ETD

• adenocarcinoma
• flash
• in vivo model
• metastasis
• pancreas
• radiotherapy

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with poor prognosis, often diagnosed at advanced stages due to the lack of early symptoms. Radiotherapy (RT) remains an essential component of multimodal treatment, but its efficacy is frequently limited by toxicity to surrounding healthy tissues. FLASH radiotherapy (FLASH RT), delivering ultra-high dose rates, has been shown in preclinical models to maintain tumor control while sparing normal tissues. However, its impact on tumor progression and metastatic dissemination remains largely unexplored.
In this thesis work, the chick chorioallantoic membrane (CAM) model has been employed to investigate the effects of FLASH RT on the growth and metastatic behavior of BxPC-3 pancreatic adenocarcinoma cells. Tumors were grafted onto the CAM at embryonic day 6 (EDD6) and irradiated at EDD10 with either conventional RT (CONV-RT, 6 Gy/min) or FLASH RT (≥240 Gy/s) at a single dose of 2 Gy. Tumor growth was monitored daily using digital imaging and volumetric measurements, while metastatic dissemination was assessed qualitatively through visual inspection of the upper CAM and quantitatively by real-time PCR analysis of lower CAM samples. Embryo survival was recorded throughout the experimental period (EDD10–EDD17).
Both FLASH and conventional RT effectively limited tumor growth compared to controls. FLASH RT significantly improved the embryo survival respect to CONV-RT, consistently with previous findings on the tissue–sparing effect. The visual assessment revealed only a few potential metastatic foci, and the quantitative analysis showed no significant differences among the groups, likely because of a survival bias. These results further confirm that FLASH RT preserves tumor control while reducing the overall toxicity, supporting its therapeutic advantage over conventional RT. The CAM model proved to be a robust platform for preclinical evaluation of radiotherapy effects on tumor biology. Future research should be directed to incorporating multiple timepoints and expanded molecular analyses to further elucidate the mechanisms underlying the FLASH effect and its potential impact on metastatic behavior.