Accelerated partial breast irradiation utilizing balloon brachytherapy techniques

Stereotactic partial breast irradiation in primary breast cancer: A comprehensive review of the current status and future directions

In selected low-risk breast cancer patients, accelerated partial breast irradiation (APBI) may represent an alternative option to the whole breast irradiation to reduce the volume of irradiated breast and total treatment duration. In the last few years, preliminary data from clinical trials showed that stereotactic partial breast radiotherapy may have the advantage to be less invasive compared to other APBI techniques, with preliminary good results in terms of local toxicity and cosmesis: the use of magnetic resonance, fiducial markers in the tumor bed, and new breast devices support both a precise definition of the target and radiation planning.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021257856, identifier CRD42021257856.

Preliminary Results of a Randomized Study on Postmenopausal Women With Early Stage Breast Cancer: Adjuvant Hypofractionated Whole Breast Irradiation Versus Accelerated Partial Breast Irradiation (HYPAB Trial)

BACKGROUND

The purpose of this study was to report preliminary data of a randomized phase III trial comparing hypofractionated whole breast irradiation (HWBI) and accelerated partial breast irradiation (APBI) using volumetric modulated arc therapy (VMAT).

MATERIAL AND METHODS

The HYPAB trial enrolled postmenopausal women with biopsy-proven infiltrating breast cancer, clinically negative axilla, single T1 to T2 tumors, who were treated with breast-conserving surgery. Patients were randomized 1:1 after surgery to HWBI (40.5 Gy whole breast, 48.0 Gy to surgical bed, 15 fractions over 3 weeks) or APBI (30 Gy delivered in 5 fractions of 6 Gy given on alternate days on the surgical bed). Cosmetic outcome was the primary end point of the study.

RESULTS

A total of 172 patients were enrolled. After a median follow-up of 36 months, 5 local failures and 3 locoregional failures were recorded, with no difference between the 2 treatment arms. Use of HWBI as compared with APBI was significantly correlated with increased incidence of overall (62% vs. 14%; P < .001) and grade 2 (18% vs. 1%; P < .001) acute skin toxicity. APBI was correlated with a lower incidence of overall late toxicity as compared with HWBI (18% vs. 41%; P = .001), but no significant difference was found in term of occurrence of grade 2 events (1% vs. 4%; P = NS). At comparative assessment between baseline and post-radiotherapy evaluation, impairment in cosmetic outcome was reported in 19 (11%) patients. Owing to premature closure of the study, no per-protocol comparison between the treatment arms was performed.

CONCLUSION

APBI with the VMAT technique is safe and feasible, with lower acute toxicity when compared with HWBI.

Partial breast irradiation with CyberKnife after breast conserving surgery: a pilot study in early breast cancer

BACKGROUND

Local recurrences after breast conserving treatment are mainly close to the original tumor site, and as such shorter fractionation strategies focused on and nearest mammary gland, i.e. accelerated partial breast irradiation (APBI), have been developed. Stereotactic APBI has been attempted, although there is little experience using CyberKnife (CK) for early breast cancer.

METHODS

This pilot study was designed to assess the feasibility of CK-APBI on 20 evaluable patients of 29 eligible, followed for 2 years. The primary endpoint was acute/sub-acute toxicity; secondary endpoints were late toxicity and the cosmetic result.

RESULTS

Mean pathological tumor size was 10.5 mm (±4.3, range 3-18), 8 of these patients were classified as LumA-like, 11 as LumB-like, and 1 as LumB-HER2-enriched. Using CK-APBI with Iris, the treatment time was approximately 60 min (range~ 35 to ~ 120). All patients received 30 Gy in five fractions delivered to the PTV. The median number of beams was 180 (IQR 107-213; range:56-325) with a median PTV isodose prescription of 86.0% (IQR 85.0-88.5; range:82-94). The median PTV was 88.1 cm3 (IQR 63.8-108.6; range:32.3-238.8). The median breast V100 and V50 was 0.6 (IQR 0.1-1.5; range:0-13) and 18.6 (IQR 13.1-21.7; range:7.5-37), respectively. The median PTV minimum dose was 26.2 Gy (IQR 24.7-27.6; range 22.3-29.3). Mild side effects were recorded during the period of observation. Cosmetic evaluations were performed by three observers from the start of radiotherapy up to 2 years. Patients' evaluation progressively increase from 60% to 85% of excellent rating; this trend was similar to that of external observer.

