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This research considers potential dose increase in target due to cisplatin (Pt) concentration and radiation type. Cisplatin concentrations from 0.003 to 120 mM were used. Monte-Carlo simulation of Linear accelerator (Elekta Synergy) and X-ray tube (Xstrahl300) was carried out using Geant4 and PClab. As the first step of this research, we performed simulation of energy spectrum from radiotherapy units (spectrum model). The next step was the modeling of linear accelerator head and X-ray tube, and the distribution of dose in the water phantom (PDD model). At the second stage, dose changes were investigated in the presence of cisplatin in the target (CIS model). The simulation results showed that the dose escalation can be caused by photon-capture therapy (PCT). There is a dose enhancement in the volume where cisplatin is accumulated. Then higher is concentration, then higher is the effect. However, the photon energy increase from 60 to 250 kV and increase of depth of target reduces the effect of PCT due the decrease of the photoelectric effect cross-section. Should be noticed, that the orthovoltage X-rays energy, listed in the table with results shows higher dose enhancement, than the megavoltage photon beam generated from linear acceleration sources. In addition, that the dose enhancement factors (DEF) are higher in linac without flattening filter, than in linac with flattening filter.