Abstract P1-08-09: Breast cancer-related deaths according to grade in ductal carcinoma in situ: A Dutch population-based study on patients diagnosed between 1999 and 2012

Background

The incidence of ductal carcinoma in situ (DCIS) has drastically increased over the past decades. Since DCIS is resected after diagnosis similarly to invasive breast cancer, the natural cause and behaviour of DCIS is not well known. We aimed to determine breast cancer-specific (BCSS) and overall survival (OS) according to grade in DCIS patients after surgical treatment in the Netherlands.

Patients and methods

All DCIS patients diagnosed between 1999-2012 were selected from the Netherlands Cancer Registry. Cause of death was obtained from 'Statistics Netherlands'. BCSS and OS were estimated using multivariable Cox regression in the entire cohort and stratified for grade.

Results

In total, 12,256 patients were included, of whom 1,509 (12.3%) presented with grade I, 3,675 (30.0%) with grade II, 6,064 (49.5%) with grade III and 1,008 (8.2%) with an unknown grade. During a median follow-up of 7.8 years, 1,138 (9.3%) deaths were observed, and 179 (1.5%) were breast cancer-related. Of these, 10 patients had grade I, 46 grade II, 95 grade III and 28 an unknown grade. After adjustment for confounding, grade II and III were related to worse BCSS compared to grade I with HRs of 1.92 (95% CI:0.97-3.81) and 2.14 (95% CI:1.11-4.12), respectively. No association between grade and OS was observed.

Conclusion

BCSS and OS rates in DCIS patients are excellent. Since superior rates were observed for low-grade DCIS, and earlier studies have shown that low-grade DCIS have a very low chance on recurrence or upstage to invasive cancer, it seems justified to investigate whether active surveillance may be a balanced alternative for conventional surgical treatment.

Citation Format: van Maaren MC, Lagendijk M, Tilanus-Linthorst MM, de Munck L, Pijnappel RM, Schmidt MK, Wesseling J, Koppert LB, Siesling S. Breast cancer-related deaths according to grade in ductal carcinoma in situ: A Dutch population-based study on patients diagnosed between 1999 and 2012 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-09.

Abstract P1-08-19: 10-year conditional recurrence risks, overall and relative survival for breast cancer patients in the Netherlands: Taking account of event-free years

Background

Survival estimates valid at the time of diagnosis are of limited value for (ex-)breast cancer patients who survived several years, as it includes information on already deceased patients. This study analyzed the 10-year conditional risk of recurrent breast cancer in specific prognostic subgroups according to T and N stage and breast cancer subtypes. Secondly, we investigated 10-year conditional overall (OS) and relative survival (RS), adjusted for confounding.

Patients and methods

We selected all women diagnosed in 2005 with operated T1-2N0-1 breast cancer from the Netherlands Cancer Registry. Patients were classified into T1N0, T1N1, T2N0 and T2N1 stage. Ten-year conditional recurrence rates were calculated for every year from diagnosis for patients without an event (local (LR), regional recurrence (RR), distant metastasis (DM) or death). Ten-year conditional OS was calculated using multivariable Cox regression. RS was estimated by dividing patient survival rates by those of the general Dutch population.

Results

We included 7,969 patients: 52.3% had T1N0, 15.3% T1N1, 19.9% T2N0 and 12.5% T2N1 stage. For T1N0, 10-year LR rates changed from 4.6% at diagnosis to 0.5% in year 10. RR rates decreased from 2.3% to 0.2% and DM rates decreased from 7.8% to 0.6%. For T2N1 stage, the LR, RR and DM rates decreased from 6.2% to 0.8%, 5.2% to 0.4% and 19.6% to 1.5%, respectively. Of all patients, 1,702 patients (21.4%) had an unknown breast cancer subtype and were consequently excluded from the analyses according to subtype. Of the remaining 6,267 patients, 3,774 (60.2%) had luminal A, 1,465 (23.4%) had luminal B, 314 (5.0%) had HER2 positive and 714 (11.4%) had triple negative disease For the luminal A subtype, LR, RR and DM rates ranged from 3.9% to 0.4%, 1.7% to 0.5% and 7.3% to 1.1%, while for triple negative these rates ranged between 5.6% to 0.7%, 4.9% to 0.2% and 16.7% to 0%, respectively. Differences between subgroups attenuated over time and all recurrence rates became ≤1.5% in year 10. Ten-year OS and RS, adjusted for confounding, showed diminishing risk differences between subgroups over time.

Conclusion

Differences in recurrence rates, OS and RS between prognostic subgroups decreased as years passed by. These results highlight the importance of taking into account disease-free years to more accurately predict (ex-)breast cancer patients' prognosis over time.

