Breast size impact on adjuvant radiotherapy adverse effects and dose parameters in treatment planning

Oncologic Safety of Immediate Oncoplastic Surgery Compared with Standard Breast-Conserving Surgery for Patients with Invasive Lobular Carcinoma

BACKGROUND

Invasive lobular carcinoma (ILC) of the breast grows in a diffuse pattern, resulting in a high risk of positive margins at surgical resection. Oncoplastic approaches have been shown to reduce this risk, but concerns persist around the safety of immediate oncoplastic surgery for those with ILC. This study evaluated the short- and long-term oncologic outcomes of immediate oncoplastic surgery for patients with ILC.

METHODS

This study retrospectively analyzed an institutional database of stages I to III ILC patients who underwent breast-conserving surgery (BCS) with or without immediate oncoplastic surgery (oncoplastic closure or oncoplastic reduction mammoplasty [ORM]). The study compared positive margin rates, rates of successful BCS, and recurrence-free survival (RFS) by type of surgery.

RESULTS

For 494 patients the findings showed that the use of immediate ORM was associated with significantly lower odds of positive margins (odds ratio [OR], 0.34; 95 % confidence interval [CI], 0.17-0.66; p = 0.002). Both lumpectomy with oncoplastic closure and ORM were significantly associated with higher rates of successful BCS than standard lumpectomy (94.2 %, 87.8 %, and 73.9 %, respectively; p < 0.001). No difference in RFS was observed between those undergoing immediate oncoplastic surgery and those undergoing standard lumpectomy alone.

CONCLUSIONS

The patients with stages I to III ILC who underwent immediate oncoplastic surgery had significant benefits including lower odds of positive margins and higher rates of successful BCS, with both types of immediate oncoplastic surgery showing similar RFS compared with lumpectomy alone. This supports the oncologic safety of immediate oncoplastic surgery for diffusely growing tumors such as ILC, providing it an ideal option for patients desiring BCS.

Use of immobilisation bra for daily setup of patients with pendulous breasts undergoing radiotherapy

PURPOSE

A feasibility study to evaluate the Chabner XRT® Radiation Bra (CIVCO Radiotherapy & Qfix, Coralville, IA, USA) as a customised immobilisation device for patients with pendulous breasts undergoing radiotherapy was conducted.

METHODS

A total of 34 patients with large pendulous breasts were fitted with the Chabner XRT® Radiation Bra during RT. A mixed-method questionnaire was administered to both radiation therapists (RTTs) and patients. RTTs evaluated the effectiveness of the bra in setup. Patients appraised its comfort level and ease of wearing. Setup reproducibility was evaluated based on a departmental imaging protocol. Acute skin side effects were documented with photos and assessed using the Radiation Therapy Oncology Group (RTOG) classification.

RESULTS

Of the patients, 27 (79.4%) completed the questionnaire. 23 patients felt comfortable wearing the bra while 20 felt less exposed during treatment. Reproducibility was acceptable, with a median (range) setup error (isocentre) of 0.0 cm (-0.6 to 0.7 cm; left/right), -0.1 cm (-0.5 to 1.2 cm; posterior) and 0.2 cm (-0.5 to 0.9 cm; inferior) achieved based on matched field borders on skin. However, repeated setups and imaging were required for 3 patients due to large breast size (cups D-G; size 4-5). Minimal skin toxicity (grade 0-1) was observed. No grade ≥ 2 was reported. 10 RTTs completed the survey. Male RTTs (n = 4) were not confident in assisting patients with bra fitting. 8 RTTs agreed that although it was difficult to reproduce the breast tissue for treatment, it helped patients to maintain the treatment position.

CONCLUSION

Our study demonstrated the feasibility of using a customised bra which provided optimal setup reproducibility while maintaining minimal skin toxicity and patient comfort, especially the value-added modesty felt among Asian women during their breast cancer radiotherapy.

A Randomised Clinical Feasibility Trial of a Breast Immobilisation Device: The SuPPORT 4 All Bra

AIMS

Despite the breast being a mobile organ, there is currently no standard suitable immobilisation device to optimise radiotherapy for women with larger breasts treated after a wide local excision. The SuPPORT 4 All (S4A) bra was co-designed with patients and radiotherapy professionals. The purpose of this study was to test the feasibility of using the S4A bra in the existing breast cancer radiotherapy pathway.

