Abstract P3-12-09: Impact of the COVID-19 outbreak on the treatment strategy of Dutch breast cancer patients
Authors: Eijkelboom Anouk H , Siesling Sabine , de Munck Linda , van den Bongard Desiree HJG , Menke-van der Houven van Oordt Willemien , Westenend Pieter J , Siemerink Ester JM , Strobbe Luc JA , Vrancken Peeters Marie-Jeanne TFD , Koppert Linetta B , Mureau Marc AM , Jager Agnes , Broeders Mireille JM , Lobbes Marc BI , Verkooijen Helena M , Wesseling Jelle , Smidt Marjolein , Tjan-Heijnen Vivianne CG ,   NABON-COVID-19 consortium,   COVID and Cancer Care NL consortium (ZONMW number10430022010014)
Published: March 2022

Introduction: The COVID-19 outbreak forced health care services to switch focus to COVID-19 patients, thereby generating pressure on all other health care services, most likely impacting breast cancer care as well. However, the impact of the COVID-19 outbreak on the breast cancer treatment strategy is unknown. Objective: To investigate the impact of the COVID-19 outbreak on the breast cancer treatment strategy. Methods: We selected women diagnosed with breast cancer between January 1st 2018 and June 30th 2020 from the Netherlands Cancer Registry. Women with previous breast cancer or with a synchronous tumor were excluded. The following periods based on COVID-19 related events were analyzed: 2018/2019 (reference), weeks 1-8, weeks 9-12, weeks 13-17, and weeks 18-26 in 2020. Patients were divided into periods based on their date of diagnosis. For patients with DCIS we used logistic regression to investigate the association between period of diagnosis and chance of being treated within six months following diagnosis. For patients with invasive tumors receiving surgery, we used logistic regression to investigate the association between period of diagnosis and chance of receiving a certain type of treatment, adjusting for tumor stage. Furthermore, time length between the following time points were calculated per tumor stage: 1) diagnosis and first treatment (of any kind), 2) diagnosis and start of neo-adjuvant treatment, 3) diagnosis and operation (no neo-adjuvant treatment was given), 4) end of neo-adjuvant treatment and operation, 5) operation and start of adjuvant systemic treatment, and 6) operation and start of radiotherapy. Time lengths were calculated for each period of 2020 and compared with 2018/2019. Results: A total of 1,795 DCIS and 11,785 invasive tumors were diagnosed in 2018, 1,826 DCIS and 11,987 invasive tumors in 2019 and 597 DCIS and 4,566 invasive tumors up to June 2020. Compared to 2018/2019, patients diagnosed with a DCIS were less likely to be treated within six months following diagnosis (ORwks1-8: 0.63, ORwks9-12: 0.50, ORwks18-26: 0.51) (Table). Patients diagnosed with an invasive tumor in weeks 9-12 2020 were less likely to receive neo-adjuvant chemotherapy (ORwks9-12: 0.63), while patients diagnosed thereafter were more likely to receive neo-adjuvant chemotherapy (ORwks13-17: 1.39, ORwks18-26: 1.41). Patients were more likely to receive neo-adjuvant endocrine therapy (ORwks1-8: 1.64, ORwks9-12: 3.14, ORwks13-17: 1.85, ORwks18-26: 1.28), mastectomy (ORwks18-26: 1.32), or adjuvant chemotherapy (ORwks9-12: 1.36), while they were less likely to receive radiotherapy (ORwks18-26: 0.74). Patients receiving a mastectomy for their invasive tumor were more likely to receive an immediate reconstruction (ORwks18-26: 1.57). Compared to 2018/2019, time between diagnosis and first treatment, diagnosis and operation, diagnosis and neo-adjuvant treatment, and operation and adjuvant systemic treatment decreased significantly for patients diagnosed with a stage I-III tumor in weeks 9-12, 13-17 or 18-26. Conclusion: The COVID-19 outbreak affected multiple aspects of the breast cancer treatment strategy and led to a shorter time to therapy, probably due to prioritizing of oncological care and a reduction in the number of patients.

Association between period of diagnosis and risk of receiving a certain treatment2018/2019Week 1-8 2020Week 9-12 2020Week 13-17 2020Week 18-26 2020Treatment within 6 months1Reference0.63 (0.42-0.93)0.50 (0.29-0.87)0.98 (0.30-3.17)0.51 (0.28-0.95)Neo-adjuvant chemotherapy2Reference0.98 (0.86-1.11)0.63 (0.52-0.77)1.39 (1.13-1.72)1.41 (1.23-1.62)Neo-adjuvant endocrine therapy2Reference1.64 (1.34-1.99)3.14 (2.50-3.95)1.85 (1.35-2.54)1.28 (1.01-1.62)Neo-adjuvant targeted therapy2Reference0.89 (0.73-1.07)0.74 (0.55-0.99)1.46 (1.11-1.92)1.21 (1.01-1.46)Mastectomy2Reference0.94 (0.84-1.05)1.05 (0.89-1.23)1.10 (0.91-1.34)1.32 (1.16-1.49)Breast conserving surgery2Reference1.04 (0.92-1.18)0.89 (0.75-1.06)0.91 (0.74-1.13)0.99 (0.86-1.13)Mastectomy with immediate reconstruction2,3Reference0.96 (0.79-1.18)0.82 (0.61-1.10)0.93 (0.66-1.32)1.57 (1.29-1.91)Adjuvant chemotherapy2Reference1.00 (0.88-1.13)1.36 (1.14-1.61)1.01 (0.81-1.27)1.06 (0.92-1.23)Adjuvant endocrine therapy2Reference0.95 (0.85-1.05)1.07 (0.92-1.24)0.97 (0.80-1.17)1.08 (0.96-1.22)Adjuvant targeted therapy2Reference0.88 (0.75-1.03)0.88 (0.70-1.11)1.21 (0.94-1.55)1.08 (0.91-1.28)Adjuvant radiotherapy2Reference0.96 (0.86-1.08)0.93 (0.79-1.09)0.94 (0.76-1.16)0.74 (0.65-0.83)Odds ratio and 95% confidence interval of the association between period of diagnosis and risk of receiving a certain treatment, adjusted for stage. Bold: significant association 1. This analyses only included patients diagnosed with a DCIS 2. This analyses only included patients diagnosed with an invasive tumor 3. This analyses only included patients treated with a mastectomy

Citation Format: Anouk H Eijkelboom, Sabine Siesling, Linda de Munck, Desiree HJG van den Bongard, Willemien Menke-van der Houven van Oordt, Pieter J Westenend, Ester JM Siemerink, Luc JA Strobbe, Marie-Jeanne TFD Vrancken Peeters, Linetta B Koppert, Marc AM Mureau, Agnes Jager, Mireille JM Broeders, Marc BI Lobbes, Helena M Verkooijen, Jelle Wesseling, Marjolein Smidt, Vivianne CG Tjan-Heijnen, NABON-COVID-19 consortium, COVID and Cancer Care NL consortium (ZONMW number10430022010014). Impact of the COVID-19 outbreak on the treatment strategy of Dutch breast cancer patients [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-12-09.