How to Order Low-Dose CT for Lung Cancer Screening
Order a low-dose, non-contrast chest CT scan specifically designated for lung cancer screening, ensuring the protocol adheres to ACR-STR practice parameters to minimize radiation exposure while maintaining diagnostic quality. 1
Patient Eligibility Criteria
Before ordering, verify the patient meets established screening criteria:
- Age 55-80 years 1
- Smoking history ≥30 pack-years 1
- Current smoker OR quit within the past 15 years 1
- No history of lung cancer 2
These criteria are based on the National Lung Screening Trial (NLST), which demonstrated a 20% reduction in lung cancer mortality with low-dose CT screening compared to chest radiography. 2, 3
Technical Specifications for the Order
Essential Order Components:
- Specify "low-dose CT chest WITHOUT IV contrast" 1
- Indicate "for lung cancer screening" to ensure proper protocol selection 1
- Request adherence to ACR-STR Practice Parameter guidelines for performance and reporting 1
Radiation Dose Considerations:
The screening CT should use approximately 25% of the radiation dose used for routine diagnostic chest CT, which has been validated as providing acceptable image quality for lung cancer screening in 100% of evaluated cases. 4 This translates to a CTDIvol significantly lower than standard chest CT protocols. 4
Pre-Order Requirements
Shared Decision-Making Discussion:
Document a shared decision-making conversation covering:
- Potential benefits: 20% mortality reduction in high-risk populations 2, 3
- Harms: High false-positive rate (27.3% at baseline screening, 39.1% cumulative) requiring follow-up imaging or invasive procedures 2
- Radiation exposure: Low but cumulative with annual screening 1
- Screening interval: Annual screening recommended 2
This discussion is mandated by CMS for coverage and must be documented. 5
Common Pitfalls to Avoid
- Do NOT order standard chest CT - this delivers 4 times the necessary radiation dose 4
- Do NOT order with IV contrast - contrast is not indicated for screening and adds unnecessary risk 1
- Do NOT order chest radiography - this modality does not reduce lung cancer mortality and is inferior to CT 1
- Do NOT screen patients <55 or >80 years old - no mortality benefit demonstrated in these age groups 1
- Do NOT screen patients with <20 pack-year history without additional risk factors - insufficient evidence of benefit 1
Follow-Up Planning
Establish a system for:
- Annual repeat screening for eligible patients who remain at high risk 2
- Nodule management protocols based on size thresholds (typically ≥4-5mm requires follow-up) 2
- Smoking cessation counseling at each screening encounter 2
The screening program should ideally be part of a structured, quality-certified program to maintain consistency with NLST standards. 5