Quarter of incident lung cancer slow growing or indolent

Jan 17 2013

By Liam Davenport, medwireNews Reporter

A quarter of incident lung cancers are slow growing or indolent, and may be overdiagnosed, suggest results from sequential low-dose computed tomography (CT) screening.

"Having identified potentially overdiagnosed lung cancer as slow-growing or indolent lesions, the problem of managing them remains," write Giulia Veronesi (European Institute of Oncology, Milan, Italy) and co-authors in the Annals of Internal Medicine.

They explain that while some researchers recommend the "wait-and-see" approach, indolent tumors can quickly increase in size between scans and become life-threatening. On the other hand, the team says, standard resection may be overtreatment for some lesions which are mostly minimally invasive adenocarcinomas, and a less aggressive approach may be appropriate.

The researchers used annual CT to monitor 4122 asymptomatic individuals aged 50 years or older who were current or former heavy smokers for 5 years. Volume doubling time (VDT) was classified as fast growing, at less than 400 days; slow-growing at 400-599 days; or indolent at 600 days or more.

In all, 175 cases of primary lung cancer were diagnosed, of which 66% were stage I and 89% were radically resected. A total of 55 cases were prevalent and 120 were incident during subsequent screening rounds. The median follow up was 5.8 years for prevalent cancer, 3.2 years for incident cancer, 3.6 years for fast-growing cancer, and 3.7 years for slow-growing or indolent cancer.

Of the incident cases, 19 were new from previous scans and fast-growing, with a median VDT of 52 days, while 101 were progressive and included 70 fast-growing and 31 slow-growing or indolent cases, at VDTs of 223 days and 545 days, respectively. Stage I cancer was identified in 62% of baseline cancer cases, 45% of new cancer cases, 66% of fast-growing progressive cancer, and 84% of slow-growing or indolent cancers.

Patients with new cancer had significantly higher lung cancer-specific mortality than those with slow-growing or indolent cancer, at 9.2% versus 0.9%. There was a nonsignificant increase in lung cancer-specific mortality associated with fast-growing cancer compared with slow-growing or indolent cancer, at 4.1% versus 0.9%.

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