"To clip or not to clip. That is no question!"

Use of tumour bed boost radiotherapy in volume replacement oncoplastic breast surgery: A systematic review

Tumour bed boost radiotherapy (RT) following breast conserving surgery reduces local recurrence in high-risk disease. There is recent debate over challenges to accurately localise tumour bed for RT boost delivery following volume replacement oncoplastic breast surgery (VR-OBS). This review evaluates the reporting of RT boost following VR-OBS in the literature published between January 2010 and December 2021. This review was in line with Preferred Reporting Items for Systematic Reviews and Metaanalysis statement.Nine studies met the inclusion criteria (n=670 patients), and RT boost was used in eight studies. Boost was administered in total to 384 patients (62.5% of irradiated patients). Only two studies reported boost planned target volumes and only one compared these against surgical specimen volumes.RT boost was not reported in most published studies on VR-OBS. Future prospective research are strongly needed to evaluate long-term outcomes of VR-OBS following RT boost, especially on breast cosmesis and patients' satisfaction. DATA AVAILABILITY: Data will be made available upon request.

Partial Breast Irradiation and Surgical Clip Usage for Tumor Bed Delineation After Breast-Conserving Surgery in Canada: A Radiation Oncology Perspective

PURPOSE

Our purpose was to evaluate the usage and perceived benefit of surgical clips for breast radiation therapy planning in Canada, focusing on partial breast irradiation (PBI) after breast-conserving surgery.

METHODS AND MATERIALS

A retrospective institutional review identified patients eligible for PBI based on clinicopathologic criteria, and tumor bed visualization was determined from computed tomography-planning scans. An online survey was subsequently distributed to Canadian radiation oncologists addressing the usage and added value of surgical clips for breast radiation therapy planning purposes. The survey also evaluated PBI usage and regimens. Responses were collected over a 4-week period. PBI regimen usage at our institution was also reviewed from May 1 to December 18, 2020.

RESULTS

Based on clinicopathologic criteria, 306 patients were identified between 2013 and 2018 who were eligible for PBI. However, only 24% (72/306) of cases were noted to have surgical clips, of which over 50% did not assist in tumor bed localization due to inconsistent clip positioning. Similarly, nearly two-thirds (28/43) of survey respondents indicated that surgical clips are placed in the tumor bed in less than 50% of cases. Almost all respondents (42/43) indicated that surgical clips facilitate breast radiation therapy planning and favor the development of guidelines to increase the consistent placement of surgical clips in the tumor bed after breast-conserving surgery. Approximately two-thirds of respondents (28/43) offer PBI to eligible patients as routine treatment, with moderate hypofractionated regimens most commonly recommended. However, the 1-week daily regimen of 26 Gy in 5 fractions is now offered to the majority (77%) of patients at our institution.

CONCLUSIONS

There was strong agreement among Canadian radiation oncologists that surgical clip placement facilitates breast radiation therapy planning, and most favor the development of surgical guidelines for the consistent placement of surgical clips in this setting. With the growing use of PBI, accurate localization of the tumor bed is extremely important.

Consensus statement on tumour bed localization for radiation after oncoplastic breast surgery

Background

Oncoplastic surgery (ops) is becoming the new standard of care for breast-conserving surgery, leading to some challenges with adjuvant radiation, particularly when accurate tumour bed (tbd) delineation is needed for focused radiation (that is, accelerated partial breast irradiation or boost radiation). Currently, no guidelines have been published concerning tbd localization for adjuvant targeted radiation after ops.

Methods

A modified Delphi method was used to establish consensus by a panel of 20 experts in surgical and radiation oncology at the Canadian Locally Advanced Breast Cancer National Consensus Group and in a subsequent online member survey.

Results

These are the main recommendations:■ Surgical clips are necessary and should, at a minimum, be placed along the 4 side walls of the cavity, plus 1-4 clips at the posterior margin if necessary.■ Operative reports should include pertinent information to help guide the radiation oncologists.■ Breast surgeons and radiation oncologists should have a basic understanding of ops techniques and work on "speaking a common language."■ Careful consideration is needed when determining the value of targeted radiation, such as boost, in higher-level ops procedures with extensive tissue rearrangement.

Conclusions

The panel developed a total of 6 recommendations on tbd delineation for more focused radiation therapy after ops, with more than 80% agreement on each statement. All are summarized, together with the corresponding evidence or expert opinion.

