Factors Influencing the Incidental Dose Distribution in Internal Mammary Nodes: A Comparative Study

Abstract

Objective: To investigate the effect of anatomic and technical parameters on the incidental internal mammary lymph node (IMN) irradiation (IIMNI) dose among postmastectomy patients. Methods: We retrospectively delineated the IMN on planning CT images from 138 patients who had undergone postmastectomy radiotherapy (PMRT). We analyzed the IIMNI dose coverage and its relationship with anatomic and technical parameters. Results: The IIMNI mean dose was 32.85 ± 9.49 Gy, and 10 of 138 patients (7.25%) treated with PMRT received ≥45 Gy. In univariate analysis, the body weight, body mass index, body surface area, thoracic transverse diameter (D T), ratio of D T to the thoracic anteroposterior diameter (D AP)(R T/AP), planning target volume of IMN (PTV IMN) included in PTV (IMNin) and the ratio of IMNin to PTV IMN (R IMNin) and PTV posterior border were the parameters affecting IIMNI dose. In multivariate analysis, body weight, R T/AP , and R IMNin were correlative factors that affected IIMNI dose. Conclusions: For patients who underwent PMRT without IMN irradiation (IMNI), there was a wide variety in IIMNI doses. A minority of patients had adequate IIMNI dose coverage, and the higher IIMNI doses were associated with the less body weights and more R IMNin .

Dosimetric Evaluation of Incidental Irradiation to the Internal Mammary Chain After Surgery in Breast Cancer Patients

“…Therefore, it will be far more meaningful to study incidental IMC irradiation in a treatment plan that includes ipsilateral breast and supra/infraclavicular field. Our previous study found that when the influence of techniques was combined in patients with MRM, there was no significant increase in the Dmean to the IMC due to the addition of SCF ( 23 ). However, these two studies included a relatively small number of patients with SCF irradiation (nine and seven patients, respectively).…”

“…According to the literature, SCF involvement is an insignificant predictor of IMC involvement dose ( 16 , 23 ). In patients who received CRT, the incidental dose delivered to the IMC showed similar coverage in the SCF group compared with the non-SCF group ( 16 ).…”

“…For patients with negative ALNs and one to three positive ALNs, the recurrence rate in IMN was <0.3% (9), and in the IMC irradiation group, the recurrence rate was 0.2% (10). The clinical outcomes of incidental radiation to regional lymph nodes in terms of locoregional control are gaining widespread attention (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). The exceptionally uncommon overall recurrence in the IMNs is associated with systemic treatment and incidental IMNI (10,20).…”

“…We have proven that incidental irradiation dose to the IMC was not associated with radiotherapy technique, both for patients who underwent BCS and modified radical mastectomy (MRM) (21)(22)(23). Given the fact that the correlation identified between IMNI dose and surgical treatment is still unclear, our study evaluated the incidental irradiation of IMC drainage routes [first to third intercostal spaces (ICS1-3)] with no formal indication for irradiation of the IMC in a real-life cohort.…”

Internal mammary lymph node metastasis in breast cancer patients based on anatomical imaging and functional imaging

“…For patients with breast cancer (stage I, II, or III), observed IMLN recurrence rate was < 1.5% after primary breast cancer treatment, even when the internal mammary chain (IMC) not excised or irradiated [11][12][13]. Patients most likely benefit from systemic therapies and incidental regional node irradiation [14][15][16][17][18]. But according to extended radical mastectomy data, 9.2% of patients with no positive axillary nodes (ALN) present IMLN metastasis [19].…”