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

Exploring the feasibility of preoperative tumor-bed boost, oncoplastic surgery, and adjuvant radiotherapy schedule in early-stage breast cancer: a phase II clinical trial

BACKGROUND

Oncoplastic breast-conserving surgery (OBCS) improves satisfaction in patients who would fare otherwise sub-optimal cosmetic outcomes while bringing challenges in tumor-bed identification during adjuvant radiotherapy. The ultra-hypofractionated breast radiotherapy further shortens treatment sessions from moderately hypofractionated regimens. To circumscribe the difficulty in tumor-bed contouring and the additional toxicity from larger boost volumes, the authors, propose to move forward with the boost session preoperatively from the adjuvant radiation part. Thus, the present study aims to evaluate the feasibility of a new treatment paradigm of preoperative primary-tumor boost before breast-conserving surgery (BCS) or OBCS followed by adjuvant ultra-hypofractionated whole-breast irradiation (u-WBRT) for patients with early-stage breast cancer.

METHODS

There was a phase II study. Patients younger than 55 years old, with a biopsy confirmed mono-centric breast cancer, without lymph node involvement were enrolled. A preoperative primary-tumor boost was given by a single 10 Gy in 1 fraction, and BCS or OBCS was conducted within 2 weeks afterwards. Adjuvant u-WBRT (26 Gy/5.2 Gy/5 f) was given in 6 weeks postoperatively without any boost, after the full recovery from surgery. Surgical complications and patient-reported outcomes, as assessed via Breast-Q questionnaires, were documented. A propensity score matching approach was employed to identify a control group at a 1:1 ratio for BREAST-Q outcomes comparison.

RESULTS

From May 2022 to September 2023, 36 patients were prospectively enrolled. Surgical complications were observed in seven cases (19.4%), including three cases with Clavien-Dindo (CD) grade 1-2 and four cases with CD grade 3 complications. All but four patients (11.1%) started the planned u-WBRT within 1 week after the predefined due dates postoperatively (≤49 days). Four patients (11.1%) developed grade 2 radiodermatitis after chemotherapy initiation. Compared to the study group, the control patients reported higher scores in chest physical well-being ( P =0.045) and in their attitudes towards arm swelling ( P =0.01). No significant difference was detected in the other of domains (Satisfaction with Breasts, Sexual and Psychosocial Well-Being, and Adverse Effects of Radiation). With a median follow-up period of 9.8 months (2.4-18.9 months), none had any sign of relapse.

CONCLUSION

This Phase II clinical trial confirmed the technical and safety feasibility of a novel radiation schedule in patients undergoing BCS or OBCS. According to the BREAST-Q questionnaire, patients who underwent novel radiation schedules reported lower satisfaction in chest physical well-being. A randomized controlled trial is necessary to further investigate these findings. Additionally, long-term follow-up is required to assess oncological outcomes.

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.