MATERIALS AND METHODS

A randomised feasibility trial was conducted in a single institution; the primary feasibility endpoint was the recruitment of 50 participants. Efficacy endpoints were also tested, including assessment of skin reactions, dose to organs at risk and patient comfort. Fifty women were randomised to receive either standard radiotherapy with no immobilisation (control) or radiotherapy with the S4A bra (intervention). A separate planning study was undertaken on the cases randomised to receive the S4A bra. Participants in the intervention arm (S4A bra) underwent two planning computed tomography scans, one with the bra on and one without the bra; allowing direct comparison of organs at risk data for S4A bra versus no bra.

RESULTS

All women who started radiotherapy wearing the S4A bra completed treatment with the bra; patient comfort did not change across the 3 weeks of treatment. Positional accuracy using the bra was comparable with existing published accuracy for methods without immobilisation. The mean ipsilateral lung doses showed some improvement when positioning with the S4A bra was compared with the no bra set-up (3.72 Gy versus 4.85 Gy for right-sided cases, 3.23 Gy versus 3.62 Gy for left-sided cases).

CONCLUSIONS

The S4A bra is feasible to use in the radiotherapy pathway with good patient adherence. The S4A bra has potential to reduce dose to organs at risk (specifically ipsilateral lung dose) while maintaining good breast tissue coverage, and improved patient dignity, warranting further investigation on a larger scale.

Volume matters: Breast induration is associated with irradiated breast volume in the Danish Breast Cancer Group phase III randomized Partial Breast Irradiation trial

PURPOSE

The relation between breast induration grade 2-3 at 3 years after radiation therapy and irradiated breast volume was investigated for patients in the Danish Breast Cancer Group (DBCG) Partial Breast Irradiation (PBI) trial. METHODS Treatment plan data was obtained from the Danish radiotherapy plan database. Dosimetric parameters for breast and organs at risk were determined. Breast induration data was obtained from the DBCG database. The volume of the whole breast (CTVp_breast) treated to various dose levels was determined for treatment plans in both arms. Logistic regression was used to assess the frequency of induration on breast volume irradiated to ≥40 Gy. RESULTS PBI and WBI was given to 433 and 432 patients, respectively. Median and interquartile ranges (IQR) for CTVp_breast were 710 mL (467-963 mL; PBI) and 666 mL (443-1012 mL; WBI) (p = 0.98). Median and IQR for CTVp_breast treated to ≥40 Gy was 24.9% (18.6-32.6%; PBI) and 59.8% (53.6-68.5%; WBI). Grade 2-3 induration was observed in 5% (PBI) and 10% (WBI) of the patients. A dose-response relationship was established between irradiated breast volume and frequency of breast induration. From the model, 5% and 10% risks of breast induration were observed for ≥40 Gy delivered to CTVp_breast volumes of 177 mL (95%CI, 94-260 mL) and 426 mL (95%CI, 286-567 mL), respectively. CONCLUSION The frequency of breast induration increased significantly with increasing irradiated breast volume, strongly favouring small volumes and PBI. Thus, treated breast volume - not the breast size itself - is the risk factor for induration. This is the first report directly linking the 40 Gy irradiated breast volume to breast induration.

Favorable safety profile of moderate hypofractionated over normofractionated radiotherapy in breast cancer patients: a multicentric prospective real-life data farming analysis

Background

Moderately hypofractionated whole-breast radiotherapy (HFRT) has proven to be as safe and efficient as normofractionated radiotherapy (NFRT) in randomized trials resulting in major changes in clinical practice. Toxicity rates observed in selected clinical trial patients may differ from those observed in unselected patients with possible comorbidities and frailty in real-life. This study aimed to examine the influence of HFRT versus NFRT on acute toxicity and identify risks factors of dermatitis in real-life patients.

Materials and methods

Prospective data from breast cancer patients, treated with locoregional radiotherapy were collected between November 2015 and February 2020 in 3 comprehensive cancer centers. Through a systematic data-farming strategy, acute toxicity evaluation forms (CTCAEv4.0) were prospectively completed and extracted electronically. The results from each center were then anonymously merged into a single database for analysis. A Chi-2 test was used to compare HFRT and NFRT. Furthermore, risk factors of dermatitis were identified in a sub-study (622 patients) by multivariate logistic regression analysis.

