diagnosis, with about half occurring within 6 months of the first diagnosis. More than 80% of second primary cancers diagnosed within 2 years were stage 1, compared with about 25% when diagnosed more than 5 years later.
“With the growing adoption of lung cancer screening, more patients are being diagnosed with early-stage lung cancers and are able to achieve excellent long-term survival. After lung cancer diagnosis, these patients remain at high risk of developing a second primary lung cancer. The incidence, timing, and survival of second primary lung cancers is not well understood, particularly in a patient population with initial primary lung cancers detected via lung cancer screening,” said Alexandra Potter, who is a study coauthor.
The results were presented by Chi-Fu Jeffrey Yang, MD, at a press conference held at the World Conference on Lung Cancer sponsored by the International Association for the Study of Lung Cancer. Dr. Yang is a thoracic surgeon at Massachusetts General Hospital, Boston.
A 2012 study analyzed data from the SEER database and found that lung cancer survivors had a four- to sixfold increase in the risk of developing a second primary lung cancer, compared with the risk of lung cancer in the general population after adjusting for sex, age, race, and calendar year. “That study demonstrated that second primary lung cancers are an important risk among lung cancer survivors. However, it did not evaluate patients diagnosed with initial lung cancers detected via lung cancer screening. Thus, the incidence, timing, characteristics, and survival of lung cancers diagnosed among patients diagnosed with initial lung cancers detected via lung cancer screening remain unknown,” said Ms. Potter, who is a research assistant at Massachusetts General Hospital and president of the American Lung Cancer Screening Initiative.
To address that question, the researchers used data from the National Lung Screening Trial, which compared low-dose computed tomography to chest x-ray and found that the former led to a 15%-20% lower risk of death. The new analysis included 1,405 patients who were diagnosed with stage I-III lung cancer and treated between 2002 and 2009. Of these patients, 5.8% went on to be diagnosed with a second primary lung cancer, at a rate of 1%-2% per year. Of the second lung cancers, 54.9% were synchronous, occurring within 6 months of the diagnosis, and 45.1% were metachronous, occurring later than 6 months; 65% of synchronous secondary cancers and 81% of metachronous cancers were diagnosed at stage I; 24% of synchronous and 14% of metachronous were stage III (P = .25). The median time to diagnosis of metachronous lung cancers was 2.7 years, and 27% of the second primary tumors were diagnosed 4 or more years after the first diagnosis.
Among those with synchronous tumors, 5- and 10-year survival rates were 55.2% and 39.5%. The rates were 90.0% and 30.8% among metachronous tumors, respectively. Ms. Potter emphasized that most patients with second primary cancer were diagnosed at stage I, suggesting that it is very possible to catch these cancers early. But patients who were diagnosed with a second primary tumor 4 or more years after their first diagnosis had a greater likelihood of later-stage second cancer. Medical societies generally recommend CT screening surveillance every 6 months for 2 years following a lung cancer diagnosis, then annually thereafter. The greater frequency of later-stage cancer detected after 4 years suggests that surveillance may be flagging as time goes on. “These data highlight the importance of lifelong follow up after initial lung cancer diagnosis,” said Ms. Potter.
She also emphasized the importance of smoking cessation and ongoing abstinence following a diagnosis of lung cancer. “About 70% of patients in the NLST who developed second primary lung cancer currently smoked at the time of entry into the trial. Smoking cessation can help reduce patients’ risk of developing second primary lung cancers,” she said. Ms. Potter has no relevant financial disclosures.