Early had no significant impact on patient survival, based on data from a randomized trial.
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Although early detection of small-cell lung cancer might improve outcomes for patients given the metastatic nature of the disease, previous studies on the value and impact of low-dose CT have been divergent, wrote Anish Thomas, MD, of the National Cancer Institute and his colleagues.
In a study published in Chest, the researchers reviewed characteristics of low-dose CT–detected small cell lung cancer (SCLC) in the randomized National Lung Screening Trial (NLST). The trial compared low-dose CT (LDCT) with chest radiography to assess patients at high risk for developing lung cancer. The study population included adults aged 55-74 years with a history of smoking of at least 30 pack-years, and former smokers who had quit within the past 15 years.
A total of 26,722 participants were randomized to the LDCT treatment arm with a median follow-up of 6.5 years; 143 SCLC cases and 926 non–small cell lung cancer (NSCLC) cases were identified in this group.
Of the 143 SCLC cases, 49 (34.2%) were screen detected, 15 (10.5%) were interval detected and 79 (55.2%) were not screened or were identified post screening.
A cancer was defined as screen detected if it was diagnosed within 1 year of a positive screening or diagnosed after a longer period but with no time gap between diagnostic procedures of more than 1 year; an interval cancer was diagnosed within a year of a negative screen, and non-screened cancers were those found in patients who received no NLST screening or other post screening.
Significantly more of the SCLC cases were at stage III or IV than the NSCLC cases (86% vs. 36%). Unfavorable stage III or IV lung cancers were identified in 80% of screen detected, 86% of interval detected, and 90% of nonscreened or postscreened cases.
In addition, 31 (63%) of the 49 screen-detected SCLC cases had at least one noncalcified nodule in the cancer lobe and 24 (49%) had a single NCN in the cancer lobe.
The 3-year cancer-specific survival rates were not significantly different for screen-detected, interval-detected, and nonscreened or postscreened cases (15.3%, 20.0%, and 13.8%, respectively).
“As expected, the majority of SCLC were late-stage cancers, but surprisingly the unfavorable stage distribution was present regardless of whether the cancer was screen-, interval- or post-screen detected,” the researchers noted.
The findings differed from the results of previous smaller studies showing more favorable stage distribution for SCLC cases detected by LDCT, but this difference may be accounted for by various factors including study populations that were smaller, younger, and lacking well-defined risk factors, the researchers said.
“Our findings underscore and provide further granularity to the premise that SCLC is a very aggressive neoplasm, and contrary to smaller prior studies, indicate that LDCT is an ineffective tool to screen for SCLC,” they said. “If early detection of SCLC were to be realistic, it would need to be detected before [lesions] are visible on LDCT,” they emphasized.
The study was supported in part by the National Cancer Institute. The researchers had no financial conflicts to disclose.
SOURCE: Thomas A et al. Chest. 2018 Aug 3. doi: 10.1016/j.chest.2018.07.029.