Automated volumetric radiomic analysis of breast cancer vascularization improves survival prediction in primary breast cancer

To investigate whether automated volumetric radiomic analysis of breast cancer vascularization (VAV) can improve survival prediction in primary breast cancer. 314 consecutive patients with primary invasive breast cancer received standard clinical MRI before the initiation of treatment according to international recommendations. Diagnostic work-up, treatment, and follow-up was done at one tertiary care, academic breast-center (outcome: disease specific survival/DSS vs. disease specific death/DSD). The Nottingham Prognostic Index (NPI) was used as the reference method with which to predict survival of breast cancer. Based on the MRI scans, VAV was accomplished by commercially available, FDA-cleared software. DSD served as endpoint. Integration of VAV into the NPI gave NPIVAV. Prediction of DSD by NPIVAV compared to standard NPI alone was investigated (Cox regression, likelihood-test, predictive accuracy: Harrell’s C, Kaplan Meier statistics and corresponding hazard ratios/HR, confidence intervals/CI). DSD occurred in 35 and DSS in 279 patients. Prognostication of the survival outcome by NPI (Harrell’s C = 75.3%) was enhanced by VAV (NPIVAV: Harrell’s C = 81.0%). Most of all, the NPIVAV identified patients with unfavourable outcome more reliably than NPI alone (hazard ratio/HR = 4.5; confidence interval/CI = 2.14-9.58; P = 0.0001). Automated volumetric radiomic analysis of breast cancer vascularization improved survival prediction in primary breast cancer. Most of all, it optimized the identification of patients at higher risk of an unfavorable outcome. Future studies should integrate MRI as a “gate keeper” in the management of breast cancer patients. Such a “gate keeper” could assist in selecting patients benefitting from more advanced diagnostic procedures (genetic profiling etc.) in order to decide whether are a more aggressive therapy (chemotherapy) is warranted.


Assessment of clinicopathological factors (CPF)
T-Stage: Tumor resection was performed by a surgical gynaecologist. After formalin fixation the surgical specimen was examined by a breast pathologist: T-Stage (1 to 3) was assigned based on the largest diameter of the tumor as measured on representative slices. In case of chest wall/skin invasion or inflammatory cancer T-4 Stage was diagnosed 1,2 .
N-Stage: If lymph nodes were clinically or pathologically positive, axillary node dissection was carried out by a surgical gynaecologist. In all other cases, the sentinel method was standard of care. It was performed subsequent to subareolar injection of technetium 99m Sulfur Colloid and blue dye. The resulting surgical specimen were formalin fixed and evaluated by the pathologist: Hereby eight representative sections were chosen, paraffin-embedded and stained with haematoxylin and eosin (HE). Then, all sections were assessed with conventional microscopic examination. In case of unclear results, immunohistochemistry was performed using dedicated Pan-Cytokeratin antibodies (AE1/AE3, MNF-116). Finally, presence of metastatic deposits was staged according to the TNM system. Additionally, the numbers of resected and affected nodes were documented in the database 1,2 .
Typing: Following paraffin-embedding and haematoxylin staining of the surgical specimen, defined field areas of representative slices where examined. Based on standard histo-morphological criteria assessed with conventional light microscopy, tumors were dichotomized as "in situ disease" (basal membrane intact; exclusion criteria -see material and methods) or "invasive cancer" 1,2 . According to the WHO criteria invasive carcinomas where further classified as "ductal", "lobular", "mixed type" to name only the most common diagnoses. In case of doubt appropriate additional stainings where performed 1 .
percentage of tubule formation, the degree of nuclear pleomorphism and mitotic count within a given field of view are assessed. Based on the Elston-Ellis method it allows to morphologically assess the degree of tumor differentiation based on a three-stage qualitative score as Grade 1 to 3 (G1 to 3) 3 .  Patients were managed according to applicable national guidelines and current evidence from clinical trials 6,7 . In the following, criteria of the guidelines are summarized and complemented by the number of patients fulfilling the given criteria: Every patient received surgical resection of the primary tumor. Hereby local control of disease was primarily gained by breast conserving therapy. Modified radical mastectomy was the treatment of choice in patients with locally advanced breast cancer at time of initial diagnosis (n=22).
Primary method for surgical axillary staging was sentinel node biopsy. It was performed after preoperative sub-areolar injection of technetium 99m sulfur colloid and blue dye. If either the sentinel lymph node biopsy was positive or in case of already clinically positive nodes, axillary lymph node resection was performed (n= 100). Hereby at least 10 nodes in Level I or II were resected (median 22, range 10-44).
Following surgical treatment, patients were routinely scheduled for breast irradiation. The typical procedure after breast conserving therapy covered the whole ipsilateral breast and the chest wall. According to the guidelines, a total dose of 50 Gy was applied in a regimen of 5 × 2.0 Gy cycles per week. Similarly, in patients eligible for radical mastectomy (n=22), irradiation therapy was indicated; hereby the irradiation field covered the ipsilateral chest wall. Note that all of these patients also had a significant axillary tumor load with a median of 15 metastatic nodes (range 5-42).
As recommended by national guidelines, cytotoxic chemotherapy was considered according to the individual patient risk factors. According to the study design, no patient received neoadjuvant systemic chemotherapy. Applicable criteria were HER2-positive cancers (n=89), estrogen and/or progesterone negative cancers (n=43), nodal-positive disease (n= 100), high tumor grade (G3: n=189), or young age <35 years (n=3).

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The 89 patients with HER2-positive cancers were treated with Trastuzumab according to the current evidence from clinical trials. Patients positive for estrogen and/or progesterone receptors received endocrine treatment after the completion of the chemotherapy normally over 5 years.
Note: As the aim of this study was an interindividual comparison, the treatment regimen was not considered as a possible confounder. Therefore no more details on treatment were documented in the database.

Magnetic resonance imaging protocol
Patients were placed in the prone position and a venous access was placed in a cubital vein. The DCE-MRI protocol consisted of repetitive radiofrequency spoiled dynamic T1-weighted gradient echo sequences (Fast Low Angle SHot, FLASH 2D), acquired at 1-minute intervals over eight minutes. After one baseline scan, Gadolinium pentetate (Magnevist, Bayer/Schering HealthCare, Leverkusen, Germany) was administered as a venous injection at a dosage of 0.2 ml/kg body weight, followed by a 20 ml saline flush. A constant flow rate of 3 ml/sec was ensured by using an automated injector (Spectris, Medrad, Pittsburgh, USA). Postcontrast scanning started 30 seconds after contrast material injection using the same adjustment settings. Acquisition parameters for DCE-MRI were 110ms (repetition time), 5ms (echo time), 80° (flip angle), 1.1*0.9*3mm 3 (spatial resolution) and 350 mm (field of view).