Tumor bed volumetric changes during breast irradiation for the patients with breast cancer

Displacement of Surgical Clips in Patients with Human Acellular Dermal Matrix in the Excision Cavity during Whole Breast Irradiation Following Breast-Conserving Surgery

PURPOSE

The purpose of this study was to investigate the displacement of surgical clips in the excision cavity during whole breast irradiation following breast-conserving surgery (BCS) with or without acellular dermal matrix (ADM) insertion, and to analyze clinicopathologic factors associated with the displacement of surgical clips.

MATERIALS AND METHODS

From 2016 to 2017, 100 consecutive breast cancer patients who underwent BCS with the placement of surgical clips (superior, inferior, medial, lateral, and deep sides) in the tumor bed were included in this study. All patients took first planning computed tomography (CT) scan (CT 1) before whole breast irradiation and second CT scan (CT 2) before boost irradiation. Between two sets of planning CT, the displacement of surgical clips was calculated from the ΔX (lateral-medial), ΔY (anterior-posterior), ΔZ (superior-inferior), and three-dimensional (3D) directions. Patients were divided into two groups according to the breast volume replacement with ADM: group A with ADM and group B without ADM.

RESULTS

The means and 1 standard deviations of 3D displacement for superior, inferior, medial, lateral and deep clips were 5.2±2.9, 5.2±3.2, 5.6±4.5, 5.6±4.3, and 4.9±4.9 mm in entire cohort (n=100); 5.6±2.6, 6.0±3.5, 6.7±5.8, 6.7±5.7, and 6.1±7.4 mm in group A (n=38); 4.9±3.1, 4.8±3.0, 5.0±3.5, 5.0±2.9, and 4.3±2.8 mm in group B (n=62), respectively. The 3D displacements of group A were longer than those of group B, but only significant difference was observed in lateral clip (p=0.047).

CONCLUSION

This study demonstrated displacement of surgical clips during whole breast irradiation in patients with ADM insertion. For patients who had breast volume replacement using ADM, adaptive boost planning should be considered.

Imaging dose of megavoltage computed tomography (MVCT) for treatment verification in the tomotherapy of breast cancer

Aim

The purpose of this study was to investigate whether significant difference exists on radiation dose delivered to organs at risks in megavoltage computed tomography (MVCT) verification using three predefined scanning modes, namely fine (2 mm), normal (4 mm) and coarse (6 mm). This will provide information for the imaging protocol of tomotherapy for the left breast.

Materials and methods

Organ doses were measured using thermoluminescent dosimeters (TLD-100) placed within a female Rando phantom for MVCT imaging. Kruskal–Wallis test was conducted with p<0·05 to evaluate the significant difference between the three MVCT scanning modes.

Results

Statistically significant difference existed in organ absorbed dose between different scan mode selections (p<0·001). Relative to the normal scan selection (4 mm), the absorbed dose to the organs of interests can be scaled down by 0·7 and scaled up by 2·1 for coarse (6 mm) and fine scans (2 mm) respectively.

Conclusions

Optimisation of imaging protocols is of paramount importance to keep the radiation exposure ‘as low as reasonably achievable’. The recommendation of undergoing daily coarse mode for MVCT verification in breast tomotherapy not only mitigates the radiation exposure to normal tissues, but also trims the scan-acquisition time.

Displacement of Surgical Clips during Postoperative Radiotherapy in Breast Cancer Patients Who Received Breast-Conserving Surgery

PURPOSE

Surgical clips are used as a target for postoperative breast radiotherapy, and displacement of surgical clips would result in inaccurate delivery of radiation. We investigated the displacement range of surgical clips in the breast during postoperative radiotherapy following breast-conserving surgery.

METHODS

A total of 178 patients who received breast-conserving surgery and postoperative radiation of 59.4 Gy in 33 fractions to the involved breast for 6.5 weeks were included. Surgical clips were used to mark the lumpectomy cavity during breast-conserving surgery. Patients undertook planning computed tomography (CT) scan for whole breast irradiation. Five weeks after beginning radiation, when the irradiation dose was 45 Gy, planning CT scan was performed again for a boost radiotherapy plan in all patients. The surgical clips were defined in both CT images and compared in lateromedial (X), anteroposterior (Y), superoinferior (Z), and three-dimensional directions.

RESULTS

The 90th percentile of displacement of surgical clips was 5.31 mm (range, 0.0-22.2 mm) in the lateromedial direction, 7.1 mm (range, 0.0-14.2 mm) in the anteroposterior direction, and 6.0 mm (range, 0.0-10.0 mm) in the superoinferior direction. The 90th percentile of three-dimensional displacement distance was 9.8 mm (range, 0.0-28.2 mm). On the multivariate analysis, seroma ≥15 mL was the only independent factor associated with the displacement of surgical clips. In patients with seroma ≥15 mL, the 90th percentile of displacement of surgical clips was 15.1 mm in the lateromedial direction, 12.7 mm in the anteroposterior direction, 10.0 mm in the superoinferior direction, and 21.8 mm in the three-dimensional distance.

CONCLUSION

A target volume expansion of 10 mm from surgical clips may be sufficient to compensate for the displacement of clips during postoperative radiotherapy after breast-conserving surgery. For patients who had a seroma, a replanning CT scan for a boost radiation should be considered to ensure exact postoperative radiotherapy in breast cancer.

