Mc van Maaren

Abstract S3-05: Higher 10-year overall survival after breast conserving therapy compared to mastectomy in early stage breast cancer: A population-based study with 37,207 patients

Background: Randomised controlled trials have shown that breast conserving therapy (conserving surgery with radiation therapy, BCT) has equal overall survival (OS) rates as mastectomy without radiation therapy (MAST) in early stage breast cancer. However, 10-year disease-free survival (DFS) in a population-based study was not investigated before. The aim of this study was to compare 10-year OS and DFS after BCT with MAST in Dutch women with early stage breast cancer. Methods: Data of all women diagnosed with primary invasive T1-2N0-1M0 stage breast cancer between 1 January 2000 and 31 December 2004, treated with either BCT or MAST, were selected from the Netherlands Cancer Registry. Multivariable Cox proportional hazard analysis was performed to estimate 10-year OS, stratified for T and N stage. Ten-year DFS was determined in a subgroup of patients diagnosed in 2003, of which an active follow-up was conducted registering all recurrent events within 10 years. Multiple imputation was performed to account for missing data. Results: Of in total 37,207 patients, 21,734 patients (58.4%) received BCT and 15,473 patients (41.6%) received MAST. The subcohort of 2003 consisted of 7,552 patients, with similar distributions of treatments and characteristics. In the total cohort, 10-year OS was 76.8% (99% CI: 76.1-77.5%) after BCT and 59.7 (99% CI: 58.7-60.7%) after MAST. After correction for confounding, 10-year OS was better after BCT than after MAST (HRadjusted: 0.79 [99% CI 0.75-0.83]). In the 2003 cohort, 10-year DFS was 83.6% (99% CI: 82.5-84.7%) after BCT and 81.5% (99% CI: 79.6-83.4%) after MAST. After correction for confounding, 10-year DFS was comparable for both treatments (HRadjusted 0.91 [99% CI 0.77-1.07]). All results were similar for all subgroups (Table). In the 2003 cohort, 11.0% of the patients experienced distant metastases (DM) after BCT compared to 14.7% after MAST (p Conclusion: BCT showed substantially improved OS compared to MAST. However, while DFS was similar, patients treated with BCT less often developed RR and DM. Although residual factors might explain part of the difference in recurrences, we hypothesise that radiation therapy might largely be responsible for better OS by eliminating residual tumour cells. Citation Format: van Maaren MC, de Munck L, de Bock GH, Jobsen JJ, van Dalen T, Poortmans P, Linn SC, Strobbe LJA, Siesling S. Higher 10-year overall survival after breast conserving therapy compared to mastectomy in early stage breast cancer: A population-based study with 37,207 patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S3-05.

Validation of the online prediction tool PREDICT v. 2.0 in the Dutch breast cancer population.

BACKGROUND PREDICT version 2.0 is increasingly used to estimate prognosis in breast cancer. This study aimed to validate this tool in specific prognostic subgroups in the Netherlands. METHODS All operated women with non-metastatic primary invasive breast cancer, diagnosed in 2005, were selected from the nationwide Netherlands Cancer Registry (NCR). Predicted and observed 5- and 10-year overall survival (OS) were compared for the overall cohort, separated by oestrogen receptor (ER) status, and predefined subgroups. A >5% difference was considered as clinically relevant. Discriminatory accuracy and goodness-of-fit were determined using the area under the receiver operating characteristic curve (AUC) and the Chi-squared-test. RESULTS We included 8834 patients. Discriminatory accuracy for 5-year OS was good (AUC 0.80). For ER-positive and ER-negative patients, AUCs were 0.79 and 0.75, respectively. Predicted 5-year OS differed from observed by -1.4% in the entire cohort, -0.7% in ER-positive and -4.9% in ER-negative patients. Five-year OS was accurately predicted in all subgroups. Discriminatory accuracy for 10-year OS was good (AUC 0.78). For ER-positive and ER-negative patients AUCs were 0.78 and 0.76, respectively. Predicted 10-year OS differed from observed by -1.0% in the entire cohort, -0.1% in ER-positive and -5.3 in ER-negative patients. Ten-year OS was overestimated (6.3%) in patients ≥75 years and underestimated (-13.%) in T3 tumours and patients treated with both endocrine therapy and chemotherapy (-6.6%). CONCLUSIONS PREDICT predicts OS reliably in most Dutch breast cancer patients, although results for both 5-year and 10-year OS should be interpreted carefully in ER-negative patients. Furthermore, 10-year OS should be interpreted cautiously in patients ≥75 years, T3 tumours and in patients considering endocrine therapy and chemotherapy.

Nationwide population-based study of trends and regional variation in breast-conserving treatment for breast cancer: Trends and variation in breast surgery in the Netherlands

Landmark trials have shown breast‐conserving surgery (BCS) combined with radiotherapy to be as safe as mastectomy in breast cancer treatment. This population‐based study aimed to evaluate trends in BCS from 1989 to 2015 in nine geographical regions in the Netherlands.

Abstract P2-01-26: Validation of a Chinese nomogram with a Dutch breast cancer population: Excellent prediction of the probability of axillary lymph node metastasis

Background: In the era of precision medicine, the surgical management of axillary lymph nodes (ALN) should be patient-tailored. Omission of sentinel lymph node biopsy (SLNB) is possible in patients with early breast cancer and very low or very high probability of ALN metastasis. Recently, we developed a nomogram to predict the probability of ALN metastasis in breast cancer patients based on clinicopathological parameters including ultrasound using a Chinese patient dataset1. In this study the nomogram performance was validated in an independent Dutch population from one hospital. Methods: Data of 170 Dutch patients with a successful SLNB or axillary lymph node dissection were collected. A lymph node containing either micro- or macrometastatic disease was considered as a positive lymph node. Performance of the nomogram was assessed by calculating the area under the receiver-operator characteristic (ROC) curve (AUC). False-negative rates (FNRs) and false-positive rates (FPRs) at several different predictive cut-off points were calculated. Results: There were 69 (40.6%) patients having a positive ALN. The AUC for the nomogram was 0.84 (95% confidence interval 0.78-0.90) compared with 0.86 in the Chinese validation population, showing excellent discrimination of the model. The FNR and FPR of the model were 10.2% and 0% for the predicted probability cut-off points of 14.5% and 90%, respectively. This means that omission of SLNB is possible for patients with a predictive probability of less than 14.5% or higher than 90%, which accounts for 45.3% of all patients in this study. Conclusions and future perspectives: In this study, the Chinese nomogram showed excellent performance in predicting the probability of ALN metastasis in an independent Dutch population. A multicentre validation of this nomogram in large Dutch patient population (>2500 patients) is ongoing. Reference 1.Qiu S-Q, Zeng H-C, Zhang F, et al. A nomogram to predict the probability of axillary lymph node metastasis in early breast cancer patients with positive axillary ultrasound. Sci Rep 2016; 6: 21196. Citation Format: Qiu S-Q, Aarnink M, van Maaren MC, Dorrius M, Koffijberg H, van Dam GM, Siesling S. Validation of a Chinese nomogram with a Dutch breast cancer population: Excellent prediction of the probability of axillary lymph node metastasis [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-01-26.