[Breast cancer radiation therapy: Current questions in 2023]

Radiation therapy is a corner stone of breast cancer treatment as it has been shown postoperatively that it improves local control and overall survival. In recent years, multidisciplinary therapeutic strategies have evolved considerably for early-stage breast cancer, both surgically and in terms of systemic treatments or radiation therapy. Each of these developments affects other treatment components and open up new questions allowing even more personalized treatments. Essentially normofractionated a few years ago, breast radiation therapy is today very largely moderately or even ultra hypofractionated. De-escalation of the surgery of the axilla has changed the indications for lymph node radiation therapy keeping similar efficacy with reduced toxicity. Indications for radiation therapy after neoadjuvant chemotherapy remain based on pre-chemotherapy staging pending the results of ongoing randomized studies. The addition of a boost to the tumor bed significantly reduces the risk of local recurrence, but the magnitude of this benefit decreases with increasing age. The main risk factors for local recurrence are young age, the associated extended ductal in situ component, hormone receptor negative and high-grade status. The results of the simultaneous integrated boost (SIB) seem similar with normo- or moderately hypofractionated radiation therapy regimen.

IOERT versus external beam electrons for boost radiotherapy in stage I/II breast cancer: 10-year results of a phase III randomized study

Background

Intraoperative radiotherapy with electrons (IOERT) boost could be not inferior to external beam radiotherapy (EBRT) boost in terms of local control and tissue tolerance. The aim of the study is to present the long-term follow-up results on local control, esthetic evaluation, and toxicity of a prospective study on early-stage breast cancer patients treated with breast-conserving surgery with an IOERT boost of 10 Gy (experimental group) versus 5 × 2 Gy EBRT boost (standard arm). Both arms received whole-breast irradiation (WBI) with 50 Gy (2 Gy single dose).

Methods

A single-institution phase III randomized study to compare IOERT versus EBRT boost in early-stage breast cancer was conducted as a non-inferiority trial. Primary endpoints were the evaluation of in-breast true recurrences (IBTR) and out-field local recurrences (LR) as well as toxicity and cosmetic results. Secondary endpoints were overall survival (OS), disease-free survival (DFS), and patient’s grade of satisfaction with cosmetic outcomes.

Results

Between 1999 and 2004, 245 patients were randomized: 133 for IOERT and 112 for EBRT. The median follow-up was 12 years (range 10–16 years). The cumulative risk of IBTR at 5–10 years was 0.8% and 4.3% after IOERT, compared to 4.2% and 5.3% after EBRT boost (p = 0.709). The cumulative risk of out-field LR at 5–10 years was 4.7% and 7.9% for IOERT versus 5.2% and 10.3% for EBRT (p = 0.762). All of the IOERT arm recurrences were observed at > 100 months’ follow-up, whereas the mean time to recurrence in the EBRT group was earlier (55.2 months) (p < 0.05). No late complications associated with IOERT were observed. The overall cosmetic results were scored as good or excellent in physician and patient evaluations for both IOERT and EBRT. There were significantly better scores for IOERT at all time points in physician and patient evaluations with the greatest difference at the end of EBRT (p = 0.006 objective and p = 0.0004 subjective) and most narrow difference at 12 months after the end of EBRT (p = 0.08 objective and p = 0.04 subjective analysis).

Conclusion

A 10-Gy IOERT boost during breast-conserving surgery provides high local control rates without significant morbidity. Although not significantly superior to external beam boosts, the median time to local recurrences after IOERT is prolonged by more than 4 years.

Impact of molecular subtype on 1325 early-stage breast cancer patients homogeneously treated with hypofractionated radiotherapy without boost: Should the indications for radiotherapy be more personalized?

Aim

We report molecular subtype impact on 1325 early breast cancer (BCa) patients treated with whole breast hypofractionated (WBH) adjuvant forward-planned intensity modulated radiotherapy (F-IMRT) without boost.

Methods and materials

From 02/2009-05/2017 1325 patients with pTis-pT3, pNx-N1aM0 BCa who underwent breast conservation surgery were treated with WBHF-IMRT in our institute, to a total dose of 40 Gy/15 fractions, without boost. Median age: 62 (interquartile range-IQR-:51.14–70.53) years. Histology: 8% in situ carcinoma (ISC), 92% invasive tumors. Molecular subtypes (invasive tumors): 49.9% Luminal A, 33.1% Luminal B Her2 negative (−), 6.2% Luminal B Her2 positive (+), 3.6% Hormone Receptor (HR)- Her2+, 7.1% Triple negative (TNBC), and 0.2% HR+. Chemotherapy (CT) was prescribed in 28% of patients, hormonal therapy in 80.3%, monoclonal antibodies (MAb) in 86.8% of Luminal B Her2+ and 97.7% of HR- Her2+ patients.

Results

Median follow up was 72.43 (IQR: 44.63–104.13) months. The 5-year Kaplan-Meier estimates of local relapse-free survival (LRFS) was 97.8%, regional-(RRFS) 98.6%, loco-regional- (LRRFS) 96.9%, distant- (DRFS) 96.6%, disease-free survival (DFS) 94.8% and overall survival (OS) 95.5%. Considering molecular subtypes, 5-year LRFS was: 99.8% for Luminal A, 96.7% for Luminal B Her2-, 94.1% for Luminal B Her2+, 87.9% for HR- Her2+, 95.1% for TNBC and 99.1% for in situ carcinoma.

