Local administration of retinoids might be an effective method of treating preinvasive lesions (ie, cancer that is still circumscribed within the tissue where it first appeared) in the lung, according to Dr James Mulshine (National Cancer Institute, Bethesda, US).
In a presentation on October 13 at the annual meeting of the European Respiratory Society in Madrid, he said that vitamin A derivatives were known to be effective against lung cancer. However, the side effects of oral retinoids had been too severe to allow conclusive tests to be undertaken in vivo.
Dr Mulshine proposed that local administration would have the advantages of allowing 100 times more active substance to be delivered to diseased tissue, as well as a 10-fold reduction in the quantity of drug getting into the bloodstream (and, thereby, causing side effects).
He hoped to test a retinoid aerosol in patients with preinvasive lung cancer before the end of the year. However, the method that he intended to use depended on detection of the preinvasive lesions before they became invasive. This would require use of spiral computerised tomography, which could achieve fine resolution (two to three millimetres). Ordinary x-rays only detected anomalies after they had become invasive. Dr Evelyne Picard (University Hospital Centre, Nancy, France) explained that retinoids were thought to work by controlling the multiplication and differentiation of epithelial bronchial cells and, therefore, they could prevent precancerous cells from becoming malignant. The efficacy of retinoids appeared to depend on various cell receptors, some of which were normally present in precancerous lesions but were downregulated in tumours.
Dr Picard speculated that administering retinoids as a spray might even prevent the recurrence of lung cancer after removal of a first tumour.