CONCLUSIONS

These preliminary results showed the safe feasibility of CK-APBI in early breast cancer, with mild acute and late toxicity and very good cosmetic results.

TRIAL REGISTRATION

The present study is registered at Clinicaltrial.gov ( NCT02896322 ). Retrospectively egistered August 4, 2016.

Clinical outcomes with the MammoSite radiation therapy system: results of a prospective trial

OBJECTIVE

The purpose of this study was to report the treatment-induced adverse events and cosmetic and treatment outcomes of accelerated partial breast irradiation (APBI) delivered with the MammoSite radiation therapy system (RTS) in breast cancer patients undergoing breast-conserving therapy (BCT).

METHODS

This is a prospective clinical trial that was approved by the institutional review board. The study included female breast cancer patients undergoing breast-conserving therapy in the form of surgery and APBI delivered with the MammoSite RTS. Patients and tumor characteristics, treatment-induced acute adverse events based on the Common Toxicity Criteria for Adverse Events (CTCAE) version 2.0, chronic AEs according to Radiation Therapy Oncology Group (RTOG) scale, treatment outcomes (including local control, disease-free survival, and overall survival), and cosmetic outcomes are reported.

RESULTS

The study included 36 eligible patients treated consecutively in our institution between November 2003 and August 2009. The age range was 45-83 years. A total of 29 patients had invasive disease (median size 1.1 cm), while 7 patients had in situ disease only (median size 0.8 cm). The skin distance in most of the patients (91.7 %) was ≥1 cm; only three patients (8.3 %) had skin distance <1 cm. The median balloon diameter was 5 cm (range 4-6 cm). At a median follow-up of 42 months (range 4-65 months), local control, disease-free survival, and overall survival were 100 %. None of the patients experienced any grade 3 or 4 toxicities; 16.7 and 5.6 % of the patients had late grade 2 fibrosis and telangiectasia, respectively. At last follow-up, cosmetic outcome was rated as good or excellent in 94 % of the patients.

CONCLUSION

APBI delivered with the MammoSite RTS is a feasible, tolerable, and effective treatment modality. Multicenter, randomized, controlled clinical trials with a larger number of patients are required for verification.

Comparative dosimetric findings using accelerated partial breast irradiation across five catheter subtypes

Purpose

Accelerated partial breast irradiation (APBI) with balloon and strut adjusted volume implants (SAVI) show promising results with excellent tumor control and minimal toxicity. Knowing the factors that contribute to a high skin dose, rib dose, and D₉₅ coverage may reduce toxicity, improve tumor control, and help properly predict patient outcomes following APBI.

Methods and materials

A retrospective analysis of 594 patients treated with brachytherapy based APBI at a single institution from May 2008 to September 2014 was grouped by applicator subtype. Patients were treated to a total of 34 Gy (3.4 Gy x 10 fractions over 5 days delivered BID) targeting a planning target volume (PTV) 1.0 cm beyond the lumpectomy cavity using a high dose rate source.

Results

SAVI devices had the lowest statistically significant values of D_maxSkin (81.00 ± 29.83), highest values of D₉₀ (101.50 ± 3.66), and D₉₅ (96.09 ± 4.55). SAVI-mini devices had the lowest statistically significant values of D_maxRib (77.66 ± 32.92) and smallest V₁₅₀ (18.01 ± 3.39). Multi-lumen balloons were able to obtain the smallest V₂₀₀ (5.89 ± 2.21). Strut-based applicators were more likely to achieve a D_maxSkin and a D_maxRib less than or equal to 100 %. The effect of PTV on V₁₅₀ showed a strong positive relationship (p < .001). PTV and D_maxSkin showed a weak negative relationship in multi-lumen applicators (p = .016) and SAVI-mini devices (p < .001). PTV and D_maxRib showed a weak negative relationship in multi-lumen applicators (p = .009), SAVI devices (p < .001), and SAVI-mini devices (p < .001).

Conclusion

PTV volume is strongly correlated with V₁₅₀ in all devices and V₂₀₀ in strut based devices. Larger PTV volumes result in greater V₁₅₀ and V₂₀₀, which could help predict potential risks for hotspots and resulting toxicities in these devices. PTV volume is also weakly negatively correlated with max skin dose and max rib dose, meaning that as the PTV volumes increase one can expect slightly smaller max skin and rib doses. Strut based applicators are significantly more effective in keeping skin and rib dose constraints under 125 and 100 % when compared to any balloon based applicator.

