The Case for Lung Ablation
Interventional oncologists often report that they have difficulty making the case for continuing to perform lung ablation, but many clinicians are convinced that lung ablation should remain within the scope of practice. Alice Gillams, MB, CHB, reviewed literature supporting lung ablation in a presentation at the Symposium on Clinical Interventional Oncology (CIO) in Hollywood Florida.
Requirements for Optimal Ablation
Dr. Gillams explained that optimal ablation has certain requirements that interventional oncologists are able to meet in appropriate cases. These include accurate depiction of tumor size and extent, as well as the ability to precisely target therapy with the assistance of computed tomography (CT).
Morbidity in metastatic disease is very low, and studies have provided good knowledge of the efficacy of lung ablation. “It’s the one technique that’s going to preserve your lung function best of all---better than surgery, better than SBRT,” said Dr. Gillams. “You want to preserve the parenchyma so that at a later stage you have more treatment options,” she added, noting that patients with lung cancer often have repeated metastases. In the long term, patients benefit from having access to a variety of treatment options and from the potential to repeat lung ablation if needed. Lung ablation can also be readily combined with other treatment techniques.
Researchers have identified factors that influence successful ablation in pulmonary metastases. Treatment is most effective in smaller tumors up to 3 to 3.5 cm in diameter, with local control rates of 95% if the tumor is less than 2 cm in diameter.1,2 “This is competitive with resection without the morbidity,” said Dr. Gillams. “Ablation is best when you are not next to a blood vessel or a bronchus that can cool, and peripheral tumors are by definition easier to target and less likely to be close to a vessel.”
The safety profile of lung ablation has been investigated and is well understood, according to Dr. Gillams. Pneumothorax occurs in approximately 40% of patients, and a chest drain is needed in 10% of cases and will typically be removed within 18 hours, she noted.
Infection of the ablation zone is a possibility, particularly among patients in United Kingdom, as they frequently have chest infections throughout the winter months that can increase their risk of developing an infection in the ablation zone. An antibiotic should be started immediately if a patient has an exacerbation of chronic obstructive pulmonary disorder (COPD), said Dr. Gillams, but infection is uncommon in most patients. Nerve palsy is another complication of lung ablation, but it can be avoided by taking proper protective measures. Pleural effusion requiring drainage is also occasionally seen in lung ablation patients.3
Dr. Gillams and her colleagues have investigated risk factors for pneumothorax and considered whether cumulative needle trajectory across aerated lung, mean number of tumors, or number of electrode positions could predict pneumothorax. Of those factors, the only significant factor upon multivariate analysis was the amount of aerated lung that was traversed.4
Lung Ablation Versus Alternative Treatment Options
Resection of colorectal metastases is the main alternative to lung ablation and is widely practiced. Five-year survival rates are between 38% to 60%, and most surgeries are performed on patients with a solitary tumor or a maximum of 3 metastases. There is no maximum tumor size if R0 is achieved, but the 5-year survival with R1 is only 14%. “The same principle applies to ablation. You must get R0,” said Dr. Gillams. Bad prognostic indicators include positive hilar lymph nodes, high preoperative CEAs, and a short disease-free interval between the primary resection and the metastases.5
Other treatment options include chemotherapy to shrink tumors on imaging, though the tumors may return. “This is really a palliation,” said Dr. Gillams. SBRT is also an option, but there are central limitations, size limitations, and the potential to be invasive when fiducial marker insertion is needed. Additionally, centers may treat 1 or 2 tumors with SBRT but are unlikely to proceed with many metastases.
Dr. Gillams assessed survival in 122 patients who had 398 colorectal lung metastases. The initial number of tumors ablated was 2.3 with but became 3.3 with sequential development of metastases and repeat ablation. The tumors had a mean size of 1.7 cm, and 3-year overall survival was 57%.6 “There is improvement [in survival] if you could get below 2 cm,” said Dr. Gillams. Bilateral metastases have an impact on survival in surgical resection but did not make a difference in ablation. Based on her study and longer-term data from others, Dr. Gillams believes that lung ablation can achieve 5-year survival of over 50%, which is competitive with surgery.
A case involving a 29-year-old man with a T3N1 rectal cancer provided an example of the type of patient who benefits from ablation. The patient’s primary cancer was resected to R0 in January 2009, but he presented with bilateral lung metastases in January 2010 that were suitable for ablation. He subsequently underwent treatment with ablation and adjuvant chemotherapy.
However, in 2012 he presented with a solitary central tumor that was invading into the bronchus. There were no other sites of disease, and the patient was 3 years post resection of the primary. He was now a surgical candidate. “Because we hadn’t done all sorts of segmentectomies to remove his initial metastasis, he was a candidate for lumpectomy, which is what he needed for this very central tumor,” said Dr. Gillams.
The patient underwent left lower lumpectomy and adjuvant chemotherapy. “And then the metastases stopped coming, which is something you do see in metastatic disease. And now he’s 7 years, 8 months out and off treatment for 5 years,” said Dr. Gillams. She added, “Now, if he had gone to surgery in 2009, when he had a problem in 2012 he would not have gotten therapy he needed.”
Number of Metastases to Treat
Ablation is a good choice for small metastases and multiple metastases, explained Dr. Gillams. In her original study, there was no significant difference in survival for patients who initially had 3 or fewer metastases or 4 or more metastases.6
Patients often develop multiple, sequential metastases and, as a result, have had ablation procedures many times. Dr. Gillams has a group of 13 patients with colorectal cancer who had an original mean number of 9 metastases but now have a mean of 17 metastases. Of those 13 patients, 2 have been disease free for more than 18 months, and 11 have developed progressive disease. Nonetheless, the overall survival for the entire group was nearly 4 years, noted Dr. Gillams.
Overall, Dr. Gillams supports lung ablation for several reasons. The efficacy and safety of lung ablation are well understood, and the procedure is easily repeated, making it ideal for patients who are likely to have multiple synchronous metastatic events. Lung ablation is the only treatment that can completely eradicate multiple, small tumors over time. “I would suggest that it is better to keep the more invasive, lung-function reducing, expensive, surgical, and SBRT for lesions that cannot be readily ablated,” she said.
1. Gillams AR, Lees WR. Radiofrequency ablation of lung metastases: factors influencing success. Eur Radiol. 2008;18(4):672-677.
2. de Baère T, Palussière J, Aupérin A, et al. Midterm local efficacy and survival after radiofrequency ablation of lung tumors with minimum follow-up of 1 year: prospective evaluation. Radiology. 2006;240(2):587-596.
3. Steinke K, Sewell PE, Dupuy D, et al. Pulmonary radiofrequency ablation--an international study survey. Anticancer Res. 2004;24(1):339-343.
4. Gillams AR, Lees WR. Analysis of the factors associated with radiofrequency ablation-induced pneumothorax. Clin Radiol. 2007;62(7):639-644.
5. Pfannschmidt J, Dienemann H, Hoffmann H. Surgical resection of pulmonary metastases from colorectal cancer: a systematic review of published series. Ann Thorac Surg. 2007;84(1):324-338.
6. Gillams A, Khan Z, Osborn P, Lees W. Survival after radiofrequency ablation in 122 patients with inoperable colorectal lung metastases. Cardiovasc Intervent Radiol. 2013;36(3):724-730.