Eligibility For Partial Breast Irradiation Research Articles

Utility of Clinical-Pathological Parameters for Exclusion of BRCA1/2 Mutation Carriers as Candidates for Partial Breast Irradiation

Several international groups have published guidelines to identify low-risk breast cancer (BC) patients who are eligible for partial breast irradiation (PBI). These include the American Society for Radiation Oncology (ASTRO), the European Society for Radiotherapy and Oncology (ESTRO), and ESTRO subgroups such as the Intraoperative radiation (IORT) Task Force and Groupe Européen de Curiethérapie (GEC) -ESTRO. Only ASTRO guidelines recommend against the use of PBI in known carriers of germline pathogenic variants (PVs) in BRCA1/2. The aim of this study was to evaluate the proportion of BC patients, subsequently found to be BRCA1/2 PV carriers who would be eligible for PBI based on clinical-pathologic criteria of the above-mentioned international guidelines. Data were extracted from the medical records of consecutive BC BRCA1/2 PV carriers treated at a single institution between 2006 and 2023. Data included patient demographics, tumor characteristics, treatment, and disease outcomes. Overall, 498 patients with 518 primary tumors were analyzed. Of these, 282 (12 of them with synchronous bilateral disease) presented with unknown genetic status at diagnosis and formed the study cohort. The median age at diagnosis was 42.7 years (range, 23.8-77.9). Based on the recent ASTRO guidelines (not including conditionally recommended criteria), 17 of 294 (5.8%) of the carriers had tumors that would be eligible for PBI, including 3 Her2-positive tumors and 5 patients diagnosed between ages 40 and 49 years. Using the ESTRO IORT and the ACROP-ESTRO PBI criteria, 9 of 294 (3%) would be eligible, whereas with the GEC-ESTRO low-risk criteria, 31 of 294 (10.5%) of the carriers would be eligible, and their intermediate risk criteria would increase eligibility for PBI by an additional 8.2% (overall 18.7%). Using clinical-pathologic criteria published in international guidelines, 3% to 18% of BRCA1/2 PV carriers will have tumors eligible for PBI. Therefore, especially in populations who are at high risk for being BRCA1/2 PV carriers, we recommend adhering to stricter guidelines. In our cohort, ASTRO, ESTRO-IORT, and ESTRO PBI had the lowest probability of identifying BRCA1/2 PV carriers as eligible for PBI.

Abstract P4-12-26: Partial breast irradiation, simultaneous integrated boost and regional nodal irradiation: A UK private provider approach to maximising patient access to advanced breast radiotherapy

