Patterns of Practice in Radiotherapy for Breast Cancer in Korea

Organ-sparing techniques and dose-volume constrains used in breast cancer radiation therapy - Results from European and Latin American surveys

Background

Advances in local and systemic therapies have improved the outcomes of patients with breast cancer (BC), leading to a possible increased risk for postoperative radiation therapy (RT) late adverse events. The most adequate technologies and dose constraints for organs at risk (OAR) in BC RT have yet to be defined.

Methods

An online survey was distributed to radiation oncologists (ROs) practicing in Europe and Latin America including the Caribbean (LAC) through personal contacts, RO and BC professional groups' networks. Demographic data and clinical practice information were collected.

Results

 The study included 585 responses from ROs practicing in 57 different countries. The most frequently contoured OAR by European and LAC participants were the whole heart (96.6 % and 97.7 %), the ipsilateral (84.3 % and 90.8 %), and contralateral lung (71.3 % and 77.4 %), whole lung (69.8 % and 72.9 %), and the contralateral breast (66.4 % and. 83.2 %). ESTRO guidelines were preferred in Europe (33.3 %) and the RTOG contouring guideline was the most popular in LAC (62.2 %), while some participants used both recommendations (13.2 % and 19.2 %). IMRT (68.6 % and 59.1 %) and VMAT (65.6 % and 60.2 %) were the preferred modalities used in heart sparing strategies, followed by deep inspiration breath-hold (DIBH) (54.8 % and 37.4 %) and partial breast irradiation (PBI) (41.6 % and 24.6 %). Only a small percentage of all ROs reported the dose-volume constraints for OAR used in routine clinical practice. A mean heart dose (Heart-Dmean) between 4 and 5 Gy was the most frequently reported parameter (17.2 % and 39.3 %).

Conclusion

 The delineation approaches and sparing techniques for OAR in BC RT vary between ROs worldwide. The low response rate to the dose constraints subset of queries reflects the uncertainty surrounding this topic and supports the need for detailed consensus recommendations in the clinical practice.

Moderately hypofractionated post-operative radiation therapy for breast cancer: preferences amongst radiation oncologists from countries in Latin America and the Caribbean

Background

The safety and effectiveness of moderately hypofractionated post-operative radiation therapy for breast cancer were demonstrated by several trials. This study aimed to evaluate the current patterns of practice and prescription preference about moderately hypofractionated post-operative radiation therapy to assess possible aspects that affect the decision-making process regarding the use of fractionation in breast cancer patients in Latin America and the Caribbean (LAC). We also aimed to identify factors that can restrain the utilization of moderately hypofractionated post-operative radiation therapy for breast cancer.

Materials an methods

Radiation oncologists from LAC were invited to contribute to this study. A 38-question survey was used to evaluate their opinions.

Results

A total of 173 radiation oncologists from 13 countries answered the questionnaire. The majority of respondents (84.9%) preferred moderately hypofractionated post-operative radiation therapy as their first choice in cases of whole breast irradiation. Whole breast plus regional nodal irradiation, post-mastectomy (chest wall and regional nodal irradiation) without reconstruction, and post-mastectomy (chest wall and regional node irradiation) with reconstruction hypofractionated post-operative radiation therapy was preferred by 72.2% 71.1%, and 53.7% of respondents, respectively. Breast cancer stage, and flap-based breast reconstruction were the factors associated with absolute contraindications for the use of hypofractionated schedules.

Conclusion

Even though moderately hypofractionated post-operative radiation therapy for breast cancer is considered a new standard to the vast majority of the patients, its unrestricted application in clinical practice across LAC still faces reluctance.

Patterns of regional recurrence according to molecular subtype in patients with pN2 breast cancer treated with limited field regional irradiation

OBJECTIVE

There is little evidence regarding the radiotherapy modification based on molecular subtypes in breast cancer. This study aimed to identify the risk and patterns of regional recurrence according to molecular subtype in patients with pN2 breast cancer.

