Unintended irradiation of internal mammary chain – Is that enough?

Abstract

Internal mammary chain RadiotherapyUnintentional irradiation 3DCRT a b s t r a c t Aim: To evaluate the unintentional coverage of the internal mammary chain (IMC) with tangential fields irradiation to the breast, and its relation with the type of surgery employed. Background:The dose distribution in regions adjacent to the treatment targets (mammary

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

“…While the IIMNI dose were consistent, regardless of the irradiation technique (3D-CRT: 33.80 Gy, F-IMRT: 29.65 Gy, and I-IMRT: 32.95 Gy, respectively) (26). Similar to Sapienza et al (14), we observed that the addition of SCF field irradiation did not significantly increase the Dmean of the IMNs in the PMRT patients. Regardless of the radiotherapy technique, patient anatomy and clinical factors could eventually influence the dose distribution.…”

“…We postulated that patient anatomy and technical parameters were the potential factors influencing IIMNI dose variance and attempted to determine whether the combination of such influencing factors could potentially indicate a subgroup of patients in whom it would be appropriate to avoid IMN radiotherapy. According to Sapienza et al (14) and Arora et al (15), the predictor for incidental dose to the IMNs is the Tstage and N-stage of the tumor. These authors revealed that advanced N-and T-stage involvement was correlated with higher average doses to IMNs.…”

“…It seems questionable whether a sub-group [that IMN receive high doses during incidental IMNI (IIMNI)] benefits from omission of IMNI, since high doses in the organs at risk (OARs) (heart and lung), comparable to IMNI, must be expected for these patients. Several studies have demonstrated the contribution of insufficient incidental radiation doses to IMNs using 3D-CRT (13)(14)(15)(16)(17). Some patients may not need IMNI, and this can minimize the risk of distant radiotherapy-induced cardiotoxicity, but there is insufficient evidence at this time to define such subgroups in detail.…”

Standard Tangential Radiation Fields Do Not Provide Incidental Coverage to the Internal Mammary Nodes

“…21,23 Furthermore, our study found that the use of reconstruction (expander or permanent) after mastectomy was an independent predictor for receiving lower IMN doses, which follows the similar findings of mastectomy versus breast-conserving surgery. This trend to provide lower IMN coverage in patients with breast reconstruction was also suggested in the publication by Sapienza et al 21 These results may have interesting implications for patients who undergo mastectomy and delayed breast reconstruction, especially those who receive deep inferior epigastric perforator flap. 26 For this technique, the internal mammary vessels are the preferred recipient vessels in microvascular autologous breast reconstruction.…”

“…13 There is a scarcity of similar dosimetric evaluations assessing the doses received by the IMN nodes with tangential field irradiation. [20][21][22][23][24] In the existing published data, the numbers of patients included are relatively small, and factors predicting IMN coverage have not been evaluated. It is theoretically possible when treating with standard tangential fields in the breast conservation or postmastectomy setting that the IMN chain may receive incidental therapeutic doses in a percentage of patients, hence eradicating microscopic disease to prevent IMN recurrences and distant metastases.…”