Implementing a multidisciplinary breast cancer pathway leads to better compliance with the national guidelines and can improve breast cancer care.

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Objective: The COVID-19 pandemic has had an impact on health care. In the Netherlands, hospital capacity for non-covid care was limited and population screening temporarily halted. The aim of this study was to investigate the impact of the pandemic on the diagnostic pathway of breast cancer. Methods: In this study, 48,425 breast cancer patients with a primary breast tumour were selected from the Netherlands Cancer Registry and the Dutch Hospital Data. Patients diagnosed in period January 2020 to July 2021 were divided into six periods, based on the number of hospitalizations due to the COVID-19 pandemic and compared to the same periods in 2017-2019. A t-test was performed to compare the number of diagnosed patients per period. Patient characteristics were compared using chi-squared test. The impact on the procedures performed was analysed using logistic regression. The median time between diagnosis and therapy and the median time between first diagnostic procedure and therapy was analysed using Cox Proportional Hazards Regression. All results were corrected for age, stage and region. Results: During the first peak of the pandemic in 2020, significantly fewer patients (-48,2%) have been diagnosed with breast cancer. This decrease is mainly seen in lower stage tumours. Mammography and echography were performed significantly less per patient during the first recovery in 2020 (OR=0.83 and OR=0.85 respectively) compared to 2017-2019. PET-CT was performed significantly more often during the first peak and first recovery in 2020 (OR=1.94 and OR=1.39 respectively). The median time between diagnosis and start of therapy significantly decreased in 2020, during the first peak by 3 days (HR=1.26), during first recovery and second peak by 1 day (HR=1.04 and HR=1.16 respectively). The median time between first diagnostic procedure and start of therapy significantly decreased in 2020, during the first peak by 4 days (HR=1.25), during the first recovery by 1 day (HR=1.04) and during the second peak by 2 days (HR=1.13). Conclusion: The decreased number of diagnosis was related to the temporary halt of the screening. Diagnostics for early stage tumours was limited and for PET-CT was performed more often reflecting the change in proportion of higher stage. A reduced time of the diagnostic pathway is the result of less hospitalized patients with cancer and the effort on keeping the oncology care in place. Table 1. Overview results diagnostic pathway of breast cancer. *significant difference between periods p<0.05 **significant difference between periods p<0.01 Citation Format: Wouter Wolfkamp, Joyce Meijer, Jolanda Van Hoeve, Jeroen Veltman, Sabine Siesling. Impact of the COVID-19 pandemic on the diagnostic pathway of breast cancer in the Netherlands: a population-based study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-05-19.

The aim of this study was to investigate how breast cancer follow-up in the Netherlands changed during the COVID-19 pandemic, compared to 2018-2019, and to what extent follow-up during the pandemic corresponded to the patient risk of recurrence. During the early phase of the pandemic the Dutch Society for Surgical Oncology (NVCO) issued a report with recommendations on how follow-up could be postponed, as a guidance for the pandemic, based on a low, intermediate or high risk of recurrence. In this study we investigated to what extent this advice was followed. A dataset of 33160 women diagnosed with primary invasive breast cancer between January of 2017 and July of 2021 was selected from the Netherlands Cancer Registry (NCR) and Dutch Hospital Data (DHD). The pandemic, 2020 and weeks 1-32 of 2021, was divided into six periods (A to F), based on the number of hospitalized COVID patients in the Netherlands. The five-year risk of locoregional recurrence (LRR) was determined for each patient with the INFLUENCE nomogram. The LRR risk was compared to the risk groups from the NVCO report with a Kruskal-Wallis test. The percentage of patients who received a mammogram during period A to F was compared to the same periods of 2018-2019 with a chi-squared test. Correlation between the LRR risk, and if patients had a mammogram, was investigated with logistic regression. This analysis was repeated separately for the risk groups. Correlation between the LRR risk, and time intervals between surgery and the first and second mammogram was analyzed using cox proportional hazard models, this was also repeated for the risk groups. There was a significant difference in LRR risk between the NVCO risk groups. In the low-risk group (n=7673), 86 patients (1.1%) had a risk >5%. In the intermediate risk group (n=19197), 18364 patients (95.7%) had a risk of < 5%, and 65 patients (0.34%) had a risk of >10%. In the high-risk group (n=2674), 2365 patients (88.4%) had a risk < 10%. The percentage of patients who received a mammogram was significantly lower in periods B to F of the pandemic. Logistic regression showed a negative correlation between the risk of LRR and if patients had a mammogram in 2020 (OR 0.93) and 2021 (OR 0.93). There was also a negative correlation between the risk groups and mammography in 2020 (OR 0.92 for intermediate and 0.80 for high), and for the risk groups and mammography in 2021 (OR 0.98 for intermediate and 0.95 for high). There was no significant impact of LRR risk, or risk group, on time intervals between mammograms. During the pandemic, patients with a higher LRR risk, or a higher risk according to NVCO advice, had lower odds of having a mammogram. If the advice would have been followed, in 0.5% of the patients scheduled for follow-up, the recommendation was to postpone in contrast to a high estimation of the individual risk. For 62.7%, a follow-up was recommended, despite a low estimated individuals risk. Because the number of high-risk patients is relatively low, individual risk prediction could be supportive, in case of future restrictions. This way the high-risk patients can be identified and prioritized for follow-up, and can also be encouraged to come to the hospital. Citation Format: Lotte Van Dongen, Joyce Meijer, Jolanda Van Hoeve, Desiree van den Bongard, Marielle Hendriks, Aafke Honkoop, Luc Strobbe, Cristina Guerrero Paez, Sabine Siesling. Follow-up in breast cancer care: guidelines and individual risks [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-17.

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