Conclusion

While the overall estimated probability of LR within 5 years after WBHF-IMRT without boost is good (2.2%), molecular subtypes have a strong impact, despite MAb therapy in Her2+ patients, and CT for TNBC patients, and could be used as a parameter in deciding the boost prescription.

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Hypofractionated three-weeks radiotherapy ensures good local control whitout boost.

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In 1325 early stage breast cancers 5-year local relapse without boost was 2.2%.

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Molecular subtypes have a strong impact on estimated probability of local relapse.

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5-year local control (LC) was 99.8% for Luminal A vs 87.9% for HR- Her2+.

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5-year LC was 96.7% for Luminal B Her2-, 94.1% for Luminal B Her2+, 95.1% for TNBC.

Cardiac serum marker alterations after intraoperative radiotherapy with low-energy x-rays in early breast cancer as an indicator of possible cardiac toxicity

Purpose

To assess acute cardiac toxicity caused by intraoperative radiotherapy (IORT) with low-energy x‑rays for early breast cancer.

Methods

We prospectively analyzed pre- and postoperative troponin I and NT-proBNP in 94 women who underwent breast-conserving surgery between 2013 and 2017 at the Department of Gynecology and Obstetrics of the University Medical Center Mannheim, Germany. Thirty-nine women received IORT using low-energy x‑rays during breast-conserving surgery while 55 patients without IORT formed the control group. Demographic and surgical parameters as well as cardiac markers were evaluated.

Results

There were no significant differences concerning age and side of breast cancer between the groups. Furthermore, no significant difference between the troponin I assays of the IORT and control groups could be found (preoperatively: 0.017 ± 0.006 ng/ml vs. 0.018 ± 0.008 ng/ml; p = 0.5105; postoperatively: 0.019 ± 0.012 ng/ml vs. 0.018 ± 0.010 ng/ml; p = 0.6225). N‑terminal fragment of B‑type natriuretic peptide (NT-proBNP) was significantly higher in the control group 24 h after surgery (preoperatively: 158.154 ± 169.427 pg/ml vs. 162.109 ± 147.343 pg/ml; p = 0.56; postoperatively: 168.846 ± 160.227 pg/ml vs. 232.527 ± 188.957 pg/ml; p = 0.0279).

Conclusion

Troponin I levels as a marker of acute cardiac toxicity did not show any significant differences in patients who received IORT during breast-conserving surgery compared to those who did not.

Electronic supplementary material

The online version of this article (10.1007/s00066-020-01671-3) contains supplementary material, which is available to authorized users.

Adding Boost to Standard Neoadjuvant Radiation for Rectal Cancer Improves Likelihood of Complete Response

BACKGROUND

Pathologic tumor response is a prognostic factor for survival in patients with rectal cancer. Standard neoadjuvant radiation (nRT) dosing for locally advanced rectal cancer ranges from 4500 to 5400 centigray (cGy), but it is unknown if tumor regression differs as a consequence adding a boost to the tumor bed.

METHODS

The National Cancer Database (NCDB) 2006-2016 was used to identify patients 18 years of age and older with clinical stage II and III rectal cancer who received pelvic nRT dosed between 4500 and 5400 cGy. Standard nRT dose (no boost, NB) and dose with boost (DWB) were defined respectively as 4500 and 5040-5400 cGy. Complete pathologic response (pCR) was defined as postoperative pathologic stage of zero. A multivariate logistic regression was performed to evaluate the association between radiation dosing and pCR.

RESULTS

The study cohort was 28,841 patients; the majority received DWB 22,701 (78.7%), while 6140 (21.3%) received NB. pCR was achieved in 3135 (14.4%) patients. On multivariate analysis, patients who received NB were significantly less likely to have complete tumor response (OR 1.41, 95% CI 1.2-1.66, p < 0.001). Other factors significantly associated with pCR included insurance, facility type, tumor characteristics, clinical stage, and time between radiation and surgery.

CONCLUSIONS

This is the first investigation demonstrating that standard dose neoadjuvant radiation for rectal cancer was associated with a lower likelihood of pCR compared with standard dose with boost. Past studies demonstrate that rectal cancer patient survival is strongly correlated with pCR. Prospective trials should focus on examining neoadjuvant radiation dosing to evaluate if DWB improves outcomes.

Adaptive radiation therapy of breast cancer by repeated imaging during irradiation

Breast cancer is the most frequent cancer among females and also a leading cause of cancer related mortality worldwide. A multimodality treatment approach may be utilized for optimal management of patients with combinations of surgery, radiation therapy (RT) and systemic treatment. RT composes an integral part of breast conserving treatment, and is typically used after breast conserving surgery to improve local control. Recent years have witnessed significant improvements in the discipline of radiation oncology which allow for more focused and precise treatment delivery. Adaptive radiation therapy (ART) is among the most important RT techniques which may be utilized for redesigning of treatment plans to account for dynamic changes in tumor size and anatomy during the course of irradiation. In the context of breast cancer, ART may serve as an excellent tool for patients receiving breast irradiation followed by a sequential boost to the tumor bed. Primary benefits of ART include more precise boost localization and potential for improved normal tissue sparing with adapted boost target volumes particularly in the setting of seroma reduction during the course of irradiation. Herein, we provide a concise review of ART for breast cancer in light of the literature.

