MammoSite Brachytherapy Research Articles

Partial Breast Reirradiation for Patients With Ipsilateral Breast Tumor Recurrence After Initial Treatment With Breast Conservation for Early Stage Breast Cancer

PurposeAccelerated partial breast irradiation (APBI), including intraoperative radiation therapy (IORT), is an evidence-based treatment option in patients undergoing breast conserving surgery (BCS) for early-stage breast cancer. However, literature regarding reirradiation for patients with ipsilateral breast tumor recurrences (IBTR) is limited. This prospective study assessed the feasibility and efficacy of using APBI in patients who had prior whole breast irradiation. Methods and MaterialsThis was a single institution, prospective study of patients who were previously treated with BCS and adjuvant whole breast radiation. At the time of enrollment, all had unifocal IBTR, histologically confirmed invasive ductal carcinoma with negative margins after repeat BCS. Patients received either IORT in a single fraction at time of BCS or MammoSite brachytherapy twice daily over 5 days. Follow-up data and patient surveys were collected at 1, 3, 6, 9, and 12 months, then annually for at least a 5-year period. ResultsFrom 2008 to 2014, 13 patients were enrolled. Median time to recurrence after initial course of radiation was 12.5 years. Median follow-up after retreatment was 7.8 years. One patient in the IORT group had a subsequent tumor bed recurrence, yielding a local control of 92%. One patient had distant recurrence. At baseline, 680 reported excellent-good cosmesis compared with 42% at 5 years. All patients indicated total satisfaction with overall treatment experience. ConclusionsAPBI using IORT was well tolerated with excellent local control and may be a reasonable alternative to mastectomy for IBTR. Further study is needed to determine the most suitable candidates for this approach.

Unusual complications after MammoSite brachytherapy: out‐of‐field rib fracture and Mondor's disease

AbstractRecent reports have documented in‐field rib fractures as a rare complication of accelerated partial breast irradiation. Here, we report a case of an out‐of‐field rib fracture, with a maximum point dose of <50% of the prescribed dose, and Mondor's disease in a 61‐year‐old woman after MammoSite brachytherapy. This is the first case in the literature in which rib fractures occurred out‐of‐field, without trauma or risk factors. It also highlights a rare clinical entity, Mondor's disease, of which its recognition is important for radiation oncologists given its potential for tumor recurrence.

Prospective Comparison of Toxicity and Cosmetic Outcome After Accelerated Partial Breast Irradiation With Conformal External Beam Radiotherapy or Single-Entry Multilumen Intracavitary Brachytherapy

PurposeThis study aimed to prospectively characterize toxicity and cosmesis after accelerated partial breast irradiation (APBI) with 3-dimensional conformal radiation therapy (CRT) or single-entry, multilumen, intracavitary brachytherapy. Methods and materialsA total of 281 patients with pTis, pT1N0, or pT2N0 (≤3.0 cm) breast cancer treated with segmental mastectomy were prospectively enrolled from December 2008 through August 2014. APBI was delivered using 3-dimensional CRT (n = 29) or with SAVI (n = 176), Contura (n = 56), or MammoSite (n = 20) brachytherapy catheters. Patients were evaluated at protocol-specified intervals, at which time the radiation oncologist scored cosmetic outcome, toxicities, and recurrence status using a standardized template. ResultsThe median follow-up time is 41 months. Grade 1 seroma and fibrosis were more common with brachytherapy than with 3-dimensional CRT (50.4% vs 3.4% for seroma; P < .0001 and 66.3% vs 44.8% for fibrosis; P = .02), but grade 1 edema was more common with 3-dimensional CRT than with brachytherapy (17.2% vs 5.6%; P = .04). Grade 2 to 3 pain was more common with 3-dimensional CRT (17.2% vs 5.2%; P = .03). Actuarial 5-year rates of fair or poor radiation oncologist-reported cosmetic outcome were 9% for 3-dimensional CRT and 24% for brachytherapy (P = .13). Brachytherapy was significantly associated with inferior cosmesis on mixed model analysis (P = .003). Significant predictors of reduced risk of adverse cosmetic outcome after brachytherapy were D0.1cc (skin) ≤102%, minimum skin distance >5.1 mm, dose homogeneity index >0.54, and volume of nonconformance ≤0.89 cc. The 5-year ipsilateral breast recurrence was 4.3% for brachytherapy and 4.2% for 3-dimensional CRT APBI patients (P = .95). ConclusionsBrachytherapy APBI is associated with higher rates of grade 1 fibrosis and seroma than 3-dimensional CRT but lower rates of grade 1 edema and grade 2 to 3 pain than 3-dimensional CRT. Rates of radiation oncologist-reported fair or poor cosmetic outcomes are higher with brachytherapy. We identified dosimetric parameters that predict reduced risk of adverse cosmetic outcome after brachytherapy-based APBI. Ipsilateral breast recurrence was equivalent for brachytherapy and 3-dimensional CRT.

