Image guidance in external beam accelerated partial breast irradiation: comparison of surrogates for the lumpectomy cavity

PURPOSE: To compare localization of the lumpectomy cavity by using breast surface matching vs. clips for image-guided external beam accelerated partial breast irradiation. METHODS AND MATERIALS: Twenty-seven patients with breast cancer with two computed tomography (CT) scans each had three CT registrations performed: (1) to bony anatomy, (2) to the center of mass (COM) of surgical clips, and (3) to the breast surface. The cavity COM was defined in both the initial and second CT scans after each type of registration, and distances between COMs (DeltaCOM(Bone), DeltaCOM(Clips), and DeltaCOM(Surface)) were determined. Smaller DeltaCOMs were interpreted as better localizations. Correlation coefficients were calculated for DeltaCOM vs. several variables. RESULTS: The DeltaCOM(Bone) (mean, 7 +/- 2 [SD] mm) increased with breast volume (r = 0.4; p = 0.02) and distance from the chest wall (r = 0.5; p = 0.003). Relative to bony registration, clip registration provided better localization (DeltaCOM(Clips) < DeltaCOM(Bone)) in 25 of 27 cases. Breast surface matching improved cavity localization (DeltaCOM(Surface) < DeltaCOM(Bone)) in 19 of 27 cases. Mean improvements (DeltaCOM(Bone) - DeltaCOM(Clips or Surface)) were 4 +/- 3 and 2 +/- 4 mm, respectively. In terms of percentage of improvement ([DeltaCOM(Bone) - DeltaCOM(Clips or Surface)]/DeltaCOM(Bone)), only surface matching showed a correlation with breast volume. Clip localization outperformed surface registration for cavities located superior to the breast COM. CONCLUSIONS: Use of either breast surface or surgical clips as surrogates for the cavity results in improved localization in most patients compared with bony registration and may allow smaller planning target volume margins for external beam accelerated partial breast irradiation. Compared with surface registration, clip registration may be less sensitive to anatomic characteristics and therefore more broadly applicable.     

Cone beam computed tomography guidance for setup of patients receiving accelerated partial breast irradiation

PURPOSE: To evaluate the role of cone-beam CT (CBCT) guidance for setup error reduction and soft tissue visualization in accelerated partial breast irradiation (APBI). METHODS AND MATERIALS: Twenty patients were recruited for the delivery of radiotherapy to the postoperative cavity (3850 cGy in 10 fractions over 5 days) using an APBI technique. Cone-beam CT data sets were acquired after an initial skin-mark setup and before treatment delivery. These were registered online using the ipsilateral lung and external contours. Corrections were executed for translations exceeding 3 mm. The random and systematic errors associated with setup using skin-marks and setup using CBCT guidance were calculated and compared. RESULTS: A total of 315 CBCT data sets were analyzed. The systematic errors for the skin-mark setup were 2.7, 1.7, and 2.4 mm in the right-left, anterior-posterior, and superior-inferior directions, respectively. These were reduced to 0.8, 0.7, and 0.8 mm when CBCT guidance was used. The random errors were reduced from 2.4, 2.2, and 2.9 mm for skin-marks to 1.5, 1.5, and 1.6 mm for CBCT guidance in the right-left, anterior-posterior, and superior-inferior directions, respectively. CONCLUSION: A skin-mark setup for APBI patients is sufficient for current planning target volume margins for the population of patients studied here. Online CBCT guidance minimizes the occurrence of large random deviations, which may have a greater impact for the accelerated fractionation schedule used in APBI. It is also likely to permit a reduction in planning target volume margins and provide skin-line visualization and dosimetric evaluation of cardiac and lung volumes.     

