Key Point

Lung removal surgery is less likely to be needed for lung cancers that are found incidentally versus those found symptomatically.

SAN FRANCISCO—It is not surprising that in the absence of an endorsed screening policy, many lung cancer cases are identified incidentally. In a study by Dan J. Raz, MD, and colleagues, incidentally detected cancers tended to be caught earlier than those investigated as a response to lung cancer symptoms and were less likely to require pneumonectomy.¹

A 2004 study involving 1,168 lung cancers diagnosed during a 28-year period found that nearly 15% of all lung cancers and 50% of stage I lung cancers were detected incidentally.² “Although we do not have any good measurement of whether there is a sizable increase in incidentally detected cancers nationally or regionally, we have seen an increased number of cases incidentally on CT at our institution over the past five years,” Dr. Raz, Surgery Resident at the University of California, San Francisco, told Pulmonary Reviews. “We attribute this rise to increased use of CT for reasons such as assessment of abdominal pain, suspicion of pulmonary embolism, and evaluation of coronary artery disease.”

In the study by Dr. Raz and associates, 274 patients who underwent surgical resection of lung cancer with negative histologic margins and mediastinal nodal sampling were included in the analysis. Of these, 100 patients (36%) had incidentally detected lung cancer—defined as lung cancer found at the time of imaging among patients who previously had no symptoms attributable to lung cancer or who had transient symptoms thought to be unrelated to lung cancer. About 30% of all lung cancers were detected incidentally by chest x-ray, 6% via CT, and 1% via PET; of incidentally detected cancers, 82% were found on chest x-ray, 17% on CT, and 2% on PET. The most common primary symptoms were cough, pneumonia, hemoptysis, dyspnea, chest wall pain, shoulder or back pain, and weight loss.

In a quarter of cases, annual physician-ordered chest x-rays led to lung cancer detection; in other cases, a long smoking history or a family history of lung cancer prompted patients to request chest x-rays. Patients with incidentally detected lung cancer had smaller cancers than patients with symptomatic lung cancer (2.5 vs 3.5 cm, respectively), were younger (mean age, 66 vs 70), were more likely to have bronchioloalveolar carcinoma (BAC; 15% vs 5%), and were more likely to have earlier-stage disease.

Among patients with incidentally detected cancer, 47% had pure BAC or adenocarcinoma with BAC features. “It is possible that some of these tumors were so indolent that they may have never gone on to cause symptoms or harm to the patient,” Dr. Raz noted. After adjustment for stage, long-term survival was similar for patients with completely resected incidentally detected lung cancer and patients with symptomatic lung cancer. “There may be lower stage-adjusted mortality among patients with lung cancers detected incidentally on CT,” although wide confidence intervals cast doubt on this finding, the investigators noted.

Pneumonectomy was significantly more prevalent among patients with symptomatic cancer than among patients with incidentally detected cancer (13% vs 3%, respectively), possibly because the latter group had smaller tumors and fewer centrally located cancers. “This observation suggests that early detection of lung cancer may reduce the frequency of pneumonectomy, which carries greater perioperative morbidity and mortality than lobectomy and may not be tolerated by patients with compromised pulmonary function,” the researchers speculated.

 “Given that lung cancer kills many more Americans than any other cancer, screening for lung cancer with CT may have a large public health impact,” Dr. Raz noted. “Recently reported results from screening studies, such as the International Early Lung Cancer Action Program,³ have been very encouraging, but we do not have conclusive data yet to support the use of lung cancer screening,” he acknowledged. “While one patient may be helped by the detection of a lung cancer at a very early stage, another may be harmed by complications of biopsy of a benign lung nodule.”            

—Adriene Marshall

Reference
1. Raz DJ, Glidden DV, Odisho AY, Jablons DM. Clinical characteristics and survival of patients with surgically resected, incidentally detected lung cancer. J Thorac Oncol. 2007;2:125-130.
2. Kanashiki M, Satoh H, Ishikawa H, et al. Outcome of patients with lung cancer detected incidentally. Oncol Rep. 2004;12:945-948.
3. International Early Lung Cancer Action Program Investigators. Survival of patients with stage I lung cancer detected on CT screening. N Engl J Med. 2006;355:1763-1771.

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