Brachytherapy in breast cancer: an effective alternative

Breast conserving surgery (BCS) with following external beam radiation therapy (EBRT) of the conserved breast has become widely accepted in the last decades for the treatment of early invasive breast cancer. The standard technique of EBRT after BCS is to treat the whole breast up to a total dose of 42.5 to 50 Gy. An additional dose is given to treated volume as a boost to a portion of the breast. In the early stage of breast cancer, research has shown that the area requiring radiation treatment to prevent the cancer from local recurrence is the breast tissue that surrounds the area where the initial cancer was removed. Accelerated partial breast irradiation (APBI) is an approach that treats only the lumpectomy bed plus a 1-2 cm margin rather than the whole breast and as a result allows accelerated delivery of the radiation dose in four to five days. There has been a growing interest for APBI and various approaches have been developed under phase I-III clinical studies; these include multicatheter interstitial brachytherapy, balloon catheter brachytherapy, conformal external beam radiation therapy (3D-EBRT) and intra-operative radiation therapy (IORT). Balloon-based brachytherapy approaches include MammoSite, Axxent electronic brachytherapy, Contura, hybrid brachytherapy devices. Another indication for breast brachytherapy is reirradiation of local recurrence after mastectomy. Published results of brachytherapy are very promising. We discuss the current status, indications, and technical aspects of breast cancer brachytherapy.

Transforming growth factor β-1 (TGF-β1) is a serum biomarker of radiation induced fibrosis in patients treated with intracavitary accelerated partial breast irradiation: preliminary results of a prospective study

PURPOSE

To examine a relationship between serum transforming growth factor β -1 (TGF-β1) values and radiation-induced fibrosis (RIF).

METHODS AND MATERIALS

We conducted a prospective analysis of the development of RIF in 39 women with American Joint Committee on Cancer stage 0-I breast cancer treated with lumpectomy and accelerated partial breast irradiation via intracavitary brachytherapy (IBAPBI). An enzyme-linked immunoassay (Quantikine, R&D, Minneapolis, MN) was used to measure serum TGF-β1 before surgery, before IBAPBI, and during IBAPBI. Blood samples for TGF-β1 were also collected from 15 healthy, nontreated women (controls). The previously validated tissue compliance meter (TCM) was used to objectively assess RIF.

RESULTS

The median time to follow-up for 39 patients was 44 months (range, 5-59 months). RIF was graded by the TCM scale as 0, 1, 2, and 3 in 5 of 20 patients (25%), 6 of 20 patients (30%), 5 of 20 patients (25%), and 4 of 20 patients (20%), respectively. The mean serum TGF-β1 values were significantly higher in patients before surgery than in disease-free controls, as follows: all cancer patients (30,201 ± 5889 pg/mL, P=.02); patients with any type of RIF (32,273 ± 5016 pg/mL, P<.0001); and women with moderate to severe RIF (34,462 ± 4713 pg/mL, P<0.0001). Patients with moderate to severe RIF had significantly elevated TGF-β1 levels when compared with those with none to mild RIF before surgery (P=.0014) during IBAPBI (P≤0001), and the elevation persisted at 6 months (P≤.001), 12 months (P≤.001), 18 months (P≤.001), and 24 months (P=.12). A receiver operating characteristic (ROC) curve of TGF-β1 values predicting moderate to severe RIF was generated with an area under the curve (AUC)ROC of 0.867 (95% confidence interval 0.700-1.000). The TGF-β1 threshold cutoff was determined to be 31,000 pg/mL, with associated sensitivity and specificity of 77.8% and 90.0%, respectively.

CONCLUSIONS

TGF-β1 levels correlate with the development of moderate to severe RIF. The pre-IBAPBI mean TGF-β1 levels can serve as an early biomarker for the development of moderate to severe RIF after IBAPBI.

Can we improve the dose distribution for single or multi-lumen breast balloons used for Accelerated Partial Breast Irradiation?

Purpose

The aim of the study was to verify dose distribution parameters for multi-lumen, and artificially created single-lumen balloon applicator used for the same patient with two optimization algorithms: inverse planning simulated annealing (IPSA) and dose point optimization with distance option.

