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Introduction: Observational studies suggest that breast conserving surgery (BCS) and radiotherapy (RT) offers superior survival compared to mastectomy. The aim was to compare patient and tumour characteristics in women with invasive breast cancer ≤30 mm treated with either BCS or mastectomy, and to explore the underlying reason for choosing mastectomy.

Methods: Women registered with breast cancer ≤30 mm and ≤4 positive axillary lymph nodes in the Swedish National Breast Cancer Register 2013–2016 were included. Logistic regression analyses were performed to assess the association of tumour and patient characteristics with receiving a mastectomy vs. BCS.

Results: Of 1860 breast cancers in 1825 women, 1346 were treated by BCS and 514 by mastectomy. Adjuvant RT was given to 1309 women (97.1 %) after BCS and 146 (27.6 %) after mastectomy. Variables associated with receiving a mastectomy vs. BCS included clinical detection (Odds Ratio (OR) 4.15 (95 % Confidence Interval (CI) 3.35–5.14)) and clinical stage (T2 vs. T1 (OR 3.68 (95 % CI 2.90–4.68)), N1 vs. N0 (OR 2.02 (95 % CI 1.38–2.96)). Women receiving mastectomy more often had oestrogen receptor negative, HER2 positive tumours of higher histological grade. The most common reported reason for mastectomy was large or multifocal tumours (53.5 %), followed by patient preference (34.5 %).

Conclusion: Choice of surgery is strongly associated with key prognostic factors among women undergoing BCS with RT compared to mastectomy. Failure to control for all relevant confounders may bias results in outcome studies in favour of BCS.

Purpose: The effectiveness of current follow-up guidelines after breast cancer treatment is uncertain. Tailored surveillance based on patient age and tumor characteristics may be more adequate. This study aimed to analyze the frequency of ipsilateral locoregional recurrences (LR) and second primary breast cancers (SP) detected outside of scheduled surveillance and to analyze risk factors associated with these events.

Methods: Patients with surgically treated early-stage breast cancer from the Malmö Diet and Cancer Study (MDCS), 1991–2014 (n = 1080), and the Västernorrland region, 2009–2018 (n = 1648), were included. Clinical and pathological information on the primary tumor and recurrences was retrieved from medical records. The mode of recurrence detection was defined as detection within (planned) or outside (symptomatic) of scheduled surveillance.

Results: The median follow-up was 6.5 years. Overall, 461 patients experienced a recurrence. The most common initial event was distant metastasis (47%), followed by locoregional recurrence (LR) (22%) and second primary (SP) (18%). 56% of LR and 28% of SP were identified outside of scheduled surveillance. Logistic regression analysis revealed that younger age (under 50 years) (OR 2.57, 95% CI 1.04–6.88), lymph node-positive breast cancer (OR 2.10, 95% CI 1.03–4.39) and breast cancer of the HER2 positive subtype (OR 5.24, 95% CI 1.40–25.90) were correlated with higher odds of detecting a recurrence outside of planned surveillance.

Conclusion: Most recurrent events were detected outside of scheduled surveillance, particularly for locoregional recurrences. Risk-based surveillance, which takes into account patient and tumor characteristics, might be more suitable for specific patient subsets.

Background: Studies identifying risk factors for death from breast cancer after ductal carcinoma in situ (DCIS) are rare. In this retrospective nested case-control study, clinicopathological factors in women treated for DCIS and who died from breast cancer were compared with those of patients with DCIS who were free from metastatic disease.

Methods: The study included patients registered with DCIS without invasive carcinoma in Sweden between 1992 and 2012. This cohort was linked to the National Cause of Death Registry. Of 6964 women with DCIS, 96 were registered with breast cancer as cause of death (cases). For each case, up to four controls (318; women with DCIS, alive and without metastatic breast cancer at the time of death of the corresponding case) were selected randomly by incidence density sampling. Whole slides of tumour tissue were evaluated for DCIS grade, comedo necrosis, and intensity of periductal lymphocytic infiltrate. Composition of the immune cell infiltrate, expression of oestrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, and proliferation marker Ki-67 were scored on tissue microarrays. Clinical information was obtained from medical records. Information on date, site, and histological characteristics of local and distant recurrences was obtained from medical records for both cases and controls.

Results: Tumour tissue was analysed from 65 cases and 195 controls. Intense periductal lymphocytic infiltrate around DCIS was associated with an increased risk of later dying from breast cancer (OR 2.21. 95% c.i. 1.01 to 4.84). Tumours with more intense lymphocytic infiltrate had a lower T cell/B cell ratio. None of the other biomarkers correlated with increased risk of breast cancer death.

