5-Year Outcomes of a Randomized Trial Comparing Prone and Supine Whole Breast Irradiation in Large-Breasted Women

Dosimetric analysis of six whole-breast irradiation techniques in supine and prone positions

In breast cancer radiation therapy, minimizing radiation-related risks and toxicity is vital for improving life expectancy. Tailoring radiotherapy techniques and treatment positions can reduce radiation doses to normal organs and mitigate treatment-related toxicity. This study entailed a dosimetric comparison of six different external beam whole-breast irradiation techniques in both supine and prone positions. We selected fourteen breast cancer patients, generating six treatment plans in both positions per patient. We assessed target coverage and organs at risk (OAR) doses to evaluate the impact of treatment techniques and positions. Excess absolute risk was calculated to estimate potential secondary cancer risk in the contralateral breast, ipsilateral lung, and contralateral lung. Additionally, we analyzed the distance between the target volume and OARs (heart and ipsilateral lung) while considering the treatment position. The results indicate that prone positioning lowers lung exposure in X-ray radiotherapy. However, particle beam therapies (PBTs) significantly reduce the dose to the heart and ipsilateral lung regardless of the patient's position. Notably, negligible differences were observed between arc-delivery and static-delivery PBTs in terms of target conformity and OAR sparing. This study provides critical dosimetric evidence to facilitate informed decision-making regarding treatment techniques and positions.

Comparison of prone and supine positioning for breast cancer radiotherapy using REQUITE data: dosimetry, acute and two years physician and patient-reported outcomes

OBJECTIVE

Most patients receive whole breast radiotherapy in a supine position. However, two randomised trials showed lower acute toxicity in prone position. Furthermore, in most patients, prone positioning reduced doses to the organs at risk. To confirm these findings, we compared toxicity outcomes, photographic assessment, and dosimetry between both positions using REQUITE data.

METHODS

REQUITE is an international multi-centre prospective observational study that recruited 2069 breast cancer patients receiving radiotherapy. Data on toxicity, health-related quality of life (HRQoL), and dosimetry were collected, as well as a photographic assessment. A matched case control analysis compared patients treated prone (n = 268) versus supine (n = 493). Exact matching was performed for the use of intensity-modulated radiotherapy, boost, lymph node irradiation, chemotherapy and fractionation, and the nearest neighbour for breast volume. Primary endpoints were dermatitis at the end of radiotherapy, and atrophy and cosmetic outcome by photographic assessment at two years.

RESULTS

At the last treatment fraction, there was no significant difference in dermatitis (p = .28) or any HRQoL domain, but prone positioning increased the risk of breast oedema (p < .001). At 2 years, patients treated in prone position had less atrophy (p = .01), and higher body image (p < .001), and social functioning (p < .001) scores. The photographic assessment showed no difference in cosmesis at 2 years (p = .22). In prone position, mean heart dose (MHD) was significantly lower for left-sided patients (1.29 Gy vs 2.10 Gy, p < .001) and ipsilateral mean lung dose (MLD) was significantly lower for all patients (2.77 Gy vs 5.89 Gy, p < .001).

CONCLUSIONS

Prone radiotherapy showed lower MLD and MHD compared to supine position, although the risk of developing breast oedema during radiotherapy was higher. At 2 years the photographic assessment showed no difference in the cosmetic outcome, but less atrophy was seen in prone-treated patients and this seems to have a positive influence on the HRQoL domain of body image.

Comparative analysis of dosimetry and predictive somatotype parameters of prone and supine whole-breast irradiation among Chinese women after breast-conserving surgery

Purpose

Finding a better treatment position (prone or supine) for whole-breast irradiation for Chinese female patients diagnosed with breast cancer by identify the associations between predictive somatotype parameters and dosimetric gains.

Materials and methods

Two volumetric-modulated arc therapy (VMAT) plans were deployed for whole-breast irradiation in supine and prone position with a total dose of 50 Gy in 25 fractions. Dose-volume parameters were compared and analysed both in the target volume and organs at risk, and equivalent uniform dose-based figure-of-merit (fEUD) models were further used to quantitatively evaluate the overall merits of the two plans. Body shape parameters, including body mass index (BMI), body surface area (BSA), breast shape, cup size, bust size and chest size, were collected. Anatomic features such as the central heart distance (CHD) were measured on supine CT. Spearman’s correlation analysis, receiver operating characteristic (ROC) curve analysis, and the linear regression models were conducted.

Results

Doses to the heart and left anterior descending coronary artery (LADCA) are greater in left-sided breast cancer (BC) patients in the prone position than in the supine position, and the opposite was true for right-sided BC patients (p&lt;0.001). 19 of 63 patients (5 left-sided and 14 right-sided BC) achieved greater benefit from the prone position according to the fEUD score. Right-sided BC patients with a bust size ≥92.25 cm, drop-type breasts and cup size ≥B are very likely to benefit from prone-position radiotherapy. The CHD is significantly positively associated with △fEUD among right-sided BC patients (rho=0.506, p=0.004). Using a cut-off point of 2.215, the CHD had 71.4% sensitivity and 81.2% specificity in predicting a successful prone plan.

