Overall, 19.3% of the elderly patients showed treatment intolerance during conventional radiotherapy. Serum albumin level and ECOG performance score should be considered as surrogate markers for radiotherapy interruption prior to the decision regarding definite conventional radiotherapy.

Residual tumor volume measured using routine boost planning computed tomography during preoperative chemoradiotherpy correlated significantly with pathologic tumor regression grade after surgery.

The purpose of this study is to assess the extent and serial pattern of setup error of conventional fractionated whole pelvic irradiation using a kilovoltage on‐board imager. The daily on‐board images of 69 patients were matched with the digitally reconstructed radiographs of simulation on the basis of pelvic bony structure. The shifts along x‐ (lateral), y‐ (longitudinal), and z‐ (vertical) axes, and the 3D vector, were measured. The shift between an origin of the first fraction and each fraction (normalΔshift1st) and the shift between an isocenter of simulation and each fraction (normalΔshiftSimfalse) were calculated. To evaluate serial changes, the shifts of each fraction were classified into four consecutive sessions, and an ANOVA and chi‐square test were used. The systematic error of the normalΔshiftSim and normalΔshift1st were 2.72 and 1.43 mm along the x‐axis, 2.98 and 1.28 mm along the y‐axis, and 4.26 and 2.39 mm along the z‐axis, respectively. The normalΔshiftSim and normalΔshift1st≥50.2emmm of the 3D vector occurred in 54.3% and 23.1%, respectively. The recommended margins to cover setup error in case of using normalΔshift1st were 3.81, 3.54, and 6.01 mm along x‐, y‐, and z‐axes, whereas those using normalΔshiftSim were 6.39, 6.95, and 9.95 mm, respectively. With the passage of time, the normalΔshift1st≥50.2emmm of 3D vector and along any axis in supine setup increased from 14.1% for first session to 22.5% for fourth session (p=0.027false) and from 10.8% to 18.5% (p=0.034false), respectively. In prone setup, first session was better than others in the normalΔshift1st≥5mm of 3D vector and along any axis. It is expected that the correction using the on‐board images on the first fraction improves geometrical uncertainties and reduces the margin for target coverage. Daily continuous OBI follow‐up during conventional fractionated pelvic irradiation can increase the reproducibility and be more effective in the late period.PACS number: 87.55.km