Results

In total, 3518 T0-4 N0-3 mostly M0 (85.8%) breast cancer patients with a median age of 60.7 (24–96 years old) were analyzed. Acute grade 2–3 dermatitis, grade 1–3 breast oedema, and grade 1–2 hyperpigmentation were less frequent with HFRT versus NFRT: respectively 8.9% versus 35.1% (Chi-2 = 373.7; p < 0.001), 29.0% versus 37.0% (Chi-2 = 23.1; p < 0.001) and 27.0% versus 55.8% (Chi-2 = 279.2; p < 0.001). Fewer patients experienced pain with HFRT versus NFRT: 33.4% versus 53.7% respectively (Chi-2 = 137.1; p < 0.001). Factors such as high BMI (OR = 2.30 [95% CI, 1.28–4.26], p < 0.01), large breast size (OR = 1.88 [95% CI, 1.07–3.28], p < 0.01) and lumpectomy over mastectomy (OR = 0.52 [95% CI, 0.27–0.97], p < 0.05) were associated with greater risk factors of grade 2–3 dermatitis in multivariate analysis regardless of NFRT or HFRT.

Conclusion

The results of this study suggests that breast HFRT may be a better option even for patients with a high BMI or large breast size. Acute toxicity was low to mild, and lower with HFRT compared to NFRT. Results from real-life data were robust, and support the use of HFRT beyond randomized study populations. Long-term real-life data awaits further investigation.

Breast Radiotherapy after Oncoplastic Surgery-A Multidisciplinary Approach

Oncoplastic breast surgery encompasses a range of techniques used to provide equitable oncological outcomes compared with standard breast surgery while, simultaneously, prioritizing aesthetic outcomes. While the outcomes of oncoplastic breast surgery are promising, it can add an extra complexity to the treatment paradigm of breast cancer and impact on decision-making surrounding adjuvant therapies, like chemotherapy and radiotherapy. As such, early discussions at the multidisciplinary team meeting with surgeons, medical oncologists, and radiation oncologists present, should be encouraged to facilitate best patient care.

Evidence-based guidelines for hypofractionated radiation in breast cancer: conclusions of the Catalan expert working group

Introduction

Daily, moderate hypofractionation has become standard treatment for breast cancer following breast-conserving surgery, although substantial variation exists in its use. This paper describes the generation of consensus-based recommendations for the utilisation of this therapy at the healthcare system level and compares these to American Society for Radiation Oncology (ASTRO) guidelines.

Materials and methods

Consensus-based guidelines were developed in three steps, including a systematic literature review and involvement of radiation oncologists specialising in breast cancer in Catalonia: (a) creation of a working group and evidence review; (b) consideration of the levels of evidence and agreement on the formulation of survey questions; and (c) performance of survey and development of consensus-based recommendations. Results were compared to the ASTRO recommendations.

Results

Consensus was above 80% for 10 of the 14 survey items. Experts supported hypofractionated radiotherapy for all breast cancer patients aged 40 years or more; with invasive carcinoma and breast-conserving surgery; without radiation of lymph nodes; and regardless of the tumour size, histological grade, molecular subtype, breast size, laterality, other treatment characteristics, or need for a boost. Over half favoured its use in all situations, even where available scientific evidence is insufficient. The resulting recommendations and the quality of the evidence are comparable to those from ASTRO, despite some differences in the degree of consensus.

Conclusion

Specialists agree that hypofractionation is the standard treatment for breast cancer following breast-conserving surgery, but some specific areas require a higher level of evidence before unequivocally extending indications.

Dosimetric Comparison of Four Different Radiotherapy Planning Techniques for Adjuvant Radiotherapy of Left-Sided Breast, Axilla, and Supraclavicular Fossa

Purpose/Aim:

Forward planned intensity-modulated radiotherapy (forward IMRT) with breath-hold (BH) technique is considered optimal by most practitioners for treating left-sided breast cancer. Regional nodal irradiation including axilla and supraclavicular fossa (SCF) increases can increase dose-to-organs at risk (OAR) especially lung. This study was done to assess the potential of inverse planned IMRT (inverse IMRT) to achieve significant reduction in dose to OAR.

Materials and Methods:

Ten patients with left-sided breast cancer treated with Active Breath Co-ordinator BH technique were included in the study. Forward IMRT plans were generated in both BH and free breathing (FB) scans. Inverse IMRT plans were generated in FB scan using Tomotherapy-Direct and Tomotherapy-Helical techniques. Contouring was done as per the ESTRO consensus contouring guidelines. The dose prescribed was 40 Gy in 15 fractions. Statistical significance was tested using one-way ANOVA for parametric data and Kruskall–Wallis test for nonparametric data. Multiple comparison tests were done by using Bonferroni test. P <0.05 was considered to denote statistical significance.