Material and methods

Group of 24 patients with multi-lumen balloon applied were investigated. Each patient received 10 fractions of 3.4 Gy (2 fractions daily). For every patient, four treatment plans were prepared. Firstly, for five-lumen balloon optimized with IPSA algorithm and optimization parameters adjusted for each case. Secondly, for the same applicator optimized with dose point optimization and distant option. Two other plans were prepared for single-lumen applicator, created by removing four peripheral lumens, optimized with both algorithms.

Results

The highest D₉₅ parameter was obtained for plans optimized with IPSA algorithm, mean value 99.3 percent of prescribed dose, and it was significantly higher than plans optimized with dose point algorithm (mean = 83.50%, p < 0.0001), IPSA single-lumen balloon plan (mean = 83.50%, p = 0.0037) and optimized to dose point single-lumen balloon (mean = 85.51%, p < 0.0001). There were no statistically significant differences concerning maximum doses distributed to skin surface for neither application nor optimization method. Volumes receiving 200% of prescribed dose in PTV were higher for multi-lumen balloon dose point optimized plans (mean = 8.78%), than for other plans (IPSA multi-lumen balloon plan: mean = 7.37%, p < 0.0001, single-lumen IPSA: mean = 7.20%, p < 0.0001, single-lumen dose point: mean = 7.19%, p < 0.0001).

Conclusions

Basing on performed survey, better dose distribution parameters are obtained for patients with multi-lumen balloon applied and optimized using IPSA algorithm with individualized optimization parameters.

Dosimetric and geometric evaluation of a novel stereotactic radiotherapy device for breast cancer: the GammaPod™

PURPOSE

A dedicated stereotactic gamma irradiation device, the GammaPod™ from Xcision Medical Systems, was developed specifically to treat small breast cancers. This study presents the first evaluation of dosimetric and geometric characteristics from the initial prototype installed at University of Maryland Radiation Oncology Department.

METHODS

The GammaPod™ stereotactic radiotherapy device is an assembly of a hemi-spherical source carrier containing 36 (60)Co sources, a tungsten collimator, a dynamically controlled patient support table, and the breast immobilization system which also functions as a stereotactic frame. The source carrier contains the sources in six columns spaced longitudinally at 60° intervals and it rotates together with the variable-size collimator to form 36 noncoplanar, concentric arcs focused at the isocenter. The patient support table enables motion in three dimensions to position the patient tumor at the focal point of the irradiation. The table moves continuously in three cardinal dimensions during treatment to provide dynamic shaping of the dose distribution. The breast is immobilized using a breast cup applying a small negative pressure, where the immobilization cup is embedded with fiducials also functioning as the stereotactic frame for the breast. Geometric and dosimetric evaluations of the system as well as a protocol for absorbed dose calibration are provided. Dosimetric verifications of dynamically delivered patient plans are performed for seven patients using radiochromic films in hypothetical preop, postop, and target-in-target treatment scenarios.

RESULTS

Loaded with 36 (60)Co sources with cumulative activity of 4320 Ci, the prototype GammaPod™ unit delivers 5.31 Gy/min at the isocenter using the largest 2.5 cm diameter collimator. Due to the noncoplanar beam arrangement and dynamic dose shaping features, the GammaPod™ device is found to deliver uniform doses to targets with good conformity. The spatial accuracy of the device to locate the radiation isocenter is determined to be less than 1 mm. Single shot profiles with 2.5 cm collimator are measured with radiochromic film and found to be in good agreement with respect to the Monte Carlo based calculations (congruence of FWHM less than 1 mm). Dosimetric verifications corresponding to all hypothetical treatment plans corresponding to three target scenarios for each of the seven patients demonstrated good agreement with gamma index pass rates of better than 97% (99.0% ± 0.7%).

CONCLUSIONS

Dosimetric evaluation of the first GammaPod™ stereotactic breast radiotherapy unit was performed and the dosimetric and spatial accuracy of this novel technology is found to be feasible with respect to clinical radiotherapy standards. The observed level of agreement between the treatment planning system calculations and dosimetric measurements has confirmed that the system can deliver highly complex treatment plans with remarkable geometric and dosimetric accuracy.

Dose correction in lung for HDR breast brachytherapy

Purpose

To evaluate the dosimetric impact of lung tissue in Ir-192 APBI.

