CT Screening Program Research Articles

M01-02: Treatment for the screen-detected lung cancer: characteristics and outcome

Owing to the advent of refined chest CT images with higher resolution and CT screening programs, smaller lung cancers are being discovered in asymptomatic patients. Most of them are more often found on a low-dose CT images, and they tend to have characteristic appearance on high-resolution CT scan as ground glass opacity (GGO), a focal intermediate/mild increase in the CT density. Of course, the screening program is still picking up the more solid tumors with/without lymph node involvement, the percentage of GGO or GGO-like lesions is obviously increased in low-dose CT screening era. These GGO tumors are pathologically characterized by the morphology of non-/minimally invasive form of well-differentiated adenocarcinoma termed as bronchioloalveolar carcinoma (BAC) of the non-mucinous type. The superb prognosis of these GGO-BAC tumors is being recognized in the surgical community. Although the gold standard operation for peripheral lung cancer has been lobectomy with lymph node sampling/dissection, the revision is thought to be necessary, especially for these screen-detected GGO-BAC tumors. The possibility of limited resection such as segmentectomy/wedge resection seems to be realistic. Enough number of institutional reports describing the equivalent surgical outcome by limited resection have been accumulated. Therefore, the randomized phase III trial between lobectomy and limited resection is being planned both in US and Japan in a non-inferiority design setting. The results of these studies might be applied in the management of screen-detected, small-sized tumors in the near future.

Subcentimeter Large Cell Neuroendocrine Carcinoma of the Lung

To our knowledge, no report exists of a subcentimeter size large cell neuroendocrine carcinoma (LCNEC) of the lung. A 75-year-old man participating in a low-dose CT screening program for lung cancer was found incidentally to have a partly-solid nodule in the right upper lung. After treatment with antibiotics, a repeat CT showed resolution of the nodule, but a new solid nodule measuring 9 x 9 mm was detected in the left lower lobe. The lesion showed marked enhancement on dynamic contrast-enhanced MRI. Video-assisted thoracic surgery and frozen section biopsy was suggestive of malignant lesion, resulting in extension of surgery to lobectomy with nodal dissection. The final diagnosis was stage IA-LCNEC. The estimated volume doubling time of the tumor was 30.1 days. These aggressive tumors may rarely have doubling times that overlap with benign processes.

Growth rate of small lung cancers detected on mass CT screening.

CT has recently been used in mass screening for lung cancer. Small cancers have been identified but the growth characteristics of these lesions are not fully understood. We identified 82 primary cancers in our 3-year mass CT screening programme, of which 61 were examined in the present study. The volume doubling time (VDT) was calculated based on the exponential model using successive annual CT images or follow-up CT images. All cases were also examined in the hospital by high resolution CT (HRCT). Lesions were divided into three types based on HRCT characteristics: type G (n = 19), ground glass opacity (GGO); type GS (n = 19), focal GGO with a solid central component; and type S (n = 23), solid nodule. 18 (95%) lesions of type G, 18 (95%) of type GS and 7 (30%) of type S were invisible on conventional chest radiographs. The mean size of the tumour was 10 mm, 11 mm and 16 mm for type G, type GS and type S, respectively. Most tumours (80%) were adenocarcinomas; 78% of these were GGO (type G and GS). Mean VDT values were 813 days, 457 days and 149 days for type G, type GS and type S, respectively; these are significantly different from each other (p < 0.05). Our results show that annual mass screening CT for 3 successive years resulted in the identification of a large number of slowly growing adenocarcinomas that were not visible on chest radiographs.