Results:

Inverse IMRT plans achieved superior homogeneity index compared to forward IMRT with BH. Tomotherapy-Direct reduced dose to ipsilateral lung, compared to the forward IMRT with BH while achieving similar doses to other OAR. Tomotherapy-Helical plans achieved significantly better conformity index and reduced maximum dose to left anterior descending artery compared to forward IMRT plans, but low dose to other OAR was significantly worse.

Conclusion:

For left-sided breast, axilla, and SCF radiotherapy, inverse IMRT with Tomotherapy-Direct plan achieved better homogeneity index and reduced dose to ipsilateral lung compared to forward IMRT with BH.

Breast clinical target volume: HU-based glandular CTVs and ESTRO CTVs in modern and historical radiotherapy treatment planning

PURPOSE

The current study aimed to compare contouring of glandular tissue only (gCTV) with the clinical target volume (CTV) as defined according to European Society for Radiotherapy and Oncology (ESTRO) guidelines (eCTV) and historically treated volumes (marked by wire and determined by palpation and anatomic landmarks) in breast cancer radiotherapy.

METHODS

A total of 56 consecutive breast cancer patients underwent treatment planning based solely on anatomic landmarks/wire markings ("wire based"). From these treatment plans, the 50% and 95% isodoses were transferred as structures and compared to the following CT-based volumes: eCTV; a Hounsfield unit (HU)-based automatic contouring of the gCTV; and standardized planning target volumes (PTVs) generated with 1‑cm safety margins (resulting in the ePTVs and gPTVs, respectively).

RESULTS

The 95% isodose volume of the wire-based plan was larger than the eCTV by 352.39 ± 176.06 cm³ but smaller than the ePTV by 157.58 ± 189.32 cm³. The 95% isodose was larger than the gCTV by 921.20 ± 419.78 cm³ and larger than the gPTV by 190.91 ± 233.49 cm³. Patients with larger breasts had significantly less glandular tissue than those with small breasts. There was a trend toward a lower percentage of glandular tissue in older patients.

CONCLUSION

Historical wire and anatomic landmarks-based treatment planning sufficiently covers the glandular tissue and the theoretical gPTV generated for the glandular tissue. Modern CT-based CTV and PTV definition according to ESTRO results in a larger treated volume than the historical wire-based techniques. HU-standardized glandular tissue contouring results in a significantly smaller CTV and might be an option for reducing the treatment volume and improving reproducibility of contouring between institutions.

Hypofractionated whole-breast radiotherapy in large breast size patients: is it really a resolved issue?

The purpose of this study was to evaluate the impact of breast size on acute and late side effects in breast cancer (BC) patients treated with hypofractionated radiotherapy (Hypo-RT). In this study we analyzed patients over 50 years with a diagnosis of early BC, candidate for Hypo-RT after conservative surgery. Acute and late skin toxicities were evaluated in accordance with the RTOG scale. Multivariable logistic analysis was performed using dosimetric/anatomical factors resulted associated with toxicity outcome in univariable analysis. Among patients treated between 2009 and 2015, 425 had at least 5 years of follow-up. At RT end, acute skin toxicity ≥ G2 and edema ≥ G2 occurred in 88 (20.7%) and 4 (0.9%) patients, respectively. The multivariable analysis showed association of skin toxicity with boost administration (p < 0.01), treated skin area (TSA) receiving more than 20 Gy (p = 0.027) and breast volume receiving 105% of the prescription dose (V105%) (p = 0.016), but not breast size. At 5 years after RT, fibrosis ≥ G1 occurred in 89 (20.9%) patients and edema ≥ G1 in 36 (8.5%) patients. Fibrosis resulted associated with breast volume ≥ 1000 cm³ (p = 0.04) and hypertension (p = 0.04). As for edema, multivariable logistic analysis showed a correlation with hypertension and logarithm of age, but not with boost administration. Breast volume had an unclear impact (p = 0.055). A recurrent association was found between acute and late toxicities and breast V105%, which is correlated with breast size. This may suggest that a more homogenous RT technique may be preferred for patients with larger breast size.

Analysis of Geometric and Dosimetric Effects of Bra Application to Support Large or Pendulous Breasts During Radiotherapy Planning: A Retrospective Single-Center Study

Purpose:

To evaluate geometric and dosimetric effects of bra application during radiotherapy planning for breast cancer patients with large and pendulous breasts.

