Abstract P6-08-20: Non-adherers of mammography screening: Delayed surgery, early discontinuation of adjuvant hormone therapy, and worse breast cancer outcomes
Authors: He W , Bergman LE , Törnberg S , Strand F , Hall P , Czene K 
Published: February 2018

Purpose: To test the hypothesis that prior non-adherence to mammography screening could predict subsequent non-adherence to breast cancer treatment. Specifically, we hypothesized that as compared with adherers, screening non-adherers may be more likely to have delayed surgery, discontinue their adjuvant hormone therapy, and consequently have worse breast cancer outcomes.

Methods: We conducted a record-linkage study based on data from the Stockholm Mammography Screening Program (1989-2013), Stockholm-Gotland Breast Cancer Register (2001-2017), Swedish Prescribed Drug Register (2005-2017), and Cause of Death Register (2001-2013). Women diagnosed with breast cancer between 2001 and 2008 in Stockholm, Sweden, were prospectively followed for treatment and survival until December 31st, 2013 (N=5106). Screening non-adherers were defined as patients who were invited but did not attend the screening mammography within 2 years before breast cancer diagnosis. Discontinuation of adjuvant hormone therapy was defined as having any interval between two consecutive dispenses exceeding 180 days during follow-up. Disease-free survival was defined as time to local recurrence, distant metastasis, contralateral breast cancer, or death from breast cancer, whichever came first.

Results: The proportion of delayed surgery (≥6 weeks) for screening adherers (restricted to interval cancers only) versus non-adherers were 15.5% versus 20.6%, respectively (P&lt;0.01). As compared with adherers, screening non-adherers were more likely to discontinue their adjuvant hormone therapy, with an adjusted hazard ratio of 1.37 (95% CI, 1.17 to 1.61). Furthermore, Cox regression analysis showed that screening non-adherence was associated with poorer disease-free survival even after adjusting for tumor characteristics and other covariates, with an adjusted hazard ratio of 1.19 (95% CI, 1.01 to 1.41) for screening non-adherers versus adherers.

 Screening AdherersScreening Non-adherers Univariable-analysisMultivariable analysis#Delayed surgery&gt;6 weeks*     No897(84.5)624(79.4) 1.00 (Reference)1.00(Reference)Yes†165(15.5)162(20.6) 1.40(1.10-1.78)1.34(1.05-1.72)Discontinuation of adjuvant hormone therapy**     No822(50.3)145(42.7) 1.00(Reference)1.00(Reference)Yes††812(49.7)195(57.3) 1.33(1.14-1.56)1.37(1.17-1.61)Disease free survival events     No3574(85.8)752(79.8) 1.00(Reference)1.00(Reference)Yes††590(14.2)190(20.2) 1.46(1.24-1.72)1.19(1.01-1.41)* Restricted to patients diagnosed with clinically detected cancers who were primary operated without neoadjuvant therapy; ** Restricted to patients diagnosed after July 1st, 2005, who initiated adjuvant hormone therapy.† Odds ratios (95% CI);† † Hazard ratios (95% CI).# Adjusting for age, tumor size, lymph node involvement, estrogen receptor status, progesterone receptor status, HER2 status, and type of surgery

Conclusions: Compared to adherers, screening non-adherers are more likely to have delayed surgery, discontinue their adjuvant hormone therapy, and subsequently have worse breast cancer outcomes even after adjusting for baseline tumor characteristics.

Citation Format: He W, Bergman LE, Törnberg S, Strand F, Hall P, Czene K. Non-adherers of mammography screening: Delayed surgery, early discontinuation of adjuvant hormone therapy, and worse breast cancer outcomes [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-08-20.