Radiological, dosimetric and mechanical properties of a deformable breast phantom for radiation therapy and surgical applications

The displacement of tumor bed walls during oncoplastic breast surgery (OBS) decreases the accuracy of using surgical clips as the sole surrogate for tumor bed location. This highlights the need for better communication of OBS techniques to radiation oncologists. To facilitate OBS practice and investigate clip placement reliability, a realistic silicone-based breast phantom was constructed with components emulating a breast parenchyma, epidermis, areola, nipple, chest wall, and a tumor. OBS was performed on the phantom and surgical clips were placed to mark the tumor bed. The phantom was imaged with CT, MRI, and ultrasound (US). The parenchyma's signal-to-noise ratio (SNR) and clips to parenchyma's contrast-to-noise ratio (CNR) were measured. The phantom's CT Hounsfield Unit (HU), relative electron density (RED), and mass density were determined. 6 and 10 MV photon beam attenuation measurements were performed in phantom material. The Young's Modulus and ultimate tensile strength (UTS) of the phantom parenchyma and epidermis were measured. Results showed that the breast phantom components were visible on all imaging modalities with adequate SNR and CNR. The phantom's HU is 130 ± 10. The RED is 0.983. Its mass density is 1.01 ± 0.01 g cm^-3. Photon attenuation measurements in phantom material were within 1% of those in water. The Young's Moduli were 13.4 ± 4.2 kPa (mechanical) and 30.2 ± 4.1 kPa (US elastography) for the phantom parenchyma. The UTS' were 0.05 ± 0.01 MPa (parenchyma) and 0.23 ± 0.12 MPa (epidermis). We conclude that the phantom's imaging characteristics resemble a fibroglandular breast's and allow clear visualization of high-density markers used in radiation therapy. The phantom material is suitable for dose measurements in MV photon beams. Mechanical results confirmed the phantom's similarity to breast tissue. The phantom enables investigation of surgical clip displacements pre- and post-OBS, and is useful for radiation therapy quality assurance applications.

Interobserver variability (between radiation oncologist and radiation therapist) in tumor bed contouring after breast-conserving surgery

PURPOSE

To examine interobserver variability between the radiation oncologist (RTO) and the radiation therapist (RTT) in delineating the tumor bed (TB) in early breast cancer (BC).

METHODS

We retrospectively analyzed patients who received a radiotherapy boost to the TB. In a first group, the clinical target volume (CTV) for the boost was the surgical bed, defined by using surgical clips. In a second group, the CTV was defined by identifying a seroma cavity or a metallic find on the scar. These contours were compared in terms of volume, number of slices, and Dice similarity coefficient (DSC).

RESULTS

Forty patients were assessed: 20 had surgical clips (group 1) while the other 20 had none (group 2). There was no difference in the number of slices contoured by the 2 operators for group 1, but a statistically significant difference emerged in the volumes: the RTT identified a TB that was a mean 45% smaller than the one identified by the RTO. Random differences were found between the 2 operators for group 2. The TBs delineated for this group were significantly larger (P<0.05) than those identified by the RTT for group 1. The mean Dice value between the RTO's and the RTT's TBs was 0.69±0.07 (range 0.53-0.81) for group 1 and 0.37±0.18 (range 0-0.58) for group 2 (P<0.05).

CONCLUSIONS

This study showed that the use of clips coincided with less interoperator variability. With appropriate training, the RTT may play an important part in the multidisciplinary radiotherapy team.

Auto-planning for VMAT accelerated partial breast irradiation

PURPOSE

To evaluate the quality of accelerated partial breast irradiation (APBI) plans generated by the Auto-Planning module of a commercial treatment planning system (TPS).

MATERIAL AND METHODS

Twenty patients, previously planned and treated with manual planning in a TPS (manM), were re-planned using manual (manP) and automatic (AP) module of a different TPS. Plans were compared in terms of dosimetric parameters, degree of modulation, monitor units and treatment time, and by blind qualitative scoring by a physician. Dosimetric verification was evaluated in terms of γ passing rate and point dose measurements. Statistical differences were evaluated using paired two-sided Wilcoxon's signed-rank test.

RESULTS

A statistically significant improvement in PTV coverage was observed for AP plans compared to clinical plans, while no differences in organs at risk doses were observed. When compared to manP plans, a statistically significant improvement was observed for PTV coverage and homogeneity and for the ipsilateral breast and lung dosimetric parameters. The modulation degree was reduced with AP compared to manM treatment plans, while it was increased compared to manP treatment plans. No differences were observed in γ passing rate. Planning time was reduced from (54.5 ± 8.0) min for manM planning and (62.8 ± 15.0) min for manP planning to (9.8 ± 1.1) min for AP. In the qualitative scoring, AP plans were considered superior both to manM (10/20 cases) and manP plans (12/20 cases) with high clinical relevance.

CONCLUSION

Automatic planning for VMAT APBI was always at least equivalent and overall superior to manual planning.