Comparison of two radiation techniques for the breast boost in patients undergoing neoadjuvant treatment for breast cancer

OBJECTIVE

After breast conservative surgery (BCS) and whole-breast radiotherapy (WBRT), the use of boost irradiation is recommended especially in patients at high risk. However, the standard technique and the definition of the boost volume have not been well defined.

METHODS

We retrospectively compared an anticipated pre-operative photon boost on the tumour, administered with low-dose fractionated radiotherapy, and neoadjuvant chemotherapy with two different sequential boost techniques, administered after BCS and standard adjuvant WBRT: (1) a standard photon beam (2) and an electron beam technique on the tumour bed of the same patients. The plans were analyzed for the dosimetric coverage of the CT-delineated irradiated volume. The minimal dose received by 95% of the target volume (D95), the minimal dose received by 90% of the target volume (D90) and geographic misses were evaluated.

RESULTS

15 patients were evaluated. The sequential photon and electron boost techniques resulted in inferior target volume coverage compared with the anticipated boost technique, with a median D95 of 96.3% (range 94.7-99.6%) and 0.8% (range 0-30%) and a median D90 of 99.1% (range 90.2-100%) and 54.7% (range 0-84.8%), respectively. We observed a geographic miss in 26.6% of sequential electron plans. The results of the anticipated boost technique were better: 99.4% (range 96.5-100%) and 97.1% (range 86.2-99%) for median D90 and median D95, respectively, and no geographic miss was observed. We observed a dose reduction to the heart, with left-sided breast irradiation, using the anticipated pre-operative boost technique, when analyzed for all dose-volume parameters. When compared with the sequential electron plans, the pre-operative photon technique showed a higher median ipsilateral lung Dmax.

CONCLUSION

Our data show that an anticipated pre-operative photon boost results in a better coverage with respect to the standard sequential boost while also saving the organs at risk and consequently fewer side effects.

ADVANCES IN KNOWLEDGE

This is the first dosimetric study that evaluated the association between an anticipated boost and neoadjuvant chemotherapy treatment.

Setup Error and Effectiveness of Weekly Image-Guided Radiation Therapy of TomoDirect for Early Breast Cancer

PURPOSE

This study investigated setup error and effectiveness of weekly image-guided radiotherapy (IGRT) of TomoDirect for early breast cancer.

MATERIALS AND METHODS

One hundred and fifty-one breasts of 147 consecutive patients who underwent breast conserving surgery followed by whole breast irradiation using TomoDirect in 2012 and 2013 were evaluated. All patients received weekly IGRT. The weekly setup errors from simulation to each treatment in reference to chest wall and surgical clips were measured. Random, systemic, and 3-dimensional setup errors were assessed. Extensive setup error was defined as 5 mm above the margin in any directions.

RESULTS

All mean errors were within 3 mm of all directions. The mean angle of gantry shifts was 0.6°. The mean value of absolute 3-dimensional setup error was 4.67 mm. In multivariate analysis, breast size (odds ratio, 2.82; 95% confidence interval, 1.00 to 7.90) was a significant factor for extensive error. The largest significant deviation of setup error was observed in the first week of radiotherapy (p < 0.001) and the deviations gradually decreased with time. The deviation of setup error was 5.68 mm in the first week and within 5 mm after the second week.

CONCLUSION

In this study, there was a significant association between breast size and significant setup error in breast cancer patients who received TomoDirect. The largest deviation occurred in the first week of treatment. Therefore, patients with large breasts should be closely observed on every fraction and fastidious attention is required in the first fraction of IGRT.

A prospective cohort study on postoperative radiotherapy with TomoDirect using simultaneous integrated boost technique in early breast cancer

PURPOSE

To evaluate the technical feasibility and toxicity of TomoDirect in breast cancer patients who received radiotherapy after breast-conserving surgery.

METHODS

155 consecutive patients with breast carcinoma in situ or T1-2 breast cancer with negative lymph node received breast irradiation with TomoDirect using simultaneous integrated boost technique in the prospective cohort study. A radiation dose of 50.4 Gy and 57.4 Gy in 28 fractions was prescribed to the ipsilateral breast and tumor bed, respectively. Dosimetric parameters of target and organ at risk and acute complication were assessed prospectively.

RESULTS

The mean dose for the tumor bed is 58.90 Gy. The mean values of V54.53Gy (95% of the prescribed dose), V63.14Gy (110% of the prescribed dose), and V66.01Gy (115% of the prescribed dose) were 99.97%, 1.26%, and 0%, respectively. The mean value of radiation conformality index was 1.01. The mean value of radical dose homogeneity index was 0.89. The average dose irradiated to the ipsilateral lung, heart, and contralateral breast was 4.72 Gy, 1.09 Gy, and 0.19 Gy, respectively. The most common toxicity was dermatitis. During breast irradiation, grade 2 and 3 dermatitis occurred in 41 (26.5%) and 6 (3.9%) of the 155 patients, respectively. Two patients had arm lymphedema during breast irradiation. Two patients had grade 2 pneumonitis 1 month after breast irradiation.

CONCLUSIONS

Radiotherapy using TomoDirect in early breast cancer patients showed acceptable toxicities and optimal results in terms of target coverage and organ at risk sparing.