Abstract Introduction: Post-operative whole breast radiotherapy reduces ipsilateral recurrence by 20% and 15-year breast cancer mortality by 5.4%. Technique offerings should evolve to maximise clinical outcomes whilst reducing toxicities. Partial breast irradiation (PBI) reduces skin toxicity while being as effective as whole breast radiotherapy, Simultaneous Integrated Boost (SIB) shortens treatment while offering better tumour control than sequential boost and regional nodal irradiation (RNI) with VMAT IMRT provides excellent target dose conformity. Access to advanced radiotherapy in UK lags behind demand, due to workforce shortages and time pressures for planning and peer review. Background: GenesisCare is the global leader in oncology services with 12 UK oncology centres, equipped with latest radiotherapy technologies and offering IMRT/VMAT for RNI (NICE guidelines), SIB (IMPORT-HIGH) and PBI (GEC-ESTRO, IMPORT LOW). GenesisCare UK (GCUK) collaborates with breast oncologists and surgeons who work in the National Health Service and who utilise those techniques inconsistently. This retrospective study aims at identifying patient eligibility for those techniques, measure uptake and devise strategies to increase patient access. Method: Patients referred for radiotherapy between November 2018 and May 2019 were screened for PBI, SIB or RNI eligibility. We focused on our Oxford and Cambridge centres because clinicians practising there are familiar with those techniques from their NHS practice. Minimum patient datasets, histology/imaging reports and multi-disciplinary team (MDT) meeting outcomes were reviewed. Patient eligibility was evaluated against uptake. Results: 408 cases were treated across the network, with 39 cases in Oxford and Cambridge. Two patients with stage IV disease and one with DCIS were excluded and remaining 36 patients were evaluated as per table 1. Table 1 Technique eligibility vs utilisationTechniqueEligible (%)Eligible & Offered (%)Eligible Not offered (%)Not eligible (%)PBI12 (33)1 (8)11 (92)24 (67)SIB15 (42)3 (20)12 (80)21 (58)RNI5 (14)5 (100)031 (86) Only 1 of 12 PBI eligible patients were offered PBI (RTOG zero acute skin toxicity). From the remaining 11 patients, 1 had grade 4 toxicity and received oral antibiotics for skin infection, 4 had grade 2, 5 had grade 1 and 1 had zero toxicity. All high-risk patients had RNI with VMAT, but only 20% eligible for a boost were offered SIB. They had sequential boost with treatment prolongation by 5-8 days. Summary and Next Steps Access to breast radiotherapy in UK lags behind demand, especially for advanced techniques like PBI, SIB and RNI. At GCUK, we set out our vision for the Breast Service of the Future (SOF), an approach that draws from best practice and evidence-based radiotherapy. We believe that patients should be offered a personalised radiotherapy approach and we have taken steps to maximise patient access to advanced breast radiotherapy (table 2). Table 2 Breast SOF StrategyActionEnablers1. Key Opinion Leader engagement, clinical protocol development, whole MDT approach to change including breast oncologists, surgeons, radiologists, eMDT & Peer Review process set upBreast SOF ConferenceContouring workshopsUK roadshowsIT and Innovation teams1. Internal staff training to advanced techniques for dosimetrists, radiographers and physicistsESTRO PBI and IGRT coursesContouring workshops1. Purchasing Auto-contouring software for Organs at risk and Internal Mammary Chain, creation of breast contouring atlasesClinician/staff training by GCUK clinical applications specialist1. Breast SOF journal development and circulation across the network (oncologists, surgeons, GPs, radiologists) to include evidence-based practice behind advanced radiotherapy techniquesBreast SOF Steering CommitteeBreast reference group and clinician engagement Citation Format: Penny Kechagioglou, Mark Bowler, Trevor Williams. Partial breast irradiation, simultaneous integrated boost and regional nodal irradiation: A UK private provider approach to maximising patient access to advanced breast radiotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-26.

Abstract P4-12-24: Evaluation of partial breast irradiation suitability in early stage breast cancer patients

Abstract Purpose: Partial Breast Irradiation (PBI) treats the tumor bed plus a margin in low risk early stage breast cancers, reducing exposure to organs at risk. Randomized trials have shown that PBI with external beam radiotherapy is non-inferior to whole breast irradiation in terms of local control with fewer late normal tissue adverse events. We aimed to determine the proportion of women with early stage breast cancer suitable for external beam PBI at our institution using adapted ASTRO guidelines for accelerated PBI whereby both clinical-pathological factors and visualization of the tumor bed/cavity on planning scans were determined to quantify PBI eligibility. Methods: Patients were identified retrospectively from January 1, 2013 to November 1, 2018 based on age (≥55), tumor size (≤2cm invasive, ≤2.5cm DCIS), nodal negativity and grade (1 or 2). Cases identified were unifocal, lymphovascular invasion negative, ER positive, HER2 negative, with margins ≥2mm (invasive) and ≥3mm (DCIS), no chemotherapy, non-lobular, no extensive intraductal component, no previous/ bilateral cancers and endocrine therapy optional. Planning scans were reviewed to assess for presence of surgical clips and assigned cavity visualization scores (CVS); CVS 1=cavity not visualized, CVS 2=cavity visualized with indistinct margins, CVS 3=cavity visualised with some distinct margins and heterogeneous appearance, CVS 4= cavity visualised with mostly distinct margins and mildly heterogeneous appearance, CVS 5= all cavity margins clearly defined and homogeneous appearance. These features were used to determine if cases were considered radiologically suitable for PBI. Results: Thirty-seven percent (1051/2824) of cases identified were deemed eligible based on age, grade and T1N0/Tis. Of the 1051, 306 (29%) met all the pathologic criteria; the main reasons for exclusion were previous breast cancer, lobular histology, or multifocality. Median age of eligible cases was 65 years (range 55-88 years). The majority (254) had invasive disease (T1mi: 6, T1a: 17, T1b: 98, T1c: 133); 52 had DCIS. There were 169 right-sided and 137 left-sided cases. Endocrine therapy was documented in 55% of cases. CVS (1-5) were: 11%, 22%, 30%, 29%, 8%. Overall, 66% (201/306) of cases were considered radiologically suitable for PBI (of the 201 cases, 97% had CVS ≥3). Seventy-two cases (72/306; 24%) had tumor bed clips, of which, 34 were considered suitable for PBI (91% CVS ≥3; 9% CVS 2). Conclusions: Overall, a low proportion of all patients were eligible for PBI based on clinical features, but two-thirds of eligible cases were suitable for PBI based on CVS score alone. In contrast, the suitability for PBI within the cohort with surgical clip placement was low. Visualization of the tumor bed is essential to safely deliver PBI and is guided by identification of the cavity seroma and/or surgical clips. Development of standard practice guidelines for surgical clip positioning to identify the tumor bed will potentially assist in increasing the proportion of early stage breast cancer patients suitable to receive PBI, even if the CVS is less favorable. Citation Format: Christine Anne Koch, Gemma Corey, Kathy Han, Grace Lee, Tom Purdie, Chris McIntosh, Patricia Lindsay, Fei-Fei Liu, Anthony Fyles, Wilf Levin, Jennifer Croke, Aisling Barry, Danielle Rodin, Nhu Tram Nguyen, Tatiana Conrad. Evaluation of partial breast irradiation suitability in early stage breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-24.