Material and methods

In a 40 × 40 × 40 cm³ water tank, an Accelerated Partial Breast Irradiation (APBI) brachytherapy balloon inflated to 4 cm diameter was situated directly below the center of a 30 × 30 × 1 cm³ solid water slab. Nine cm of solid water was stacked above the 1 cm base. A parallel plate ion chamber was centered above the base and ionization current measurements were taken from the central HDR source dwell position for channels 1, 2, 3 and 5 of the balloon. Additional ionization data was acquired in the 9 cm stack at 1 cm increments. A comparable data set was also measured after replacing the 9 cm solid water stack with cork slabs. The ratios of measurements in the two phantoms were calculated and compared to predicted results of a commercial treatment planning system.

Results

Lower dose was measured in the cork within 1 cm of the cork/solid water interface possibly due to backscatter effects. Higher dose was measured beyond 1 cm from the cork/solid water interface, increasing with path length up to 15% at 9 cm depth in cork. The treatment planning system did not predict either dose effect.

Conclusions

This study investigates the dosimetry of low density material when the breast is treated with Ir-192 brachytherapy. HDR dose from Ir-192 in a cork media is shown to be significantly different than in unit density media. These dose differences are not predicted in most commercial brachytherapy planning systems. Empirical models based on measurements could be used to estimate lung dose associated with HDR breast brachytherapy.

Accelerated partial breast irradiation: the need for well-defined patient selection criteria, improved volume definitions, close follow-up and discussion of salvage treatment

Breast-conserving therapy, including whole breast irradiation, has become a well-established alternative to mastectomy in early-stage breast cancer patients, with similar survival rates and better cosmetic outcome. However, many women are still treated with mastectomy, due to logistical issues related to the long course of radiotherapy (RT). To reduce mastectomy rates and/or omission of RT after breast-conserving surgery, shorter, hypofractionated RT treatments have been introduced. More recently, the necessity of routinely treating the entire breast in all patients has been questioned, leading to the development of partial breast radiotherapy. With accelerated partial breast irradiation (APBI) these two approaches have been combined: the tumor bed with a 1-2 cm margin is irradiated either intra-operatively (single fraction) or postoperatively over 5-15 days. Different techniques have been developed, including interstitial brachytherapy, intra-cavity brachytherapy, intra-operative radiotherapy and external beam radiotherapy. These techniques are being evaluated in several ongoing phase III studies. Since its introduction, APBI has been the subject of continuous debate. ASTRO and GEC-ESTRO have published guidelines for patient selection for APBI, and strongly recommend that APBI be carried out within ongoing clinical trials. Recently, the patient selection criteria for APBI have also been up for debate, following the publication of results from different groups that do/do not confirm a difference in recurrence risk among the ASTRO defined risk groups. This paper reviews the different APBI techniques, current recommendations for patient selection, available clinical data and ongoing clinical trials. A case report is included to illustrate the need for careful follow-up of patients treated with APBI.

Brachytherapy in accelerated partial breast irradiation (APBI) - review of treatment methods

Breast conserving surgery (BCS) with following radiotherapy (EBRT) of the conserved breast became widely accepted in the last decades as the treatment of early invasive breast cancer. In an early stage of breast cancer, research has shown that the area requiring radiation treatment to prevent cancer from local recurrence is the breast tissue that surrounds the area where the initial cancer was removed. Accelerated partial breast irradiation (APBI) is an approach that treats only the lumpectomy bed with 1-2 cm margin, rather than the whole breast and as a result allows accelerated delivery of the radiation dose in four to five days. Published results of APBI are very promising. It is evident that APBI will play a role in the management of a selected group of early breast cancer. We discuss current status, indications, technical aspects and recently published results of APBI using different brachytherapy techniques.

Breast cancer recurrence after inadvertent malpositioning of a partial breast radiation catheter

Accelerated partial breast irradiation (APBI) is an alternative to receiving whole breast radiation in carefully selected patients. Because breast cancer local recurrence rates are low and follow-up has been short-term, the exact cause of recurrences after APBI has been difficult to evaluate. We report the first case of documented radiation balloon catheter malpositioning that resulted in local recurrence. Patients undergo CT imaging of the breast after radiation balloon catheter placement for radiotherapy treatment planning, which evaluates adequate conformance of the balloon to the surrounding breast parenchyma and confirms a >7 mm distance between the balloon surface and the skin surface. Although true local recurrences are rare in appropriately selected partial breast irradiation candidates, inadvertent malpositioning of the radiation treatment catheter can increase the risk. This case is presented to illustrate the importance of comparing CT radiation planning images, with treatment catheter in place, to the original diagnostic breast imaging studies to confirm proper catheter positioning (in addition to measuring balloon to skin distance and conformance) prior to initiating radiotherapy.

