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TomoDirect (TD) is an intensity‐modulated radiotherapy system that uses a fixed gantry angle instead of rotational beam delivery. Here, we investigated the effect of the multiple beam technique of TomoDirect on dose distribution compared with commonly‐used tangential beams. We included 45 consecutive patients with right breast cancer who underwent postoperative radiotherapy in our institute in the present study. Clinical target volume (CTV) was the whole right breast. The planning target volume (PTV) was created by expanding the CTV by a 0.5 cm margin. Paired TD plans were generated for each patient; a two‐beam plan using paired tangential beams and a six‐beam plan with four additional beams with modified gantry angles of ± 5° from the original tangential beam set. A prescribed dose of 50 Gy was defined for 50% isodoses of the PTV. The six‐beam plan delivered significantly more homogeneous doses to the PTV than the two‐beam plan; and the mean dose to the PTV in the six‐beam plan more closely reflected the prescribed dose. V20Gy and mean dose to the right lung and mean dose to the whole body were also significantly decreased in the six‐beam plan. However, duration of radiation exposure was 1 min longer in the six‐beam plan than in the two‐beam plan. The dose distribution to the target and organs at risk were improved with the six‐beam plan relative to the two‐beam plan without increasing the whole‐body radiation dose. The six‐beam plan using TD is a simple technique that can be routinely applied to whole‐breast irradiation in clinical practice.PACS number: 87.55

Intensity-modulated radiation therapy (IMRT) delivers an excellent dose distribution compared with conventional three-dimensional conformal radiation therapy (3D-CRT) for postoperative radiation including the lymph nodes in breast cancer patients. The TomoTherapy system, developed exclusively for IMRT, has two treatment modes: TomoDirect (TD) with a fixed gantry angle for beam delivery, and TomoHelical (TH) with rotational beam delivery. We compared the characteristics of TD with TH and 3D-CRT plans in the breast cancer patients. Ten consecutive women with left breast cancer received postoperative radiation therapy using TD including the chest wall/residual breast tissue and level II–III axial and supraclavicular lymph node area. Fifty percent of the planning target volume (PTV) was covered with at least 50 Gy in 25 fractions. TD, TH and 3D-CRT plans were created for each patient, with the same dosimetric constraints. TD and TH showed better dose distribution to the PTV than 3D-CRT. TD and 3D-CRT markedly suppressed low-dose spread to the lung compared with TH. Total lung V5 and V10 were significantly lower, while V20 was significantly higher in the TD and 3D-CRT plans. The mean total lung, heart and contralateral breast doses were significantly lower using TD compared with the other plans. Compared with 3D-CRT and TH, TD can provide better target dose distribution with optimal normal-organ sparing for postoperative radiation therapy including the chest wall/residual breast tissue and lymph node area in breast cancer patients. TD is thus a useful treatment modality in these patients.

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IntroductionRectal bleeding after radiotherapy impacts the quality of life of long‐term surviving prostate cancer patients. We sought to identify factors associated with late rectal bleeding following intensity modulated radiation therapy (IMRT) using TomoTherapy for prostate cancer.MethodsWe retrospectively analysed 82 patients with localised prostate cancer treated with TomoTherapy. Most patients (95.1%) received neoadjuvant and concurrent hormone therapy. Forty‐two patients (51.2%) graded as high risk using D'Amico's classification underwent radiotherapy involving the pelvic nodal area. Late bleeding complications were quantified using the Common Terminology Criteria for Adverse Events v4.0. Multiple clinical and dosimetric factors were considered with reference to rectal bleeding.ResultsThe median follow‐up period was 538 (range, 128–904) days. Grades 1, 2 and 3 rectal bleeding were observed in 14 (17.1%), four (4.9%) and one (1.2%) patient respectively. In multivariate analysis, the following factors were significantly associated with Grade ≥1 late rectal bleeding: volume, mean dose (P = 0.012) and rectal V30 (P = 0.025), V40 (P = 0.011), V50 (P = 0.017) and V60 (P = 0.036). When exclusively considering Grade 2–3 rectal bleeding, significant associations were observed with the use of anticoagulants or antiaggregates (P = 0.007), rectal V30 (P = 0.021) and V40 (P = 0.041) in univariate analysis.ConclusionsOur results suggested that the intermediate rectal dose‐volume (V30–V60) was a significant predictor for mild to severe late rectal bleeding (Grade ≥1). Rectal dose‐volumes >V70, which represented the volume of the highest doses, were not predictive in this study.