|Year : 2020 | Volume
| Issue : 6 | Page : 1522-1523
Contouring for radiotherapy in carcinoma breast – why a robust uniform guideline is (nearly) impossible
Department of Radiation Oncology, Manipal Hospital, Dwarka, New Delhi, India
|Date of Submission||15-Jul-2019|
|Date of Acceptance||01-Dec-2019|
|Date of Web Publication||26-Nov-2020|
Department of Radiation Oncology, Manipal Hospital, Dwarka - 110 075, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Munshi A. Contouring for radiotherapy in carcinoma breast – why a robust uniform guideline is (nearly) impossible. J Can Res Ther 2020;16:1522-3
While contouring guidelines for many body sites have emerged and achieved acceptance in the past few years, a uniform breast contouring practice has never taken off., In a relevant study representing eight institutions, breast contouring volume variations had standard deviations up to 60%. In another study involving 15 centers and 42 radiation oncologists, less than half of the centers could claim to have a good agreement between the internal radiation oncologists for contouring axilla.
Various factors contribute to high variability in breast contouring across individual practitioners and centers. For most body sites, there is a standard position for radiotherapy simulation and treatment. The breast remains a site where one can adopt prone or supine simulation (or a lateral position for giving boost). These positional variations in simulation can affect target and organs at risk doses.,
Breast volume is a possible determinant in breast contouring landmarks. Variation in breast contour in the population is significant. In a study of 30 patients scheduled for total mastectomy, the mean mastectomy specimen volume was 623.5 ml, with a range (as variable as) of 150–1490 ml. Whether this variation in breast volume correlates and is proportionate with other bony/soft-tissue landmarks used for contouring has never been studied.
For whole breast or chest wall radiotherapy, the dorsal boundary again lacks consensus. The dorsal boundary could be (a) anterior aspect of pectoralis major (the European Society for Radiotherapy and Oncology) and (b) anterior pleural surface (the Radiation Therapy Oncology Group) or anterior rib surface as is practiced at some institutions., The cranial boundary of the breast again is a fluctuating line, depending whether or not a supraclavicular field is used. The lateral edge of the breast is perhaps the most subjective of all boundaries because of the merging of breast tissue with the fatty tissue laterally. Whether the contoured breast volume should be 2 mm, 3 mm or 5 mm inside the skin (on the anterior side) is again a matter of debate.
Contouring for the boost volume after whole breast radiotherapy can be equally challenging. There is hardly any consensus on whether to take ultrasonography assistance, to do computed tomography (CT) or magnetic resonance imaging, or to use surgically placed clips during contouring of the cavity. Cavity shape itself could change depending on the timing of radiation (immediately after surgery versus postsurgery and postchemotherapy)., Even after delineation of cavity/tumor bed, there is a lack of consensus about clinical target volume (margin for microscopic disease) needed. Conventionally, the margin beyond the cavity was 1–1.5 cm. However, trials like TARGIT using intrabeam have used which use only 1 mm margin to the cavity site, challenging the long-standing larger margins that were used for boost/tumor bed delineation.,
Regional nodal irradiation contouring is even more controversial. An emerging consensus is treating only “undissected axilla” with radiotherapy. However, CT simulation scans at the time of radiotherapy do not allow ready discrimination of the “undissected axilla.” The extent of supraclavicular fields and issues in contouring for internal mammary radiotherapy are other areas of concern.
No wonder then, that breast radiation oncology clinicians and researchers globally have occasionally expressed the feelings of despair with respect to breast contouring. Unfortunately for the numerous patients of breast cancer undergoing irradiation, this lack of concordance in contouring shall prevail across individuals and across centers (and across guidelines!).
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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