Citation Format: van Maaren MC, Strobbe LJ, Smidt ML, Moossdorff M, Poortmans PM, Siesling S. 10-year conditional recurrence risks, overall and relative survival for breast cancer patients in the Netherlands: Taking account of event-free years [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-19.

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.

Table 1 False-negative rates (FNRs) and false-positive rates (FPRs) of the nomogram at different predictive cut-off pointsPredicted rishPatient number and percentage (%)Number of patients with positive ALNFNR (%)< 14.5%59 (34.7)610.2< 20%79 (46.5)1113.9  Number of patients with negative ALNFPR (%)> 70%27 (15.9)13.7> 90%18 (10.6)00ALN: axillary lymph node

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.

Abstract P1-10-21: Influence of timing of radiation therapy following breast-conserving surgery on 10-year disease-free survival

Background

In the Netherlands, one of the indicators of quality of care is that radiation therapy (RT) should start within six weeks following breast-conserving surgery (BCS). However, there is still much controversy regarding timing of RT in literature. This study investigated the effect of timing of RT on disease-free survival (DFS) in a Dutch nationwide population-based cohort.

Methods

All women diagnosed with primary invasive stage I-IIIA breast cancer in 2003, treated with BCS plus RT, of whom the start date of RT was known, were included. Patients who received chemotherapy between surgery and RT were excluded, as this affects delay. Patients were categorised into three groups: <42 days, 42-55 days and >55 days, between surgery and start of RT. The primary outcome was 10-year DFS. Secondary outcomes were 10-year locoregional recurrence-free (LRRFS) and distant metastasis-free survival (DMFS). Multivariable Cox regression was used to correct for confounding. Since adjuvant systemic therapy largely influences DFS, all analyses were stratified for use of adjuvant systemic therapy (chemotherapy and/or endocrine therapy).

Results

In total, 2,759 patients were included. The median number of days between BCS and RT was 45 (IQR 37-54 days). The hazard ratio (HR) for 10-year DFS was 0.79 (95% CI: 0.65-0.96) for 42-55 days and 0.71 (95% CI: 0.56-0.90) for >55 days, both compared to <42 days. While no significant differences in 10-year LRRFS were found, 10-year DMFS (HR 0.64 [95% CI: 0.45-0.91]) was significantly higher for BCS-RT interval >55 days compared to <42 days. After stratification, no significant differences were found for any outcome in patients not treated with adjuvant systemic therapy, while in patients who were treated with adjuvant systemic therapy, 10-year DFS was significantly improved for 42-55 days (HR 0.70 (95% CI: 0.51-0.97) and >55 days (HR 0.63 (95% CI: 0.42-0.96) compared to <42 days. Significantly improved 10-year DMFS was confirmed after stratification for longer delays (HR 0.69 (95% CI: 0.47-1.00 for 42-55 days) and 0.59 (95% CI: 0.36-0.96) for >55 days, compared to <42 days)

10-year DFS, LRRFS and DMFS for different time intervals between BCS and RT, stratified for use of adjuvant systemic therapy Entire cohort (n=2,759)No adjuvant treatment (n=1,761)Adjuvant treatment (n=998)Time intervalHR [95% CI]*HR [95% CI]*HR [95% CI]*10-year DFS<42 days11142-55 days0.79 [0.65-0.96]0.83 [0.65-1.05]0.70 [0.51-0.97]>55 days0.71 [0.56-0.90]0.77 [0.57-1.03]0.63 [0.42-0.96]10-year LRRFS<42 days11142-55 days0.74 [0.51-1.06]0.79 [0.52-1.21]0.55 [0.28-1.11]>55 days0.90 [0.59-1.37]0.99 [0.61-1.60]0.67 [0.29-1.57]10-year DMFS<42 days11142-55 days0.90 [0.69-1.17]1.13 [0.77-1.66]0.69 [0.47-1.00]>55 days0.64 [0.45-0.91]0.73 [0.44-1.22]0.59 [0.36-0.96]* Corrected for all relevant confounders. HRs in bold are statistically significant (p<0.05).

Conclusion and interpretation

In conclusion, patients treated with adjuvant systemic therapy following RT showed increasing 10-year DFS and DMFS with longer BCS-RT intervals, which was not the case for patients not receiving adjuvant systemic therapy. Possible explanations for these results have to be explored further.

Citation Format: van Maaren MC, Bretveld RW, Jobsen JJ, Veenstra R, Groothuis-Oudshoorn KCGM, Struikmans H, Maduro JH, Strobbe LJA, Poortmans P, Siesling S. Influence of timing of radiation therapy following breast-conserving surgery on 10-year disease-free survival [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 P1-10-21.

Abstract P1-11-14: Breast conserving therapy and mastectomy revisited: overall and breast cancer-specific survival and the influence of age, stage, receptor status and comorbidities in 143,376 patients

This abstract was withdrawn by the authors.