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Unintended irradiation of internal mammary chain - Is that enough?

ABSTRACT: 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 gland or chest wall), with incidental irradiation of the IMC, could translate into clinical benefit, due to the proximity of these regions. MATERIALS AND METHODS:One hundred and twelve consecutive conformal radiotherapy plans were correlating the average dose to the IMC with the type of surgery employed, the extent of disease and the irradiation techniques. RESULTS:The mean doses to IMC after modified radical mastectomy (MRM), modified radical mastectomy with immediate reconstruction (MRM + R), and breast conservative surgery (BCS) were 30.34 Gy, 30.26 Gy, and 18.67 Gy, respectively. Significant differences were identified between patients who underwent MRM or MRM + R over BCS (p = 0.01 and 0.003, respectively), but not between MRM and MRM + R (p = 0.88). Mean doses to IMC were greater in patients with T3-T4 tumors when compared with more initial stages (?T2) (p = 0.0096). The lymph node involvement also correlated with higher average doses to IMC (node positive: 26.1 Gy × node negative: 17.8 Gy, p = 0.0017). CONCLUSIONS:The moderate dose level to the IMC in the unintentional irradiation scenario seems to be insufficient to treat the subclinical disease, although it could have an impact in patients undergoing mastectomy.

SUBMITTER: Sapienza LG

PROVIDER: S-EPMC4716404 | biostudies-literature | 2016 Jan-Feb

REPOSITORIES: biostudies-literature

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Unintended irradiation of internal mammary chain - Is that enough?

Sapienza Lucas Gomes LG Chen Michael Jenwei MJ Gomes Maria José Leite MJ Mansur David B DB

Reports of practical oncology and radiotherapy : journal of Greatpoland Cancer Center in Poznan and Polish Society of Radiation Oncology 20150811 1

<h4>Aim</h4>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.<h4>Background</h4>The dose distribution in regions adjacent to the treatment targets (mammary gland or chest wall), with incidental irradiation of the IMC, could translate into clinical benefit, due to the proximity of these regions.<h4>Materials and methods</h4>One hundred and twelve consecutive conformal rad ...[more]

PMID: 26900354

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Project description:AimsIn patients undergoing locoregional radiotherapy (RT) for breast cancer including the internal mammary chain (IMC), VMAT has been shown to be superior to tangential-field radiotherapy in terms of target coverage and minimising dose to heart and lungs. In this study we describe and validate organ motion-based robust optimisation for generating breast and locoregional lymph node VMAT plans that are robust to inter-fractional changes.Materials and methodsIn this retrospective study of five patients with left-sided breast cancer requiring locoregional breast radiotherapy including the IMC, non-robust plans were generated in the nominal scenario (planning-CT) and corresponding robust plans were created by optimising over a range of simulated CTs representing worst-case scenario shape changes to the breast. Both plans were re-calculated on CBCT images (n = 67) acquired prior to RT to generate estimates of delivered fractional dose. Plan robustness to inter-fractional changes was assessed in terms of the estimated target coverage and OAR dose.ResultsOrgan motion-based robust optimisation was able to generate clinically acceptable treatment plans in the nominal scenario on the planning CT with no significant differences to OAR dose between the robust and non-robust planning techniques. All plans (robust and non-robust) achieved the mandatory target coverage requirements. Estimates of delivered dose demonstrated a significant improvement in breast target coverage for the robust plans compared to non-robust plans. For the breast CTV, 92% of the robust plans achieved the optimal D98% > 95% clinical goal as compared to 71% of the non-robust plans (p < 0.01). 94% of robust plans achieved acceptable superficial breast coverage, as compared to 55% for the non-robust technique.ConclusionsOrgan motion-based robust optimisation VMAT is able to produce clinically acceptable organ-at-risk sparing plans for locoregional breast radiotherapy (including the IMC) that are robust to inter-fractional changes, therefore reducing the likelihood of reactive adaptive re-planning.

Project description:BackgroundThe irradiation of breast cancer patients with included internal mammary lymph nodes challenges radiation planning with regard to robustness and protection of OARs. In this publication, a feasible hybrid radiation technique is presented with a retrospective dosimetric and radiobiological analysis of patient data of our institute from 2016 to 2020 and robustness analysis.MethodsThe proposed hybrid irradiation technique consists of two IMRT tangents and two partial VMAT fields. The retrospective dosimetric and radiobiological evaluation are made for 217 patient treatments (right- and left-sided). The robustness is evaluated regarding an artificial swelling from 0.4 to 1.5 cm for a random example patient and compared to a pure VMAT planning technique with use of a virtual bolus. The out of field stray dose is calculated for a selected patient plan and compared to alternative radiation techniques.ResultsThe coverage D95% of the PTVEval (with breast swelling of 1.5 cm) changes for the hybrid plan from 96.1 to 92.1% of prescribed dose and for the pure VMAT plan from 94.3 to 87%. The retrospective dosimetric evaluation of patient irradiations reveals a Dmean for total lung 6.5 ± 0.9 Gy (NTCP[Semenenko 2008] 2.8 ± 0.5%), ipsilateral lung 10.9 ± 1.5 Gy, contralateral lung 2.2 ± 0.6 Gy, heart 2.1 ± 1.1 Gy (ERR[Schneider 2017] 0.02 ± 0.17%) and contralateral breast 1.7 ± 0.6 Gy. The scatter dose of the hybrid irradiation technique is higher than for pure VMAT and lower than for pure IMRT irradiation.ConclusionsThe feasibility of the proposed planning technique is shown by treating many patients with this technique at our radiotherapy department. The hybrid radiation technique shows a good sparing of the OARs in the retrospective analysis and is robust with regards to a breast swelling of up to 1.5 cm. The slightly higher stray dose of the hybrid technique compared to a pure VMAT technique originates from higher number of MUs and lower conformity.

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Unintended irradiation of internal mammary chain - Is that enough?

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Unintended irradiation of internal mammary chain - Is that enough?

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