Special issue. De-escalation of loco-regional treatment in breast cancer: Time to find the balance? Partial breast irradiation

Omission of postoperative radiotherapy after breast-conserving surgery in low-risk breast cancer

BACKGROUND

This prospective cohort study aimed to assess whether postoperative radiotherapy could safely be omitted in women aged 65 years and older with low-risk, estrogen receptor-positive T1N0 breast cancer treated with breast-conserving surgery and adjuvant endocrine therapy.

METHODS

Eligible patients were women aged 65 years and older with unifocal, nonlobular, grade 1 or 2, estrogen receptor-positive, pT1N0 breast cancer treated with breast-conserving surgery and endocrine therapy for 5 years. Patients were followed up with mammography at least annually for 10 years. The primary endpoint was local recurrence. Secondary endpoints were contralateral breast cancer, recurrence-free survival, and overall survival.

RESULTS

The final study cohort included 601 patients with a median age of 71 years (range = 65-90 years) and a median tumor size of 11 mm (range = 3-20 mm). Median follow-up time was 119 months (interquartile range = 103-121 months). The cumulative incidence of local recurrence was 1.5% (95% confidence interval [CI] = 0.8% to 2.8%) and 5.5% (95% CI = 3.8% to 7.6%) at 5 and 10 years, respectively. The cumulative incidence of contralateral breast cancer was 1.7% (95% CI = 0.9% to 3.0%) at 5 years and 4.5% (95% CI = 3.0% to 6.6%) at 10 years. The overall survival rate at 10 years was 83.1% (95% CI = 80.8% to 85.4%). In total, 3 (0.5%) patients died because of breast cancer.

CONCLUSION

Our results support the possibility to omit radiotherapy after breast-conserving surgery in a well-defined subgroup of women aged 65 years and older with low-risk, estrogen receptor-positive, pT1N0 breast cancer receiving adjuvant endocrine therapy.

Stabilised hyaluronic acid gel marker versus surgical clips for tumour bed delineation in breast cancer radiotherapy using MRI-simulation

BACKGROUND AND PURPOSE

Compare breast cancer tumour bed (TB) delineation using stabilised hyaluronic acid (sHA) gel and MRI-simulation versus surgical clips and CT-simulation within same patient cohort.

MATERIALS AND METHODS

Prospective single arm study of patients undergoing breast conserving surgery. Patients had both clips (≥5) and sHA gel markers inserted to define the TB and underwent MRI and CT simulation scans. Six observers delineated the TB aided by gel on MRI, and clips on CT. The primary measure was the inter-observer variability (inter-OV) of the delineated TB using the overlap difference of using clips and CT versus sHA gel and MRI, measured according to the general definition of the conformity index (CIgen).

RESULTS

Of 35 patients recruited, 30 underwent inter-OV analysis of contours and 5 required further breast surgery for positive margins. There was no significant difference in mean CIgen between TB delineated using gel and MRI versus clips and CT (0.463 vs 0.434, p = 0.235). Observers reported higher usefulness of gel in patients who underwent oncoplastic surgery (median utility score 8.2 vs 6.6, p = 0.024), and higher visibility of gel in patients who had their scans within 6 weeks than beyond post-op (median visibility score 8.1 vs 6.1, p = 0.013). When the cavity visualisation score was higher (4-5), the median utility score of gel was lower (5.54 vs 8.0, p < 0.001), and the mean CIgen of clips and CT delineated TB was higher (0.64 vs 0.37, p < 0.001).

CONCLUSION

sHA gel has similar inter-OV of TB delineation compared to ≥5 clips, hence is a reliable alternative to clips when MRI-simulation is used.

Potential of MRI in Assessing Treatment Response After Neoadjuvant Radiation Therapy Treatment in Breast Cancer Patients: A Scoping Review

The objective of this scoping review is to evaluate the potential of Magnetic Resonance Imaging (MRI) and to determine which of the available MRI techniques reported in the literature are the most promising for assessing treatment response in breast cancer patients following neoadjuvant radiotherapy (NRT). Ovid Medline, Embase, CINAHL, and Cochrane databases were searched to identify relevant studies published from inception until March 13, 2023. After primary selection, 2 reviewers evaluated each study using a standardized data extraction template, guided by set inclusion and exclusion criteria. A total of 5 eligible studies were selected. The positive and negative predictive values for MRI predicting pathological complete response across the studies were 67% to 88% and 76% to 85%, respectively. MRI's potential in assessing postradiotherapy tumor sizes was greater for volume measurements than uni-dimensional longest diameter measurements; however, overestimation in surgical tumor sizes was observed. Apparent diffusion coefficient (ADC) values and Time to Enhance (TTE) was seen to increase post-NRT, with a notable difference between responders and nonresponders at 6 months, indicating a potential role in assessing treatment response. In conclusion, this review highlights tumor volume measurements, ADC, and TTE as promising MRI metrics for assessing treatment response post-NRT in breast cancer. However, further research with larger cohorts is needed to confirm their utility. If MRI can accurately identify responders from nonresponders to NRT, it could enable a more personalized and tailored treatment approach, potentially minimizing radiation therapy related toxicity and enhancing cosmetic outcomes.

Deep Inspiration breath Hold facilitates surgical cavity registration on cone beam imaging for Partial breast irradiation

BACKGROUND AND PURPOSE

The quality of the Cone Beam Computed Tomography (CBCT) images used for patient set-up is essential to avoid geographical miss when narrower margins or shorter fractionation are used for example in Accelerated Partial Breast Irradiation (APBI). This study evaluates deep inspiration breath hold (DIBH) with skin guided radiotherapy as a tool for image improvement reducing motion artifacts.

MATERIALS AND METHODS

Daily CBCT images of left and right breast cancer patients with well-defined surgical cavity on CT simulation were used for this study. Only left sided CBCT were acquired with DIBH. Trained and experienced radiation therapists were asked to evaluate the image quality using a cavity visualization score (CVS), an image quality Likert score, and to perform registration shifts. Images were anonymized and therapists were blinded to the use of DIBH.

RESULTS

Images from 21 patients, with 15 CBCT each, were evaluated by 6 radiation therapists, generating 4,015 evaluation points. Statistically significant improvements were observed in CVS and image quality (p < 0.001) with DIBH. Also, the rate of surgical cavity identification increased to 76 % with DIBH compared to 56 % without (p < 0.001). DIBH significantly reduced the inter-observer variability in registration shift corrections (p < 0.001) CONCLUSION: Utilizing DIBH for motion control improves both the image quality and the surgical cavity identification. This results in a decrease in registration variability, which is important for APBI accuracy.