Patient selection for partial breast irradiation by intraoperative radiation therapy: can magnetic resonance imaging be useful?-perspective from radiation oncology point of view.

The guidelines of the European and American Societies of Radiation Oncology (GEC-ESTRO and ASTRO) defined the selection criteria to offer partial breast irradiation (PBI) after lumpectomy in patients with low risk breast cancer regardless pre-operative staging. A recent publication by Tallet et al. explored the impact of preoperative magnetic resonance imaging (MRI) on patient eligibility for PBI. From their study, an ipsilateral BC was detected in 4% of patients, excluding these patients from intraoperative radiotherapy (IORT). The authors suggested that preoperative MRI should be used routinely for patient's candidate to IORT, because of the rate of ipsilateral breast cancer detected. In view of Tallet's article, we analyzed some aspects of this issue in order to envisage some possible perspective on how to better identify those patients who could benefit from PBI, especially using IORT. From historical studies, the risk of breast cancer recurrence outside index quadrant without irradiation is in the range of 1.5-3.5%. MRI sensitivity for detection of invasive cancer is reported up to 100%, and it is particularly useful in dense breast. Other imaging technique did not achieve the same sensibility and specificity as conventional MRI. Of note, none of randomized trials published and ongoing on PBI included preoperative MRI as part of staging. To perform a preoperative MRI in PBI setting is an interesting issue, but the available data suggest that this issue should be preferably studied in the setting of prospective clinical trials to clarify the role of MRI and the clinical meaning of the discovered additional foci.

MR Imaging for Selection of Patients for Partial Breast Irradiation: A Systematic Review and Meta-Analysis.

To systematically review articles that estimated the ineligibility for partial breast irradiation (PBI) after magnetic resonance (MR) imaging. No ethics committee approval was needed. A systematic search was performed by using MEDLINE and EMBASE. The rate of patients eligible at standard assessment (ie, clinical examination, mammography, and/or ultrasonography) but ineligible after MR imaging was a study outcome. Odds ratios (ORs) were calculated to identify predictors. Quality was appraised by using the Strengthening Reporting of Observational Studies in Epidemiology checklist. Of 93 retrieved articles, six were included (total, 3136 patients). For PBI eligibility, all studies applied National Surgical Adjuvant Breast and Bowel Project B-39 criteria. Ineligibility at standard assessment varied from 21% to 80%; MR imaging prompted ineligibility for PBI in 6%-25% of patients who were initially deemed eligible or in 2%-20% if calculated on the overall number of patients initially screened. Meta-regression showed a negative correlation between ineligibility at standard assessment and ineligibility after MR imaging (P < .001). The pooled percentage of patients eligible at standard assessment but ineligible after MR imaging was 11% (95% confidence interval [CI]: 6%, 19%). Predictors for ineligibility after MR imaging were cancers stage pT2 or greater versus less than stage pT2 (OR, 8.8 [95% CI: 4.7, 16.7]; P < .001), invasive lobular histopathologic results versus invasive ductal pathologic results (OR, 3.0 [95% CI: 1.6, 6.6]; P = .007), pre- versus postmenopausal status (OR, 1.9 [95% CI: 1.3, 2.6]; P < .001), invasive cancer versus ductal carcinoma in situ (OR, 1.6 [95% CI: 1.0, 2.4]; P = .031). Study quality ranged from 17 to 20 (maximum quality, 22). The risk of publication bias was moderate. One of nine women (11%), who on the sole basis of standard assessment were candidates to undergo PBI, was found to be ineligible after undergoing MR imaging. Breast MR imaging should be used to select patients for PBI.

