Peter Littrup, director of imaging research and image-guided therapy at the Karmanos Cancer Institute (Detroit, MI), described the use of multiprobe cryotherapy to treat breast cancer. "Minimally invasive cryotherapy opens the door for a potential new treatment for breast cancer and needs to be further tested," he said. "This is the first reported study of successfully freezing breast cancer without having to undergo surgery afterward to prove that it was completely treated."
In a study of 13 patients who had refused invasive surgery, researchers from Karmanos Cancer Institute and Wayne State University (Detroit, MI) treated 25 breast-cancer foci in 13 cryotherapy sessions. Multiple 2.4 mm cryoprobes inserted through a small hole in the skin delivered extremely cold gas directly to the tumour. Breast MRI was employed for treatment planning, as well as for post-treatment monitoring of the ablation zones.
Littrup noted that one difference between this study and prior uses of breast cryotherapy was the confirmation of sufficient deadly temperatures when using multiple cryoprobes spaced evenly throughout the breast-cancer region. The cold gas creates an ice ball around the probe tip, which expands and destroys tumour cells in its path. One of the benefits of cryotherapy is the ability to visualize this ice zone during the procedure.
For six patients with smaller tumours, ultrasound guidance alone was used to visualize the ice margins. Seven patients (with larger regions needing more than three probes or deep lesions) required both CT and ultrasound to better define the overall ice extent. The pre-treatment breast-tumour diameter was 1.7 cm (range 0.5–5.8 cm) and an average of 3.3 cryoprobes produced ice-ball diameters of 5.2 cm (range 2–10 cm).
Littrup explained that surgeons and radiation oncologists try to provide a treatment margin of at least 1 cm around a localized breast cancer, and that it was important to ensure a similar margin of lethal temperatures during cryotherapy. "We made sure that the lethal isotherm of approximately –30 °C extended beyond all tumour margins," he said.
Another advantage of cryotherapy is its low pain profile, with the treatment only requiring local anaesthesia with mild sedation. Saline injections protected the skin and chest wall. No significant complications were noted, with all patients reporting minimal discomfort and satisfaction with cosmetic results. Biopsies at the margins of the cryotherapy site immediately after the procedure were all negative. No local recurrences were noted at an average follow up of 18 months.
"With recent developments of powerful new cryotechnology, multiple directions for breast cryotherapy can be pursued, including translating the current, somewhat challenging, procedure done with ultrasound and/or CT guidance to a more consistent and reproducible MR-guided approach," said Littrup.
Soft-tissue treatment
In a separate presentation at the SIR meeting, Littrup reported on initial experience using cryotherapy to treat cancer that has metastasized to soft tissues and bones. Patients with such multifocal metastatic disease are often not candidates for surgery.
In this study, 157 CT and/or ultrasound-guided percutaneous cryotherapy procedures were performed in 97 patients (30 retroperitoneal locations, 51 intraperitoneal, 47 superficial, 29 bone). Adjacent tissue was protected from cytotoxic temperatures using thermocouple monitoring, saline injection and/or direct skin warming.
The cryotherapy zone was well defined by CT as a hypodense ice ball with an average ablation diameter of 5.4 cm; the average tumour diameter was 3.5 cm. Major complications occurred in 4% of patients. After an average follow up (via CT or MRI) of 14 months, 23 recurrences (15%) were seen. By 24 months, there was an average of 77% tumour shrinkage.
"Percutaneous soft-tissue cryotherapy is a well tolerated treatment option, especially for patients with anaesthesia risks, painful lesions or those seeking local control during chemotherapy," said Littrup. "Tumour size and/or location do not preclude thorough treatment or pose greater risk with appropriate precautions."