With the improvement of living standard, people pay more and more attention to the usual health checkups, and the application of CT in lung is increasing, and the detection of lung nodules is significantly more than before. To address the many issues of lung cancer screening that patients are concerned about, I would like to share with you the key points of the recent NCCN lung cancer screening guidelines for your reference.
The NCCN (National Comprehensive Cancer Network) published its first lung cancer screening guidelines in late October 2011. The guidelines were based on the results of the National Lung Cancer Screening Study (NLST) published by the New England Journal of Medicine (NEJM) in August 2011. The study applied low-dose spiral CT (LDCT) to a high-risk population for routine annual screening and found that LDCT screening reduced lung cancer mortality by 20% and reduced mortality from any cause by 7% compared to chest radiograph screening. Based on this result, the guidelines explicitly include LDCT as a lung cancer screening tool and make different guidelines for the management of different findings on LDCT.
Overall, the NCCN guidelines recommend annual low-dose spiral CT of the lungs for people at high risk for lung cancer. High-risk groups are defined as.
A, 55-74 years of age, who are smoking or have quit smoking for less than 15 years and have a smoking index greater than 30 pack-years.
B. Those who are older than 50 years old, have a smoking index greater than 20 pack-years, and have a combination of one of the following: history of tumor; history of lung disease; family members with lung cancer; occupational exposure to radon and carcinogens in the residence (including arsenic, chromium, asbestos, nickel, cadmium, beryllium, silica and diesel fumes).
The above high-risk groups of lung cancer are recommended to have low-dose spiral CT (LDCT) examination annually for at least 3 years (the optimal duration of years is unknown), while routine LDCT examination is not recommended for other medium and low-risk groups.
Depending on the CT findings, different management measures are taken.
A. Absence of pulmonary nodules.
Annual LDCT examinations for at least 3 years (optimal duration is not known).
B, finding solid or partially solid nodules in the lungs (nodules without benign calcification, fatty or inflammatory manifestations).
a, ≤4mm, with annual LDCT for at least 3 years (optimal duration not yet known).
b, >4-6mm, LDCT reviewed after 6 months, if no growth, LDCT reviewed after 12 months, still no growth, LDCT reviewed annually for at least 2 years (optimal duration of years not yet known).
c, >6-8mm, review LDCT after 3 months, if there is no growth, review LDCT after 6 months, no change then review LDCT after 12 months, still no change, review LDCT every year for at least 2 years (the optimal duration of years is not known).
d, >8mm, consider PET/CT examination, if lung cancer is suspected, surgery or biopsy; not consider lung cancer, dynamic observation as above.
In the above case under dynamic observation, if nodule growth is found, surgical resection is recommended.
e, find endobronchial nodules, recheck LDCT after 1 month, if no regression, do fiberoptic bronchoscopy for clarification.
C. Lung ground glass shadow (GGO) or other non-solid nodules (without clear benign indications) are found.
a, <5mm, repeat CT after 12 months, if stable, annual LDCT examination for at least 2 years (optimal duration is not known).
b.5-10mm, review CT after 6 months, if stable, annual LDCT examination for at least 2 years (the optimal duration is not known).
c, >10mm, review LDCT after 3-6 months, if stable, LDCT can be reviewed after 6-12 months, or biopsy or surgical resection.
If the nodules are found to be enlarged or solid during the above dynamic observation, they should be surgically removed except for those with a diameter of <5mm, which can be considered for dynamic review of LDCT in 3-6 months.
These are the guidelines for LDCT lung screening in the NCCN guidelines. In addition, the majority of patients and friends are concerned about the accuracy of screening, the malignancy ratio of various nodules and the impact of CT radiation on the body, and the following information on these aspects is provided for your reference.
1, the malignant rate of various pulmonary nodules.
Li et al. reported that among nodules with a diameter of 3-20 mm, the malignancy rate of ground glass shadow was 59%, the malignancy rate of mixed images of ground glass shadow + solid nodules was 48%, and the malignancy rate of solid nodules was 11%. Kim et al. reported that 75% of persistent ground glass shadow was confirmed to be malignant. The majority of lung cancers presenting with ground glass shadow are adenocarcinoma in situ, which is previously referred to as fine bronchoalveolar carcinoma, with a 100% survival rate at 5 years after surgery. Lung cancers that show solid or mixed solid nodules are mostly invasive and fast-growing lung cancers.
2.Leakage rate of LDCT screening for lung cancer.
Low-dose spiral CT screening still has a certain degree of leakage. It was reported that among 88 patients who were finally diagnosed with lung cancer, 33 cases (37.5%) had been missed in 39 LDCTs, among which 23 cases (59%) were due to LDCT failure to display effectively and 16 cases (41%) were due to physician’s error in film reading. Reasons for poor LDCT display included: A. 91% due to microscopic glassy lesions B. 83% due to lesions that overlapped, were obscured, or were similar to normal lung tissue structures (e.g., pulmonary vessels).
87% of the missed readers were due to underlying lung disease such as emphysema, tuberculosis and pulmonary fibrosis.
3. Radiation risk issues with LDCT.
How much effect will frequent CT have on the body? I believe this is a common concern, and its main risk is to induce the occurrence of malignant tumors.
The average radiation of traditional CT scan is 7mSv, while the average effective radiation of spiral CT with low dose technology is 1.4mSv, which is about 10 times of the radiation of chest X-ray (comparison reference: the average background radiation of the world is 2.4mSv/year, 0.001mSv/hour of airplane, 1mSv/year of a pack of cigarettes per day, 0.5mSv/year of soil and air, 0.2mSv/year of food. (0.2mSv/year for soil and air and 0.2mSv/year for food).
Brenner et al. concluded, based on a study of Japanese A-bomb survivors, that if a 50-year-old woman who smoked underwent annual chest CT (radiation dose 5.2 mSv/session) until age 75, the estimated probability of radiation-induced lung cancer was 0.85%; whereas the risk of lung cancer from a single lung CT scan (radiation dose 5.2 mSv) was about 0.056%. Mascalchi et al. reported the application of multi-row CT (radiation dose of 3.3 mSv) and single-row CT (radiation dose of 5.8 or 7.1 mSv) to annual lung cancer screening scans in people aged 50-70 years for 4 years, and calculated the risk of lung cancer due to radiation to be 0.011% for multi-row CT and 0.020-0.024% for single-row CT.
It seems that the risk of CT radiation does exist, but it is clearly acceptable compared to the 20% reduction in lung cancer mortality that CT can achieve.