Conclusion: The immune response to DCIS may influence the risk of dying from breast cancer.

Background: International guidelines recommend open surgery for atypical ductal hyperplasia (ADH) in the breast due to risk of underestimating malignant disease. Considering the ongoing randomized trials of active surveillance of low-risk ductal carcinoma in situ (DCIS), it seems reasonable to define a low-risk group of women with ADH where a conservative approach is appropriate. The aim here was to evaluate the management and risk for upgrade of lesions diagnosed as ADH in percutaneous breast biopsies in two Swedish hospitals.

Methods: All women with a screen-detected or symptomatic breast lesion breast imaging-reporting and data system (BI-RADS) 2–4 and a percutaneous biopsy showing ADH between 2013 and 2022 at Sundsvall Hospital and Umeå University Hospital were included. Information regarding imaging, histopathology, clinical features, and management was retrieved from medical records. Odds ratio (OR) and 95% confidence intervals (CI) for upgrade to malignant diagnosis after surgery were calculated by logistic regression analysis.

Results: Altogether, 101 women were included with a mean age 56.1 (range 36–93) years. Most women were selected from the national mammography screening program due to microcalcifications. Biopsies were performed with vacuum-assisted biopsy (60.4%) or core-needle biopsy (39.6%). Forty-eight women (47.5%) underwent surgery, of which 11 were upgraded to DCIS, and 7 to invasive breast cancer (upgrade rate 37.5%). Among the 53 women managed conservatively (median follow-up 74 months), one woman (1.9%) developed subsequent ipsilateral DCIS. The combined upgrade rate was 18.8%. No clinical variable statistically significantly correlating to risk of upgrade was identified.

Conclusions: The upgrade rate of 37.5% in women undergoing surgery compared to an estimated 5-year risk of ipsilateral malignancy at 1.9% in women managed conservatively indicate that non-surgical management of select women with ADH is feasible. Research should focus on defining reproducible criteria differentiating high-risk from low-risk ADH.

Background: Retrospective observational studies suggest a potential role of beta-blockers as a protective strategy against progression and metastasis in invasive breast cancer. In this context, we investigated the impact of beta-blocker exposure on risk for progression to invasive breast cancer after diagnosis of ductal cancer in situ (DCIS).

Methods: The retrospective study population included 2535 women diagnosed with pure DCIS between 2006 and2012 in three healthcare regions in SwedenExposure to beta-blocker was quantified using a time-varying percentage of days with medication available. The absolute risk was quantified using cumulative incidence functions and cox models were applied to quantify the association between beta-blocker exposure and time from DCIS diagnosis to invasive breast cancer, accounting for delayed effects, competing risks and pre-specified confounders.

Results: The median follow-up was 8.7 years. One third of the patients in our cohort were exposed to beta-blockers post DCIS diagnosis. During the study period, 48 patients experienced an invasive recurrence, giving a cumulative incidence of invasive breast cancer progression of 1.8% at five years. The cumulative exposure to beta-blocker was associated with a reduced risk in a dose-dependent manner, though the effect was not statistically significant.

Conclusion: Our observational study is suggestive of a protective effect of beta-blockers against invasive breast cancer after primary DCIS diagnosis. These results provide rationales for experimental and clinical follow-up studies in carefully selected DCIS groups.

Background: Breast angiosarcoma is a rare disease mostly observed in breast cancer (BC) patients who have previously received radiotherapy (RT). Little is known about angiosarcoma aetiology, management, and outcome. The study aim was to estimate risk and to characterize breast angiosarcoma in a Swedish population-based cohort.

Methods: The Swedish Cancer Registry was searched for breast angiosarcoma between 1992 and 2018 in three Swedish healthcare regions (population 5.5 million). Information on previous BC, RT, management, and outcome were retrieved from medical records.

Results: Overall, 49 angiosarcomas located in the breast, chest wall, or axilla were identified, 8 primary and 41 secondary to BC treatment. Median age was 51 and 73 years, respectively. The minimum latency period of secondary angiosarcoma after a BC diagnosis was 4 years (range 4–21 years). The cumulative incidence of angiosarcoma after breast RT increased continuously, reaching 1.4‰ after 20 years. Among 44 women with angiosarcoma treated by surgery, 29 developed subsequent local recurrence. Median recurrence-free survival was 3.4 and 1.8 years for primary and secondary angiosarcoma, respectively. The 5-year overall survival probability for the whole cohort was 50 per cent (95 per cent c.i., 21 per cent–100 per cent) for primary breast angiosarcoma and 35 per cent (95 per cent c.i., 23 per cent–54 per cent) for secondary angiosarcoma.