Partial breast irradiation techniques in early breast cancer

Whole breast irradiation represents an integral part of combined breast-conserving treatment of early breast cancer. A new concept includes replacing traditionally fractionated whole breast postoperative radiotherapy by accelerated partial breast irradiation. The latter involves a variety of techniques and may be applied intraoperatively or shortly after the surgery. The intraoperative techniques include photon or electron external beam irradiation and interstitial high dose rate (HDR) brachytherapy, whereas the postoperative techniques comprise interstitial brachytherapy, be it HDR, pulse dose rate (PDR) or low dose rate (LDR), intracavitary brachytherapy and external beam radiotherapy using electrons, photons or protons. This article presents accelerated partial breast irradiation techniques, ongoing phase III trials evaluating their value and recommendations for clinical practice.

Image guided, adaptive, accelerated, high dose brachytherapy as model for advanced small volume radiotherapy

Brachytherapy has consistently provided a very conformal radiation therapy modality. Over the last two decades this has been associated with significant improvements in imaging for brachytherapy applications (prostate, gynecology), resulting in many positive advances in treatment planning, application techniques and clinical outcome. This is emphasized by the increased use of brachytherapy in Europe with gynecology as continuous basis and prostate and breast as more recently growing fields. Image guidance enables exact knowledge of the applicator together with improved visualization of tumor and target volumes as well as of organs at risk providing the basis for very individualized 3D and 4D treatment planning. In this commentary the most important recent developments in prostate, gynecological and breast brachytherapy are reviewed, with a focus on European recent and current research aiming at the definition of areas for important future research. Moreover the positive impact of GEC-ESTRO recommendations and the highlights of brachytherapy physics are discussed what altogether presents a full overview of modern image guided brachytherapy. An overview is finally provided on past and current international brachytherapy publications focusing on "Radiotherapy and Oncology". These data show tremendous increase in almost all research areas over the last three decades strongly influenced recently by translational research in regard to imaging and technology. In order to provide high level clinical evidence for future brachytherapy practice the strong need for comprehensive prospective clinical research addressing brachytherapy issues is high-lighted.

Objective method to report planner-independent skin/rib maximal dose in balloon-based high dose rate (HDR) brachytherapy for breast cancer

PURPOSE

An objective method was proposed and compared with a manual selection method to determine planner-independent skin and rib maximal dose in balloon-based high dose rate (HDR) brachytherapy planning.

METHODS

The maximal dose to skin and rib was objectively extracted from a dose volume histogram (DVH) of skin and rib volumes. A virtual skin volume was produced by expanding the skin surface in three dimensions (3D) external to the breast with a certain thickness in the planning computed tomography (CT) images. Therefore, the maximal dose to this volume occurs on the skin surface the same with a conventional manual selection method. The rib was also delineated in the planning CT images and its maximal dose was extracted from its DVH. The absolute (Abdiff = [D(max) Man - D (max)DVH]) and relative (Rediff[%] = 100 x ([D(max)Man-D(max)DVH])/D(max)DVH) maximal skin and rib dose differences between the manual selection method (D(max)Man) and the objective method (D(max)DVH) were measured for 50 balloon-based HDR (25 MammoSite and 25 Contura) patients.

RESULTS

The average +/- standard deviation of maximal dose difference was 1.67% +/- 1.69% of the prescribed dose (PD). No statistical difference was observed between MammoSite and Contura patients for both Abdiff and Rediff[%] values. However, a statistically significant difference (p value < 0.0001) was observed in maximal rib dose difference compared with maximal skin dose difference for both Abdiff (2.30% +/- 1.71% vs 1.05% +/- 1.43%) and Rediff[%] (2.32% +/- 1.79% vs 1.21% +/- 1.41%). In general, rib has a more irregular contour and it is more proximally located to the balloon for 50 HDR patients. Due to the inverse square law factor, more dose difference was observed in higher dose range (D(max) > 90%) compared with lower dose range (D(max) < 90%): 2.16% +/- 1.93% vs 1.19% +/- 1.25% with p value of 0.0049. However, the Rediff[%] analysis eliminated the inverse square factor and there was no statistically significant difference (p value = 0.8931) between high and low dose ranges.

