For operable disease in young women, the primary treatment of breast cancer is normally breast-conserving surgery or mastectomy, in association with axillary surgery and radiation therapy. Numerous prospective and retrospective trials have demonstrated that breast conservation therapy, consisting of segmental mastectomy with or without axillary lymph node dissection, is equivalent to mastectomy in terms of overall survival and disease-free survival for patients with early stage breast carcinoma.
Radiotherapy (50Gy) prevents local recurrence of breast cancer after breast-conserving surgery. In patients who receive an additional dose of 16Gy of radiation to the tumour bed, the risk of local recurrence is further reduced, especially in patients younger than 50 years of age. The incidence of tumoral recurrence after lumpectomy without radiation seems to be directly correlated to the size of the tumour, but also decreases with advancing age.
In elderly women (>70 years old) the disease is at stage I-II in 92% of cases. Comorbid conditions that may influence treatment planning are reported in up to 50% of the patients. Rates of locoregional recurrence decline with age, indicating that the benefit of radiation therapy would be more limited. The locoregional recurrence at 4-years median follow-up is 5%, and occurs almost exclusively at the original tumoral bed.
The rate of distant metastases is 11% (mainly in the lung), and the 5-year and 10-year disease specific survival rates are 96% and 91%.
Because of the increasing use of screening mammography, most women with breast cancer now present with small tumours that can be removed with surgical or percutaneous minimally invasive procedures (1), which preserve the breast and the woman's body image, as well as allowing rapid recovery.
As the sentinel lymph node mapping procedure, rather than routine axillary node dissection, becomes the standard of care, the challenge for interventional radiologists is to treat the primary tumour without surgery, with a minimally invasive percutaneous treatment.
Alternatives to traditional surgery and radioguided surgery that are currently being explored include different approaches; their goal is either to excise the primary tumour percutaneously (Mammotome, MIBB, ABBI, site select system), cool it (cryotherapy), heat it with focused ultrasound, laser interstitial therapy or RFA, or focally deliver radiation therapy via the Mammotome.
Böhm et al. (2) explored the in vitro feasibility of saline-enhanced RFA for the treatment of breast tumours. Interstitial perfusion is important to improve the electrical conditions for ablation by the spread of hot liquid. The irregular expansion of RF lesions may be due to the inhomogeneous tissue impedance resulting in electrical inhomogeneities and irregular heating; the presence of multiple ductal structures, which may result in possible propagation of the hot emulsion into the surrounding tissue; or a high infusion rate of interstitial saline solution. The authors concluded that percutaneous thermolysis is feasible with a better control of lesioning with a low saline interstitial infusion rate. Optimal NaCl concentration (38.5% saturated solution) of the interstitial saline solution may increase energy deposition, tissue heating and induced coagulation.
We think that the problems of irregularity in thermolysis/RFA tend to reduced in fatty breast tissue ("oven effect" and rare ductal structures) and in the early-stage neoplastic nodules (size <30mm) without microcalcifications found in older women.
Invasive lobular carcinoma may not be treated under US monitoring because of discrepancies between imaging and histogical spread.
The first study of feasibility of RFA in human breast tumours was reported in 1999 by Jeffrey et al., who treated five women with locally advanced breast cancer (4-7cm). In four patients, complete ablation was found in an area of 8-18mm diameter; the tumour in the fifth patient had a small area of viable cells lining a cyst. The authors concluded that PRA may be most effective for the treatment of cancers smaller than 30mm (3).
Izzo et al. reported a 96% complete necrosis rate in tumours less than 30mm, under US control of T1 and T2 breast carcinomas (4). One patient had a microscopic focus of viable tumour adjacent to the needle shaft site. The only complication was a full thickness burn in one patient whose tumour was immediately beneath the skin.
Tumour recurrence may be detected by clinical examination and multimodal imaging (US, Mammogram, core biopsy and MRI). Particular attention should be paid to the original tumour bed, and along the needle tract (as described in patients with RFA-treated hepatocellular carcinomas).
An increase in the size of the lesion on mammogram/US/MRI or nodular enhancing areas on MRI may suggest tumour recurrence at follow-up (5). Percutaneous biopsy may give histological proof.
MRI is very sensitive to tissue-water mobility and distribution; and the temperature dependence of MR relaxation parameters such as T1 relaxation times and diffusion coefficients make it particularly suitable for the demonstration of thermal energy deposition in breast tissue. Potentially, the use of real-time MR imaging to monitor RFA in breast carcinomas, and the availability of open-access breast coils may facilitate complete tumour ablation with MR-compatible needles, in the future. Moreover, MRI may depict any further recurrence as well as US/Mammogram/clinical examination (5).
KEY POINTS
1. Definitive RFA should never be undertaken without histological confirmation of malignancy.
2. The objective of RFA ablation is clearance of the local disease with a margin of clear tissue, and to achieve an acceptable cosmetic outcome, in elderly patients with early stage breast cancer T1-2N0M0.
3. For successful RFA treatment, the breast carcinoma needs to be of the invasive ductal type, a centrally located solid mass without any microcalcifications, less than 30mm in diameter, and distant to the skin and the pectoralis muscle.
4. RFA may be an alternative treatment option to lumpectomy in elderly patients with comorbid conditions, who fear surgery. The procedure is cheaper and much less invasive than surgery (no scar).
5. Typically, percutaneous RFA-lumpectomy under US/MRI guidance is given as an outpatient procedure, with the patient lightly sedated. That point is of utmost importance for elderly women, handicapped by mobility and/or transportation problems, who fear surgery.