Materials and Methods:

Twenty patients with chest sizes >38 inches between April 2019 and July 2019 underwent radiotherapy planning with and without a radiation bra (Chabner XRT^®). Geometric and dosimetric parameters included the breast volume, superior-inferior (SI) distance, separation (S) as the distance of the longest diameter of the clinical target volume (CTV), conformity number (CN), and homogeneity index (HI) of CTV. The organs at risk (OARs) were defined as the lungs, heart, and liver.

Results:

The use of the radiation bra provided mean changes of −0.51 cm for S, −1.45 cm for SI, and −61.18 cc for breast volume (all P < 0.05). Breast volume was correlated with bra-related changes in cross diameter (r = 0.641, P = 0.002) and volume (r = 0.680, P = 0.001). Significant dose reductions were observed for the lungs (mean V₁₀: 19.58 cc, V₂₀: 17.13 cc, D_mean: 86.24 cGy) and heart (D_mean: 170.23 cGy). No significant differences were observed for CN (0.62-0.67) and HI (0.19-0.20) of the CTV.

Conclusion:

The application of a radiation bra was associated with better geometric and dosimetric planning parameters, with a smaller CTV and lower doses to the OARs (lungs and heart) in the radiotherapy field. In addition, we expect that bra use during radiotherapy would provide emotional benefits.

Cosmetic Outcomes and Symmetry Comparison in Patients Undergoing Bilateral Therapeutic Mammoplasty for Breast Cancer

Background

Breast-reduction techniques are increasingly used in oncoplastic breast surgery. Bilateral therapeutic mammoplasty has the benefit of decreasing breast volume, enabling resection of larger tumors, and the potential to assure good postoperative symmetry. The aims of this study were to objectively asses the cosmetic outcomes of therapeutic mammoplasty in patients with breast cancer, using the breast cancer conservative treatment cosmetic results (BCCT.core) software, to compare this score with the surgeon’s score and the patient’s assessment, and to evaluate if other defined parameters have an impact on cosmetic outcomes. The secondary aim was to compare breast symmetry pre- and postoperatively.

Materials and Methods

We enrolled 146 consecutive patients with primary breast cancer who underwent therapeutic mammoplasty between 2011 and 2018 in Kristianstad Central Hospital, Sweden. We retrospectively collected data from patients’ records. We analyzed the BCCT.core score using postoperative photographs to objectively evaluate cosmetic outcomes on a four-grade scale and compared with preoperative photographs to evaluate symmetry. Cosmetic outcomes were also assessed subjectively by patients and surgeons, using a 10-point Likert scale.

Results

The majority of patients (89%) had good or excellent BCCT.core scores, which correlated with surgeons’ scores, rs =  − 0.22 (p < 0.001). Overall, patients were more satisfied with the cosmetic outcomes than the surgeons (p < 0.001). Evidence supporting an association between the defined clinicopathological variables, for example, tumor size, and cosmetic outcomes, was weak.

Conclusion

Therapeutic mammoplasty yields a very good cosmetic outcome, evaluated both by subjective and objective measurements. Importantly, symmetry can be improved in patients with asymmetry.

Supplementary information

The online version contains supplementary material available at (10.1007/s00268-020-05941-0).

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.

Hypofractionated Whole Breast Irradiation and Simultaneous Integrated Boost in Large-breasted Patients: Long-term Toxicity and Cosmesis

INTRODUCTION

The purpose of this study was to evaluate the impact of breast size on long-term toxicity and cosmesis in patients with breast cancer treated with hypofractionated simultaneous integrated boost (SIB) using volumetric modulated arc therapy (VMAT).

PATIENTS AND METHODS

Patients with early stage breast cancer were treated with 3-week hypofractionated SIB-VMAT to the whole breast (40.5 Gy) and tumor bed (48 Gy). Two cohorts were identified: small/medium- (< 1000 cm³) and large- (> 1000 cm³) breasted patients. Acute and late (at 2 and 5 years) skin toxicity and cosmetic data were analyzed. Univariate and multivariate analysis evaluated associations between toxicity and dosimetric/anatomical variables.

RESULTS

From August 2010 to March 2017, a total of 1160 patients were treated; 831 had at least 2 years of follow-up and were analyzed. Treated skin area (TSA) receiving at least 20 Gy > 400 cm² and V_{105% of Boost} > 5 cm³ were significant predictors for acute skin toxicity. Multivariate analysis at 2 years was significant for boost volume > 70 cm³, TSA > 400 cm², and breast size > 1500 cm³. At 5 year analysis (352 patients), none of the analyzed variables was significant. For cosmetic outcome, only the breast size (> 1000 cm³) and the boost size > 70 cm³ at 2 and 5 years, respectively, confirmed significance.

