OUTCOMES AND PROGNOSTIC FACTORS OF THE ADENOID CYSTIC CARCINOMA OF THE BREAST

Keywords:

Breast cancer - adenoid cystic carcinoma - special histological type

Background: Adenoid cystic carcinoma (ACC) of the breast accounts for approximately 0.1% of all breast tumors. Histologically, ACC typically consists of luminal and myoepithelial-basal cells population, which are generally triple-negative (TNBC). Although some series suggest that ACC has a favorable prognosis, the rarity of the disease imposes challenges for a clear comprehension of its behavior and proper treatment selection.Objective: To characterize the clinical features and outcomes of patients (pts) with ACC, and to identify prognostic factors associated with outcomes.Methods: Pts with a histological diagnosis of ACC of the breast treated in a tertiary cancer center had their medical records analyzed retrospectively from Jan 2009 to Jun 2022. Kaplan-Meier method was used for survival analyses, with prognostic factors evaluated using Cox regression.Results: We analyzed 21 female pts, with median age of 55 years (range 31 - 78). All were TNBC. Fourteen pts had the ACC subtype detailed; 8 were basaloid and 4 classic subtype. Most pts (n=18) had localized disease at diagnosis (7 were stage I, 9 stage II, and 2 stage III). All pts were submitted to surgery, 4 received neoadjuvant chemotherapy, 3 received adjuvant chemotherapy, and 12 received adjuvant radiotherapy (RT). With a median follow-up of 46 months, 5 pts had a recurrence (3 had distant recurrence only and 2 had both local and distant recurrence). The 5-year recurrence-free survival (RFS) was 51.8% (95% CI 22.4% - 75%). Adjuvant RT was the only factor associated with a reduction in the risk of recurrence or death (HR 0.05; 95%CI 0.01-0.54; P=0.013). (Neo)adjuvant chemotherapy or ACC subtype were not associated with RFS. Considering the 8 pts with metastatic disease (3 de novo and 5 recurrent), only 2 received chemotherapy, with a median progression-free survival of 1.8 and 2.8 months at first-line. The median overall survival (OS) from the time of metastasis diagnosis was 7.9 months. Nevertheless, two pts had OS greater than 90 months. Both of them had low volume metastatic disease treated with local therapy.Conclusions: In this cohort, ACC of the breast had a higher proportion of metastatic disease and poorer prognosis than previously reported in smaller series. Pts with localized disease seem to benefit from adjuvant radiotherapy, while those with low volume metastatic disease might benefit from local therapy for the oligometastases. The role of cytotoxic chemotherapy, otherwise, seems limited.

 

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No conflict of interest has been declared by the author(s).

Publication History

Article published online:
03 November 2022