CONCLUSIONS

The objective method using volumetric information of skin and rib can determine the planner-independent maximal dose compared with the manual selection method. However, the difference was < 2% of PD, on average, if appropriate attention is paid to selecting a manual dose point in 3D planning CT images.

Determination of exit skin dose for 192Ir intracavitary accelerated partial breast irradiation with thermoluminescent dosimeters

PURPOSE

Intracavitary accelerated partial breast irradiation (APBI) has become a popular treatment for early stage breast cancer in recent years due to its shortened course of treatment and simplified treatment planning compared to traditional external beam breast conservation therapy. However, the exit dose to the skin is a major concern and can be a limiting factor for these treatments. Most treatment planning systems (TPSs) currently used for high dose-rate (HDR) 192Ir brachytherapy overestimate the exit skin dose because they assume a homogeneous water medium and do not account for finite patient dimensions. The purpose of this work was to quantify the TPS overestimation of the exit skin dose for a group of patients and several phantom configurations.

METHODS

The TPS calculated skin dose for 59 HDR 192Ir APBI patients was compared to the skin dose measured with LiF:Mg,Ti thermoluminescent dosimeters (TLDs). Additionally, the TPS calculated dose was compared to the TLD measured dose and the Monte Carlo (MC) calculated dose for eight phantom configurations. Four of the phantom configurations simulated treatment conditions with no scattering material beyond the point of measurement and the other four configurations simulated the homogeneous scattering conditions assumed by the TPS. Since the calibration TLDs for this work were irradiated with 137Cs and the experimental irradiations were performed with 192Ir, experiments were performed to determine the intrinsic energy dependence of the TLDs. Correction factors that relate the dose at the point of measurement (center of TLD) to the dose at the point of interest (basal skin layer) were also determined and applied for each irradiation geometry.

RESULTS

The TLD intrinsic energy dependence for 192Ir relative to 137Cs was 1.041 +/- 1.78%. The TPS overestimated the exit skin dose by an average of 16% for the group of 59 patients studied, and by 9%-15% for the four phantom setups simulating treatment conditions. For the four phantom setups simulating the conditions assumed by the TPS, the TPS calculated dose agreed well with the TLD and MC results (within 3% and 1%, respectively). The inverse square geometry correction factor ranged from 1.023 to 1.042, and an additional correction factor of 0.978 was applied to account for the lack of charged particle equilibrium in the TLD and basal skin layer.

CONCLUSIONS

TPS calculations that assume a homogeneous water medium overestimate the exit skin dose for intracavitary APBI treatments. It is important to determine the actual skin dose received during intracavitary APBI to determine the skin dose-response relationship and establish dose limits for optimal skin sparing. This study has demonstrated that TLDs can measure the skin dose with an expanded uncertainty (k = 2) of 5.6% when the proper corrections are applied.

Patient selection for accelerated partial-breast irradiation (APBI) after breast-conserving surgery: recommendations of the Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) breast cancer working group based on clinical evidence (2009)

PURPOSE

To give recommendations on patient selection criteria for the use of accelerated partial-breast irradiation (APBI) based on available clinical evidence complemented by expert opinion.

METHODS AND MATERIALS

Overall, 340 articles were identified by a systematic search of the PubMed database using the keywords "partial-breast irradiation" and "APBI". This search was complemented by searches of reference lists of articles and handsearching of relevant conference abstracts and book chapters. Of these, 3 randomized and 19 prospective non-randomized studies with a minimum median follow-up time of 4 years were identified. The authors reviewed the published clinical evidence on APBI, complemented by relevant clinical and pathological studies of standard breast-conserving therapy and, through a series of personal communications, formulated the recommendations presented in this article.