METHODS

We identified 454 patients who underwent radical surgery for breast cancer with 4-9 axillary lymph node metastases. All patients underwent axillary lymph node dissection, adjuvant chemotherapy and limited-field regional nodal irradiation. The rates and patterns of regional recurrence were compared between the following three subgroups: luminal type (estrogen receptor- and/or progesterone receptor-positive), HER2-type (estrogen receptor- and progesterone receptor-negative and HER2-positive) and triple-negative type (estrogen receptor-, progesterone receptor- and HER2-negative).

RESULTS

Regional recurrence occurred in 18/454 patients (4%). The risk of regional recurrence was higher in the triple-negative (hazard ratio 7.641) and HER2-type (hazard ratio 4.032) subtypes than in the luminal subtype. The predominant pattern of regional recurrence was inside the radiotherapy field in triple-negative breast cancer and outside the radiotherapy field in HER2-type and luminal-type cancers.

CONCLUSIONS

In patients with pN2 breast cancer, the risk of regional recurrence was higher in the triple-negative and HER2-type than in the luminal type. In-field recurrence was predominant in triple-negative cancer, while out-field recurrence was frequent in luminal and HER2-type breast cancers.

Hypofractionated Radiotherapy for Early-Stage Breast Cancer: A Propensity Score Matched Analysis

BACKGROUND

In patients with early-stage breast cancer, the treatment results of hypofractionated radiation therapy (RT) and conventional RT are evaluated in efficacy and cost.

METHODS

We retrospectively evaluated 280 patients with early-stage (Tis-2N0M0) breast cancer (including 100 hypofractionated RT patients) with regards to treatment outcomes according to the RT schedule. The median whole-breast RT dose was 42.56 Gy/16 fractions for hypofractionated RT and 50.4 Gy/28 fractions for conventional RT. Most patients (n = 260, 92.9%) additionally received a tumor bed boost RT. We used propensity score matching (PSM) analysis to balance the baseline risk factors for recurrence. The co-primary endpoints of this study were disease-free survival (DFS) and ipsilateral breast tumor recurrence (IBTR). DFS or IBTR was analyzed using the Kaplan-Meier survival curve and log-rank test.

RESULTS

Total 89 pairs of matched patients (1:1 matching, n = 178) were finally evaluated. The median follow-up was 23.6 months. After matching, the 3-year DFS was 100% in the hypofractionated RT group and 98.4% in the conventional RT group; there was no significant difference in DFS between the groups (P = 0.374). Furthermore, the IBTR did not differ between the hypofractionated RT and conventional RT groups (P = 0.374) after matching. The 3-year overall survival was not different between two groups (both 100%). Hypofractionated RT saved 26.6% of the total cost of RT compared to conventional RT. Additionally, the acute skin toxicity rate (≥ grade 2) was also not significantly different between the groups (hypofractionated RT: 10.1% vs. conventional RT: 2.2%).

CONCLUSION

Hypofractionated RT showed good IBTR and DFS, which were compatible to those in conventional RT in breast cancer. Hypofractionated RT is expected to be used more widely because of its low cost and convenience.

Optimal Timing of Expander-to-Implant Exchange after Irradiation in Immediate Two-Stage Breast Reconstruction

BACKGROUND

Time intervals for expander-to-implant exchange from radiation therapy have been reported to reduce device failure. This study investigated the optimal timing of expander-to-implant exchange after irradiation in terms of short- and long-term outcomes.

METHODS

This retrospective review enrolled consecutive patients who underwent immediate two-stage breast reconstruction and radiation therapy to tissue expanders from 2010 to 2019. Receiver operating characteristic curves and the Youden index were used to estimate the optimal time from radiation therapy to implant placement in terms of 49-day (early) and 2-year (late) complications. Logistic regression analysis was performed to identify the risk factors for each complication.

RESULTS

Of the 1675 patients, 133 were included. The 49-day and 2-year complication rates were 8.3 percent and 29.7 percent, respectively. Capsular contracture was the most common 2-year complication. The Youden index indicated that implant placement at 131 days after radiation therapy was most effective in reducing the 49-day complications, but that the 2-year complication was less significant, with lower sensitivity and area under the curve. Modified radical mastectomy, expander fill volume at radiation therapy, and size of permanent implant increased the odds of 49-day complications; none of them was associated with the odds of 2-year complications.