Dosimetric comparison of two different three-dimensional conformal external beam accelerated partial breast irradiation techniques

PURPOSE: We compare the dosimetry of two techniques for three-dimensional, conformal, external beam, accelerated partial breast irradiation (3D-CPBI) in the supine position. METHODS AND MATERIALS: Sixteen patients with Stage I breast cancer had PBI treatment plans generated using the multiple, noncoplanar photon field technique and the three-field, mixed-modality technique. Planning target volumes (PTVs; lumpectomy site plus 1.5-2.0 cm margin) and total dose (32 Gy) were held constant to facilitate dosimetric comparisons. Plans were optimized for conformality and PTV coverage. RESULTS: Mixed-modality plans employed fewer fields than multiple, noncoplanar photon field plans (mean 3.2 vs. 4.1). Both techniques provided comparable PTV coverage and in all cases, 95% of the PTV received 90% of the prescribed dose. Volumes of ipsilateral breast receiving greater than 16 Gy were similar; however, the mean volume of ipsilateral breast receiving 8 Gy was significantly lower for mixed-modality plans (58% vs. 66%). No differences in the volumes of ipsilateral lung or heart receiving greater than 5 Gy were observed, however, the mixed-modality technique delivered 2.5 Gy to larger volumes of these organs. CONCLUSIONS: Both techniques for supine position, 3D-CPBI provides excellent normal tissue sparing with adequate PTV coverage. The multiple, noncoplanar photon field technique exposes smaller volumes of ipsilateral lung and heart to low dose radiation at the expense of increased plan complexity and larger irradiated breast volumes.     

早期乳腺癌部分乳腺加速放疗

随着乳腺癌术后复发模式的研究进展,部分乳腺照射方法 成为乳腺癌放疗的热点.组织间插植、球囊近距离治疗、术中放疗及三维适形放疗和调强放疗等部分乳腺加速放疗已进入临床研究.其局部控制率和安全性与全乳腺照射比较相当,同时具有治疗周期短、方便患者等优势.部分乳腺加速放疗在部分患者有望代替全乳腺放疗,成为早期乳腺癌保乳术后放疗的标准治疗之一.

Abstract：

With a view to patterns of local recurrence after breast conserving surgery, whole breast irradiation(WBI) after surgery is controversial and partial-breast irradiation(PBI) came up. Many clinical trials related with accelerated partial-breast irradiation using a variety of radiotherapeutic techniques such as interstitial brachytherapy (IBT), MammoSite Radiation Therapy System, intraoperative radiotherapy(IORT), threedimensional conformal radiotherapy(3-DCRT)and intensity modulated radiation therapy(IMRT) in selected patients have been carried out. Accelerated partial-breast irradiation that provides faster, more convenient treat-ment demonstrates local control rate and safety comparable to that of whole breast irradiation. Partial breast irradiation may be an alternative way to whole breast radiotherapy and will be one of the standard treatments in women with early breast cancer seeking breast conservation.     

Dosimetric comparison of proton and photon three-dimensional, conformal, external beam accelerated partial breast irradiation techniques

PURPOSE: To compare the dosimetry of proton and photon-electron three-dimensional, conformal, external beam accelerated partial breast irradiation (3D-CPBI). METHODS AND MATERIALS: Twenty-four patients with fully excised, Stage I breast cancer treated with adjuvant proton 3D-CPBI had treatment plans generated using the mixed-modality, photon-electron 3D-CPBI technique. To facilitate dosimetric comparisons, planning target volumes (PTVs; lumpectomy site plus 1.5-2.0 cm margin) and prescribed dose (32 Gy) were held constant. Plans were optimized for PTV coverage and normal tissue sparing. RESULTS: Proton and mixed-modality plans both provided acceptable PTV coverage with 95% of the PTV receiving 90% of the prescribed dose in all cases. Both techniques also provided excellent dose homogeneity with a dose maximum exceeding 110% of the prescribed dose in only one case. Proton 3D-CPBI reduced the volume of nontarget breast tissue receiving 50% of the prescribed dose by an average of 36%. Statistically significant reductions in the volume of total ipsilateral breast receiving 100%, 75%, 50%, and 25% of the prescribed dose were also observed. The use of protons resulted in small, but statistically significant, reductions in the radiation dose delivered to 5%, 10%, and 20% of ipsilateral and contralateral lung and heart. The nontarget breast tissue dosimetric advantages of proton 3D-CPBI were not dependent on tumor location, breast size, PTV size, or the ratio of PTV to breast volume. CONCLUSIONS: Compared to photon-electron 3D-CPBI, proton 3D-CPBI significantly reduces the volume of irradiated nontarget breast tissue. Both approaches to accelerated partial breast irradiation offer exceptional lung and heart sparing.     

