Variability in lymph node irradiation in patients with breast cancer—results from a multi-center survey in German-speaking countries

Combs

et al. 2021

Preprint

BACKGROUNDThe aim of the present study was to generate an atlas of lymphatic drainage in breast cancer patients to be used in cross sectional diagnostic and therapeutic imaging. METHODSThe distribution of healthy lymph nodes is investigated as a surrogate for lymphatic drainage in cross sectional imaging. 2094 healthy LN were contoured contralateral to the primary tumor site on PET-CT datasets of 153 breast cancer patients. Using rigid and non-rigid registration techniques 1939 LN were transferred to a “standard patient” CT data set. Thus, a healthy lymph node atlas was generated. The location of the healthy LN was compared to the RTOG and ESTRO clinical target volumes radiotherapy contouring recommendations.RESULTSThe mean volume of healthy LN was 0.17cm3±0.28cm3 and the mean diameter was 0.77cm±0.36cm. Most LN were in level I (69.20%), supraclavicular (14.80%) and level II (10.50%). The remaining LN were in the internal mammary (2.70%), intraglandular (1.80%) and level III (1.00%). The ESTRO guideline encompassed the healthy LN in 35.00% completely, in 31.10% partly and in 33.90% not at all. The RTOG encompassed 48.00% of the healthy LN completely, 28.80% in part and 23.20% not at all.CONCLUSIONOur study lead to the most comprehensive 3D-imaging atlas of healthy LN in cross sectional imaging. The results can be used to generate a strategy to further reduce the rate of lymphedema by irradiation. Further, the atlas can be used to determine the probability of a visible LN in a specific location to be healthy.

“…With surgery and radiotherapy being the two pillars of local therapy in breast cancer, an inclusive de nition of the same regions is imperative [11][12][13].…”

Section: Discussionmentioning

confidence: 99%

A Probabilistic Cross Sectional Imaging Atlas of Healthy Axillary and Paraclavicular Lymph Nodes in Breast Cancer Patients

Ernst

Combs

et al. 2021

Preprint

“…The principle of excluding lung tissue for the PTV is widely used in clinical practice and has been applied in previous studies on adjuvant radiotherapy in breast cancer [17,20]. However, to our knowledge there is no evidence or scientific background regarding this practice.…”

Section: Discussionmentioning

confidence: 99%

“…While several international consensus contouring-recommendations address the definition of the clinical target volume (CTV) during RNI [18,19], standardized definitions regarding the PTV margins are missing. Pattern of care surveys reveal, that most radiation oncologists use a CTV to PTV margin of 5 mm during RNI to compensate position and treatment inaccuracies [20]. However, up to 40% of radiation oncologists [20] exclude lung tissue from the PTV during RNI in order to reduce the dose to the OARs [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…Pattern of care surveys reveal, that most radiation oncologists use a CTV to PTV margin of 5 mm during RNI to compensate position and treatment inaccuracies [20]. However, up to 40% of radiation oncologists [20] exclude lung tissue from the PTV during RNI in order to reduce the dose to the OARs [21][22][23]. This decreases drastically the dorsal PTV-margin of the IMN region.…”

Section: Introductionmentioning

confidence: 99%

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Excluding Lung Tissue from the PTV during Internal Mammary Irradiation. A Safe Technique for OAR-Sparing?

Hofmann

Düsberg

et al. 2021

Cancers

The current study aims to determine whether exclusion of lung tissue from planning treatment volume (PTV) is a valid organ at risk (OAR)-sparing technique during internal mammary irradiation (IMNI). Twenty patients with left-sided breast cancer undergoing adjuvant radiotherapy including IMNI after mastectomy or lumpectomy with daily ConeBeam CT (CBCT; median n = 28) were enrolled in the current study. The daily dose distribution of the patients was estimated by recalculating treatment plans on CBCT-scans based on a standard PTV (PTV margin: 5mm-STD) and a modified PTV, which excluded overlapping lung tissue (ExLung). Using 3D-deformable dose accumulation, the dose coverage in the target volume was estimated in dependence of the PTV-margins. The estimated delivered dose in the IMN-CTV was significantly lower for the ExLung PTV compared to the STD PTV: ExLung: V95%: 76.6 ± 22.9%; V90%: 89.6 ± 13.2%, STD: V95%: 95.6 ± 7.4%; V90%: 99.1 ± 2.7%. Daily CBCT imaging cannot sufficiently compensate the anatomic changes and intrafraction movement throughout the treatment. Therefore, to ensure adequate delivery of the prescribed dose to the IMN-CTV, exclusion of lung tissue from the PTV to spare the OARs is not recommended.

“…IGRT “employs imaging to maximize accuracy and precision throughout the entire process of treatment delivery” 5 , which is achieved by correcting the patient’s position prior to treatment delivery by aligning an online image to the planning CT. Online imaging can be implemented using either planar x-rays (2D), CBCT or surface scanners. Since the position of the breast is highly variable and the target volume is in close proximity to critical organs at risk, image guidance is widely used 6 . Previous studies on IGRT in breast cancer patients indicate that CBCT is superior or at least equivalent to 2D-based techniques regarding position correction 7 – 9 .…”

Section: Introductionmentioning

confidence: 99%

Impact of CBCT frequency on target coverage and dose to the organs at risk in adjuvant breast cancer radiotherapy

Junker

Düsberg

et al. 2021

Sci Rep

The current study aims to assess the effect of cone beam computed tomography (CBCT) frequency during adjuvant breast cancer radiotherapy with simultaneous integrated boost (SIB) on target volume coverage and dose to the organs at risk (OAR). 50 breast cancer patients receiving either non-hypofractionated or hypofractionated radiotherapy after lumpectomy including a SIB to the tumor bed were selected for this study. All patients were treated in volumetric modulated arc therapy (VMAT) technique and underwent daily CBCT imaging. In order to estimate the delivered dose during the treatment, the applied fraction doses were recalculated on daily CBCT scans and accumulated using deformable image registration. Based on a total of 2440 dose recalculations, dose coverage in the clinical target volumes (CTV) and OAR was compared depending on the CBCT frequency. The estimated delivered dose (V95%) for breast-CTV and SIB-CTV was significantly lower than the planned dose distribution, irrespective of the CBCT-frequency. Between daily CBCT and CBCT on alternate days, no significant dose differences were found regarding V95% for both, breast-CTV and SIB-CTV. Dose distribution in the OAR was similar for both imaging protocols. Weekly CBCT though led to a significant decrease in dose coverage compared to daily CBCT and a small but significant dose increase in most OAR. Daily CBCT imaging might not be necessary to ensure adequate dose coverage in the target volumes while efficiently sparing the OAR during adjuvant breast cancer radiotherapy with SIB.