ESTRO 2024 - Abstract Book

S2269

Clinical - Upper GI

ESTRO 2024

In the simulation process, we utilized a ExaCradle multidampening stereotactic system (Anatge), the MoldCareBR 3(ALCARE CO., Ltd) and a CT-Sim Toshiba Aquilion Big Bore. Our approach involved a slowCT scan with a 700mm field of view (FOV) and a 3-second acquisition time across the entire abdominal area for dose calculations. This wasfollowed by a 4DCT scan with a 240mm FOV focused on the lesion to define the internal target volume (ITV). Lastly, a high-resolution CT (HRCT) scan with arterial and lavage phase contrast, acquired during breath-hold, was used to determine the gross target volume (GTV). No fiducial markers were used.We created planning risk volumes (PRVs) as expansions of the volumes of the organs at risk (OARs), which included the complete duodenum, stomach, liver, and intestinal loops. A new volume, PTVSIP, was defined as the intersection of the planning target volume (PTV) with the PRV. The maximum dose consistent with OAR tolerance was prescribed to this volume, while the remaining PTV received the full prescription dose. Cone beam CT scans were performed before and after each fraction, particularly for SBRT.

Results:

From August 2016 to March 2023, we treated 39 patients. The mean age was 59 years. In 35/39 patients, we had histological confirmation of malignancy (90% adenocarcinoma). 30/39 patients received FOLFIRINOX prior to RT, with a mean number of cycles of 9 (range 5-16), followed by gemcitabine monotherapy (5/39) (range 3-8) and others (4/39). SIB-SIP was used in 29/39 patients. The minimum dose prescribed on PTV was 50,4, 30 and 25 Gy in 28,10 and 5 fractions, for N-RT, MH-RT and EH-RT, respectively. The maximum prescription dose administered at the end of treatment on PTVSIB was 70, 39 and 40 Gy for N-RT, MH-RT and EH-RT, respectively. The median volume of the PTV was 204 cc (range 20-517 cc) and PTVSIB-SIP was 25.19 cc (range 1.33-104 cc)

The mean total time to administer the treatment was 43,16 and 11 calendar days for N-RT, MH-RT and EH-RT, respectively. The treatment time for each fraction in each patient was less than 10 minutes in all cases.

At the time of analysis, 32/39 patients had already died. The median follow-up period for the entire cohort was 21.39 months (7.8-62.3 months). The median OS from diagnosis to death or last follow-up was 20.73 months (range 7,8-62,3 months) and 21,86 months (range 15.1-60.93 m) for entire cohort and alive patients, respectively. The mean OS since the end of SBRT treatment was 10.46 months. The median OS was 18, 20,5 and 22.36 months for N-RT, MH-RT and EH-RT, respectively. 20/39 patients had suffered local relapse (within PTV). The median LPFS (from the end of RT to local event or last follow-up) of the entire cohort was 8.5 months, and 5.4 months for those with local progression (range 1.2-22.7 months).

Conclusion:

In our experience, SBRT-like approach, including multidampening device and SIB-SIP techniques in LAPC is feaseble and recommended for all RT-squemes in LAPC patients. Regarding clinical results in terms of LPFS and OS, the 3 fractionations showed similar results and compared favorably to published data of others cohorts.

Ongoing and future clinical trials will offer more information about the controversial role of RT in this field.

Keywords: pancreatic cancer, multidampening, radiotherapy