Increased Rates of Long-Term Complications after MammoSite Brachytherapy Compared with Whole Breast Radiation Therapy

Due to its short duration of therapy and low rates of local recurrence, women undergoing breast conservation are increasingly opting for partial breast irradiation with the MammoSite (Cytyc/Hologic) catheter. In early follow-up studies, few complications were reported. Few data, however, exist regarding longer-term complications. We compared the long-term local toxicities of MammoSite partial breast irradiation with those resulting from whole breast radiation. This was a retrospective study performed in a single academic medical center. All patients who underwent breast-conserving surgery between 2003 and 2008, who met institutional criteria for brachytherapy, were included. We compared women treated with MammoSite with patients treated with whole breast radiation therapy (WBRT). Endpoints included incidence of palpable masses at the lumpectomy site, telangiectasias, and local recurrence. Seventy-one MammoSite patients and 245 WBRT patients were well matched with regard to clinical characteristics. Median follow-up was 4 years. A palpable mass developed at the site of lumpectomy in 27% of the MammoSite patients compared with 7% of the WBRT patients (p < 0.0001). Telangiectasias developed more frequently in the MammoSite group than in the WBRT group (24% vs 4%, p < 0.001). Forty-two percent of patients treated with MammoSite developed a palpable mass, telangectasia, or both. Palpable masses and telangiectasias are frequent long-term complications after MammoSite brachytherapy and occur at a significantly higher rate after MammoSite brachytherapy than after WBRT. This increased rate of long-term local toxicity should be considered when counseling women on options for adjuvant radiation therapy after breast-conserving surgery.

Impact of partial versus whole breast radiation therapy on fatigue, perceived stress, quality of life and natural killer cell activity in women with breast cancer

IntroductionThis pilot study used a prospective longitudinal design to compare the effect of adjuvant whole breast radiation therapy (WBRT) versus partial breast radiation therapy (PBRT) on fatigue, perceived stress, quality of life and natural killer cell activity (NKCA) in women receiving radiation after breast cancer surgery.MethodsWomen (N = 30) with early-stage breast cancer received either PBRT, Mammosite brachytherapy at dose of 34 Gy 10 fractions/5 days, (N = 15) or WBRT, 3-D conformal techniques at dose of 50 Gy +10 Gy Boost/30 fractions, (N = 15). Treatment was determined by the attending oncologist after discussion with the patient and the choice was based on tumor stage and clinical need. Women were assessed prior to initiation of radiation therapy and twice after completion of radiation therapy. At each assessment, blood was obtained for determination of NKCA and the following instruments were administered: Perceived Stress Scale (PSS), Functional Assessment of Cancer Therapy-Fatigue (FACT-F), and Functional Assessment of Cancer Therapy-General (FACT-G). Hierarchical linear modeling (HLM) was used to evaluate group differences in initial outcomes and change in outcomes over time.ResultsFatigue (FACT-F) levels, which were similar prior to radiation therapy, demonstrated a significant difference in trajectory. Women who received PBRT reported progressively lower fatigue; conversely fatigue worsened over time for women who received WBRT. No difference in perceived stress was observed between women who received PBRT or WBRT. Both groups of women reported similar levels of quality of life (FACT-G) prior to initiation of radiation therapy. However, HLM analysis revealed significant group differences in the trajectory of quality of life, such that women receiving PBRT exhibited a linear increase in quality of life over time after completion of radiation therapy; whereas women receiving WBRT showed a decreasing trajectory. NKCA was also similar between therapy groups but additional post hoc analysis revealed that better quality of life significantly predicted higher NKCA regardless of therapy.ConclusionsCompared to WBRT, PBRT results in more rapid recovery from cancer-related fatigue with improved restoration of quality of life after radiation therapy. Additionally, better quality of life predicts higher NKCA against tumor targets, emphasizing the importance of fostering quality of life for women undergoing adjuvant radiation therapy.