Is tumor bed boost necessary in patients who achieved ypCR following neoadjuvant chemotherapy and breast conserving therapy? (KROG 12-05 and 16-16)

PURPOSE

This multi-institutional study intended to investigate the effect of tumor bed boost in patients who achieved pathologic complete response (ypCR) following neoadjuvant chemotherapy (NAC) and breast-conserving therapy (BCT).

MATERIALS AND METHODS

We identified 180 patients who initially had lymph node (LN) metastasis and achieved ypCR (ypT0/isN0) following NAC and BCT from the 13 institutions of the Korean Radiation Oncology Group (KROG) 16-16 and KROG 12-05. The effect of tumor bed boost on loco-regional control (LRC), disease-free survival (DFS), and overall survival (OS) rates was analyzed.

RESULTS

In all patients, five-year LRC, DFS and OS rates were 97.5%, 95.4%, and 99.4%, respectively. Tumor bed boost was performed in 158 (87.8%) patients. Advanced N-stage (cN2-3, p = 0.036), close resection margin (p < 0.001), and sentinel lymph node biopsy (p = 0.040) were unfavorable factors for DFS. Tumor bed boost was not a significant factor for LRC, DFS, and OS.

CONCLUSIONS

This study suggests the benefit of tumor bed boost might be minimal in ypCR patients following NAC and BCT. Larger prospective studies are needed to address this issue.

Evaluation of adaptive radiotherapy (ART) by use of replanning the tumor bed boost with repeated computed tomography (CT) simulation after whole breast irradiation (WBI) for breast cancer patients having clinically evident seroma. Jpn J Radiol. 2018;36:401-406. [PMID: 29623550 DOI: 10.1007/s11604-018-0735-2]

PURPOSE

The aim of this study is to evaluate adaptive radiotherapy (ART) by use of replanning the tumor bed boost with repeated computed tomography (CT) simulation after whole breast irradiation (WBI) for breast cancer patients having clinically evident seroma.

MATERIALS AND METHODS

Forty-eight patients with clinically evident seroma at the time of planning CT simulation for WBI were included. Two RT treatment plannings were generated for each patient based on the initial CT simulation and tumor bed boost CT simulation to assess seroma and boost target volume (BTV) changes during WBI. Also, dosimetric impact of ART was analyzed by comparative evaluation of critical organ doses in both RT treatment plannings.

RESULTS

Median time interval between the two CT simulations was 35 days. Statistically significant reduction was detected in seroma volume and BTV during the conventionally fractionated WBI course along with statistically significant reduction in critical organ doses with ART (p < 0.0001).

CONCLUSION

Our data suggest significant benefit of ART by use of replanning the tumor bed boost with repeated CT simulation after WBI for patients with clinically evident seroma.

Targeted intraoperative radiotherapy tumour bed boost during breast-conserving surgery after neoadjuvant chemotherapy

INTRODUCTION

The use of targeted intraoperative radiotherapy (TARGIT-IORT) as a tumour bed boost during breast-conserving surgery (BCS) for breast cancer has been reported since 1998. We present its use in patients undergoing breast conservation following neoadjuvant therapy (NACT).

METHOD

In this retrospective study involving 116 patients after NACT we compared outcomes of 61 patients who received a tumour bed boost with IORT during lumpectomy versus 55 patients treated in the previous 13 months with external (EBRT) boost. All patients received whole breast radiotherapy. Local recurrence-free survival (LRFS), disease-free survival (DFS), distant disease-free survival (DDFS), breast cancer mortality (BCM), non-breast cancer mortality (NBCM) and overall mortality (OS) were compared.

RESULTS

Median follow up was 49 months. The differences in LRFS, DFS and BCM were not statistically significant. The 5‑year Kaplan-Meier estimate of OS was significantly better by 15% with IORT: IORT 2 events (96.7%, 95%CI 87.5-99.2), EBRT 9 events (81.7%, 95%CI 67.6-90.1), hazard ratio (HR) 0.19 (0.04-0.87), log rank p = 0.016, mainly due to a reduction of 10.1% in NBCM: IORT 100%, EBRT 89.9% (77.3-95.7), HR (not calculable), log rank p = 0.015. The DDFS was as follows: IORT 3 events (95.1%, 85.5-98.4), EBRT 12 events (69.0%, 49.1-82.4), HR 0.23 (0.06-0.80), log rank p = 0.012.

CONCLUSION

IORT during lumpectomy after neoadjuvant chemotherapy as a tumour bed boost appears to give results that are not worse than external beam radiotherapy boost. These data give further support to the inclusion of such patients in the TARGIT-B (boost) randomised trial that is testing whether IORT boost is superior to EBRT boost.