Simplified field-in-field technique for a large-scale implementation in breast radiation treatment
Introduction
Breast-conserving surgery, followed by whole-breast radiotherapy (RT), is the standard of care for patients with early-stage breast cancer.1, 2, 3 Patients also benefit from the addition of a tumor bed boost, which has been shown to decrease local recurrence after conservative treatment.4, 5 Although the use of boost irradiation is recommended, the standard technique and definition of the tumor bed volume have not been clearly established.6, 7 This issue is becoming paramount with the improvement of RT planning, such as the use of techniques adapted to the patient's anatomy8 or intensity-modulated radiotherapy (IMRT) boost,9, 10 and is essential in the case of dose escalation.11
In addition, some authors have already suggested that minimization of unwanted radiation dose heterogeneity in the breast could reduce late adverse effects. Incidence of change in breast appearance was statistically higher in patients in the standard 2D treatment arm compared with the IMRT arm.12 A beneficial effect on quality of life remains to be demonstrated. It was already shown that breast IMRT significantly reduces the occurrence of moist desquamation compared with a standard wedged technique.13
Today, there is a large choice of techniques for breast radiation treatment owing to advances in linear accelerators (LINAC) technology and treatment planning systems. Ideally, we need a technique that is applicable to the large majority of breast patients, that simplifies and shortens treatment delivery, that is well understood by dosimetrists and technologists to avoid unwanted events, that requires very little quality assurance (QA), and that is not labor-intensive for the treatment machines.
At our institution, forward planned breast fields are set on the virtual simulation after computed tomography (CT) scan acquisition. Contouring the breast planning target volume (PTV) is rarely performed (except in complex cases for patients who undergo tomotherapy). A time lapse of 5–7 working days includes CT with virtual simulation, dosimetry, approval by radiation oncologist, physics quality assurance (QA), plan transfer to LINAC record and verify, approval for treatment. It is therefore important that each step in the treatment preparation is kept as short as possible.
The aim of this study was to assess a simplified field-in-field technique (SFF) that is easily implemented in a Department of Radiation Oncology and to compare it with the state-of-the-art electronic surface compensation (ESC) regarding dose homogeneity and coverage. Early skin toxicity in 15 patients is reported.
Section snippets
Patients
This study evaluated 15 consecutive patients (7 right and 8 left-breast patients) treated with a SFF technique at the Institut Curie. All patients underwent conserving surgery for early-stage breast cancer, followed by whole-breast irradiation to the total dose of 50 Gy in 25 fractions, and a boost of 16 Gy in 8 fractions to the tumor bed using a technique described previously.9, 10
In our standard practice, all patients are followed up weekly during RT and acute toxicity is assessed using the
Clinical outcome
Treatment tolerance was very good, with no patient experiencing acute side effects superior to grade 1. The skin pigmentation during radiation was homogenous; there was no increase of toxicity at the breast inferior fold nor in the axillary superficial region. At 2-month follow-up, all patients showed no sign of residual dermatitis.
Dosimetric comparison of SFF and ESC
Table 1a, Table 1b show dosimetric results for the 2 techniques.
The median irradiated volume was 1114 mL (range, 576–2431). Nonoptimized plans showed a median volume
Implementation of SFF
Before releasing the SFF into clinical use, tests have been performed to check the accuracy of dose calculation and treatment delivery. QA plans were created that allowed dose calculation in flat homogeneous phantoms using the optimized fluence from patients' plans. Main discrepancies were found at leaf edges and beam corners but were within acceptable levels: <3% in high dose−low dose gradient regions, <3 mm in low dose–high dose gradient areas. We have fixed rules for minimum subfield MU and
Conclusion
This study presents a SFF breast technique that was implemented in our radiation oncology department. This technique creates homogenous 3D dose distribution equivalent to electronic surface compensation with dynamic leaves. It is easily implemented in an RT department without adding workload in the planning, QA, and treatment processes. It allows the integration of a forward-planned concomitant tumor bed boost as an additional MLC subfield of the tangential fields. Shorter treatment times allow
References (26)
- et al.
Placing the boost in breast-conservation radiotherapy: A review of the role, indications and techniques for breast-boost radiotherapy
Clin. Oncol.
(2006) - et al.
Breast radiotherapy in the lateral decubitus position: A technique to prevent lung and heart irradiation
Int. J. Radiat. Oncol. Biol. Phys.
(2005) - et al.
How to boost the breast tumor bed?A multidisciplinary approach in eight steps
Int. J. Radiat. Oncol. Biol. Phys.
(2008) - et al.
Improving the definition of tumor bed boost with the use of surgical clips and image registration in breast cancer patients
Int. J. Radiat. Oncol. Biol. Phys.
(2010) - et al.
The addition of a boost dose on the primary tumor bed after lumpectomy in breast conserving treatment for breast cancerA summary of the results of EORTC 22881–10882 ‘boost versus no boost’ trial
Cancer. Radiother.
(2008) - et al.
Randomised trial of standard 2D radiotherapy (RT) versus intensity modulated radiotherapy (IMRT) in patients prescribed breast radiotherapy
Radiother. Oncol.
(2007) - et al.
CTCAE v3.0: Development of a comprehensive grading system for the adverse effects of cancer treatment
Semin. Radiat. Oncol.
(2003) - et al.
The impact of central lung distance, maximal heart distance, and radiation technique on the volumetric dose of the lung and heart for intact breast radiation
Int. J. Radiat. Oncol. Biol. Phys.
(2002) - et al.
Optimizing breast cancer treatment efficacy with intensity-modulated radiotherapy
Int. J. Radiat. Oncol. Biol. Phys.
(2002) - et al.
Three-dimensional photon dosimetry: A comparison of treatment of the intact breast in the supine and prone position
Int. J. Radiat. Oncol. Biol. Phys.
(2003)
Cardiac and lung complication probabilities after breast cancer irradiation
Radiother. Oncol.
IMRT delivery performance with a Varian multileaf collimator
Int. J. Radiat. Oncol. Biol. Phys.
Effects of radiotherapy and of differences in the extent of surgery for early breast cancer on local recurrence and 15-year survival: An overview of the randomised trials
Lancet
Cited by (31)
Concurrent radiation therapy and dual HER2 blockade in breast cancer: Assessment of toxicity
2021, Cancer/RadiotherapieIn Reply to Khosla et al
2019, International Journal of Radiation Oncology Biology PhysicsDisseminated Tumor Cells Predict Efficacy of Regional Nodal Irradiation in Early Stage Breast Cancer
2019, International Journal of Radiation Oncology Biology PhysicsCitation Excerpt :The IMN region was treated by a mixed photon–electron technique. Whole breast or chest wall and SCN/axillary regions were irradiated, using previously described techniques set up at Institut Curie.17-19 Follow-up was performed at Institut Curie for the first 5 years after treatment and included clinical examination every 6 months and annual bilateral mammography.
Radiation therapy after sentinel lymph node biopsy for early stage breast cancer using a magnetic tracer: Results of a single institutional prospective study of tolerance
2019, Cancer/RadiotherapieCitation Excerpt :In case of positive sentinel lymph node biopsy (with or without axillary lymph node dissection), a normofractionated regimen was delivered (46 to 48 Gy in 23 to 24 fractions to the supraclavicular and axillary lymph nodes and a photon/electron mix to internal mammary lymph nodes). Patients were placed in the standard supine or isocentric lateral supine positions depending on anatomical and/or dosimetric constraints [8,9]. Delineation of lymph node areas was based on atlases published in the literature [10–13].