The impact of uncertainties associated with MammoSite brachytherapy on the dose distribution in the breast

The MammoSite radiation therapy system is a novel technique for treatment of patients with early‐stage breast cancer. It was developed to overcome the longer schedules associated with external‐beam radiation therapy. It consists of a small balloon (4 cm in diameter) connected to an inflation channel and a catheter for the passage of a high dose rate 192Ir brachytherapy source. The device is placed into the tumor resection cavity and inflated with a mixture of saline and radiographic contrast agent to a size that fills the cavity. A high dose rate 192Ir source is driven into the balloon center using a remote afterloader to deliver the prescribed dose at a point 1 cm away from the balloon surface. There are several uncertainties that affect the dose distribution in the MammoSite brachytherapy. They include source position deviation, balloon deformation, and the concentration of the contrast medium inside the balloon. The purpose of this study is to investigate the extent of the dose perturbation for various concentrations of the contrast medium in a MammoSite balloon using Monte Carlo simulations and thermoluminescent dosimetry. This study also combines the impact of these uncertainties on the MammoSite treatment efficacy. The current study demonstrates that the combined uncertainties associated with the MammoSite brachytherapy technique — up to the value of 2 mm balloon deformation, 1 mm source deviation, and 15% contrast concentration — have no impact on the tumor control probability.PACS number: 87.53.‐j

Seroma is an Expected Consequence and not a Complication of MammoSite Brachytherapy

Seroma has long been listed as a complication of MammoSite brachytherapy. Palpable abnormalities are clinically apparent months after treatment and a vast majority of patients demonstrate seroma formation in radiologic studies. We embarked on this study to evaluate the actual sonographic incidence and eventual sonographic resolution, possible contributing factors, cosmesis, pain, and local control associated with seroma formation after MammoSite partial breast irradiation (PBI). We investigated 160 patients who underwent MammoSite PBI from 2002 to 2006 of whom 100 patients had serial sonographic information. Clinical and tumor variables, infection, pain, and cosmesis were investigated. Dosimetric data including volume of balloon, dose at balloon surface, and at skin were analyzed. After a median follow-up of 36 months, the incidence of sonographically confirmed post-radiation seroma was 78% within the first 1 year following radiation and steadily decreased with time. The average size of a seroma cavity was 2.3 cm (range 0.6-6 cm) with a decline to an average of 1.4 cm after 1 year, with complete resolution in 65% of patients at 2 years. No statistically significant correlation was found between patient characteristics, tumor variables, and volumetric or dosimetric data for seroma formation. Excellent/good cosmetic scores were achieved in 94% of women with and 92% without seroma. Local control was equivalent between patients with and without seroma. Consecutive sonographic imaging reveals a high rate of seroma formation after MammoSite PBI, with resolution in 65% of patients by 2 years without intervention. Seroma formation does not prevent an excellent cosmetic result or alter local control.

Modeling the risk of secondary lung malignancy in patients treated with breast radiation therapy.

