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BACKGROUND: Patients with a biopsy diagnosis of ductal carcinoma in situ (DCIS) might be diagnosed with invasive breast cancer at excision, a phenomenon known as underestimation. Patients with DCIS are treated based on the risk of underestimation or progression to invasive cancer. The aim of our study was to expand the knowledge on underestimation and to develop a prediction model. METHODS: Population-based data were retrieved from the Dutch Pathology Registry and the Netherlands Cancer Registry for DCIS between January 2011 and June 2012. RESULTS: Of 2892 DCIS biopsies, 21% were underestimated invasive breast cancers. In multivariable analysis, risk factors were highgrade DCIS (odds ratio (OR) 1.43, 95% confidence interval (CI): 1.05-1.95), a palpable tumour (OR 2.22, 95% CI: 1.76-2.81), a BI-RADS (Breast Imaging Reporting and Data System) score 5 (OR 2.36, 95% CI: 1.80-3.09) and a suspected invasive component at biopsy (OR 3.84, 95% CI: 2.69-5.46). The predicted risk for underestimation ranged from 9.5 to 80.2%, with a median of 14.7%. Of the 596 invasive cancers, 39% had unfavourable features. CONCLUSIONS: The risk for an underestimated diagnosis of invasive breast cancer after a biopsy diagnosis of DCIS is considerable. With our prediction model, the individual risk of underestimation can be calculated based on routinely available preoperatively known risk factors (https://www.evidencio.com/models/show/1074). BACKGROUNDPatients with ductal carcinoma in situ (DCIS) are treated based on the risk of underestimation or progression to invasive cancer. The standard treatment for patients with a biopsy diagnosis of DCIS is wide local excision with radiation or mastectomy. Often a sentinel lymph node (SLN) biopsy is advised for axillary staging. 1,2 Both the standard treatment and the use of the SLN biopsy can constitute overtreatment. The standard treatment might be disproportionate for screen-detected DCIS patients who have a high chance that the DCIS would not even have been detected during their lifetime. 3 It has been estimated that between 14 and 53% of DCIS progress into invasive breast cancer. 4,5 To address overtreatment, phase III trials investigate the safety of active surveillance of DCIS patients at low risk for developing or having invasive breast cancer. 6-11 Active surveillance is based on the result of the biopsy. By modelling of active surveillance of DCIS patients, the disease-specific cumulative mortality was related to underestimation. 12,13 Underestimation is the phenomenon that the invasive breast cancer is undetected at preoperative biopsy and only becomes evident after pathological examination of the excision material. The use of the SLN biopsy can also constitute overtreatment. The SLN biopsy is done if a mastectomy is chosen, and also for patients undergoing wide local excision who are at high risk of having an underestimated invasive breast cancer. 1,2 The reported risk of underestimation varies from 14 to 43% 14,15 , and in a meta-analysis it was estimated to be 25.9% (95% confidence inte...

Background: Recent Dutch guidelines recommend adjuvant systemic treatment (AST) for women with high grade stage I breast carcinoma >1 cm. High grade is defined as Bloom and Richardson grade 3 (B&R3), Nottingham modification, or mitotic activity (MAI) >10/1.59 mm 2 . Aims: To investigate the validity of these histological prognostic factors as the exclusive defining criteria. Materials/methods: Fifty patients with stage I breast carcinoma who developed distant metastases and 50 matched controls without metastasis were studied; none had received AST. Results: Cases more often had tumours >1 cm (p = 0,019), B&R3 tumours (p = 0.059), grade 3 nuclei (p = 0.005), and vascular invasion (p = 0.007). No differences were found for MAI >10 (p = 0.46). In multivariate analysis, the only significant variables were vascular invasion and tumour size (odds ratios: 8.21 and 5.35, respectively). In a separate analysis, the 50 cases were divided into 25 patients with early and 25 with late metastasis. Those with early metastasis more often had B&R3 tumours (p = 0.009) and grade 3 nuclei (p = 0.006). No differences were found for tumours >1 cm, vessel invasion, or MAI >10. Using the present Dutch guidelines for AST, based on B&R3, 20 cases and 11 controls would have received AST. Based on MAI >10, 14 cases and 11 controls would have received AST. Conclusions: Tumour size and vessel invasion are the best prognostic factors for disease free survival in patients with stage I breast cancer. Dutch selection criteria for AST for these patients need to be improved. Some prognostic factors are time dependent, making their use as selection criteria for AST more complicated.

These results show that resections can be performed at acceptable risk in selected elderly patients with cancer.

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