CONCLUSIONS

To reduce short-term complications, the best time point for permanent implant placement was 131 days after radiation therapy. However, there was no significant time interval for reducing long-term complications. Capsular contracture was an irreversible complication of radiation injury that was not modified by postirradiation variables including the time from irradiation or size of permanent implant.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Evaluation of apical clips placed during axillary dissection demonstrates potential under-coverage of axillary radiation therapy target volumes during breast cancer regional nodal irradiation

INTRODUCTION

Evidence-based Australian guidelines (eviQ) recommend adjuvant supraclavicular fossa irradiation after axillary lymph node dissection (ALND) in node-positive breast cancer patients. Disparity between surgically determined versus computed tomography (CT) determined nodal volumes may result in discontiguous nodal volumes and untreated nodal tissue. We examine the extent of untreated nodal tissue in women with breast cancer post-level II or III ALND and adjuvant radiation therapy (RT) using ESTRO contouring guidelines.

METHODS

Female breast cancer patients who underwent level II and III ALND with apical clip placement from 2016 to 2020 and CT simulated in supine position were included. CT-defined axillary level II-IV volumes were contoured using ESTRO guidelines. The distance between the apical clip and RT nodal volumes was measured to indicate extent of untreated tissue.

RESULTS

Of 34 eligible patients treated by 7 surgeons, 76% had level II ALND and 24% level III ALND. Only 5.9% of clips entirely encompassed the corresponding RT nodal volumes. 55.9% of clips fell within and 44.1% fell inferolaterally outside the corresponding RT nodal volumes. A median 3.6 cm (range 0-7.5 cm) of undissected nodal tissue would not be included within standard RT target volumes following eviQ recommendations.

CONCLUSION

There is a disparity between surgically determined versus CT determined axillary nodal volumes, leading to discontiguous nodal volumes and untreated axillary nodal tissue, despite following standard radiation contouring guidelines. Intraoperatively placed apical axillary clips may assist radiation oncologists to accurately delineate undissected nodal tissues at risk.

Should the management of radiation therapy for breast cancer be standardized? Results of a survey on current French practices in breast radiotherapy

Background

Breast cancer is the most frequent cancer in women in France. Its management has evolved considerably in recent years with a focus on reducing iatrogenic toxicity. The radiotherapy indications are validated in multidisciplinary consultation meetings; however, questions remain outstanding, particularly regarding hypofractionated radiotherapy, partial breast irradiation, and irradiation of the internal mammary chain and axillary lymph node area.

Materials and methods

An online survey was sent to 47 heads of radiotherapy departments in France. The survey consisted of 22 questions concerning indications for irradiation of the supraclavicular, internal mammary and axillary lymph node areas; irradiation techniques and modalities; prescribed doses; and fractionation.

Results

Twenty-four out of 47 centers responded (response rate of 51%). This survey demonstrated a wide variation in the prescribed dose regimen, monoisocentric radiotherapy, and indications of irradiation of the lymph node areas.

Conclusion

This survey provides insight into the current radiotherapy practice for breast cancer in France. It shows the need to standardize practices.

Prognostic value of the 21-gene recurrence score for regional recurrence in patients with estrogen receptor-positive breast cancer

PURPOSE

To evaluate the prognostic value of the 21-gene recurrence score (RS) for regional recurrence (RR) in patients with estrogen receptor-positive breast cancer.

METHODS

We reviewed the medical records of 446 patients who underwent 21-gene RS assay after breast-conserving surgery or mastectomy. The high-RS group was defined as patients who were (1) older than 50 years with an RS of 26 or higher, or (2) 50 years or younger with an RS of 16 or higher.

