C. Hitchen

Breast, chest wall, and nodal irradiation with prone set-up: Results of a hypofractionated trial with a median follow-up of 35 months

PURPOSE To test clinical feasibility, safety, and toxicity of prone hypofractionated breast, chest wall, and nodal radiation therapy. METHODS AND MATERIALS Following either segmental or total mastectomy with axillary node dissection, patients were treated in an institutional review board-approved prospective trial of prone radiation therapy to the breast, chest wall, and supraclavicular and level III axillary lymph nodes. A dose of 40.5 Gy/15 fractions with a concomitant daily boost to the tumor bed of 0.5 Gy (total dose, 48 Gy) was prescribed. In postmastectomy patients, the same treatment was prescribed, but without a tumor bed boost. The primary endpoint was incidence of >grade 2 acute skin toxicity. The secondary endpoints were feasibility of treatment using prone set-up, compliance with protocol-defined dosimetric constraints, and incidence of late toxicity. A dosimetric comparison was performed between protocol plans (prone) and nonprotocol plans (supine), targeting the same treatment volumes. RESULTS Sixty-nine patients with stage IB-IIIA breast cancer enrolled in this trial. Surgery was segmental mastectomy (n = 45), mastectomy (n = 23), and bilateral mastectomy (n = 1), resulting in 70 cases. None experienced >grade 2 acute skin toxicity according to the Common Terminology Criteria for Adverse Events, v 3.0, meeting our primary endpoint. Ninety-six percent of patients could be treated with this technique prone. However, 17 plans (24%) exceeded protocol constraints to the brachial plexus. Maximum long-term toxicity was 1 grade 2 arm lymphedema, 1 grade 3 breast retraction, and no occurrence of brachial plexopathy. Dosimetric comparison of protocol with nonprotocol plans demonstrated significantly decreased lung and heart doses in prone plans. CONCLUSIONS Prone hypofractionated breast, chest wall, and nodal radiation therapy is safe and well tolerated in this study. Although the initial pattern of local and regional control is encouraging, longer follow-up is warranted for efficacy and late toxicity assessment, particularly to the brachial plexus.

Dose to craniofacial region through portal imaging of pediatric brain tumors.

The purpose of this study was to determine dose to the planning target volume (PTV) and organs at risk (OARs) from portal imaging (PI) of the craniofacial region in pediatric brain tumor patients treated with intensity‐modulated radiation therapy (IMRT). Twenty pediatric brain tumor patients were retrospectively studied. Each received portal imaging of treatment fields and orthogonal setup fields in the craniofacial region. The number of PI and monitor units used for PI were documented for each patient. Dose distributions and dose‐volume histograms were generated to quantify the maximum, minimum, and mean dose to the PTV, and the mean dose to OARs through PI acquisition. The doses resulting from PI are reported as percentage of prescribed dose. The average maximum, minimum, and mean doses to PTV from PI were 2.9±0.7%, 2.2±1.0%, and 2.5±0.7%, respectively. The mean dose to the OARs from PI were brainstem 2.8±1.1%, optic nerves/chiasm 2.6±0.9%, cochlea 2.6±0.9%, hypothalamus/pituitary 2.4±0.6%, temporal lobes 2.3±0.6%, thyroid 1.6±0.8%, and eyes 2.6±0.9%. The mean number of portal images and the mean number of PI monitor units per patient were 58.8 and 173.3, respectively. The dose from PI while treating pediatric brain tumors using IMRT is significant (2%–3% of the prescribed dose). This may result in exceeding the tolerance limit of many critical structures and lead to unwanted late complications and secondary malignancies. Dose contributions from PI should be considered in the final documented dose. Attempts must be made in PI practices to lower the imaging dose when feasible. PACS numbers: 87.55ne, 87.55Qr

Reducing excess radiation from portal imaging of pediatric brain tumors

Previously we have shown that our routine portal imaging (PI) of the craniofacial region in pediatric brain tumor patients contributed an additional 2%‐3% of the prescribed dose and up to 200 cGy to the planning target volume (PTV) and nearby organs at risk (OARs). The purpose of this study is to quantify the reduction in dose to PTV and OARs from portal imaging (PI) of the craniofacial region of pediatric patients treated after the implementation of changes in our portal imaging practices. Twenty consecutive pediatric patients were retrospectively studied since the implementation of changes to our portal imaging procedure. Each received portal imaging of treatment fields and orthogonal setup fields to the craniofacial region. PI modifications included a reduction in the field size of setup orthogonal fields without loss of radiographic information needed for treatment verification. In addition, treatment fields were imaged using a single exposure, rather than double exposure. Dose‐volume histograms were generated to quantify the dose to the target and critical structures through PI acquisition. These results were compared with our previous cohort of 20 patients who were treated using the former portal imaging practices. The mean additional target dose from portal imaging following the new guidelines was 1.5% of the prescribed dose compared to 2.5% prior to the new portal image practices (p < 0.001). With the new portal imaging practices, the percentage decrease in portal imaging dose to the brainstem, optic structures, cochlea, hypothalamus, temporal lobes, thyroid, and eyes were 25%, 35%, 35%, 51%, 45%, 80%, and 55%, respectively. Reductions in portal imaging doses were significant in all OARs with exception of the brainstem, which showed a trend towards significance. Changes to portal imaging practices can reduce the radiation dose contribution from portal imaging to surrounding OARs by up to 80%. This may have implications on both late toxicity and second cancer development in pediatric brain tumors. PACS number: 87