(P 14) PERCUTANEOUS CRYOABLATION OF PROGRESSING EXTRA-ABDOMINAL DESMOID TUMOURS

Objective: To evaluate the feasibility and efficacy of percutaneous cryoablation of extra-abdominal desmoid tumours progressing after first-line treatments.

Methods: We retrospectively evaluated baseline and post-treatment MRI and/or CT imaging of all consecutive patients with histologically confirmed progressing extra-abdominal desmoid tumours treated with percutaneous cryoablation at our Institution between May 2021 and November 2022.
Treatment response was assessed both with standard and modified RECIST 1.1 criteria.
Modified RECIST 1.1 criteria evaluate viable tumour alone, defined as such by the uptake of contrast agent in the arterial phase of dynamic imaging at either CT or MRI, with the underlying premise that dimensional reduction alone does not adequately capture tissue viability and may therefore incompletely depict responses to local treatments.
The variables of our analysis were disease progression, treatment safety and alleviation of pain and disability.

Results: The study cohort comprised 19 patients (17 females and 2 males), with a median age of 36 years (range 13-59 years), in radiological and/or clinical progression after first-line treatments (14 patients were enrolled in active surveillance, 3 patients received chemotherapy and 2 patients had undergone surgery).
Ten patients were not eligible for the procedure because of the close proximity of the lesion to the skin surface and/or neurovascular bundles.
One patient was excluded from the analysis because developed local infection at the site of insertion of the cryoprobe and the presence of inflammatory alterations hampered the evaluation of treatment response.
Tumour locations included the head & neck (3), the trunk (3), the abdominal wall (11) and the lower extremities/girdle (2), with an average maximum diameter of 80,2 mm (range 40-125 mm).
Five out of nineteen patients didn’t have adequate contrast-enhanced pre-treatment imaging and couldn’t therefore be evaluated with modified RECIST 1.1 criteria.
No RECIST progressions were detected at a median follow-up time of 149 days (range 29-254 days).
According to standard RECIST 1.1 criteria, 16/19 (84,2%) patients showed stable disease (SD) and 3/19 (15,8%) patients displayed a partial response (PR). According to modified RECIST 1.1 criteria, 9/14 (64,3%) patients presented with SD, 4/14 (28,6%) patients with PR and 1/14 (7,1%) patient with a complete response (CR), with 2 SD patients being reallocated to PR and CR categories, respectively.
Of note, 84% of patients reported significant improvement of symptoms.

Conclusion: Our preliminary results further support the emerging role of percutaneous cryoablation for the treatment of progressing extra-abdominal desmoid tumours and highlight that modified RECIST 1.1 criteria outperform standard RECIST1.1 in this clinical scenario.