1085 Background: The risk of secondary lung malignancy (SLM) is a concern for women treated with breast radiation therapy after breast conserving surgery for early stage breast cancer. The purpose of this study was to estimate the absolute and relative risks of developing secondary lung malignancies in patients treated either with supine or prone whole breast radiotherapy or with Mammosite brachytherapy. Methods: Twenty-two women treated with breast radiotherapy were enrolled in the study. Fifteen patients underwent CT simulation and standard fractionated and hypofractionated whole breast radiation treatment planning in both the prone and the supine positions. Seven patients underwent CT simulation and treatment planning for Mammosite brachytherapy. Dose-volume histograms of the ipsilateral breast and the lungs were calculated and incorporated into a biologically-based mathematical model of spontaneous and radiation-induced carcinogenesis to quantitatively predict the lifetime absolute and relative risks ...

Axillary Failure in Patients Treated with MammoSite Accelerated Partial Breast Irradiation

The risk of axillary failure (AF) after accelerated partial breast irradiation (APBI) using MammoSite brachytherapy is unknown and has been source of concern as the axillary region is not treated with this technique. We aimed to determine the rate of AF in patients treated with APBI and identify factors associated with its occurrence. Data from the American Society of Breast Surgeons MammoSite Registry Trial were reviewed and patients with AF were identified. Clinical, pathologic and treatment-related variables were analyzed to determine which factors were associated with AF. A total of 1440 patients underwent MammoSite APBI. A total of 1449 cases were treated (9 patients received bilateral treatment), 1255 cases (87%) of invasive breast cancer and 194 cases (13%) of ductal carcinoma in situ (DCIS). The median length of follow-up was 59 months. There were 10 patients who had an AF. Of these, 9 patients had an initial diagnosis of invasive cancer and 1 had an initial diagnosis of DCIS. The 5-year actuarial rate of AF was 0.79%. The only independent risk factor for AF identified by multivariate analysis was the presence of high-grade disease (P=.008). The 5-year overall survival rate in patients with an AF was 77.8% (there was 1 death related to breast cancer). The rate of AF after MammoSite APBI is low and appears to be similar to that achieved with whole-breast irradiation.

Association Between Maximal Skin Dose and Breast Brachytherapy Outcome: A Proposal for More Rigorous Dosimetric Constraints

Multiple investigations have used the skin distance as a surrogate for the skin dose and have shown that distances <6 mm have been associated with late toxicity after MammoSite brachytherapy. No publications have yet described the relationship between the actual maximal skin dose and the outcome. The present study analyzed the maximal skin dose delivered and the occurrence of late toxicity in a large cohort of patients with prolonged follow-up. A total of 96 patients treated with breast brachytherapy between 2000 and 2007 for whom complete planning and follow-up data were available were included in the present analysis. The median follow-up was 48 months (range, 24-111). Of the 96 patients, 40 were treated with multicatheter interstitial brachytherapy and 56 with MammoSite. A multivariate statistical analysis was performed to determine the relationship between several dosimetric parameters and patient outcome. The treatment was well tolerated, with 98% of patients experiencing good to excellent cosmesis. Significant late toxicity was uncommon. The maximal dose delivered to the skin was significantly associated with the incidence of any degree of telangiectasia (p= .009) and moderate to severe fibrosis (p= .010). The incidence of late toxicity was significantly increased when the dose to the skin was >4.05 Gy/fraction. The initial skin dose recommendations have been based on safe use and the avoidance of significant toxicity. The results from the present study have suggested that patients might further benefit if more rigorous constraints were applied and if the skin dose were limited to 120% of the prescription dose.

Preliminary Results in 173 Breast Cancer Patients Treated with Post-Lumpectomy MammoSite Single-Lumen Brachytherapy or Multi-Catheter Brachytherapy