Conclusion: Breast angiosarcoma is a rare disease strongly associated with a history of previous BC RT. Overall survival is poor with high rates of local recurrences and distant metastasis.

Background: Adjuvant radiotherapy (RT) after breast-conserving surgery for DCIS lowers the relative local recurrence risk by half. To identify a low-risk group with the minimal benefit of RT could avoid side effects and spare costs. In this study, the outcome was compared for different RT-strategies using data from the randomized SweDCIS trial.

Material and methods: Five strategies were compared in a Swedish setting: RT-to-none or all, RT to high-risk women defined by DCISionRT, modified Radiation Therapy Oncology Group (RTOG) 9804 criteria, and Swedish Guidelines. Ten-year recurrence risks and cost including adjuvant RT and local recurrence treatment cost were calculated.

Results: The mean age at recurrence was 64.4 years (36–90) and the mean cost for treating a recurrence was $21,104. In the SweDCIS cohort (n = 504), 59 women developed DCIS, and 31 invasive recurrence. Ten-year absolute local recurrence risk (invasive and DCIS) according to different strategies varied between 18.6% (12.5–23.6%) and 7.8% (5.0–12.6%) for RT-to-none or to-all, with an additional cost of $2614 US dollars per women and $24,201 per prevented recurrence for RT-to-all. The risk differences between other strategies were not statistically significant, but the larger proportion receiving RT, the fewer recurrences. DCISionRT spared 48% from RT with 8.1% less recurrences compared to RT-to-none, and a cost of $10,534 per prevented recurrence with additional cost depending on the price of the test. RTOG 9804 spared 39% from RT, with 9.7% less recurrences, $9525 per prevented recurrence and Swedish Guidelines spared 13% from RT, with 10.0% less recurrences, and $21,521 per prevented recurrence.

Conclusion: It seems reasonable to omit RT in pre-specified low-risk groups with minimal effect on recurrence risk. Costs per prevented recurrence varied more than two-fold but which strategy that could be considered most cost-effective needs to be further evaluated, including the DCISionRT-test price.

Purpose: To investigate if molecular subtype is associated with outcome in stage 1 breast cancer (BC). Methods: Tissue samples from 445 women with node-negative BC ≤ 15 mm, treated in 1986–2004, were classified into surrogate molecular subtypes [Luminal A-like, Luminal B-like (HER2−), HER2-positive, and triple negative breast cancer (TNBC)]. Information on treatment, recurrences, and survival were gathered from medical records. Results: Tumour subtype was not associated with overall survival (OS). Luminal B-like (HER2−) and TNBC were associated with higher incidence of distant metastasis at 20 years (Hazard ratio (HR) 2.26; 95% CI 1.08–4.75 and HR 3.24; 95% CI 1.17–9.00, respectively). Luminal B-like (HER2−) and TNBC patients also had worse breast cancer-specific survival (BCSS), although not statistically significant (HR 1.53; 95% CI 0.70–3.33 and HR 1.89; 95% CI 0.60–5.93, respectively). HER2-positive BC was not associated with poor outcome despite no patient receiving HER2-targeted therapy, with most of these tumours being ER+. Conclusions: Stage 1 TNBC or Luminal B-like (HER2−) tumours behave more aggressively. Women with HER2+/ER+ tumours do not have an increased risk of distant metastasis or death, absent targeted treatment.

Adjuvant radiotherapy (RT) for breast cancer (BC) has been associated with an increased risk of later radiation-induced lung cancer (LC). We examined the risk of primary LC in a population-based cohort of 52300 women treated for BC during 1992 to 2012, and 253796 age-matched women without BC. Cumulative incidence of LC was calculated by the Kaplan–Meier method, and the risk of LC after BC treatment was estimated by Cox proportional hazards regression analyses. Women with BC receiving RT had a higher cumulative incidence of LC compared to women with BC not receiving RT and women without BC. This became apparent 5 years after RT and increased with longer follow-up. Women with BC receiving RT had a Hazard ratio of 1.59 (95% confidence interval 1.37–1.84) for LC compared to women without BC. RT techniques that lower the incidental lung doses, e.g breathing adaption techniques, may lower this risk.