The disclosed subject-matter relates to a system (1) for treatment of a patient (2) by irradiating a tumor (3), the system (1) comprising: a scanner (105) configured to scan at least a part of a body (4) of the patient (2)； a processor (106) being configured to localize the tumor (3) in the scan (S') and to determine a hypoxic and a normoxic region (H, N) of the tumor (3) and a micro-environment (M) surrounding the tumor (3)； an irradiation device (109) configured to emit irradiation beams (12, 12') in different irradiation directions (di) that intersect in the hypoxic region (H)； and a controller (108) configured to control the irradiation device (109) such that an accumulated irradiation dose delivered to the hypoxic region (H) during the treatment is greater than 8 Gy and an accumulated irradiation dose delivered to the micro-environment (M) during the treatment is, in an average over said micro-environment, less than 3 Gy.