CONCLUSIONS

The TSA > 400 cm² resulted as a significant predictor of both acute and late skin toxicity at 2 years; however, at 5 years, no breast size or dosimetric parameter suggested indications for increased toxicity. A worse cosmetic outcome was recorded at the 2-year follow up for large breasts, but was not confirmed at the 5-year follow-up. These long-term data suggest that hypofractionated SIB-VMAT is a viable modality also in large-breasted patients.

Dosimetric consequences of image guidance techniques on robust optimized intensity-modulated proton therapy for treatment of breast Cancer

PURPOSE

To investigate the consequences of residual setup error on target dose distribution using various image registration strategies for breast cancer treated with intensity-modulated proton therapy (IMPT).

MATERIALS AND METHODS

Among 11 post-lumpectomy patients who received IMPT, 44 dose distributions were computed. For each patient, the original plan (Plan-O) and three verification plans were calculated using different alignments: bony anatomy (VPlan-B), breast tissue (VPlan-T), and skin (VPlan-S). The target coverage were evaluated for each alignment technique. Additionally, 2 subvolumes-BreastNearSkin (1-cm rim of anterior CTV) and BreastNearCW (1-cm rim of posterior CTV)-were created to help localize CTV underdosing. Furthermore, we divided the setup error into the posture error and breast error. Patients with a large posture error and those with good posture setup but a large breast error were identified to evaluate the effect of posture error and breast error.

RESULTS

For Plan-O, VPlan-B, VPlan-T, and VPlan-S, respectively, the median (interquartile range) breast CTV D95 was 95.7%(94.7-96.3%), 95.1% (93.9-95.7%), 95.2% (94.8-95.6%), and 95.2% (94.9-95.7%); BreastNearCW D95 was 96.9% (95.6-97.3%), 94.8% (93.5-97.0%), 95.6% (94.8-97.0%), 95.6% (94.8-97.1%); and BreastNearSkin D95 was 94.1% (92.7-94.4%), 93.6% (92.2-94.5%), 93.5% (92.4-94.5%), and 94.4% (92.2-94.5%) of the prescription dose. 4/11 patients had ≥1% decrease in breast CTV D95, 1 of whom developed breast edema while the other 3 all had a > 2^o posture error. The CTV D95 variation was within 1% for the patients with good posture setup but >2^o breast error.

CONCLUSION

Acceptable target coverage was achieved with all three alignment strategies. Breast tissue and skin alignment maintained the breast target coverage marginally better than bony alignment, with which the posterior CTV along the chest wall is the predominant area affected by under-dosing. For target dose distribution, posture error appears more influential than breast error.

An audit of radiation-induced skin reactions in the inframammary fold; does breast size impact on the severity of the reaction?

INTRODUCTION

Skin toxicity is a clinically significant side effect of external beam radiation; moist desquamation is particularly prevalent for breast patients, mainly in the axilla and inframammary fold (IMF). The aim of this audit was to assess if there is a correlation between patient breast size and the presence and extent of radiotherapy skin reaction in the IMF.

METHODS

Between 22/12/2017 and 31/05/2018 forty patients undergoing standard whole breast radiotherapy using 3D planned medial and lateral tangential fields had their skin reaction recorded weekly, whilst on treatment, using the Radiotherapy Oncology Group (RTOG) scoring system. Skin reactions were also documented at three and eight weeks post radiotherapy. A measurement of the patients IMF length and bra size were also noted. Statistical analysis was carried out using IBMÒ SPSS Statistics 24.

RESULTS

Six patients presented with grade ≥2 during week three of radiotherapy. The mean IMF length of six patients with adverse reactions 6.1 cm (±3.6 cm). As the length of the IMF increases, severity of skin reactions also increases; a positive correlation was identified between the two at both week three of radiotherapy and three weeks post radiotherapy (r = 0.401, n = 34, p = 0.05 and r = 0.671, n = 29, p = 0.00 respectively). Only one patient displayed grade 2 at eight weeks post radiotherapy (IMF length 7.5 cm).

CONCLUSION

The findings from this study would suggest that larger breasted patients do present earlier, and with more severe radiation-induced skin reactions.

IMPLICATIONS FOR PRACTICE

Changes to skin care practice could be considered for patients with larger breasts. This could be in the form of more frequent check-ups during treatment or proactive side effect management rather than reactive management.