Modified simultaneous integrated boost radiotherapy for an unresectable huge refractory pelvic tumor diagnosed as a rectal adenocarcinoma

Figure 1 Simultaneous integrated boost irradiation. A: The concept behind standard simultaneous integrated boost (SIB) irradiation. A prophylactic dose is delivered to clinical target volume, and a curative (higher) dose is delivered to gross tumor volume (GTV). Dose distribution within GTV is usually homogeneous; B: The concept of the modified SIB irradiation technique. It is almost the same as the standard SIB technique, but the modified SIB technique can deliver a much higher dose to the part of GTV without excessive irradiation of the surrounding healthy tissue by allowing for heterogeneity of dose distribution within GTV.