RESULTS

The 5-year rates of local recurrence (LR), RR, and distant metastasis (DM) were 2.2%, 2.7%, and 4.7%, respectively. The 5-year overall survival (OS) rate was 99.1%. Of the patients, 269 (60.3%) had low-RS, while 177 (39.7%) had high-RS. The 5-year OS rate of the high-RS group was significantly lower than that of the low-RS. The 5-year rates of RR and DM in the high-RS group were significantly higher than those in the low-RS group, while the LR rates did not differ significantly. In multivariable analysis, the high-RS group had a significant relationship with increased RR rate (p = 0.037). Patients who had both high-RS and clinical high-risk features had a significantly higher 5-year RR rate (7.9%) compared with other groups.

CONCLUSIONS

High-RS was an independent risk factor for RR. The significantly higher RR rate of patients with both high-RS and clinical high-risk features compared with other groups suggests that this patient group can be a potential candidate for regional nodal irradiation.

Hypofractionated radiation therapy for breast cancer: Preferences amongst radiation oncologists in Europe - Results from an international survey

BACKGROUND AND PURPOSE

We aimed to assess the prescription preference about hypofractionated radiation therapy (HFRT) for breast cancer (BC) patients amongst radiation oncologists (ROs) practicing in Europe and to identify restraints on HFRT utilisation.

MATERIALS AND METHODS

An online survey was circulated amongst ROs in Europe through personal, RO and BC societies' networks, from October 2019 to March 2020. The statistical analyses included descriptive statistics, chi-squared testing, and logistic regression analysis.

RESULTS

We received 412 responses from 44 countries. HFRT was chosen as the preferred schedule for whole breast irradiation (WBI) by 54.7% and for WBI with regional nodes irradiation (RNI) by 28.7% of the responding ROs. In the case of postmastectomy RT with or without reconstruction, HFRT was preferred by 21.1% and 29.6%, respectively. Overall, 69.2% of the responding ROs selected at least one factor influencing the decision to utilise HFRT, the most frequent of which included age (51.4%), RNI (46.9%), internal mammary lymph nodes irradiation (39.7%), BC stage (33.5%) and implant-based breast reconstruction (31.6%). ROs working in academic centres (odds ratio, (OR), 1.7; 95% confidence interval, (CI); 1.1-2.6, p = 0.019), practicing in Western Europe (OR, 4.2; 95%CI; 2.7-6.6, p < 0.0005) and/or dedicating >50% of clinical time to BC patients (OR, 2.5; 95%CI; 1.5-4.2, p = 0.001) more likely preferred HFRT.

CONCLUSION

Although HFRT is recognised as a new standard, its implementation in routine RT clinical practice across Europe varies for numerous reasons. Better dissemination of evidence-based recommendations is advised to improve the level of awareness about this clinical indication.

Breast size and dose to cardiac substructures in adjuvant three-dimensional conformal radiotherapy compared to tangential intensity modulated radiotherapy

Background

The aim of the study was to quantify planned doses to the heart and specific cardiac substructures in free-breathing adjuvant three-dimensional radiation therapy (3D-CRT) and tangential intensity modulated radiotherapy (t-IMRT) for left-sided node-negative breast cancer, and to assess the differences in planned doses to organs at risk according to patients’ individual anatomy, including breast volume.

Patients and methods

In the study, the whole heart and cardiac substructures were delineated for 60 patients using cardiac atlas. For each patient, 3D-CRT and t-IMRT plans were generated. The prescribed dose was 42.72 Gy in 16 fractions. Patients were divided into groups with small, medium, and large clinical target volume (CTV). Calculated dose distributions were compared amongst the two techniques and the three different groups of CTV.

Results

Mean absorbed dose to the whole heart (MWHD) (1.9 vs. 2.1 Gy, P < 0.005), left anterior descending coronary artery mean dose (8.2 vs. 8.4 Gy, P < 0.005) and left ventricle (LV) mean dose (3.0 vs. 3.2, P < 0.005) were all significantly lower with 3D-CRT technique compared to t-IMRT. Apical (8.5 vs. 9.0, P < 0.005) and anterior LV walls (5.0 vs. 5.4 Gy, P < 0.005) received the highest mean dose (D_mean). MWHD and LV-D_mean increased with increasing CTV size regardless of the technique. Low MWHD values (< 2.5 Gy) were achieved in 44 (73.3%) and 41 (68.3%) patients for 3D-CRT and t-IMRT techniques, correspondingly.

