From the Department of Radiation Oncology, Virginia Mason Medical Center, CB-RO, 110O Ninth Ave, Seattle, WA 98111(M.A.H., K.A.H.); and the Departments of Radiation Oncology (M.A.H., K.A.H.) and Surgery (T.A.M.), Valley Medical Center, Renton, Wash. From the 1995 RSNA scientific assembly. Received December 4, 1995; revision requested January 31, 1996; revision received February 26; accepted March 4. Address reprint requests to M.A.H.
(c) RSNA, 1996
Volume 200 9 Number 1
Michael A. Hunter, MD
Tori A. McFall, MD
Kathleen A. Hehr, RTT
Radiographs obtained at definitive and boost irradiation in 50 patients with stage I-11 breast cancer were retrospectively examined. Tangent target fields planned on the basis of surgical clips placed at excision biopsy were evaluated with simulation radiographs. Four (8%) of 50 tangent target fields would have been inadequate without clips, and 23 (467o) of the boost targets would have been missed (12 [24%1, totally; 11 (22'7o), marginally). Radiopaque surgical clips placed at excision biopsy help plan boost-irradiation target fields.
Radiology 1996; 200:281-282
At the National Institutes of Health Consensus Conference of 1991,
physicians concluded that breast-conserving surgery is an appropriate
primary therapy for the majority of women with stage 1-11 breast
cancer and is preferable in selected patients because it preserves
the breast while yielding equivalent overall survival (1). Refinements
in the delivery of definitive irradiation continue, and controversies
regarding optimal technique remain, including the value of boost
irradiation to the breast. The vast majority of practitioners
advocate administration of boost irradiation, but in the B-06
study of the National Surgical Adjuvant Breast Project, no boost
irradiation was administered to the tumor bed.
The decision to administer breast boost irradiation is based on
the several considerations. First, the frequency of residual carcinoma
in the breast after excisional biopsy in patients who later undergo
mastectomy is as high as 43% (2). Holland et al (2) performed
serial subgross and correlated mammographic examinations in patients
who underwent excisional biopsy; they found the frequency of residual
disease to be inversely proportional to the distance from the
index primary tumor. Among patients with stage Tl and T2 tumors,
437o had tumor beyond 2 cm, with 18% of all residual disease within
3 cm and 11'7,, within 4 cm of the index primary tumor (2). The
second consideration is the pattern of failure after definitive
radiation therapy. The majority of recurrent breast tumors after
definitive irradiation are located in the vicinity of the index
primary tumor: Such marginal recurrences compose 46%-100% of cases
of recurrent breast tumors (3-11).
Boost irradiation to the tumor bed is generally administered by
means of either a radioactive implant or electrons with varying
energies. The boost-irradiation dose is based on findings in the
margins of the excisional biopsy specimen (12). The boost-irradiation
tangent-target-field volume is the entirety of the surgical bed
with a margin and is based on pathologic features such as the
size of the tumor and the assessment of the surgical margins,
as well as whether re-excision was performed.
No relationship was shown between local recurrence and margin
status (unknown, focally positive, close, or negative) when boost
irradiation was administered (13), but the microscopic status
of the surgical margins has been reported to be the most important
indicator for local recurrence in early-stage breast carcinoma
(14). Smitt (14) suggests that administration of a total radiation
dose of at least 6,600 cGy improved the chances of local control
in patients with positive tumor margins (957o versus 82% [ >
6,600 vs < 6,600 cGy, respectively] at 5 years). This difference,
however, was of borderline importance.
Techniques for delivery of boost irradiation have been described
by a number of researchers. Solin et al (15) and Regine et al
(16) defined radiation targets by placing surgical clips in the
excision cavity and performing concomitant computed tomography
(CT). Solin et al (17) also used surgical clips and orthogonal
radiography. Lichter et al (18) studied the technical details
of radiation delivery and found localization of the tumor bed
on the basis of the excisional biopsy scar alone to be unreliable
compared with localization on the basis of the location of surgical
clips. Machtay et a] (19) and Bedwinek (20) report similar findings.
It was our purpose to compare definition of the surgical bed for
boost irradiation to the breast on the basis of the surgical scar
alone compared with definition on the basis of the location of
surgical clips.
From January 1993 through January 1996, 91 female patients were
seen at our institution to undergo radiation therapy for early-stage
breast cancer. At excision biopsy, surgical clips had been placed
in 50 (55%) of these patients, and they became our study population.
The women were aged 41-83 years (mean, 57 years), and they had
stage 0 (Tis), 1, and II (American joint Committee on Cancer Staging)
breast carcinoma, which had been treated with breast-conserving
surgery and definitive irradiation. In all patients, surgical
clips had been placed at the superior, inferior, medial, lateral,
and posterior borders of the tumor bed.
In all cases, tangential definitive irradiation was administered
to the breast for a total radiation dose of 4,600-5,040 cGy, with
the technique that has been previously reported (21), followed
by boost irradiation. To plan the target fields for boost irradiation,
we identified the surgical scar and areola and placed a 3-cm margin
around all portions of the scar by using radiopaque solder wire.
We made no attempt to correlate this target field with patient
or physician recollection of a palpable mass, findings on diagnostic
mammograms, postoperative induration, or directions of the surgeon.
We selected a gantry angle that was perpendicular to the breast
contour in the region of the surgical scar. We then obtained a
simulation radiograph.
We analyzed the simulation radiographs to determine if the surgical
clips were included in the target fields. A case was classified
as a "miss" if the surgical clips were not surrounded
by the radiation field. If any surgical clip was within 0.5 cm
of the target field edge, the case was scored as a "marginal
miss". If any clip was more than 0.5 cm beyond the target
field edge, the case was scored as a "total miss". To
define the tangent target fields, we arbitrarily elected to use
the one consistent setup we used in our clinic at the time the
study was designed.