those in which the PET-GTV volume extended the most outside of the HR-CTV.

PET imaging modality has the potential to identify residual cervical cancer otherwise not visible on MRI and CT studies. This work has found that MRI target contouring regularly does not include regions of PET activity, and PET-based planning can lead to improved coverage over plans using MRI alone without sacrificing OAR sparing.

PET/CT scans for cervical brachytherpy planning provide more accurate GTV contours and allow increased dose to regions of active tumour.

Anderson, J, Kiel, K, Liao, Y, Yao, R, Bernard, D, Turian, J, Chu, J, PET Image-guided Dose Escalation Study for Cervical Cancer Patients Receiving HDR Brachytherapy.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13028056.html