Impact of preoperative magnetic resonance imaging in breast cancer patients candidates for an intraoperative partial breast irradiation

Objective: Partial breast irradiation (PBI) could be a reasonable option in patients with early breast cancer (BC) provided that an adequate patient selection, based on robustly established criteria is performed. A preoperative magnetic resonance imaging (MRI) in patient selection for PBI is not consensual. The aim of this retrospective study was to assess the impact of preoperative MRI on patient eligibility for PBI. Methods: Since March 2012, patients with early BC, meeting the Inca’s criteria for PBI were offered the possibility of shortened treatment through intra-operative radiation therapy, either in a prospective trial or off protocol. Eligibility criteria based on physical examination, mammography and ultrasound, and a pathological exam of biopsy, were as follows: menopaused woman 55 years or older with a T1, N0, hormonal-receptor-positive and HER2-negative, invasive, non-lobular epithelioma, without extensive intraductal component (defined as more than 25% of ductal component on biopsy), non-fast-growing tumor, without lymphovascular invasion (LVI), without criteria for adjuvant chemotherapy. A contrast-enhanced MRI was not routinely performed, but at the discretion of the physician as was the rule in TARGIT-A trial. We assessed the rate of additional cancer revealed by the preoperative MRI, remote in the same breast not detected by mammography and/or ultrasound. Results: Between March 2012 and February 2014, 179 early BC patients meeting the required criteria were planned for an intraoperative radiotherapy (IORT)-PBI. Seventy nine percent of them (141/179) underwent a breast MRI as part of preoperative assessment. ACR3-ACR4 abnormalities not detected by mammograms or ultrasound were found in 44 patients (31%), which prompted a focused mammary ultra-sound, and a biopsy was realized in 29/141 patients (21%). A second breast carcinoma was found in 10 patients (7% of patients with a preoperative MRI, 4 ipsilateral lesions, 5 contralateral lesions, and one both ipsi- and contralateral lesion, precluding IORT-PBI in 5/141 patients (4%). Conclusions: The use of preoperative MRI in patient staging leads to diagnosis of an ipsilateral second BC in 4% of cases, which appears substantial in a highly selected population. We therefore support the routine use of this exam for the staging of patient candidate for a PBI.

Classification System for Identifying Women at Risk for Altered Partial Breast Irradiation Recommendations After Breast Magnetic Resonance Imaging

To study the utility of preoperative breast MRI for partial breast irradiation (PBI) patient selection, using multivariable analysis of significant risk factors to create a classification rule. Between 2002 and 2009, 712 women with newly diagnosed breast cancer underwent preoperative bilateral breast MRI at Mayo Clinic Florida. Of this cohort, 566 were retrospectively deemed eligible for PBI according to the National Surgical Adjuvant Breast and Bowel Project Protocol B-39 inclusion criteria using physical examination, mammogram, and/or ultrasound. Magnetic resonance images were then reviewed to determine their impact on patient eligibility. The patient and tumor characteristics were evaluated to determine risk factors for altered PBI eligibility after MRI and to create a classification rule. Of the 566 patients initially eligible for PBI, 141 (25%) were found ineligible because of pathologically proven MRI findings. Magnetic resonance imaging detected additional ipsilateral breast cancer in 118 (21%). Of these, 62 (11%) had more extensive disease than originally noted before MRI, and 64 (11%) had multicentric disease. Contralateral breast cancer was detected in 28 (5%). Four characteristics were found to be significantly associated with PBI ineligibility after MRI on multivariable analysis: premenopausal status (P=.021), detection by palpation (P<.001), first-degree relative with a history of breast cancer (P=.033), and lobular histology (P=.002). Risk factors were assigned a score of 0-2. The risk of altered PBI eligibility from MRI based on number of risk factors was 0:18%; 1:22%; 2:42%; 3:65%. Preoperative bilateral breast MRI altered the PBI recommendations for 25% of women. Women who may undergo PBI should be considered for breast MRI, especially those with lobular histology or with 2 or more of the following risk factors: premenopausal, detection by palpation, and first-degree relative with a history of breast cancer.

