Abstract B015: MRI features can identify DCIS patients who can be managed with endocrine therapy alone

Background: Ductal carcinoma in situ (DCIS) represents almost a quarter of newly diagnosed breast cancers in the US. It is currently treated like a stage 1 cancer, with surgical excision, radiation, and endocrine therapy (ET). Not all cases will progress to invasive cancer and thus we may be overtreating some lesions. Using a cohort of women who participated in an Active Surveillance (AS) with neoadjuvant ET and serial MR imaging, we aimed to identify features on MRI that could stratify DCIS lesions with low- and high-risk of progressing to invasive cancer. Materials/Methods: This was an IRB-approved retrospective study of women with DCIS who chose AS for treatment and were enrolled in MR imaging studies between 2002 and 2020. All women in this study had at least 2 breast MRI scans, which consisted of normal sequences with two post-contrast timepoints. Two radiologists, who were blinded to outcomes, analyzed MRI sequences for each patient at each timepoint for features that may be indicative of risk. Baseline imaging features collected were utilized in an RPART recursive partitioning algorithm that created a classification tree based on a DCIS lesions likelihood to progress to invasive cancer. Our final cohort consisted of 63 cases of DCIS (62 women, 1 with bilateral disease) with a mean age of 58.3 years (range of 29.8-78.8 years). All 62 patients (63 cases, 100%, 63/63) agreed to take hormone therapy for their DCIS. Results: The RPART algorithm showed two baseline features that were important in predicting risk: 1) the presence of a lesion that is distinct from the surrounding tissue and 2) background parenchymal enhancement (BPE). It separated our cohort into three sub-groups based on risk of progression: A (n=32) with the lowest-risk, B (n=17) with the second lowest-risk, and C (n=14) with the highest-risk. In A and B, 6 cases of DCIS progressed to invasive cancer (12.2%, 6/49). These groups had an enrichment of mild, moderate, and marked BPE. Group A (12.5%, 4/32 progressed to IDC) did not have any lesions that were distinct above BPE. All cases in B (11.8%, 2/17 progressed to IDC) had lesions that were distinct above BPE initially but reduced in response to endocrine therapy. In C, 10 cases of DCIS progressed to invasive cancer (71.4%, 10/14). In this group, the combination of minimal BPE and a distinct lesion above BPE was enriched (78.6%, 11/14). Conclusion: Our results suggest that imaging features, such as BPE, lesion distinctness and change in BPE and lesion provide information about risk for invasive cancer. MRI features provide insight as to whether risk is diffuse or focal, and which women can safely undergo AS with hormone treatment and avoid surgery, and which women are at higher-risk and have focal lesions better treated with surgical excision. We plan to validate the use of these features to triage patients in an upcoming prospective multisite trial to stratify DCIS patients for active surveillance vs. surgical resection.

Citation Format: Cristian K. Maldonado Rodas, Heather Greenwood, Rita Freimanis, Alexander D. Borowsky, Gillian Hirst, Nola Hylton, Laura Esserman, Amrita Basu. MRI features can identify DCIS patients who can be managed with endocrine therapy alone [abstract]. In: Proceedings of the AACR Special Conference on Rethinking DCIS: An Opportunity for Prevention?; 2022 Sep 8-11; Philadelphia, PA. Philadelphia (PA): AACR; Can Prev Res 2022;15(12 Suppl_1): Abstract nr B015.

Identifying Good Candidates for Active Surveillance of Ductal Carcinoma In Situ: Insights from a Large Neoadjuvant Endocrine Therapy Cohort

Ductal carcinoma in situ (DCIS) is a biologically heterogenous entity with uncertain risk for invasive ductal carcinoma (IDC) development. Standard treatment is surgical resection often followed by radiation. New approaches are needed to reduce overtreatment. This was an observational study that enrolled patients with DCIS who chose not to pursue surgical resection from 2002 to 2019 at a single academic medical center. All patients underwent breast MRI exams at 3- to 6-month intervals. Patients with hormone receptor-positive disease received endocrine therapy. Surgical resection was strongly recommended if clinical or radiographic evidence of disease progression developed. A recursive partitioning (R-PART) algorithm incorporating breast MRI features and endocrine responsiveness was used retrospectively to stratify risk of IDC. A total of 71 patients were enrolled, 2 with bilateral DCIS (73 lesions). A total of 34 (46.6%) were premenopausal, 68 (93.2%) were hormone-receptor positive, and 60 (82.1%) were intermediate- or high-grade lesions. Mean follow-up time was 8.5 years. Over half (52.1%) remained on active surveillance without evidence of IDC with mean duration of 7.4 years. Twenty patients developed IDC, of which 6 were HER2 positive. DCIS and subsequent IDC had highly concordant tumor biology. Risk of IDC was characterized by MRI features after 6 months of endocrine therapy exposure; low-, intermediate-, and high-risk groups were identified with respective IDC rates of 8.7%, 20.0%, and 68.2%. Thus, active surveillance consisting of neoadjuvant endocrine therapy and serial breast MRI may be an effective tool to risk-stratify patients with DCIS and optimally select medical or surgical management.

Significance

A retrospective analysis of 71 patients with DCIS who did not undergo upfront surgery demonstrated that breast MRI features after short-term exposure to endocrine therapy identify those at high (68.2%), intermediate (20.0%), and low risk (8.7%) of IDC. With 7.4 years mean follow-up, 52.1% of patients remain on active surveillance. A period of active surveillance offers the opportunity to risk-stratify DCIS lesions and guide decisions for operative management.