The objective of this study was to report our single-institution results with MammoSite and multi-catheter brachytherapy. Between February 2003 and January 2009, 173 women with unifocal pathological Tis, T1, or T2 (up to 30 mm), N0 or N1 carcinomas of the breast were treated with post-lumpectomy brachytherapy to 34 Gy in 10 fractions over 5-10 days. We treated 137 patients with MammoSite single-lumen balloon brachytherapy, and 36 patients with multi-catheter brachytherapy. Patients with small and/or nonspherical lumpectomy cavities were usually treated with multi-catheter brachytherapy using 4-12 interstitial catheters. Median follow-up was 33 months. Three-year ipsilateral breast tumor control, disease-free, and overall survival rates for MammoSite brachytherapy were 100%, 100%, and 99%, respectively. Similar rates were obtained with multi-catheter brachytherapy. Minimum distances from the planning target volume for plan evaluation to a rib were 10 ± 8 mm (mean ± standard deviation) and 8 ± 4 mm (mean ± standard deviation) for MammoSite brachytherapy and multi-catheter brachytherapy, respectively (p = 0.48). Maximum rib doses were 101 ± 14% (mean ± standard deviation) and 74 ± 10% (mean ± standard deviation) of the prescribed dose for MammoSite brachytherapy and multi-catheter brachytherapy, respectively (p = 0.001). Multi-catheter brachytherapy results in more conformal radiation dose delivery and a significantly lower rib dose than MammoSite single-lumen brachytherapy. Long-term follow-up is needed to determine if the delivery of a lower radiation dose to the ribs will translate into a lower incidence of rib pain and fractures.

Outcomes in Women Treated With MammoSite Brachytherapy or Whole Breast Irradiation Stratified by ASTRO Accelerated Partial Breast Irradiation Consensus Statement Groups

The American Society for Radiation Oncology published a Consensus Statement for accelerated partial breast irradiation identifying three groups: Suitable, Cautionary, and Unsuitable. The objective of this study was to compare oncologic outcomes in women treated with MammoSite brachytherapy (MB) vs. whole breast irradiation (WBI) after stratification into Statement groups. Eligible women had invasive carcinoma or ductal carcinoma in situ (DCIS) ≤ 3 cm, and ≤ 3 lymph nodes positive. Women were stratified by radiation modality and Statement groups. Survival analysis methods including Kaplan-Meier estimation, Cox regression, and competing risks analysis were used to assess overall survival (OS), disease-free survival (DFS), time to local failure (TTLF), and tumor bed failure (TBF). A total of 459 (183 MB and 276 WBI) patients were treated from 2002 to 2009. After a median follow-up of 45 months, we found no statistical differences by stratification group or radiation modality with regard to OS and DFS. At 4 years TTLF or TBF were not statistically different between the cohorts. Univariate analysis in the MB cohort revealed that nodal positivity (pN1 vs. pN0) was related to TTLF (hazard ratio 6.39, p = 0.02). There was a suggestion that DCIS histology had an increased risk of failure when compared with invasive ductal carcinoma (hazard ratio 3.57, p = 0.06). MB and WBI patients stratified by Statement groups seem to combine women who will have similar outcomes regardless of radiation modality. Although outcomes were similar, we remain guarded in overinterpretation of these preliminary results until further analysis and long-term follow-up data become available. Caution should be used in treating women with DCIS or pN1 disease with MB.

Reduced Skin Toxicity with Multiple Dwell Position Mammosite Brachytherapy: Preliminary Phase II Trial Results

Reduced Skin Toxicity with Multiple Dwell Position Mammosite Brachytherapy: Preliminary Phase II Trial Results

