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  • Thus the use of electron radiation on liver


    Thus, the use of electron radiation on liver offers a better dose distribution in tissues due to its unique dosage BQ-788 sodium salt feature consistent with the marginal distribution of liver metastasis from pan-creatic cancer, minimizing the damage to liver capsule as well as deeper healthy tissues.
    Prophylactic intraoperative 3 MeV electron radiation therapy on the surface of liver may prevent postoperative liver metastasis of pancreatic cancer
    For patients with pancreatic cancer, only 15% −20% of them have the opportunity for receiving radical surgery in time when diagnosed
    Fig. 4. Interoperation found tumor tissue of marginal liver metastasis from pancreas.
    Fig. 5. Prophylactic intraoperative electron radiation prevents postoperative liver metastasis in pancreatic cancer patients with surgery indications.
    cancer [51]. What's worse, even if R0 radical resection of pancreatic cancer is successfully implemented, the median survival time of pa-tients is only 12–20 months, and the 5-year survival rate is still less than 20% [52]. Intraoperative manipulation as one of main factors affecting the spread of tumor cells, postoperative distant metastasis usually predicts a worse prognosis [48,49], in which liver metastasis accounts for the majority (40%–90%) [8–10] and occurs relatively early (about 5–11 months) [53]. However, there is a lack of effective treatment for pancreatic cancer with liver metastasis [54]. Similarly, the brain is a 
    frequent metastasis site of lung cancer, which is responsible for life threatening and survival shortening [55]. As for blood brain barrier is poorly penetrable for most drugs, prophylactic cranial irradiation is thought as a strategy to eliminate non-detectable brain metastases from lung cancer showing a decrease on the overall brain metastases rate [56,57]. Therefore, we try to apply prophylactic intraoperative electron radiation to pancreatic cancer patients with surgery indications, that is, without liver metastasis (Fig. 5).
    To be more precise, the CT images of the retrospective study men-tioned above (Fig. 1) and intraoperative probes of patients with liver metastasis (Fig. 4) showed that the depth of marginal liver metastasis was ≤1 cm primarily. Basically, energy value, therapeutic apparatus structure, and various substances along the path will affect the percent depth dose curve of the electron radiation [40]. As for the structure of the therapeutic apparatus is determined by different medical units and substance along the path is liver tissue mainly, depending more on the clinical situation, we only discuss about the electronic energy value here [40]. When selecting electronic energy value, if there is no vul-nerable normal tissue behind the target area, 95% or 90% percentage depth dose can be used to cover the back edge of the target area, so as to ensure that the target area is treated adequately and uniformly. Otherwise, the percentage depth of the back edge of the target area should be set at 80% or 85% to protect the normal tissue behind. For prophylactic radiation on liver in our hypothesis, this is a situation that tumor cells from pancreas have not formed new tumor lesions yet. To consider both safety and effectiveness together, we suggest 80% or 85% is a better choice. Some textbooks suggest [43] that if the percentage depth is set at 85%, the electron energy can be approximately selected as E = 3(MeV/cm)*d (cm). As for the depth of marginal liver metastasis ≤1 cm, E = 3 MeV is suitable in theory.
    Thus, we hypothesize that prophylactic intraoperative 3 MeV elec-tron therapy on the surface of liver may prevent postoperative liver metastasis of pancreatic cancer.