Conclusions

Our study confirms a considerable range of the planned doses within the heart for adjuvant 3D-CRT or t-IMRT in node-negative breast cancer. We observed differences in heart dosimetric metrics between the three groups of CTV size, regardless of the radiotherapy planning technique.

First Experience in Korea of Stereotactic Partial Breast Irradiation for Low-Risk Early-Stage Breast Cancer

Purpose: Accelerated partial breast irradiation (A-PBI) in Korean women has been considered impracticable, owing to small breast volume and lack of high-precision radiotherapy experience. We present the first experience of stereotactic-PBI (S-PBI) with CyberKnife M6 to investigate feasibility of use and early toxicities in Korean women with early breast cancers.

Materials and Methods: A total of 104 breasts receiving S-PBI at our institution between September 2017 and October 2018 were reviewed. Patients were selected based on the American Society for Radiation Oncology (ASTRO), American Brachytherapy Society, American Society of Breast Surgeons, and Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology guidelines. A dose of 30 Gy in 5 fractions (NCT01162200) was used. Gold fiducials were routinely inserted near the tumor bed for tracking. Constraints regarding organs-at-risk followed the NSABP-B39/RTOG 0413 protocol.

Results: Median follow-up was for 13 months. Patients were categorized as “suitable” (71.2%) or “cautionary” (28.8%) according to 2017 the ASTRO guidelines. No tracking failure of inserted gold fiducials occurred. Median planning target volume (PTV) and PTV-to-whole breast volume ratio was 73.6 mL (interquartile range, 58.8–103.9 mL) and 17.0% (13.3–19.1%), respectively. Median PTV V_95%, PTV D_max, and ipsilateral breast V_50% were 97.8% (96.2–98.8%), 105.3% (104.2–106.4%), and 35.5% (28.3–39.8%), respectively. No immediate post-S-PBI toxicity ≥ grade 2 was reported, except grade 2 induration in three breasts. All patients remain disease-free to date.

Conclusion: The first use of S-PBI in Korean women was feasible and safe for selected early breast cancer. Based on these results, we have initiated a prospective study (NCT03568981) to test S-PBI in whole-breast irradiation for low-risk early breast cancer.

Influence of Radiation Dose to Reconstructed Breast Following Mastectomy on Complication in Breast Cancer Patients Undergoing Two-Stage Prosthetic Breast Reconstruction

Purpose: This study investigated the association between radiation dose and complication rate in patients who underwent breast reconstruction to understand the role of radiation hypofractionated regimen, boost radiation therapy (RT), and RT techniques.

Methods: We retrospectively evaluated 75 patients treated with post-mastectomy adjuvant RT for breast cancer in the setting of two-stage prosthetic breast reconstruction. Near maximum radiation dose (D_max) in the 2 or 0.03 cc of reconstructed breast or overlying breast skin was obtained from dose-volume histograms.

Results: Post-RT complications occurred in 22.7% of patients. Receiver operating characteristic analysis showed that all near D_max parameters were able to predict complication risk, which retained statistical significance after adjusting other variables (odds ratio 1.12 per Gy, 95% confidence interval 1.02–1.23) with positive dose-response relationship. In multiple linear regression model (R² = 0.92), conventional fractionation (β = 11.7) and 16 fractions in 2.66 Gy regimen (β = 3.9) were the major determinants of near D_max compared with 15 fractions in 2.66 Gy regimen, followed by utilization of boost RT (β = 3.2). The effect of bolus and dose inhomogeneity seemed minor (P > 0.05). The location of hot spot was not close to the high density metal area of the expander, but close to the surrounding areas of partially deflated expander bag.

Conclusions: This study is the first to demonstrate a dose-response relationship between risk of complications and near D_max, where hypofractionated regimen or boost RT can play an important role. Rigorous RT-quality assurance program and modification of dose constraints could be considered as a critically important component for ongoing trials of hypofractionation. Based on our findings, we initiated a multi-center retrospective study (KROG 18-04) and a prospective study (NCT03523078) to validate our findings.