Conclusions

Right-sided BC patients had better dosimetric gain in the prone position than left-sided BC patients. The CHD is an especially good and novel predictor that could help to select prone-benefitting right-sided BC patients.

Comparison of fulfilling the criteria for critical organs in irradiation of patients with breast cancer using the deep inspiration breath-hold and free breathing techniques

Introduction: The aim of the study was to evaluate organ-at-risk dose sparing in treatment plans for patients with left-sided breast cancer irradiated with Deep Inspiration Breath Hold (DIBH) and Free Breathing (FB) techniques.

Material and methods: Twenty patients with left-sided breast cancer were analyzed and divided into two groups. Group A included 10 patients with non-metastatic breast cancer, while group B involved 10 patients with metastatic breast cancer spreading to regional lymph nodes. All patients went through the DIBH coaching. For planning purposes, CT scans were obtained in both DIBH and FB. Mean heart dose (Dmean,heart), mean heart volume receiving 50% of the prescribed dose (V50), V20 (V20L.lung), V10 (V10L.lung) and V5 for left lung (V5L.lung), the volume of the PTV receiving a dose greater than or equal to 95% of the prescribed dose (V95 [%]), the maximum point dose (Dmax), and the volume of PTV receiving 107% of the prescribed dose were reported.

Results: In all 20 analyzed pairs of plans, a reduction by more than half in the mean heart dose in DIBH technique plans was achieved, as well as a significant reduction was found in DIBH plans for the heart V50. In 19 patients, the use of the DIBH technique also reduced the volume of the left lung receiving doses of 20 Gy, 10 Gy, and 5 Gy compared to the FB technique.

Conclusions: Dosimetric analysis showed that the free breathing plans don’t fulfill the criteria for a mean heart dose (group B) and the left lung receiving a 20 Gy dose (group A) compared to the DIBH plans. Radiation therapy of left breast cancer with the use of the DIBH technique results in a significant dose reduction in the heart and also reduces the dose in the left lung in the majority of patients, compared to the FB procedure.

Prone Breast and Lymph Node Irradiation in 5 or 15 Fractions: A Randomized 2 × 2 Design Comparing Dosimetry, Acute Toxicity, and Set-Up Errors

PURPOSE

Prone whole breast irradiation results in lower dose to organs at risk compared with supine position, especially lung dose. However, the adoption of prone position for whole breast irradiation + lymph node irradiation remains limited and data on lymph node irradiation in 5 fractions are lacking. Although the study was ended prematurely for the primary endpoint (breast retraction at 2 years), we decided to report acute toxicity for prone and supine positions and 5 and 15 fractions. Additionally, dosimetry and set-up accuracy between prone and supine positions were evaluated.

METHODS AND MATERIALS

A randomized open-label factorial 2 × 2 design was used for an acute toxicity comparison between prone and supine positions and 5 and 15 fractions. The primary endpoint of the trial was breast retraction 2 years after treatment. In total, 57 patients were evaluated. Dosimetry and set-up errors were compared between prone and supine positions. All patients were positioned on either our in -house developed prone crawl breast couch or a Posirest-2 (Civco).

RESULTS

No difference in acute toxicity between prone and supine positions was found, but 5 fractions did result in a lower risk of desquamation (15% vs 41%; P = .04). Prone positioning resulted in lower mean ipsilateral lung dose (2.89 vs 4.89 Gy; P < .001), mean thyroid dose (3.42 vs 6.61 Gy; P = .004), and mean contralateral breast dose (0.41 vs 0.54 Gy; P = .007). No significant difference in mean heart dose (0.90 vs 1.07 Gy; P = .22) was found. Set-up accuracy was similar between both positions.

CONCLUSIONS

Unfortunately, the primary endpoint of the trial was not met due to premature closure of the trial. Acceleration in 5 fractions resulted in a lower risk of desquamation. Prone positioning did not influence acute toxicity or set-up accuracy, but did result in lower ipsilateral mean lung dose, thyroid dose, and contralateral breast dose.

Two-year toxicity of simultaneous integrated boost in hypofractionated prone breast cancer irradiation: Comparison with sequential boost in a randomized trial

INTRODUCTION

A simultaneous integrated boost (SIB) leads to less acute toxicity. Less is known for late toxicity due to SIB. In this first and only randomized trial, two-years toxicity is analysed.

MATERIALS AND METHODS

Physician-assessed toxicity, using the LENT SOMA scale, and photographs, analysed with the BCCT.core software, was examined for 150 patients, randomized between SIB and sequential boost (SEB).

RESULTS

Differences in physician-assessed two-years toxicity and photographic analysis between SIB and SEB are very small and not significant.

CONCLUSION

There is no indication that a SIB leads to an excess in toxicity or worse cosmetic outcome at 2 years.