Evaluation of three APBI techniques under NSABP B‐39 guidelines

Abstract

This work compares two accelerated partial breast irradiation modalities, MammoSite brachytherapy and three‐dimensional conformal radiotherapy (3D‐CRT), to a new method, strut‐adjusted volume implant (SAVI) brachytherapy, following NSABP B‐39 guidelines. A total of 21 patients treated at UC San Diego with the SAVI device were evaluated in this comparison. Nine of the 21 patients were eligible for all three modalities and were dosimetrically compared evaluating V90, V150, V200, total target volume, maximum skin, lung, and chestwall/rib dose. The target volumes (PTV_EVAL) differed with SAVI, having the least total volume at 59.9 cc vs. 71.5 cc and 351.6 cc for MammoSite and 3D‐CRT, respectively. The median V90, V150 and V200 for the three modalities were 97.7%, 25.0 cc, 10.4 cc (SAVI) vs. 97.6%, 23.9 cc, 5.0 cc (MammoSite) vs. 100% (V90 3D‐CRT). The maximum dose for SAVI, MammoSite, and 3D‐CRT, respectively, relative to the prescribed dose, for the lung: 80.0%, 150.0%, and 104.9%; for rib: 108.8%, 225.0%, and 114.7%; for skin: 75.0%, 135.0%, and 108.6%. Comparing modalities, PTV coverage varied between 97.6%–100.0% with more breast tissue covered by 3D‐CRT, as expected, given the differences between external beam and brachytherapy. The maximum lung, skin and rib doses were lowest for the SAVI, highlighting its ability to conform to exclude normal tissues. In offering partial breast radiation, the availability of a variety of techniques allows for maximal patient eligibility, and comparison of individual method pros and cons may guide the most appropriate choice for each patient.PACS number: 87.53.Jw; 87.53.Kn; 87.55.D

Dosimetric comparison of preoperative single‐fraction partial breast radiotherapy techniques: 3D CRT, noncoplanar IMRT, coplanar IMRT, and VMAT

“…Noncoplanar 3D CRT included four to five beams following typical APBI 3D CRT planning, (1,14) among which one to three beams included wedges. The couch rotation was applied to one to three beams with a limited angle up to to avoid collision.…”

“…Given the relative novelty of this approach, the optimal treatment delivery technique was unknown. Although 3D CRT has been traditionally used for postoperative APBI, (1,13,14) significantly reduced dose to normal surrounding tissue and critical structures with more conformal target coverage have been reported in studies using IMRT or VMAT techniques (15‐20) . However, all prior IMRT or VMAT studies for breast patients did not include constraints for the skin, which, we were concerned, could be a major limitation for single‐fraction breast radiotherapy.…”

Treatment planning of a skin‐sparing conical breast brachytherapy applicator using conventional brachytherapy software

“…For APBI, the maximum acceptable skin dose was 145% of the prescription dose according to NSABP B-39/ RTOG 0413. 18 However, skin D MAX is larger than twice that of the prescription dose. This is solved by using a four-field arrangement, in which skin D MAX is divided by 2 when assuming no skin overlap between the two orthogonal axes.…”

“…The optimal applicator type and size for each data set was determined to achieve at least 90% of the prescription dose to 90% of the PTV volume ͑ PTV V 90 Ն 90%͒ while minimizing OAR dose. 18 Table I shows volumetric and dimensional information used for guiding the applicator selection.…”

Accelerated Partial-Breast Irradiation: A State of the Art Strategy.

“…-SAVI consists of a central strut surrounding by 6,8 or 10 peripheral struts, the device is inserted in a collapsed form through a small incision; once placed, it is then expanded to fit the lumpectomy cavity [43,44,45].SAVI device is surgically implanted using ultrasound guidance with the patient under local anesthesia. A CT scan is performed immediately following the implant surgery, both for the verification of the proper deployment of the device and for treatment planning [45] ( Figure 4 d,e).…”