On workup of a person who had prior “breast cancer surgery,” consider obtaining a more comprehensive history and physical– paying specific attention to receipt of neoadjuvant systemic therapy and on physical exam, note any surgical sites, palpable nodes, nipple discharge, and skin discoloration, along with a full bilateral breast exam. Assess menopausal status, if she were premenopausal, consider a pregnancy test. In anticipation of upcoming treatment. Consultation with a fertility specialist for consideration of future family planning should be considered as well. Obtain all historical data I could find, including workup imaging, surgical reports, and pathology reports.
In this case, histology shows an IDC, 2.5 cm in size, grade 3 without any associated DCIS. There is LVSI present with negative margins. 1 of 3 removed sentinel nodes showed disease, the largest deposit of 5mm without any associated extracapsular extension. She is ER/PR negative, Her2 positive, Ki67 70%. The patient was considered a pT2pN1, stage IIb
NCCN recommends NAC for HER2+/TNBC if >=cT2 or N+ at presentation. In this case, she likely fulfilled both criteria. The most common NAC for HER2+ disease include Adriamycin/cyclophosphamide followed by paclitaxel/herceptin OR TCHP. Since this case did not receive NAC, consider adjuvant docetaxel, trastuzumab, and pertuzumab (NEOSPHERE trial).
It was recommended to recieve whole breast radiotherapy that would include comprehensive regional nodal irradiation with 50.4 Gy in 28 fractions with a boost to the tumor bed with 10 Gy in 5 total fractions. The nodal basins would include level 1-4 axilla and IMNs.
When treating with regional nodal irradiation for patients with 1-2 positive SLNs. This is often a topic of discussion and there is no clear standard for patients with 1-2 positive SLNB. In this population, the patient’s overall risk profile for recurrence should be considered when deciding whether to include RNI. This patient had 1 SLN positive but she has other risky features for recurrence such as her young age, high grade, high Ki67, and +LVSI so very reasonable to include RNI in this case. If the patient had less aggressive tumor biology and more favorable features, one could consider treating WBRT alone with high tangents to cover the level 1 and 2 axilla.
Simulation included a headfirst, supine setup on a breast board with the patient’s left arm raised and head turned to her right side. If a breast board is unavailable, a wingboard or vac-loc are alternatives for fixation. Consider wiring scars, and mark breast borders; given this is a left-sided breast cancer, also consider a Deep Inspiratory Breath Hold scan.
Breast borders are marked as: superior border at the level of the inferior clavicle head, medial border at the patient’s midline, lateral border at the mid-axillary line, and inferiorly mark 1-2 cm below the inframammary fold.
Contour the tumor bed, adding a 1cm margin for a PTV. Also contour the ipsilateral axillary nodes levels 1-3, the ipsilateral supraclavicular nodes, and the ipsilateral IMN’s.
For field arrangements, create opposing tangential fields with the isocenter placed at the level of my superior border to create a half beam block sup/inf. This is called a mono-isocentric technique
Set Beams eye view’s field borders to encompass those marked borders, with the tangent breast beam angles adjusted so the posterior field edges align on a straight edge. Also ensure atleast a 2-3cm flash anteriorly. Evaluate the lung and heart involved in the field and make adjustments as fit to reduce dose without too much compromise to coverage.
Add a superior nodal anterior field, angled 5-10 degrees towards the opposing side to avoid the spinal cord. This field would be bordered to block the spinal cord medially, laterally just past the humeral head to cover the contoured level 1 and 2 axillary nodes, inferiorly to match the half beam blocked breast tangents border, and superiorly to cover the contours supraclavicular nodes.
Adjust the MLC’s to block the humeral head, spinal cord, and thyroid, without compromising nodal coverage. A PA beam can be considered as well later in the planning process if the anterior fields alone do not adequately cover the axillary nodes. It would be dosed so the primary dose contribution would come from the anterior field.
If the IMN’s are not properly covered and the heart and lung coverage permit, begin field adjustments with partially-wide tangents. If inadequate, a medial electron field can be brought it. This would require lateralization of our tangent fields to permit for a suitable electron field that is wide enough for clinical use. If the IMNs are too deep, an electron photon mix can be used for this field. When placing in an IMN electron field, ensure the gantry angle is matched your anterior breast tangent gantry angle but adjusted further anteriorly 5-7 degrees to account for the lateral bowing of the electron dose distribution. Feathering of this field with the tangent fields should be considered as well.
For planning evaluation, ensure that the lung V20 is ideally less than 30%, although consider up to 35%. For the heart, ensure that <5% of the heart received no more than 40% of the prescription dose, but ideally as low as possible. Ensure the mean heart dose can be held to <5Gy, but the lower the better, ideally less than 2Gy. Also evaluate the thyroid dose and ensure there are no high doses in this region, looking for less than 3% of the Rx dose.
Tumor boost plans are typically electron versus photon based boosts, with electrons selected for more superficial tumor beds, and mini tangents versus non-coplanar arrangements with photons for deeper tumor beds. The superficiality of the tumor doesn’t preclude either modality from being used, the overall goal is to minimize breast and OAR dose while ensuring appropriate tumor bed dose.
With electron beam planning, you should adjust your energy to make sure you have adequate deep coverage, and ensure at least a 1.5 cm margin around your PTV, to account for the larger penumbra of electrons.
In regards to side effects, acutely, discuss fatigue and skin changes. Long term, monitor for lymphedema, radiation pneumonitis, increased risk for rib fracture, thyroid toxicity, cardiotoxicity, breast edema/fibrosis, and a low risk for secondary malignancies.
Follow up includes appointments 1-4 x per year for a H&P for up to 5 years, then annually with a clinical exam. Consider obtaining a mammogram at 6 months, then yearly
In this case, if the patient presents to you initially, but has a 6 cm tumor, bulky fixed LAD and is ER/PR- HER2+, they would be considered cT3N2.
Having residual disease after NAC is a poor prognostic sign. Consider additional HER2 directed therapy with TDM1 in this secondary case.
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