TU‐E‐500‐01: Advanced Technologies for Breast RT

Breast conservation therapy (BCT) combining lumpectomy and post‐lumpectomy radiation therapy (RT) is a well established alternative to mastectomy for most patients with early stage breast cancer (ESBC). The fact that most of local recurrences occur in close proximity to the original tumor bed indicates that the whole breast irradiation (WBI) may not be necessary in all cases of ESBC. This led to the development of partial breast irradiation (PBI) which reduces the amount of irradiated normal tissue. Moreover, accelerated PBI can shorten the treatment time from 4–5 weeks for the current standard breast RT for ESBC to 5 days. In the current clinical practice of PBI, large CTV to PTV margins (e.g., 1.5 cm) are being used due to the variations in patient setup, anatomy change between treatment fractions, and respiratory motion during the treatment. These large margins limit the patient eligibility for PBI and lead to more normal tissue irradiated with high dose. Advanced technologies, including IMRT, IGRT, respiration motion management, and adaptive replanning, are being rapidly introduced in to the clinic to reduce these large margins and to enable conformal irradiation of either whole or partial breast. The purpose of this session is to review and update physicists on this exciting and rapidly developing area.Learning Objectives:1. Understanding rationale, indications and promise for using advanced RT Technologies for breast cancer2. Review of recent advances in imaging, planning, and delivery technologies for breast RT3. Discussing clinical implementation, and experience for using the advanced technologies for breast RT

A Prospective Study of the Utility of Magnetic Resonance Imaging in Determining Candidacy for Partial Breast Irradiation

Retrospective data have demonstrated that breast magnetic resonance imaging (MRI) may change a patient's eligibility for partial breast irradiation (PBI) by identifying multicentric, multifocal, or contralateral disease. The objective of the current study was to prospectively determine the frequency with which MRI identifies occult disease and to establish clinical factors associated with a higher likelihood of MRI prompting changes in PBI eligibility. At The University of Chicago, women with breast cancer uniformly undergo MRI in addition to mammography and ultrasonography. From June 2009 through May 2011, all patients were screened prospectively in a multidisciplinary conference for PBI eligibility based on standard imaging, and the impact of MRI on PBI eligibility according to National Surgical Adjuvant Breast and Bowel Project protocol B-39/Radiation Therapy Oncology Group protocol 0413 entry criteria was recorded. Univariable analysis was performed using clinical characteristics in both the prospective cohort and in a separate cohort of retrospectively identified patients. Pooled analysis was used to derive a scoring index predictive of the risk that MRI would identify additional disease. A total of 521 patients were screened for PBI eligibility, and 124 (23.8%) patients were deemed eligible for PBI based on standard imaging. MRI findings changed PBI eligibility in 12.9% of patients. In the pooled univariable analysis, tumor size ≥ 2 cm on mammography or ultrasonography (P=.02), age <50 years (P=.01), invasive lobular histology (P=.01), and HER-2/neu amplification (P=.01) were associated with a higher likelihood of MRI changing PBI eligibility. A predictive score was generated by summing the number of significant risk factors. Patients with a score of 0, 1, 2, and 3 had changes to eligibility based on MRI findings in 2.8%, 13.2%, 38.1%, and 100%, respectively (P<.0001). MRI identified additional disease in a significant number of patients eligible for PBI, based on standard imaging. Clinical characteristics may be useful in directing implementation of MRI in the staging of PBI candidates.