RESULTS

The GEC-ESTRO Breast Cancer Working Group recommends three categories guiding patient selection for APBI: (1) a low-risk group for whom APBI outside the context of a clinical trial is an acceptable treatment option; including patients ageing at least 50 years with unicentric, unifocal, pT1-2 (<or=30 mm) pN0, non-lobular invasive breast cancer without the presence of an extensive intraductal component (EIC) and lympho-vascular invasion (LVI) and with negative surgical margins of at least 2mm, (2) a high-risk group, for whom APBI is considered contraindicated; including patients ageing <or=40 years; having positive margins, and/or multicentric or large (>30 mm) tumours, and/or EIC positive or LVI positive tumours, and/or 4 or more positive lymph nodes or unknown axillary status (pNx), and (3) an intermediate-risk group, for whom APBI is considered acceptable only in the context of prospective clinical trials.

CONCLUSIONS

These recommendations will provide a clinical guidance regarding the use of APBI outside the context of a clinical trial before large-scale randomized clinical trial outcome data become available. Furthermore they should promote further clinical research focusing on controversial issues in the treatment of early-stage breast carcinoma.

Accelerated partial-breast irradiation using high-dose-rate interstitial brachytherapy: 12-year update of a prospective clinical study

BACKGROUND AND PURPOSE

To report the 12-year updated results of accelerated partial-breast irradiation (APBI) using multicatheter interstitial high-dose-rate (HDR) brachytherapy (BT).

PATIENTS AND METHODS

Forty-five prospectively selected patients with T1N0-N1mi, nonlobular breast cancer without the presence of an extensive intraductal component and with negative surgical margins were treated with APBI after breast-conserving surgery (BCS) using interstitial HDR BT. A total dose of 30.3 Gy (n=8) and 36.4 Gy (n=37) in seven fractions within 4 days was delivered to the tumour bed plus a 1-2 cm margin. The median follow-up time was 133 months for surviving patients. Local and regional control, disease-free (DFS), cancer-specific (CSS), and overall survival (OS), as well as late side effects, and cosmetic results were assessed.

RESULTS

Four (8.9%) ipsilateral breast tumour recurrences were observed, for a 5-, 10-, and 12-year actuarial rate of 4.4%, 9.3%, and 9.3%, respectively. A total of two regional nodal failures were observed for a 12-year actuarial rate of 4.4%. The 12-year DFS, CSS, and OS was 75.3%, 91.1%, and 88.9%, respectively. Grade 3 fibrosis was observed in one patient (2.2%). No patient developed grade 3 teleangiectasia. Fat necrosis requiring surgical intervention occurred in one woman (2.2%). Cosmetic results were rated excellent or good in 35 patients (77.8%).

CONCLUSIONS

Twelve-year results with APBI using HDR multicatheter interstitial implants continue to demonstrate excellent long-term local tumour control, survival, and cosmetic results with a low-rate of late side effects.

A Contura catheter offers dosimetric advantages over a MammoSite catheter that increase the applicability of accelerated partial breast irradiation

PURPOSE

The purpose of this study was to determine whether a Contura catheter (SenoRx, Inc, Aliso Viejo, CA) can increase the applicability of accelerated partial breast irradiation.

METHODS AND MATERIALS

One hundred eighty-two women with early stage breast carcinomas were treated with postlumpectomy brachytherapy using a Contura multilumen catheter (n=45) or a MammoSite single-lumen catheter (Cytyc Corp, Marlborough, MA) (n=137). Hypothetical MammoSite catheter treatment plans were created for the Contura patients. Treatment planning goals were to (1) avoid a radiation "hot spot" in the skin and (2) have only a small air/fluid pocket next to the balloon.

RESULTS

The median followup was 16 months. Eighty-nine percent (40 of 45) of Contura plans satisfied both treatment planning goals vs. only 36% (16 of 45) of MammoSite plans (p<0.0001). A Contura catheter did not require explantation in 16% (7 of 45) of patients where balloon-to-skin spacing was only 3-6mm and 11% (5 of 45) of patients where there was an air/fluid pocket >10% of the planning target volume for plan evaluation (PTV_EVAL). A MammoSite catheter was explanted in 10% of cases where the minimum balloon-to-skin distance was <7mm and in 13% of cases where there was a large air/fluid pocket next to the balloon. Our incidence rates of acute toxicity with a Contura catheter were similar to those with a MammoSite catheter.

CONCLUSIONS

A Contura catheter provides important dosimetric advantages over a MammoSite catheter and does not require explantation in cases where balloon-to-skin spacing is only 3-6mm or an air/fluid pocket next to the balloon is >10% of PTV_EVAL.