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Women with early-stage breast cancer who couldn't enter clinical trials of cryoablation because of "unfavorable" tumor or patient characteristics nevertheless enjoyed a high rate of treatment success and few adverse events (AE) after undergoing the procedure anyway, a multicenter study showed.

Cryoablation procedures were considered technically successful in 98.2% of cases, which were associated with an AE rate of 6.3%, all considered minor. During a median follow-up of 2 years, 10.9% of patients had ipsilateral breast tumor recurrence (IBTR), which proved to be new primary disease in almost half of recurrences.

The outcomes compared favorably with those of prior studies of cryoablation in patients with favorable characteristics, reported Karim Oueidat, MD, of Brown University's Warren Alpert School of Medicine in Providence, Rhode Island, and co-authors in the .

"This multi-institutional center represents, to our knowledge, the largest study of breast cancer cryoablation in women who are ineligible for clinical trials due to the presence of at least one unfavorable patient or tumor characteristic in terms of the likelihood of ablation success," the authors stated. "Of these patients, 54.3% had at least one comorbidity."

"In select individuals with unfavorable patient or tumor characteristics, cryoablation remains a safe alternative to surgery that has overall good outcomes," they added. "These findings may be particularly relevant in patients who are also poor surgical candidates due to comorbidities."

Cryoablation for early breast cancer has attracted considerable attention in recent years, not only as an option for patients considered unsuitable for surgery, but as a and a means of treatment de-escalation. Potential advantages over surgery include use of local anesthesia, faster recovery, better cosmesis, and cost savings.

Cryoablation does not yet have an for breast cancer. The only approved indication is for treatment of fibroadenomatous lesions. The American Society of Breast Surgeons has a for use of ablative techniques to treat benign or malignant breast lesions.

Oueidat and colleagues noted that prospective clinical trials of cryoablation for early breast cancer have had strict inclusion criteria associated with favorable outcomes with cryoablation. Patients with clinical or tumor characteristics considered unfavorable have generally been excluded. The trials have shown that cryoablation "is a safe and efficacious alternative to surgery for breast cancer treatment in this restricted patient population."

A paucity of data exist for cryoablation outcomes in trial-ineligible patients, the authors continued. Many such patients might have potentially treatable disease despite less-than-optimal candidacy. The lack of data provided the impetus for a multicenter retrospective review of patients who didn't meet inclusion criteria for clinical trials of cryoablation for early breast cancer.

Investigators at seven U.S. centers contributed data for 112 patients with median age of 71, and 60 (53.6%) had one or more comorbidities. All patients had pretreatment assessment by mammography and ultrasound, and some had contrast-enhanced breast MRI. All patients had follow-up imaging by mammography, ultrasound, and MRI, and some centers also used CT or FDG PET/CT for follow-up.

Common reasons for trial ineligibility included target lesions that were too large or too close to the skin, histology other than invasive ductal carcinoma, hormone receptor status other than that specified in the protocols, and unwillingness or inability to tolerate adjuvant therapy.

The primary outcomes were technical success of cryoablation, IBTR, and AEs. Success was defined as a procedure that was "not prematurely terminated and achieved intended treatment parameters, and the first imaging follow-up showed no evidence of residual disease."

Baseline characteristics included a median largest tumor dimension of 1 cm by ultrasound, and median distance from the nipple, skin, and pectoralis of 5.0, 0.7, and 0.6 cm, respectively. Five patients had N1 disease and/or distant metastases. Invasive ductal carcinoma accounted for 78.6% of all primary lesions. Tumors were grade 1 in 54.5% of patients, grade 2 in 35.7%, and grade 3 in 9.8%. Almost 80% of the patients had hormone receptor-positive/HER2-negative cancer, and 8.9% had triple-negative disease.

Seven patients had AEs, none of which were considered moderate or major. All but two procedures met criteria for treatment success. During follow-up, 22 (20%) patients had biopsies for suspicious findings on imaging in the ipsilateral breast. Pathology results showed benign findings in nine patients and IBTR in 12, resulting in an IBTR rate of 10.9% in the 110 patients with technical success.

After accounting for death as a competing risk, the cohort had a cumulative incidence of IBTR of 5.3%, 12.2%, and 18.2% at 1, 2, and 3 years.

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