Accuracy and Completeness of Pathology Reporting - Impact on Partial Breast Irradiation Eligibility

Accuracy and Completeness of Pathology Reporting - Impact on Partial Breast Irradiation Eligibility

Accuracy and Completeness of Pathology Reporting — Impact on Partial Breast Irradiation Eligibility

AimsAccelerated partial breast irradiation (APBI) is an alternative to whole breast irradiation that is delivered over a shorter period of time with less toxicity. Appropriate patient selection is critical to its success and the American Society for Radiation Oncology (ASTRO) has published detailed selection criteria for ‘suitable’ patients. This study evaluated the effect of those selection criteria on APBI eligibility based on pathology reports. Materials and methodsFrom March 2004 to March 2007 all patients referred to a single cancer centre for breast radiotherapy were screened for participation in a phase I/II trial of permanent breast seed implant brachytherapy. Eligible patients underwent a computed tomography simulation and those referred from an outside institution had a secondary expert breast pathology assessment. Initial and expert pathology reports were compared regarding completeness and accuracy. ResultsIn total, 143 patients were eligible for the trial; 79 patients had surgery carried out outside our institution. In the initial pathology report, the most frequently missing critical information was the resection margin width (29.1%) and the presence of extensive in situ carcinoma (11.4%). Comparing initial and reviewed pathology, the agreement was higher than 90% for most features. The main source of disagreement was the width of the negative resection margin, with 34.4% disagreement (P=0.016), although it changed eligibility in only 3.6%. There was major disagreement in the evaluation of lymphovascular invasion. Overall, pathology review changed the eligibility for a patient from ‘suitable’ for APBI to ‘cautionary’ in 18.6% of the cases. ConclusionUsing stringent eligibility criteria has a direct effect on patient screening for APBI. The use of synoptic pathology reporting and a quality assurance programme with secondary expert assessments are recommended.

Abstract P4-11-11: Preoperative Radiotherapy Increases Eligibility for Partial Breast Irradiation by Significantly Reducing Normal Tissue Exposure

Abstract Introduction: External-beam accelerated partial breast irradiation (EB-APBI) is the most common technique used on NSABP B-39 primarily due to the non-invasive nature of the treatment. Many patients thought to be eligible for EB-APBI become ineligible at the time of planning due to inability to meet dose-volumetric constraints. EB-APBI in the preoperative setting will reduce the volume of normal tissue treated potentially increasing the number of patients eligible for APBI. This study tested the hypothesis that pre-operative EB-APBI will not only decrease target volumes but will decrease normal tissue exposure significantly increasing eligibility for APBI. Materials and Methods: Forty patients with 41 previously treated early stage breast cancers (tumors ≥4 cm) were retrospectively analyzed from a prospective cohort. Imaging studies (MRI, US and mammogram) were utilized to create a spherical pre-op tumor volume using the largest reported dimension centered within the previously contoured lumpectomy cavity (LPC). Plans were created and optimized for each patient using the pre-operative tumor volume (pre-op) and LPC (post-op) using NSABP B-39 guidelines. Dose-volumetric constraints were analyzed between the cohorts using a t-test analysis. The primary end-point was to evaluate for differences in patient eligibility and normal tissue exposure. Results: The median tumor volume was 93 cc (range 24-570 cc) and 250 cc (range 46-879 cc) in the pre-and post-operative setting respectively. This reduction in tumor volume translated into an increase in patient eligibility for EB-APBI with 35/41 (85%) cases being eligible for EB-APBI in the preop setting versus 18/41 (44%) cases in the post-op setting (p=0.0002). In the pre-op setting 6 cases were ineligible due to violation of one constraint by 5% and no case violated multiple constraints. In the post-op setting, 12 cases had 1 and 11 cases multiple reasons for ineligibility due to exceeding dose constraints by 5%. The most common reason for ineligibility in both groups was &amp;gt; 60% of the ipsilateral breast volume receiving 50% of the dose. The mean volume of ipsilateral breast receiving 50% of the dose was 42% and 63% in the pre-and post-op groups respectively. The mean contralateral breast dose and ipsilateral lung V20 in the pre-and post-op groups were 1 versus 4% and 3 versus 9%. All DVH criteria were statistically significantly improved in the pre-op setting including heart V5 and V40, ipsilateral breast V5, V20, V50 and V80, contralateral breast dose, chest wall V5, V10 and V20; ipsilateral lung V5, V10, V20 and volume of skin receiving 50% of the dose. Contralateral lung dose and thyroid max dose were not significantly different between plans. Conclusions: Administration of EB-APBI in the pre-op setting decreases the size of the target volume which significantly increases the utility of APBI nearly doubling the eligibility for APBI in this cohort. The largest benefit is seen by reducing the volume of breast receiving 50% of the dose. This decreased dose to normal tissues will potentially result in decreased morbidity and improved cosmesis. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-11-11.

