Pulmonary metastasectomy is a medical term used to indicate surgical resection or removal of a metastatic lung lesion. This terminology reflects the presence of an underlying non-lung primary cancer. This terminology can sometimes be confusing for patients; particularly as the surgical procedure itself is unchanged (from lung procedures for other lung lesions.)
In lay person’s terms; this is also sometimes called “cherry-picking”.
The Procedure: Lung Resection
Usually, patients undergo the standard VATs or open wedge resection used for other primary lung lesions, to remove the cancerous tissue. The amount and type of surgery depends on the location and size of the lung lesion, so in some cases patients have bigger procedures such as lobectomies or pneumonectomies for this condition.
The reason for delineating a difference in terminology is related to long-term outcomes and adjuvant treatment strategies. This means that the accompanying treatments such as chemotherapy or radiation are different for different underlying diseases (ie. primary lung tumor versus metastatic disease from different area.)
Patient A has a wedge resection for a primary lung tumor, which turns out to be a bronchiogenic adenocarcinoma during intra-operative pathologic reporting (the lesion is sent to the pathologist during surgery & we wait for his report before completing the rest of the surgery.) The best treatment for this is a lobectomy, which is completed while the patient is still in the operating room.
Patient X has a history of colon cancer which was previously treated with surgical resection of the colon, and chemotherapy. X has been doing well but a recent CT scan shows a lesion in the right lower lobe of his lung, with no other lesions seen. Since Mr. X has a history of colon cancer – this lesion may be a metastatic colon lesion – and the adjuvant treatment, as well as the post-operative prognosis is very different.
How do we know who would benefit from pulmonary metastasectomy? (A brief look at the published literature)
1. The International Registry of Lung Metastases (IRLM): (the link is to a nice article explaining more about the history of registry and initial results). The registry was first started in 1990, and as the name suggests, this is an international registry that was created to track the outcomes of patients with lung metastases. By tracking this data, we are able to better understand which treatment therapies are useful/ life-saving and which treatments aren’t, according to patient disease characteristics (i.e patient with breast cancer and a lung lesion may fare differently than a patient X from our example above.)
The initial data from the registry actually came from fifty years of chart reviews, starting from 1945 to 1995. This study, by Pastorino, is considered the Hallmark for pulmonary metastases. All other studies build on this body of work, to either confirm, refute or expand on their findings.
Other researchers have looked at this as well: (this is just a small sample of recent research findings)
2. Zabaleta et. al (April 2011) published an article in Cirugia Espanola, “Review and update of prognostic factors in lung metastasis surgery” which nicely explains their findings. Zabaleta and his team compiled data on ten years worth of patients (146 total) and determined that the most important factors for predicting outcomes were: age of patient, disease free interval (after initial disease treated), the number of lung nodules and the size of these nodules. This study confirms the original findings.
Unsurprisingly, the patients that did the best (lived the longest and least or re-operations for more lesions) were the patients aged 41 – 79 who had long periods before the lesion appeared, with a solitary nodule less than one centimeter in size. Clear surgical margins were not determined to be statistically significant (due to low-frequency of positive margins in study population) but all of the patients with positive surgical margins failed to survive the study period (only nine cases with + margins).
Patient Population: The majority of the patients in this study (54.8%) had colo-rectal primaries, but there was a sizable sarcoma primary population
(12.3%) as well as several other primary types which adds to the generalizability of the study.
Patient outcomes: 38 patients (26%) developed recurrent lung lesions after lung surgery – with a mean time to recurrence of 18 months (range of 3 to 60 months). I would have liked to have known which primaries were responsible in the recurrence group, since certain cancers are more aggressive than others. Overall mean survival was 67 months, with a five-year survival rate of 52.4% While the authors mention the poor prognosis of sarcoma, it would have been nice if they could have broken down the survival statistics better by primary cancer type – as the authors attribute survivability by cancer factors rather than type (i.e. sarcoma usually has multiple mets).
3. A Japanese study published this winter in the Annals of Thoracic Surgery looking at colorectal patients with metastatic liver metastasis who underwent pulmonary metastasectomy (lung resection). Study population was small (19 patients) despite a long study period (1992 – 2006) but findings were interesting with a five-year survival rate of 60%.
4. This is a nice retrospective case review by Sardenberg, et. al (2010) in San Paulo, Brazil looking at pulmonary metastases and surgical lung resection in patients with soft tissue sarcomas.
Patient population: 77 patients who had 122 surgeries involving 273 nodules – this gives you a bit more of an idea how sarcoma can differ from other cancers (more lung mets – multiple nodules). Study period was a chart review of patients referred to thoracic surgery from 1990 to 2006.
Findings: number of metastatic lesions less important than resectability, meaning “Were they able to get it all?” This; [complete resectability] was the greatest predictor of survival – and 34.7 % of patients in this study survived 90 months (then investigators stopped looking). Mean survival was 36 months.
This is just a fraction of the literature out there, but all of these studies were well-written, and freely available without subscriptions. There are a couple of interesting studies that are awaiting journal publication – so I will try to update this article once they are published.
 The term cherry picking referred to the patients that are selected to undergo surgery for their metastatic lesions. Usually the patient has only one or two metastatic lesions – which can essentially be surgically removed or ‘plucked out’. This procedure is less feasible / successful in patients with multiple, bilateral lesions.