Workshop on Partial Breast Irradiation: State of the Art and the Science, Bethesda, MD, December 8–10, 2002

Radiation Research Program, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
CancerSpectrum Knowledge Environment (Impact Factor: 15.16). 03/2004; 96(3):175-84. DOI: 10.1093/jnci/djh023
Source: PubMed

ABSTRACT Breast conserving surgery followed by radiation therapy has been accepted as an alternative to mastectomy in the management of patients with early-stage breast cancer. Over the past decade there has been increasing interest in a variety of radiation techniques designed to treat only the portion of the breast deemed to be at high risk for local recurrence (partial-breast irradiation [PBI]) and to shorten the duration of treatment (accelerated partial-breast irradiation [APBI]). To consider issues regarding the equivalency of the various radiation therapy approaches and to address future needs for research, quality assurance, and training, the National Cancer Institute, Division of Cancer Treatment and Diagnosis, Radiation Research Program, hosted a Workshop on PBI in December 2002. Although 5- to 7-year outcome data on patients treated with PBI and APBI are now becoming available, many issues remain unresolved, including clinical and pathologic selection criteria, radiation dose and fractionation and how they relate to the standard fractionation for whole breast irradiation, appropriate target volume, local control within the untreated ipsilateral breast tissue, and overall survival. This Workshop report defines the issues in relation to PBI and APBI, recommends parameters for consideration in clinical trials and for reporting of results, serves to enhance dialogue among the advocates of the various radiation techniques, and emphasizes the importance of education and training in regard to results of PBI and APBI as they become emerging clinical treatments.

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    ABSTRACT: This pathologic analysis was conducted to help define the clinical target volume (CTV) for partial breast irradiation (PBI) by analyzing the amount and distance of residual disease found at reexcision after an initial lumpectomy. The study population consisted of 441 patients derived from a dataset of 607 consecutive cases of Stage I and II breast cancer (reviewed by one pathologist) who underwent reexcision (after lumpectomy) before radiation therapy (RT) as part of their standard breast-conserving therapy (BCT). The assumption in this analysis was that the maximal measured extension distance from the initial excision specimen margin (in the reexcision specimen) represents the minimum distance that needs to receive full-dose RT for PBI to be successful. In 333 of the 441 cases, it was possible to measure this distance. Margins were classified as negative (carcinoma > 1/2 low-power field [LPF] from the margin), near (< 1/2 LPF from the margin), or positive. The amount of carcinoma near the final margin was quantified as the width of invasive carcinoma and number of ductal carcinoma in situ (DCIS) ducts near the margin and divided into three groups: least, intermediate, and greatest amount. Of the 333 cases, 119 (35.7%) had no residual carcinoma in the reexcision specimen, 67 (20.1%) had maximum extension (invasive carcinoma or DCIS) distances of >0<5 mm beyond the initial excision cavity edge, 83 (24.9%) extended 5 to <10 mm, 34 (10.2%) extended 10 to <15 mm, and 30 (9.0%) extended > or =15 mm. In 90% of 134 patients with negative initial lumpectomy margins (per National Surgical Breast and Bowel Project criteria) at lumpectomy, if any residual disease was present (38.2% of cases), it was limited to <10 mm from the edge of the original lumpectomy margin. The initial lumpectomy margin status was then combined with the invasive carcinoma: specimen maximum dimension ratio to determine if these two criteria (when combined) could better identify patients with residual disease limited to <10 mm from the initial margin. Analyzed in this fashion, all 13 of the reexcision specimens (9.7%) with >10 mm of maximum extension by carcinoma beyond the edge of the initial excision specimen cavity could be identified. A margin of 10 mm around the tumor bed should be adequate in covering disease remaining in the breast after lumpectomy in >90% of patients treated with PBI. However, it is possible to accurately identify all patients with disease extending beyond 10 mm using more restrictive pathologic selection criteria. These results can also be used as a guide for defining the CTV for boost treatment after whole-breast RT and the amount of breast tissue to remove at reexcision.
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    ABSTRACT: Breast conservation therapy (BCT) is a safe, effective alternative to mastectomy for many women with newly diagnosed breast cancer. This approach involves local excision of the malignancy with tumor-free margins, followed by 5-7 weeks of external beam whole breast (WB) radiotherapy (XRT) to minimize the risk of an in-breast tumor recurrence (IBTR). Though clearly beneficial, the extended course of almost daily postoperative radiotherapy interrupts normal activities and lengthens care. Additional options are now available that shorten the radiotherapy treatment time to 1-5 days (accelerated) and focus an increased dose of radiation on just the breast tissue around the excision cavity (partial breast). Recent trials with accelerated, partial breast irradiation (APBI) have shown promise as a potential replacement to the longer, whole breast treatments for select women with early-stage breast cancer. Current APBI approaches include interstitial brachytherapy, intracavitary (balloon) brachytherapy, and accelerated external beam (3-D conformal) radiotherapy, all of which normally complete treatment over 5 days, while intraoperative radiotherapy (IORT) condenses the entire treatment into a single dose delivered immediately after tumor excision. Each approach has benefits and limitations. This study covers over 2 decades of clinical trials exploring APBI, discusses treatment variables that appear necessary for successful implementation of this new form of radiotherapy, compares and contrasts the various APBI approaches, and summarizes current and planned randomized trials that will shape if and how APBI is introduced into routine clinical care. Some of the more important outcome variables from these trials will be local toxicity, local and regional recurrence, and overall survival. If APBI options are ultimately demonstrated to be as safe and effective as current whole breast radiotherapy approaches, breast conservation may become an even more appealing choice, and the overall impact of treatment may be further reduced for certain women with newly diagnosed breast cancer.
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