Utility of Breast Magnetic Resonance Imaging in Determining Candidacy for Partial Breast Irradiation

Utility of Breast Magnetic Resonance Imaging in Determining Candidacy for Partial Breast Irradiation

Magnetic resonance imaging identifies multifocal and multicentric disease in breast cancer patients who are eligible for partial breast irradiation

In this retrospective study, the authors hypothesized that magnetic resonance imaging (MRI) would alter partial breast irradiation (PBI) eligibility by identifying cancers outside the PBI volume compared with mammography alone. Since 2002, MRI was used nonselectively at the authors' institution for the staging of patients with nonmetastatic breast cancer. Of 450 consecutive patients with invasive breast cancer, 110 patients who were eligible for PBI were identified by using criteria outlined by National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Oncology Group trial 0413 based on mammography, ultrasonography, and initial pathology. In that trial, patients were randomized (stage I/II invasive cancers that measured <or=3 cm and <or=3 positive lymph nodes) to receive either whole-breast radiotherapy or PBI. MRI reports were reviewed to determine whether MRI identified secondary lesions 1) within the same quadrant (multifocal), 2) in a different quadrant (multicentric), or 3) in the contralateral breast. These lesions were pathologically proven carcinoma and would have rendered the patient ineligible for PBI. MRI identified secondary lesions in 10% of patients (95% confidence interval [CI], 4.4%-15.6%). Multifocal disease was identified in 3.6% (95% CI, 1.4%-9%), multicentric disease was identified in 4.5% (95% CI, 2%-10.2%), and contralateral disease was identified in 1.8% (95% CI, 0.5%-6.4%). The proportion of patients with false-positive MRI findings was 4.5% (95% CI, 2%-10.2%). The positive predictive value of MRI was 72.2% (95% CI, 46.4%-89.3%). MRI identified frequent secondary cancers that would not be removed routinely by surgery or targeted in the radiation field if treated with PBI. The current data suggest that MRI should be considered to assess PBI eligibility to minimize potential local failures.

Pre-operative breast magnetic resonance imaging (MRI) influences patient selection for partial breast irradiation

604 Background: Many patients with localized breast cancer undergo breast conservation therapy. Partial breast irradiation (PBI) is a technique that reduces irradiated tissue volume and decreases treatment time. Appropriate patient selection for this technique is critical. We studied the influence of pre-operative breast MRI on patient selection for PBI. Methods: Between 05/04 and 05/05, 231 women with newly diagnosed breast cancer underwent pre-operative bilateral breast MRI (median age = 64, range 34 to 89). Following initial clinico-pathologic review, patients were deemed to be eligible for PBI based on the NSABP B39 protocol if they satisfied its inclusion criteria (tumor size ≤3 cm, ≤3 positive nodes, negative surgical margins, lack of multicentric disease), derived through physical examination, mammography and/or ultrasonography. Breast MRI scans of all patients deemed eligible for PBI by these criteria were then reviewed to determine the impact of the MRI findings on their eligibility for PBI. Only patients who had pathological assessment to correlate with the MRI findings were included in the analysis. Results: Based on the NSABP B39 inclusion criteria, 186 patients (81%) were considered to be appropriate candidates for PBI without influence from MRI findings. Of these 186 women, MRI findings led to pathologically proven additional disease that altered the recommendations for PBI in 26 patients (14%). Mammographically occult, biopsy proven multicentic disease was detected in the ipsilateral breast in 13 patients (7%), whereas 5 women (2.7%) had mammographically occult, biopsy proven multicentric disease in the contralateral breast. In 8 patients (4.3%), pathological assessment confirmed more extensive local disease than was detected by breast MRI. Conclusions: Up to 14% of patients initially deemed eligible for PBI were later found to be ineligible because of breast MRI findings. Ipsilateral multicentric disease was identified in 7%, contralateral disease was discovered in 2.7%, and more extensive local disease was noted in 4.3%. Bilateral breast MRI complements other imaging modalities in determining eligibility for PBI by identifying mammographically occult disease in patients for whom PBI may be inappropriate. No significant financial relationships to disclose.