Accelerated Partial Breast Irradiation for Pure Ductal Carcinoma in Situ

To report outcomes for ductal carcinoma in situ (DCIS) treated with breast-conserving therapy using accelerated partial breast irradiation (APBI). From March 2001 to February 2009, 53 patients with Stage 0 breast cancer were treated with breast conserving surgery and adjuvant APBI. Median age was 62 years. All patients underwent excision with margins negative by ≥1 mm before adjuvant radiotherapy (RT). A total of 39 MammoSite brachytherapy (MS) patients and 14 three-dimensional conformal external beam RT (3DCRT) patients were treated to the lumpectomy bed alone with 34 Gy and 38.5 Gy, respectively. Of the DCIS cases, 94% were mammographically detected. All patients with calcifications had either specimen radiography or postsurgical mammography confirmation of clearance. Median tumor size was 6 mm, and median margin distance was 5 mm. There were no statistically significant differences according to APBI method for race/ethnicity, tumor detection method, tumor grade, estrogen receptor (ER) status, or use of tamoxifen (p = NS). Recurrence and survival were calculated using the Kaplan-Meier method. Cosmesis was scored by the Harvard criteria. With a median follow-up of 3.6 years (range, 0.4-6.3 years), the overall and cause-specific survival rates were 98% and 100%, respectively. Three-year actuarial ipsilateral breast tumor recurrence was 2%. One failure was observed at the resection bed 11 months post-RT. No other elsewhere breast failures, regional recurrences, or distant metastases were noted. Cosmesis was excellent or good in 92.4% of cases, with no statistically significant differences according to the APBI method (92.3% with MammoSite and 92.8% with 3DCRT; p = 0.649). APBI as part of breast-conserving therapy for pure DCIS was associated with excellent local control and survival rates, with the vast majority of patients having good to excellent cosmesis. This finding supports the recent analysis by the American Society of Breast Surgeons on a subset of DCIS patients treated efficaciously with APBI.

Angiosarcoma following MammoSite® partial breast irradiation

Angiosarcoma is a rare tumor of endothelial origin which commonly arises in small blood or lymphatic vessels. Its development in the treated breast following adjuvant external beam radiation is also rare. To our knowledge, there are no reported cases in the literature or MammoSite registry which describe the occurrence of angiosarcoma in the treated breast following MammoSite brachytherapy. This is a case report of a 74 year old female who developed angiosarcoma 4 years after receiving MammoSite balloon brachytherapy following surgical resection of a T1mic N0 M0 infiltrating ductal carcinoma.

Status of Accelerated Partial Breast Irradiation

Breast-conserving therapy is accepted as a standard of care option for patients with early-stage breast cancer. However, studies examining patterns of failure after treatment suggest that a lengthy course of adjuvant whole breast irradiation delivered as a component of breast-conserving therapy may not always be necessary; indeed, in appropriately selected patients, radiation therapy delivered only to the tumor bed may be acceptable. Several modalities of delivering accelerated partial breast irradiation (APBI) have been developed, the most prevalent being multi-catheter interstitial brachytherapy, the MammoSite breast brachytherapy catheter (Hologic Corporation, Bedford, MA) and three-dimensional conformal external-beam radiation therapy. The purpose of this article is to review the published experiences on the most common modalities of delivering APBI and to outline the current open national phase 3 trial. To date, phase 1/2 studies have demonstrated excellent local control and cosmetic outcomes in early-stage breast cancer patients treated with APBI. As increasing knowledge is accumulated regarding the efficacy and safety of APBI, a consensus will emerge regarding its potential replacement of whole breast irradiation in selected early-stage breast cancer patients.

A Comparison of Skin and Chest Wall Dose Delivered With Multicatheter, Contura Multilumen Balloon, and MammoSite Breast Brachytherapy

Skin and chest wall doses have been correlated with toxicity in patients treated with breast brachytherapy . This investigation compared the ability to control skin and chest wall doses between patients treated with multicatheter (MC), Contura multilumen balloon (CMLB), and MammoSite (MS) brachytherapy. 43 patients treated with the MC technique, 45 patients treated with the CMLB, and 83 patients treated with the MS were reviewed. The maximum doses delivered to the skin and chest wall were calculated for all patients. The mean maximum skin doses for the MC, CMLB, and MS were 2.3 Gy (67% of prescription dose), 2.8 Gy (82% of prescription dose), and 3.2 Gy per fraction (94% of prescription dose), respectively. Although the skin distances were similar (p = 0.23) for the two balloon techniques, the mean skin dose with the CMLB was significantly lower than with the MS (p = 0.05). The mean maximum rib doses for the MC, CMLB, and MS were 2.3 Gy (67% of prescription dose), 2.8 Gy (82% of prescription dose), and 3.6 Gy per fraction (105% of prescription dose), respectively. Again, the mean rib dose with the CMLB was significantly lower than with the MS (p = 0.002). The MC and CMLB techniques are associated with significantly lower mean skin and rib doses than is the MS. Treatment with the MS was associated with significantly more patients receiving doses to the skin or rib in excess of 125% of the prescription. Treatment with the CMLB may prove to yield less normal tissue toxicity than treatment with the MS.

