International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationA Prospective Pathologic Study to Define the Clinical Target Volume for Partial Breast Radiation Therapy in Women With Early Breast Cancer
Introduction
Partial breast radiation therapy (PBRT) as a component of breast conservation therapy is an emerging paradigm in the treatment of women with early breast cancer (1). The rationale for PBRT is based on the premise that limiting the radiation target volume to the breast tissue immediately surrounding the surgical cavity where the majority of local recurrences are observed will achieve local control equivalent to whole breast radiation therapy.
The clinical target volume (CTV) for PBRT defines the volume of breast tissue that encompasses the residual microscopic carcinoma after wide local excision (WLE) of the primary breast cancer. However, the optimal CTV margin surrounding the surgical cavity remains uncertain and there is a paucity of contemporary pathologic data to validate current approaches. Clinical trials investigating PBRT have mostly defined a radial CTV margin of 10-15 mm based on studies describing the clinical patterns of local recurrence and historical retrospective series that examined the patterns of residual disease in mastectomy and re-excision specimens 2, 3, 4.
The primary objective of the present study was to determine an appropriate margin surrounding the surgical cavity after WLE to form the CTV for PBRT based on the spatial distribution of residual carcinoma in a prospective cohort of women with early breast cancer or ductal carcinoma in situ (DCIS) who were potential candidates for PBRT. The secondary objective was to determine the clinicopathologic factors associated with the presence and extent of residual carcinoma in the re-excision or completion mastectomy specimens.
Section snippets
Study schema
We performed a prospective pathologic assessment of a cohort of women who underwent re-excision or completion mastectomy after WLE for early breast cancer or DCIS. The study was approved by the ethics boards of the Peter MacCallum Cancer Centre and St. Vincent's Hospital in Melbourne, Australia. Patients who required re-excision or completion mastectomy were identified and their eligibility for entry to the study was assessed. The re-excision or completion mastectomy was performed at the
Results
The study population comprised 133 women with a median age of 59 years (range, 27-82 years). Re-excision was performed at the time of initial WLE in 65 patients or as a second procedure in 61 patients. Completion mastectomy after WLE was performed in 7 patients and after re-excision in 5 patients.
Table 1 shows the pathologic stage of the cases that are presented by the initial WLE margin status (involved or noninvolved), since an involved margin typically excluded patients from PBRT. The
Discussion
To our knowledge, this study is the first prospective pathologic analysis of the spatial distribution of residual carcinoma in re-excision or completion mastectomy specimens from a cohort of women who were potential candidates for PBRT.
Early retrospective studies examining mastectomy specimens reported a high incidence of multifocal and multicentric disease. The largest series, by Holland et al, included 314 cases in which multifocal disease was present in 63% and tumor foci were found more
Conclusions
Our study showed that a CTV margin of 10 mm would encompass microscopic residual disease in >90% of patients who had a noninvolved surgical margin after WLE for unifocal DCIS or T1/2 invasive breast cancer. This finding supports the American Society for Radiation Oncology (ASTRO) consensus recommendation for a 10-20mm CTV margin for PBRT (1). An involved margin, tumor size >30 mm, and premenopausal status were associated with larger MRE of residual disease. Patients with an involved surgical
References (19)
- et al.
Accelerated partial breast irradiation consensus statement from the American Society for Radiation Oncology (ASTRO)
Int J Radiat Oncol Biol Phys
(2009) - et al.
Target volume definition for external beam partial breast radiotherapy: clinical, pathological and technical studies informing current approaches
Radiother Oncol
(2010) - et al.
Defining the clinical target volume for patients with early-stage breast cancer treated with lumpectomy and accelerated partial breast irradiation: a pathologic analysis
Int J Radiat Oncol Biol Phys
(2004) - et al.
The value of breast lumpectomy margin assessment as a predictor of residual tumor burden
Int J Radiat Oncol Biol Phys
(1997) - et al.
Meta-analysis of the impact of surgical margins on local recurrence in women with early-stage invasive breast cancer treated with breast-conserving therapy
Eur J Cancer
(2010) - et al.
The validity of surgical clips as a radiographic surrogate for the lumpectomy cavity in image-guided accelerated partial breast irradiation
Int J Radiat Oncol Biol Phys
(2004) - et al.
How does knowledge of three-dimensional excision margins following breast conservation surgery impact upon clinical target volume definition for partial-breast radiotherapy?
Radiother Oncol
(2010) - et al.
The pancake phenomenon contributes to the inaccuracy of margin assessment in patients with breast cancer
Am J Surg
(2002) - et al.
Specimen shrinkage and its influence on margin assessment in breast cancer
Asian J Surg
(2007)
Cited by (12)
What is the dosimetric impact of isotropic vs anisotropic safety margins for delineation of the clinical target volume in breast brachytherapy?
2021, BrachytherapyCitation Excerpt :Accurate delineation of the TB and clinical target volume (CTV) is therefore important (13, 14). In the past, various authors have studied about the appropriate safety margins that should be generated for target coverage in APBI (15–17). As a routine practice, the CTV was delineated by uniform 1- to 2-cm expansion of the TB guided by the surgical cavity and clips to cover the microscopic disease adequately.
Treatment constraints for single dose external beam preoperative partial breast irradiation in early-stage breast cancer
2017, Clinical and Translational Radiation OncologyCitation Excerpt :An MRI and histopathology correlation study showed that in the absence of extensive intraductal component, no subclinical invasive disease was present in 93% of lumpectomy cases more than 10 mm beyond the edge of the lesion as measured on MRI [28]. In a recent prospective pathology study on the appropriate CTV margin for APBI, the maximum radial extension of residual carcinoma was assessed in 133 women requiring re-excision or completion mastectomy after initial lumpectomy [29]. In the 58% patients with non-involved initial margins, residual disease, if present, was ≤10 mm in 97.4% of the cases.
Comparison of Treatment Outcome Between Invasive Lobular and Ductal Carcinomas in Patients Receiving Partial Breast Irradiation With Intraoperative Electrons
2017, International Journal of Radiation Oncology Biology PhysicsBreast Cancer: Stages I-II
2015, Clinical Radiation OncologyRecommendations from GEC ESTRO Breast Cancer Working Group (I): Target definition and target delineation for accelerated or boost Partial Breast Irradiation using multicatheter interstitial brachytherapy after breast conserving closed cavity surgery
2015, Radiotherapy and OncologyCitation Excerpt :The size of the proposed total safety margins (resection margins and, “added” safety margins) should to be at least 1–2 cm (Fig. 2). The corresponding pathological data [12,30,32,55] are controversial (8–30 mm), and the clinical guidelines in USA and Europe are different. The optimal value of total safety margins (sum of the resection margin size and “added” safety margins size) is about 2 cm for both APBI and boost irradiation.
Conflict of interest: none.