Colorectal Metastases to the Lung

Introduction

Colorectal carcinoma metastasizes to the lung in 10% to 15% of patients. The decision about whether to perform surgery for a patient with lung metastasis must take into account the patient’s ability to tolerate surgery, as well as the likelihood of achieving long-term survival. Most reports detailing the treatment of lung metastases are single-center retrospective reviews that have used overall survival as the endpoint. During the past 10 to 15 years, several multicenter reviews have been published, and a single prospective randomized trial has been initiated. This chapter will review the indications for resection of metastases to the lungs, prognostic factors derived from prior single and multi-institution reports, the issue of combined lung and liver metastases, the surgical approach, and the concepts behind the development of a prospective randomized trial.

Indications for Resection of Colorectal Metastases

Many factors are involved in the decision of whether to offer the option of surgical resection to a patient with metastatic disease to the lungs. A basic set of criteria has long been adopted by most surgeons:

• 1.

  The operative risk for the patient must be acceptable. Severe comorbidities such as recent congestive heart failure, unstable angina, and severe or critical aortic stenosis would preclude most patients from any procedures except for immediately lifesaving operations. In addition, pulmonary capacity and the ability to withstand lung resection must be taken into account. Patients should undergo full pulmonary function testing, including forced expiratory volume in the first second of expiration (FEV1) and diffusion capacities. Commonly held parameters for lung resection dictate that the postoperative FEV1 or diffusion capacity (when adjusted for hemoglobin and total alveolar ventilation) should not be less than 35% to 40% of predicted. Patients with numbers below these values have been shown to have an excess of perioperative complications and postoperative respiratory problems. A preoperative FEV1 is obtained, and the percentage of functioning segments that would be removed is estimated to obtain a number. These calculations are typically used in reference to anatomic resections such as lobectomies or segmental resections. Small, peripheral wedge resections usually do not have a significant effect on lung function and often can be performed even in persons with very poor baseline function.

• 2.

  A complete resection of all metastatic disease should be achievable. This goal has recently been modified with the development of stereotactic body radiation, which delivers fairly good long-term control for lesions smaller than 3 cm in diameter.

• 3.

  The primary malignancy should be removed, and the patient should have no evidence of recurrence.

• 4.

  Patients should have no evidence of disease elsewhere. Certain patients with combined hepatic and lung metastases who may have good long-term outcomes are an exception to this dictum.