Patterns of Chest Wall Recurrence and Suggestions on the Clinical Target Volume of Breast Cancer: A Retrospective Analysis of 121 Postmastectomy Patients.

Purpose: Radiotherapy is a powerful strategy to prevent chest wall recurrence (CWR) of postmastectomy breast cancer (BC). This retrospective study aims at analyzing patterns of CWR to explore the delineation of clinical target volume. Patients and Methods: Detailed clinicopathological information of postmastectomy BC patients with CWR was collected from our single cancer center based on clear criteria. To describe recurrent positions more accurately, the chest wall was divided into three layers: skin layer (skin and subcutaneous tissues), pectoralis layer (pectoralis major and minor), and rib layer (rib and intercostal muscle). The frequency distribution of recurrence location and its association with clinical pathological factors were analyzed. Results: A total of 121 postmastectomy BC with CWR were included in this study. The percentages of breast tumor located in the upper outer quadrant, upper inner quadrant, lower inner quadrant, lower outer quadrant, overlapping quadrant, and areola area were 31.0% (35/113), 26.5% (30/113), 12.4% (14/113), 5.3% (6/113), 21.1% (25/113), and 2.7% (3/113), respectively. HER2-positive BC (51/113, 45.1%) is the most common BC subtype. Analysis on the patterns of CWR showed that recurrences locating in the skin layer, pectoralis layer, rib layer, mixed layers, and incision periphery accounted for 58.6% (68/116), 9.5% (11/116), 1.7% (2/116), 30.2% (35/116), and 60.5% (46/76), respectively. Rates of recurrences located in the skin and/or pectoralis layers for all BC patients, patients with concomitant distance metastasis, and patients without concomitant distance metastasis were 82.8% (96/116), 85.9% (49/57), and 81.0% (47/58), respectively. Conclusion: For BC patients receiving mastectomy, skin, subcutaneous tissues, pectoralis, and area around incision have a high risk of recurrence, which should be paid more attention in chest wall radiotherapy.