Lung cancer screening

Why are we not screening for lung cancer?

So began an editorial in a recent edition of 'The Blue Journal'. In this particular edition, an Italian group was reporting on the DANTE trial, which investigated - in a randomised and controlled structure - the use of low dose CT scanning (LDCT) as a screening tool for lung cancer.

Now, although - as previously blogged - lung cancer is the leading cause of cancer death in our community, discussions about lung cancer screening don't rate a mention in the mainstream news. (Contrast this with prostate, breast, cervical and bowel cancer for example).

Efforts to determine whether our new, super-duper, multi-camera CT scanners can be utilised to screen for lung cancer have - to date - fallen over at the first hurdle. While they have demonstrated, repeatedly, that if you perform CT scans on lots of middle-aged smokers you identify lots of asymptomatic, early, curable tumours they have not yet proven that taking out these tumours saves lives.

The recent study has struggled at the same point.

What did they do? A total of 2,472 men aged 60 to 75 years, with at least a 20 pkt year smoking history (a packet a day for 20 years equivalent) were randomised to either a baseline LDCT scan and annual LDCT scans over 5 years, or else a baseline chest xray with annual clinical review. The current data cover follow up over a mean of 33 months (ie not a very long time yet).

What did they find? They found 60 patients (4.70%) with lung cancer in the LDCT group (63 cancers in total - some patients had more than one). Twenty-eight cancers were found in the initial scan ( ie over 2% of these people had cancers they didn't know about to begin with ), 25 were found on subsequent scans and ten were found because people developed symptoms between their annual scans. In the control group, they found 36 cancers in 34 patients; 8 at basline, 3 at routine review and the others because patients developed symptoms.

What did they do next? Lots of intervention! Thirty-nine of the 60 patients in the LDCT arm with cancer had resections, and of these 36 were complete resection. In the control group it was 18 of 34 resected, 17 completely. In the LDCT group there were 96 invasive procedures, vs 36 in the control group. As the investigators put it ''we performed three times as many invasive procedures and found twice as many lung cancer cases with LDCT than without it, ...(but) .. the absolute numbers of advanced and lethal lung cancer cases were unfortunately identical in the two arms.....moreover a significant proportion of major surgical procedures (13%) were performed for pulmonary lesions that ultimately turned out to be benign..."

What happened next after all that intervention? Mortality rates in the groups are identical to date. Put in plain English, the same number of people died in each arm of the study.

So, LDCT screening for lung cancer in asymptomatic patients with no history of cancer detects nearly twice as many cancers as a 'chest xray and annual specialist review' approach, leads to a raft of invasive and expensive interventions, and has not been proven to save any lives. Yet.

Andrew

High resolution CT scanning and IPF

With the recent arrival of a new CT scanner in Hamilton, I've been reading an article in this month's Respirology journal by a group from the University of Michigan. This review recaps evidence and their clinical practice when it comes to diagnosis of idiopathic pulmonary fibrosis.

An editorial in the same journal reiterates that there are, as yet, no proven treatments for this condition - although colleagues at the Royal Melbourne Hospital and The Alfred Hospital in Melbourne are currently participating in a trial of two novel endothelin receptor antagonists (like Bosentan, currently used to trat pulmonary hypertension) in IPF. (These trials are currently enrolling patients with IPF, with minimal honeycomb change and with a forced vital capacity on spirometry of over 50% predicted).

Idiopathic pulmonary fibrosis is a diagnosis now often made without lung biopsy. A multidisciplinary evaluation must exclude known causes of pulmonary fibrosis which can result in the same radiological appearance - such as pulmonary fibrosis associated with connective tissue disease (eg rheumatoid arthritis or scleroderma); chronic hypersensitivity pneumonitis; or asbestosis - and must include a high resolution CT scan of the chest. If the CT appearance is agreed to demonstrate features of usual interstitial pneumonia - which is the pathological/radiological appearance in idiopathic pulmonary fibrosis - in the absence of an underlying cause then IPF is diagnosed.

As simple as that! The major centres / city hospitals tell us, however, that there is a lot of operator variability outside of the major centres. Which means that it is important for people with this condition to be evaluated in an environment where people really know their stuff. Or perhaps, according to the major centres, all patients with IPF should be evaluated in the major centres.

The following table was offered as, in my opinion, a quite useful summary of the important radiological features of usual interstitial pneumonia:

Definite usual interstitial pneumonia

• subpleural basal distribution
• predominant honeycomb
• interlobular septal thickening
• traction bronchiectasis
• no predominant ground glass attenuation

Consistent with usual interstitial pneumonia

• subpleural, basal distribution
• minimal or equivocal honeycomb
• interlobular septal thickening
• traction bronchiectasis
• no predominant ground glass attenuation

Suggestive of alternate diagnosis

• No honeycomb, with one or more of the following as the predominant HRCT finding;
• upper or mid lung distribution
• peribronchovascular distribution
• ground glass attenuation
• micronodules
• discrete cysts
• air trapping
• consolidation

This seems to be the poster they hang on the wall of the registrars' reporting room at Ann Arbor. I'll have to run it past my local radiology colleagues and see what they think - but it looks pretty good to me.

Supports for patients with a diagnosis of pulmonary fibrosis are lacking in the Australian community. The Pulmonary Fibrosis Foundation in the USA runs a pretty informative website and supports good research. I am not aware of a comparable group in Australia.

Andrew