Mammographic Appearance Following Accelerated Partial Breast Irradiation by Using MammoSite Brachytherapy

To describe a single institution's experience with mammographic appearance in low-risk patients with early stage breast cancer who have received accelerated partial breast irradiation (APBI) by using MammoSite balloon brachytherapy. This study was approved by an institutional review board and was conducted under strict adherence to the Privacy Rule of HIPAA. This was a retrospective review of patients who underwent MammoSite brachytherapy from October 2003 to March 2007. Informed consent for participation in the research project was waived by the institutional review board. Posttherapy mammograms were categorized as showing mild, moderate, or severe distortion and were correlated with patient complaints and complications. Twenty-two women were included in the study, and 93 mammograms were obtained during a median follow-up period of 46 months (range, 22-58 months). Median age was 61 years (range, 47-81 years). One patient developed severe distortion after APBI, while two patients developed only mild distortion throughout follow-up. Eleven (79%) of 14 patients developed moderate distortion, with a median peak in distortion occurring at 21 months. Four (18%) patients developed fat necrosis, two (9%) developed seromas, and two (9%) developed both fat necrosis and seromas. None of the patients required biopsy, and none had an ipsilateral breast recurrence. One patient died of metastatic disease with no evidence of local recurrence. Patients treated with MammoSite APBI developed peak distortion 21 months following therapy, which may be sooner than distortion following conventional whole breast radiation.

Investigation of source position uncertainties &amp; balloon deformation in MammoSite brachytherapy on treatment effectiveness

The MammoSite breast high dose rate brachytherapy is used in treatment of early-stage breast cancer. The tumour bed volume is irradiated with high dose per fraction in a relatively small number of fractions. Uncertainties in the source positioning and MammoSite balloon deformation will alter the prescribed dose within the treated volume. They may also expose the normal tissues in balloon proximity to excessive dose. The purpose of this work is to explore the impact of these two uncertainties on the MammoSite dose distribution in the breast using dose volume histograms and Monte Carlo simulations. The Lyman-Kutcher and relative seriality models were employed to estimate the normal tissues complications associated with the MammoSite dose distributions. The tumour control probability was calculated using the Poisson model. This study gives low probabilities for developing heart and lung complications. The probability of complications of the skin and normal breast tissues depends on the location of the source inside the balloon and the volume receiving high dose. Incorrect source position and balloon deformation had significant effect on the prescribed dose within the treated volume. A 4 mm balloon deformation resulted in reduction of the tumour control probability by 24%. Monte Carlo calculations using EGSnrc showed that a deviation of the source by 1 mm caused approximately 7% dose reduction in the treated target volume at 1 cm from the balloon surface. In conclusion, accurate positioning of the (192)Ir source at the balloon centre and minimal balloon deformation are critical for proper dose delivery with the MammoSite brachytherapy applicator. On the basis of this study, we suggest that the MammoSite treatment protocols should allow for a balloon deformation of < or = 2 mm and a maximum source deviation of < or = 1 mm.

Partial Breast Irradiation as an Alternative to Whole Breast Radiation

Accelerated partial breast irradiation (APBI) is a novel method of post-operative radiotherapy that consists of irradiation of a limited volume of mammary gland immediately surrounding the tumour bed over a shorter time than whole breast irradiation. Several modalities are currently being explored as a means to deliver APBI, including multicatheter interstitial brachytherapy, the MammoSite breast brachytherapy catheter (Cytyc Corporation, Marlborough, MA), intraoperative radiation therapy and 3D conformal external-beam radiation therapy. To date, although still limited, randomised evidence is encouraging about the future role of APBI since it does not seem to jeopardise overall survival in patients with early breast cancer. Additional phase III studies are under way to determine the subgroups of patients who will really benefit from APBI.