[Risk assessment of internal mammary lymph node metastasis and choice of irradiation of internal mammary lymphatic drainage area in breast cancer patients with negative internal breast lymph nodes on imaging].

Objective: To explore the independent risk factors of internal mammary lymph nodes (IMN) metastasis and the risk assessment method of IMN metastasis preoperatively in breast cancer patients with negative IMN in imaging examination, and guide the radiotherapy of IMN in patients with different risk stratification of IMN metastasis. Methods: The clinical and pathological data of 301 breast cancer patients who underwent internal mammary sentinel node biopsy(IM-SLNB) and/or IMN dissection in Shandong Cancer Hospital with negative IMN on CT and/or MRI from January 2010 to October 2019 were analyzed retrospectively. The independent risk factors were analyzed by univariate and multivariate logistic regression, and the independent risk factors of IMN metastasis were used to risk stratification. Results: Among the 301 patients, 43 patients had IMN metastasis, and the rate of IMN metastasis was 14.3%. Univariate analysis showed that vascular tumor thrombus, progesterone receptor (PR) expression, T stage and N stage were associated with IMN metastasis. Multivariate logistic regression analysis showed that tumor located in medial quadrant, positive PR and axillary lymph node metastasis were independent risk factors for IMN metastasis. The risk of IMN metastasis was assessed according to the independent risk factors of the patients: low-risk group is including 0 risk factor, medium-risk group is including 1 risk factor, and high-risk group is including 2-3 risk factors. According to this evaluation criteria, 301 patients with breast cancer were divided into low-risk group (with 0 risk factors), medium-risk group (with 1 risk factor) and high-risk group (with 2-3 risk factors). The IMN metastasis rates were 0 (0/34), 4.3% (6/140) and 29.1% (37/127), respectively. Conclusions: The risk stratification of IMN metastasis according to three independent risk factors of IMN metastasis including tumor located in medial quadrant, positive PR and axillary lymph node metastasis in breast cancer patients can guide the radiotherapy of IMN in newly diagnosed breast cancer patients. For N1 patients, radiotherapy of IMN is strongly recommended when the primary tumor is located in the medial quadrant and/or PR positive.

[Cone beam CT-derived adaptive radiotherapy for setup error assessment and correction in whole breast intensity modulated radiotherapy].

OBJECTIVE: To quantify the setup error (SE) in breast cancer patients treated with intensity modulated radiotherapy (IMRT) based on cone beam CT (CBCT), and to explore the feasibility of using several CBCT scans to presume and correct SE in the treatment for breast cancer patients. METHODS: Eighteen breast cancer patients after breast conserving surgery who underwent whole breast IMRT were included in this study. Three dimensional interfraction motion before and after on-line CBCT-based corrections were quantified. The on-line CBCT-based corrections were performed using automated greyscale match. The system SE (Σ) and random error (σ) were calculated for each patient based on the consecutive multiple online scanning based on CBCT (≥5). The trends in magnitudes of Σ and σwere assessed during the treatment. RESULTS: The magnitude variation of Σ was less than 1 mm before and after on-line CBCT-based corrections. As the CBCT scanning times increase (before 10 times), the Σ in anteroposterior (AP) direction was increased significantly, and σin three dimensional directions was also increased after 7 times of CBCT scanning. After on-line CBCT-based corrections, the Σ showed a steady trend by variation near zero for the first 20 times irradiation; but after 20 times, the Σ in AP and superoinferior (SI) directions was increased slightly (less than 0.5 mm), and σdecreased in three-dimensional directions. There were no significant differences for Σ, σand setup margin (SM) before and after on-line CBCT-based corrections in all three directions (P>0.05). CONCLUSIONS: For breast cancer patients who underwent IMRT after breast conserving surgery, the setup error is relatively stable during the whole irradiation. The first 5 CBCT scans are suitable to presume and correct SE, and also can be used as the right time for adaptive radiotherapy planning revision.

An inexact two-stage stochastic programming model for water resources management in Nansihu Lake Basin, China.

In this study, an inexact two-stage water resources management model was developed for multi-regional water resources planning in the Nansihu lake Basin, China. Four planning districts, four water users, and five water sources were considered in the optimization model, with net system benefit, recourse cost, water supply cost, and wastewater treatment cost being analyzed. Methods of interval-parameter programming (IPP) and two-stage stochastic programming (TSP) were incorporated into the model to tackle uncertainties described by both interval values and probability distributions. A number of scenarios corresponding to different river inflow levels were examined, and the results indicated that different inflow levels could lead to different water allocation schemes with varied system benefit and system-failure risk. In general, the developed model can provide an effective linkage between economic benefits and the associated penalties attributed to the violation of predefined policies. The modeling results were valuable for supporting the adjustment or justification of the existing water allocation schemes within a complicated water resources system under uncertainty.