乳腺癌保乳术后加速部分乳腺照射的研究进展

传统的乳腺癌保乳术后放疗是对全乳腺进行5周-6周的放疗。随着放射治疗技术的发展,加速部分乳腺照射可能会成为另一选择。该文就加速部分乳腺照射在乳腺癌治疗中的研究进展作一综述。     

MRI定位对乳腺癌保乳术后部分乳腺照射的靶区和剂量的影响

目的:比较乳腺癌保乳术后仰卧位CT与MRI定位图像的靶区和剂量的差异,探讨MRI定位在保乳术后部分乳腺照射中的应用价值。方法:29例早期乳腺癌患者保乳术后放疗前在仰卧位下行CT及MRI定位扫描,分别对CT与MRI图像上的瘤床进行术腔可视化评分(CVS),勾画瘤床(TB)、临床靶区(CTV)、计划靶区(PTV),并基于C...     

Early outcomes data for accelerated partial breast irradiation using balloon brachytherapy

Accelerated partial breast irradiation has been investigated in selected patients with early-stage breast cancer. Accelerated partial breast irradiation limits the radiation target to the volume of tissue immediately surrounding the lumpectomy cavity and reduces the overall treatment time from approximately 6 weeks to 5 days. Balloon brachytherapy was introduced in 2000. Since that time, several clinical experiences have demonstrated excellent outcomes in carefully selected patients. Modern intracavitary brachytherapy offers patients with early-stage breast cancer a promising new option for radiation therapy. This treatment appears to offer high rates of local control with minimal toxicity. Newer multilumen devices allow optimal target coverage while minimizing the dose delivered to the skin and chest wall.     

Current status of accelerated partial breast irradiation

Accelerated partial breast irradiation (APBI) is a radiotherapy method used in breast-conserving therapy. In APBI, the tumor bed is topically irradiated over a short period after breast-conserving surgery. The fundamental concept underlying APBI is that more than 70% of ipsilateral breast tumor recurrence occurs in the neighborhood of the original tumor, and that hypofractionated radiotherapy can be applied safely when the irradiated volume is small enough. It is expected to reduce the time and cost required for conventional whole breast irradiation while maintaining equivalent local control. Several techniques including multicatheter interstitial brachytherapy, intracavitary brachytherapy, intraoperative radiation therapy, and 3D conformal external beam radiation therapy have been proposed, and each of them has its own advantages and drawbacks. Although APBI is increasingly used in the United States and Europe, and the short-term results are promising, its equivalence with whole breast radiation therapy is not fully established. In addition, because the average breast size in Japan is considerably smaller than in the West world, the application of APBI to Japanese patients is technically more challenging. At this point, APBI is still an investigational treatment in Japan, and the optimal method of radiation delivery as well as its long-term efficacy and safety should be clarified in clinical trials.     

Biologic comparison of partial breast irradiation protocols

PURPOSE: To analyze the dose/fractionation schedules currently used in ongoing clinical trials of partial breast irradiation (PBI) by comparing their biologically effective dose (BED) values to those of three standard whole breast protocols commonly used after segmental mastectomy in the treatment of breast cancer. METHODS AND MATERIALS: The BED equation derived from the linear-quadratic model for radiation-induced cell killing was used to calculate the BEDs for three commonly used whole breast radiotherapy regimens, in addition to a variety of external beam radiotherapy, as well as high-dose-rate and low-dose-rate brachytherapy, PBI protocols. RESULTS: The BED values of most PBI protocols resulted in tumor control BEDs roughly equivalent to a 50-Gy standard treatment, but consistently lower than the BEDs for regimens in which the tumor bed receives a total dose of either 60 Gy or 66 Gy. The BED values calculated for the acute radiation responses of erythema and desquamation were nearly all lower for the PBI schedules, and the late-response BEDs for most PBI regimens were in a similar range to the BEDs for the standard treatments. CONCLUSION: Biologically effective dose modeling raises the concern that inadequate doses might be delivered by PBI to ensure optimal in-field tumor control.