A total of 1371 scans were performed on 449 subjects in the 2 year period. Twenty two subjects (4.9%) withdrew from the study during the 2 years and a further 14 (3.1%) did not complete because of intercurrent illness or death; 413 subjects (92%) completed the 2 year repeat screening. The results are presented in table 1.
Table 1Rates of non‐calcified nodules and lung cancer detected during the 2 year study period
Non‐calcified nodules were identified in 93 subjects on the prevalence scan. A further 12 subjects were found to have nodules on repeat scanning which, in retrospect, were visible on the prevalence scan. Nodules measuring less than 10 mm on prevalence scanning were followed without change for 24 months in 97 of these 105 subjects; four did not complete the study, two were resected at the initial presentation (one NSCLC stage 1 and one hamartoma), and two demonstrated nodule growth.
Both cases of nodule growth were observed on the second interval scan. FNAB revealed no malignant cells in either subject. A spiculated appearance on the CT scan was suspicious for malignancy in one nodule with interval growth from 8 mm to 12 mm, and lobectomy was performed revealing adenocarcinoma stage 1. The other case with interval growth from 4 mm to 10 mm had a negative positron emission tomographic (PET) scan and no further interval growth on the follow up LDCCT scan so was deemed benign.
Six subjects were found to have new nodules during the 2 year follow up period, of which one proceeded to lobectomy revealing a neuroendocrine tumour. The other five subjects continue to be followed according to the study protocol and none has shown interval growth to date.
Three subjects had lung cancer detected in the mediastinum or hilum. One was identified on the prevalence scan and another had a small cell carcinoma and liver metastases at annual incidence screening. The third presented with paraneoplastic cerebellar syndrome 5 months after a normal prevalence scan and had a large central lung mass with lymphadenopathy. Bronchoscopy, mediastinoscopy and FNAB were non‐diagnostic. The patient suffered a myocardial infarction precluding further intervention and was palliated.
By comparison, over the 2 years of the study eight subjects (1.6%) were diagnosed with an extrathoracic malignancy (two pancreatic, two brain, one breast, one ovarian, one renal, and one laryngeal). Unlike the Mayo Clinic group who reported incidental detection of extrathoracic malignancy in 7.9% of their subjects as a favourable byproduct of screening,5
none of these cancers was identified by LDCCT scanning in our cohort. Other significant pathology was noted in 221 subjects (49.2%)—largely emphysema, bronchiectasis, and coronary artery disease—as previously reported.4
Three hundred and seven subjects (68.4%) were current smokers at the start of the study. Smoking cessation advice was given by the study coordinator and reinforced at each follow up. Referral to a smoking cessation group was offered to all participants of whom only four (1.3%) accepted. Fifty nine subjects (19.2%) reported stopping smoking during the study period while five (1.6%) restarted. We did not validate smoking status with expired carbon monoxide levels as self‐reported abstinence has previously been shown to be very reliable.6
Our smoking cessation rate is comparable to the 14%6
quit rates reported by the Mayo group and a subset of the ELCAP cohort, respectively, and is higher than the 5–7% per year rates expected in the population.8
Greater motivation to quit smoking might be expected in a self‐selected volunteer population, but these higher quit rates also probably reflect the effectiveness of such simple measures as smoking cessation advice and positive reinforcement. Despite demonstrating their concern regarding the harmful effects of smoking by participating in a screening programme, it is disappointing that 251 of 413 subjects (60.8%) who completed the study did so while continuing to smoke.
None of the nodules progressed to advanced stage cancer within the screening interval, suggesting that our re‐screening interval is appropriate. Five subjects (1.1%) had invasive interventions for benign lesions triggered by baseline screening—one mediastinoscopy and four FNABs, one of which proceeded to lobectomy. A further FNAB for a benign lesion was triggered by nodule growth on interval screening. This was complicated by a pneumothorax. Selective use of PET in combination with CT scanning has been suggested as a means of reducing benign intervention but led to surgical biopsy for benign disease in three of five resections and false negative results in two cases of adenocarcinoma in the cohort of 1035 patients reported by Pastorino et al
FNAB, in contrast, resulted in no false positives and one false negative of five negative biopsies. Of four surgical resections in our cohort, only one was found to be a benign lesion.