Single‐isocenter hybrid IMRT plans versus two‐isocenter conventional plans and impact of intrafraction motion for the treatment of breast cancer with supraclavicular lymph nodes involvement

Abstract

The purpose of this study was to compare the single‐isocenter, four‐field hybrid IMRT with the two‐isocenter techniques to treat the whole breast and supraclavicular fields and to investigate the intrafraction motions in both techniques in the superior direction. Fifteen breast cancer patients who underwent lumpectomy and adjuvant radiation to the whole breast and supraclavicular (SCV) fossa at our institution were selected for this study. Two planning techniques were compared for the treatment of the breast and SCV lymph nodes. The patients were divided into three subgroups according to the whole breast volume. For the two‐isocenter technique, conventional wedged or field‐within‐a‐field tangents (FIF) were used to match with the same anterior field for the SCV region. For the single‐isocenter technique, four‐field hybrid IMRT was used for the tangent fields matched with a half blocked anterior field for the SCV region. To simulate the intrafraction uncertainties in the longitudinal direction for both techniques, the treatment isocenters were shifted by 1 mm and 2 mm in the superior direction. The average breast clinical tumor volume (CTV) receiving 100% (V100%) of the prescription dose (50 Gy) was 99.3%±0.5% and 96.4%±1.2% for the for two‐isocenter and single‐isocenter plans (p<0.05), respectively. The breast CTV receiving 95% of the prescription dose (V95%) was close to 100% in both techniques. The average breast CTV receiving 105% (V105%) of the prescription dose was 32.4%±19.3% and 23.8%±13.3% (p=0.08). The percentage volume of the breast CTV receiving 110% of the dose was 0.4%±1.2% in the two‐isocentric technique vs. 0.1%±0.2% in the single‐isocentric technique. The average uniformity index was 0.91±0.02 vs. 0.91±0.01 in both techniques (p=0.04), but had no clinical impact. The percentage volume of the contralateral breast receiving a dose of 1 Gy was less than 2.3% in small breast patients and insignificant for medium and large breast sizes. The percentage of the total lung volume receiving g>20 Gy (normalV20Gy) and the heart receiving >30 Gy (normalV30Gy) were 13.6% vs. 14.3% (p=0.03) and 1.25% vs. 1.2% (p=0.62), respectively. Shifting the treatment isocenter by 1 mm and 2 mm superiorly showed that the average maximum dose to 1 cc of the breast volume was 55.5±1.8 Gy and 58.6±4.3 Gy in the two‐isocentric technique vs. 56.4±2.1 Gy and 59.1±5.1 Gy in the single‐isocentric technique (p=0.46, 0.87), respectively. The single‐isocenter technique using four‐field hybrid IMRT approach resulted in comparable plan quality as the two‐isocentric technique. The single‐isocenter technique is more sensitive to intrafraction motion in the superior direction compared to the two‐isocentric technique. The advantages of the single‐isocenter include elimination of isocentric errors due to couch and collimator rotations and reduction in treatment time. This study supports consideration of a single‐isocenter four‐field hybrid IMRT technique for patients undergoing breast and supraclavicular nodal irradiation.PACS number: 87.55.D...

Single click automated breast planning with iterative optimization

“…The hybrid technique has been shown to provide high-quality plans that are robust to patient breathing motion. [13][14][15][16] The primary characteristic of the technique is conformal fields that deliver the majority of breast dose accompanied with a small weighting of modulated multileaf collimator (MLC) fields to fine tune the distribution.…”

“…• x iso , y iso are the x and y co-ordinates of the plan isocenter • AE is dependent on laterality of patient hybrid IMRT technique. [14][15][16]20,21 At this point the plan is passed to the iterative optimization code. Following the iterative optimizer all plan DVH statistics were exported for analysis within the AP code.…”

“…The beam set is created such that objective functions are optimized with consideration of the initial open beam dose as background dose as per instructions from the well-published hybrid IMRT technique. [14][15][16]20,21 At this point the plan is passed to the iterative optimization code.…”

Evaluation of the dosimetric and radiobiological parameters in four radiotherapy regimens for synchronous bilateral breast cancer

“…In general, the dual-isocenter technique is traditionally applied for the treatment of patients with breast cancer with supraclavicular and axillary lymph node involvement as well as mastectomy. [12][13][14] Boman et al investigated the feasibility of utilizing dual isocenters in VMAT planning for bilateral lymph node-positive breast cancer. 12 They reported that the dose parameters slightly favored the dual-isocenter option over the singleisocenter one.…”

Using Robust Optimization for Skin Flashing in Intensity Modulated Radiation Therapy for Breast Cancer Treatment: A Feasibility Study

“…Intensity modulated radiation therapy (IMRT) has demonstrated improved ipsilateral lung sparing at moderate and high doses and a better conformal index (CI) for breast cancer and nodal irradiation compared with 3DCRT. 1,2 Although there are many published dosimetric studies investigating modulated beams for breast cancer treatment, [3][4][5][6][7][8][9][10][11] few discuss how to account for skin flashing when using inverse optimized modulated beams and the effectiveness of these techniques. The breast is a highly mobile structure for which setup reproducibility is poor, which can lead to suboptimal dose distributions and variations from the expected dosimetry if the geometry error is not properly accounted for.…”