Dosimetric evaluation of whole breast radiotherapy using field-in-field technique in early-stage breast cancer.

BACKGROUND: The purpose of this study is to evaluate the dosimetric benefits of whole breast radiotherapy (WBRT) using the field-in-field technique compared with conventional tangential field radiotherapy with physical wedges for WBRT. METHODS: In this planning study, 20 patients were included. For each patient, two different treatment plans were created for the entire treated breast. The dosimetric parameters of the planning target volume for dose evaluation and the organs at risk for each planning technique were compared. In the clinical outcome, acute skin toxicity for each treatment technique was compared. RESULTS: The field-in-field technique significantly reduced the maximum dose, the volumes receiving >107% of the prescription dose, and homogeneity index for the planning target volume for dose evaluation compared with the tangential field technique. For each dosimetry of the organs at risk, excluding the contralateral breast, the field-in-field technique significantly reduced the maximum dose and the volumes receiving >10, 30, and 50 Gy of the prescribed dose. The volume receiving <1 Gy of the prescription dose for the contralateral breast was significantly decreased using the field-in-field technique. In addition, the dose distribution using the field-in-field technique in the target volume was less sensitive to the effects of breast motion during normal breathing. In the clinical outcome, the field-in-field technique significantly reduced Radiation Therapy Oncology Group (RTOG) grade II acute skin toxicity compared with the tangential field technique (3.1 vs. 10.6%). CONCLUSIONS: WBRT using the field-in-field technique improved dose distribution in the treated breast and decreased RTOG grade II acute skin toxicity compared with conventional tangential field radiotherapy with physical wedges.

Rectal dose reduction using three-dimensional conformal radiotherapy for locally advanced prostate cancer: A combination of conformal dynamic-arc and five-static field technique.

BACKGROUND AND PURPOSE: The aims of this study are to compare our three-dimensional conformal radiotherapy (3D-CRT) plan using a combination of conformal dynamic-arc and five-static field (DASF) technique with other 3D-CRT plans for prostate cancer, and to estimate whether dose escalation is possible with DASF radiotherapy (DASF-RT). METHODS AND MATERIALS: Twenty patients with prostate cancer were included in this study. For each patient, five different treatment plans including DASF-RT were created to entire prostate and seminal vesicles. Dose distribution and rectal dose-volume histogram (DVH) for each planning technique were compared. RESULTS: In DASF-RT treatment plan, rectum V40, V50, V60, and V70 were 61.6%, 39.6%, 21.4%, and 0.6%, respectively. Compared with four 3D-CRT techniques, DASF-RT technique significantly reduce rectum V50 to V70 without increasing irradiated bladder and femoral head volumes. In addition, in the simulation of dose escalation to 76Gy, the increase of each rectal dose-volume parameter (V40 to V75) was small enough. However, in dose escalation to 78Gy, rectum V75 exceeded 5%. CONCLUSION: DASF-RT technique could significantly reduce rectal volumes receiving 50-70Gy compared with other 3D-CRT techniques. DASF-RT was safe and feasible for dose escalation to 76Gy in prostate radiotherapy.