Treatment plans for each modality with isodose lines: brachytherapy (top left), three-dimensional conformal radiotherapy (top right), prone tomotherapy (bottom left), and supine tomotherapy (bottom right). The lumpectomy cavity is enhanced with Omnipaque contrast. The shown isodose lines are 100% (red), 75% (yellow), 50% (green), and 25% (blue).
A Dosimetric Comparison of Accelerated Partial Breast Irradiation Techniques: Multicatheter Interstitial Brachytherapy, Three-Dimensional Conformal Radiotherapy, and Supine Versus Prone Helical Tomotherapy

Rakesh R. Patel, M.D. IJROBP Volume 68, Issue 3, Pages 935-942 (1 July 2007)

To compare dosimetrically four different techniques of accelerated partial breast irradiation (APBI) in the same patient.

Methods and Materials: Thirteen post-lumpectomy interstitial brachytherapy (IB) patients underwent imaging with preimplant computed tomography (CT) in the prone and supine position. These CT scans were then used to generate three-dimensional conformal radiotherapy (3D-CRT) and prone and supine helical tomotherapy (PT and ST, respectively) APBI plans and compared with the treated IB plans. Dose–volume histogram analysis and the mean dose (NTDmean) values were compared.
Results: Planning target volume coverage was excellent for all methods. Statistical significance was considered to be a p value <0.05. The mean V100 was significantly lower for IB (12% vs. 15% for PT, 18% for ST, and 26% for 3D-CRT). A greater significant differential was seen when comparing V50 with mean values of 24%, 43%, 47%, and 52% for IB, PT, ST, and 3D-CRT, respectively. The IB and PT were similar and delivered an average lung NTDmean dose of 1.3 Gy3 and 1.2 Gy3, respectively. Both of these methods were statistically significantly lower than the supine external beam techniques. Overall, all four methods yielded similar low doses to the heart.

Conclusions: The use of IB and PT resulted in greater normal tissue sparing (especially ipsilateral breast and lung) than the use of supine external beam techniques of 3D-CRT or ST. However, the choice of APBI technique must be tailored to the patient’s anatomy, lumpectomy cavity location, and overall treatment goals.