A Computed Tomography-based Protocol vs Conventional Clinical Mark-up for Breast Electron Boost

Magnetic Resonance Imaging for Breast Tumor Bed Delineation: Computed Tomography Comparison and Sequence Variation

Purpose

Our purpose was to investigate the interobserver variability in breast tumor bed delineation using magnetic resonance (MR) compared with computed tomography (CT) at baseline and to quantify the change in tumor bed volume between pretreatment and end-of-treatment MR for patients undergoing whole breast radiation therapy.

Methods and Materials

Forty-eight patients with breast cancer planned for whole breast radiation therapy underwent CT and MR (T1, T1 fat-suppression [T1fs], and T2) simulation in the supine treatment position before radiation therapy and MR (T1, T1fs, and T2) at the end of treatment in the same position. Two observers delineated 50 tumor beds on the CT and all MR sequences and assigned cavity visualization scores to the images. The primary endpoint was interobserver variability, measured using the conformity index (CI).

Results

The mean cavity visualization scores at baseline were 3.14 (CT), 3.26 (T1), 3.41 (T1fs), and 3.58 (T2). The mean CIs were 0.65, 0.65, 0.72, and 0.68, respectively. T1fs significantly improved interobserver variability compared with CT, T1, or T2 (P < .001, P < .001, and P = .011, respectively). The CI for T1fs was significantly higher than T1 and T2 at the end of treatment (mean 0.72, 0.64, and 0.66, respectively; P < .001). The mean tumor bed volume on the T1fs sequence decreased from 18 cm³ at baseline to 13 cm³ at the end of treatment (P < .01).

Conclusions

T1fs reduced interobserver variability on both pre- and end-of-treatment scans and measured a reduction in tumor bed volume during whole breast radiation therapy. This rapid sequence could be easily used for adaptive boost or partial breast irradiation, especially on MR linear accelerators.

Target localisation for tumour bed radiotherapy in early breast cancer

INTRODUCTION

To compare clinical and CT techniques in localisation of the tumour bed in patients undergoing adjuvant breast radiotherapy for breast cancer.

METHODS

Patients were CT scanned in the treatment position following clinical delineation of the whole breast, surgical scar and boost volume. Computed tomography boost volumes were contoured in three dimensions. A definitive treatment plan was generated to encompass the CT-localised planning target volume (PTV) with ≥90% isodose using electrons. A hypothetical plan was also generated to cover the clinically determined boost field for comparison. The primary end point was the difference in PTV coverage by the 90% isodose between the plans based on clinically and CT localised boost volumes.

RESULTS

The plans for 50 patients were evaluated. The median percentage of PTV encompassed by the 90% isodose using the clinical and CT techniques was 29% (range 5-90%) and 83% (range 25-100%), respectively. PTV coverage by the 90% isodose using the clinical technique was at least 10% less than that using CT technique in 88% of patients (95% confidence interval 77-95%; P < 0.0001).

CONCLUSION

Tumour bed boost PTV coverage was insufficient using clinical determination as compared with CT localisation. This study supports CT planning for target volume localisation of the tumour bed boost in patients treated with breast-conserving therapy for breast cancer.

A nationwide survey of radiation oncologists' management practices of radiation-induced skin reaction (RISK)

Purpose:A questionnaire was developed to explore variations among radiation oncologists in managing early-stage breast cancer, specifically radiation-induced skin reaction (RISK).

Materials and methods:A survey was designed to target a database of 962 radiation oncologists, self-identified as ‘interested in treatment of breast cancer’. This database was obtained from the American Society of Therapeutic Radiology & Oncology (ASTRO). Participants submitted the survey online or by mail. Overall response to the survey was 282 out of 962 (29.3%). Data were handled as rates.

Results:Out of 282 respondents, 275 (97.5%) agreed on delivering 4500–5040 cGy. The most frequently employed dose was 5040/180 cGy. Three-dimensional-conformal (3DCRT) treatment was used by 55.4%, intensity-modulated radiotherapy (IMRT) by 24.5%, and conventional by 20.1%. Almost all (92.5%) agreed on using boost in ductal carcinoma in situ (DCIS). Image-guided boost placement (IGBP) was used by 87.3%. Boost dose included variations: 50.2, 7.3, and 18% used 1000, 1200, and 1400 cGy, respectively; the remaining used higher doses. In management of RISK, Aquaphor was the most popular agent (72.1%). Other agents were utilized either alone or in combination. Almost all (99%) agreed that large breast size increases RISK.

Conclusion:This survey offers a glimpse of management practices in early-stage breast cancer amongst a cross-section of radiation oncologists in the United States. Although there appears to be an overall congruence on the doses and techniques of radiation delivery, the management of RISK is varied. Additional efforts are warranted to standardize practices in order to practice evidence based medicine in a cost-effective manner.

An anthropomorphic phantom study of visualisation of surgical clips for partial breast irradiation (PBI) setup verification

Surgical clips were investigated for partial breast image-guided radiotherapy (IGRT). Small titanium clips were insufficiently well visualised. Medium tantalum clips were best for megavoltage IGRT and small tantalum clips were best for floor mounted kilovoltage IGRT (ExacTrac). Both small tantalum and medium titanium clips were suitable for isocentric kilovoltage IGRT.