(P 088) RETHINKING THE MANAGEMENT OF AGGRESSIVE ANGIOMYXOMA: A REPORT FROM FOUR CANADIAN SARCOMA CENTRES.

Objective: Aggressive Angiomyxoma (AA) is a rare, benign, but locally aggressive entity, typically affecting women of reproductive age and occurring in the pelvic, vulvovaginal and perineal regions. Literature on AA is sparse, consisting of case reports or small case series, with no consensus on optimal management. Treatment approaches have included surgical resection, radiation therapy, hormonal therapy and watchful waiting. We aimed to describe the diagnosis, treatment and outcomes of AA patients over the past two decades in a large Canadian case series, and to propose a modern management approach.

Methods: 30 consecutive cases of AA treated from 1999 to 2022 in four centres across Canada were identified from their respective sarcoma databases. Patient and tumour characteristics, diagnostic and management strategies were collected and outcomes (recurrence, progression, survival) assessed. Trends over time were descriptively characterized.

Results: Median age at diagnosis was 45y (range: 21-75y), and 29 of 30 patients were female. The most common presenting symptom was a subjective feeling of fullness (n=21; 70%), followed by pain (n=10, 30%). The perineum (n=10; 33%), pelvis (n=10; 30%) and vulvo-vaginal region (n=8; 27%) were common sites. Median tumour size at presentation was 10cm (range 1.3-25cm). Estrogen & progesterone receptor (ER/PR) status was available in half the cohort (n=15;50%), and positive in all 15. Surgical resection was used as 1st line treatment in 63% of patients (n=19/30), while 23% (n=7/30) received 1st line hormonal treatment. In patients who had the diagnosis confirmed by percutaneous biopsy prior to initiating treatment, hormonal therapy or surgery were used equivalently as 1st line treatment. Hormonal therapy was increasingly used as 1st line in the latter period of the study. The most common type of hormonal therapy used was aromatase inhibition. The majority (n=5/7; 71%) of patients who received hormonal therapy as 1st line had a symptomatic and radiologic response. One patient progressed while on 1st line hormonal therapy (progression-free interval 29mo) and underwent surgical resection. One patient experienced progression after stopping previously successful 1st line hormonal therapy. Of patients managed surgically as 1st line (n=19), 88% underwent a complete macroscopic resection with a recurrence rate of 16% and a serious complication rate of 16%. In the case of recurrent disease, hormonal therapy was the modality of choice with an overall response rate of 90%.

Conclusion: Management of AA is evolving and the paradigm of surgical resection as 1st line treatment should be challenged. Our series demonstrates that 1st line hormonal therapy can result in good symptom control and radiologic response, while avoiding the morbidity of surgery. Surgical intervention can be reserved for those who fail hormonal treatment. Pathological diagnosis with biopsy, and cross-sectional imaging are critical to treatment planning, permitting safe omission of upfront surgical resection. The use of hormonal treatment should be discussed with all patients, and should be considered an appropriate 1st line strategy, especially for those with minimal symptoms or in cases of borderline resectable tumours.