Influence of active breathing control on the dose distribution in the target of forward whole-breast intensity-modulated radiotherapy after breast conserving surgery / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To explore the influence of intrafraction and interfraction target displacement on the dose distribution in the target of forward whole-breast intensity-modulated radiotherapy (IMRT) assisted by active breathing control (ABC).</p><p><b>METHODS</b>Each of the selected patient who had received breast conserving surgery was immobilized and received the primary CT simulation assisted by ABC device to get five sets of CT images in three different breathing status, including free breathing (FB) (one set), moderate deep inspiration breathing hold (mDIBH)(two sets) and deep expiration breathing hold (DEBH) (2 sets). After 10 to 15 fractions of radiation, the repeated CT simulation was completed and the same five sets of CT images were obtained at FB, mDIBH, and DEBH, respectively. In the Pinnacle3 treatment planning system, the forward IMRT planning was completed on the first set of mDIBH CT images from the primary CT simulation, and the planning was separately copied by the special system order to the second set of CT images from the primary CT simulation and to the first set of CT images from the repeated CT simulation, keeping the primary angle, direction, size and shape of the MLC field and prescribed dose un-changed. the volumes covered by selected high dose area in the selected segment were compared.</p><p><b>RESULTS</b>In the planning based on the first set of mDIBH CT images from the primary CT simulation, the volume irradiated by equal and more than 103% of prescribed dose in the segment was (1.16 +/- 0.39) cm3, and the volumes were (3.88 +/- 1.07) cm3 and (51.66 +/- 8.68) cm3 in the plannings copied from the first set of mDIBH CT images from the primary CT simulation respectively to the second set of CT images from the primary CT simulation and first set of CT images from the repeat CT simulation, the difference of the volume in the two plannings based on the two set mDIBH CT image from the primary CT simulation was not statistically significant (t = -1.672, P = 0.103). The difference of the volume in the two plannings based on the two sets of mDIBH CT images respectively from the primary and repeat CT simulations had a significant difference (t = -5.728, P < 0.01).</p><p><b>CONCLUSION</b>If the same threshold of mDIBH is maintained during IMRT after breast conserving surgery, the influence of the intrafraction target displacement on the dose distribution is not significant. However, if set-up error is not adjusted, the interfraction change of position of the segment given to cover the high dose area in the IMRT planning will be significant, resulting in a significant change of dose distribution in the breast.</p>

Study on the target movement in external-beam partial breast irradiation with active breathing control after breast-conserving surgery / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To explore the displacement of surgical clip and cavity during different respiratory status, intrafraction and interfraction for the patients treated by external-beam partial breast irradiation (EB-PBI) assisted by active breathing control (ABC) device after breast-conserving surgery.</p><p><b>METHODS</b>After breast-conserving surgery, twenty-five patients with stage I/II breast cancer who was identified to be feasible for EB-PBI underwent CT-simulation positioning assisted with ABC device. Five series of CT images were done during three respiratory status, which included one series of images during free breathing status (FB), two series of images during moderate deep inspiration breath hold (mDIBH), two series of images during deep expiration breath hold (DEBH) at 75% maximum inspiration capacity, and all of the five series of images were transferred to ADAC Pinnacle3 treatment planning system. This procedure was repeated after 10 - 15 days. The targets were delineated and the first appeared clips were marked by the same radiotherapist on the CT images in mDIBH and DEBH status from the first CT simulation positioning to analyze the displacement of the targets produced by respiratory status. The targets were also delineated and all of the clips were marked by the same radiotherapist on another two series of CT images during mDIBH from the first and repeated CT-simulation positioning for analyzing the intrafraction and interfraction movement of cavity and clips, respectively.</p><p><b>RESULTS</b>There was a significant difference between mDIBH and DEBH in the movement of the point of interest (POI) of the first appeared clip in the directions of X (0.22 cm), Y (1.27 cm) and Z axis (0.50 cm) (chi2 =9.558, P = 0.008); and this was also found to be present in the movement of POI of the cavity in the directions of X (0.10 cm), Y (1.08 cm) and Z axis (0.50 cm) (chi2 = 20.44, P <0.01). Regardless of the clip and the cavity, the movement extent along the direction of Y axis was the biggest. However, no significant difference was found in the displacements of POI of the geometric form constructed by all clips in the directions of X (0.09 cm, 0.68 cm), Y (0.14 cm, 0.37 cm) and Z axis (0.25 cm, 0.50 cm) in the same respiratory status of mDIBH at different moment in the intrafraction and interfraction, respectively; and this was also found in the displacements of POI of the cavity in the direction of X (0.15 cm, 0.66 cm), Y (0.17 cm, 0.45 cm) and Z axis (0.25 cm, 0.75 cm)in the same respiratory status of mDIBH at different moment in the intrafraction and interfraction, respectively.</p><p><b>CONCLUSION</b>The margin of planning target volume for external beam partial breast irradiation in different respiratory status is found to be different, the margin displacement along the different axis is also different in free breathing status. However, it can be controlled almost at the same extent in moderate deep inspiration breath hold if assisted by active breathing control device.</p>