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A history of detecting lung cancer at desert radiologists

I Conception and design: None; II Administrative support: None; III Provision of study materials or patients: None; IV Collection and assembly of data: None; V Data analysis and interpretation: None; VI Manuscript writing: All authors; VII Final approval of manuscript: Henschke, Principal Investigator, David F. Smith, Mark Pasmantier; Cornell University: Javier Zulueta, Juan P. Stefano Canitano, Salvatore Giunta; St. Shari-Lynn Odzer; Aurora St. CT screening for lung cancer is a complex undertaking requiring specifications of all of its components.

This includes questions as to who should be screened, how frequently screening should be performed, and an optimal regimen of screening. The regimen of screened defines who requires further workup during the year the screening is performed in addition to the specification of the CT acquisition parameters, how the readings are performed, and the results communicated to the participants being screened.

In addition to looking for suspicious pulmonary nodules, the CT scan also shows the heart, mediastinum thyroid, and the organs in the upper abdomen. The recommendations for abnormal findings in all these organs and the workup also need to be interpreted in light of the fact that they are found in asymptomatic people at risk of lung cancer and not that they presented for clinical care because of symptoms.

Desert Radiologists - Horizon Ridge

This protocol has been continually updated in light of advancing CT and diagnostic technology and knowledge that has emerged as a result of screening, particularly large databases that have been developed. Lung cancer; screening; baseline; annual repeat rounds; positive results Received: Regarding lung cancer screening, thinner collimation on modern CT scanners has led to the detection of smaller pulmonary nodules.

Desert Radiologists - Palomino

Along with advances in imaging, there have been evolutions in diagnostic techniques such as percutaneous biopsies, navigational bronchoscopies, and PET scans. As these advances have altered clinical care, they have been integrated into the ongoing screening program.

The goal of any lung screening program is to find lung cancer as early as possible. However, in the context of screening asymptomatic individuals, unnecessary interventions that do not lead to the diagnosis of an invasive lung cancer will decrease the value of screening.

Thus, there needs to be a balance between the goal of finding the cancer as early as possible and limiting unnecessary tests, especially invasive ones. Ultimately, this requires constant updating of the entire screening process. Critical questions for any screening program are: Who should be screened, in other words, what are the indications for screening?

  • For example, the NELSON study 35 performed their first repeat screening one year after the baseline round, while the second and third scans were performed 2 and 2;
  • The measured diameters should be supplemented by computer-based assessments of volume, but these techniques are still considered experimental and there is considerable variation in the volumetric measurements, particularly for complex nodules 27 , 28 , 54 - 56;
  • To determine whether growth has occurred, the reader carefully compares the current images with the corresponding previous ones, displayed side-by-side;
  • The Bach model was developed to estimate the absolute risk that one will be diagnosed with lung cancer within 10 years 21;
  • The NLST studied adults 55 to 80 years old who were current smokers or quit in the past 15 years, and had a 30 or greater pack-year smoking history.

How frequently should screening be performed? What is the optimal screening regimen? The answers to these questions determine the effectiveness of the screening program, as well as its costs. Also, considerations need to be taken as to how the results are communicated to the referring physician and to a history of detecting lung cancer at desert radiologists screening participant, typically with a lay summary provided to the latter.

Smoking cessation is a vital component of the screening program, not only for current smokers but also for former smokers to prevent relapse.

ELCAP demonstrated that a high proportion of patients with lung cancer were diagnosed in Stage I utilizing CT, with a shift to smaller tumor sizes on annual repeat screening studies 23. Initial results were widely publicized and stimulated debate about the benefits of lung cancer screening. Indications for screening Approximately 222,500 new cases of lung cancer will be diagnosed in 2017, including about 44,500 in never smokers 9. Other studies have shown similarly high rates of stage I diagnoses 1314.

Screening is indicated for asymptomatic persons who are free of potential manifestations of lung cancer. Symptoms of lung cancer include worsening cough with hoarseness or hemoptysis, and unexplained weight loss. Individuals with these symptoms need a clinical workup, which should include a diagnostic CT of the chest.

Of note, there used to be an obvious difference in the image quality between diagnostic CT scans and low dose screening CTs, but advancing technologies, like iterative reconstruction, have made this less of an issue. There remains, however, a difference in radiation dose, with a typical diagnostic CT being 10—20 times higher in dose than a low dose screening CT. The NLST studied adults 55 to 80 years old who were current smokers or quit in the past 15 years, and had a 30 or greater pack-year smoking history.

These CMS criteria state that screening should be discontinued if one has not smoked for more than 15 years or has developed a health problem that greatly reduces life expectancy or the ability or willingness to have curative lung surgery.

  • None; V Data analysis and interpretation;
  • A part-solid nodule is one whose solid internal components completely obscure the lung parenchyma, while a nonsolid nodule has none of its lung parenchyma completely obscured, allowing for visualization of background pulmonary vessels;
  • As these advances have altered clinical care, they have been integrated into the ongoing screening program;
  • All participants for whom the biopsy considered to be adequate did not lead to a diagnosis of lung cancer, a repeat CT 12 months after the initial baseline CT is to be performed;
  • Follow-up options for positive results on baseline are:

This requirement is a concern, as it has been well-established that the risk of lung cancer persists long after smoking cessation, and these individuals remain at high risk 18. Screening is recommended for high-risk individuals for whom the potential benefits of LDCT outweigh the risks.

The use of pack-years should be reconsidered as it is well known that duration and intensity of smoking are independent risk factors that should be considered separately, while pack-years of smoking combines these two factors 19. The USPSTF criteria dichotomize the continuous variables of age and smoking history and are thus limited for determining risk of individuals.

Asbestos exposure is an example of an occupational risk factor 20 which markedly increases the risk of lung cancer. There are also other identifiable occupational and clinical risk factors that might be considered.

Risk prediction models using additional risk factors seem promising, and as more information regarding their specificity and sensitivity emerges, such models may provide a better basis for selecting individuals at high-risk of lung cancer for screening.

Various analytic models have been developed to address the multitude of individual risk factors for developing lung cancer. The Bach model was developed to estimate the absolute risk that one will be diagnosed with lung cancer within 10 years 21. This model considers multiple risk factors: However, similarly to the NLST, it only recruited individuals 55 to 74 years of age.

Current research is looking into strengthening this idea that risk-based models are crucial for determining the screening population. A 2017 retrospective analysis focused on nine previously established risk models including the Bach and PLCO Models and compared them to the NLST, to show that selection of the lung screening population using individual risk factors is superior to selection criteria of age and pack-years alone 23.

Risk prediction models could also improve the shared decision-making process for patients and clinicians through easily accessible online risk calculators.

Ultimately, more research on these models needs to be done. Frequency of screening There is a complex relationship between screening frequency and healthcare costs.

A decrease in the frequency of screening with a loss in effectiveness will markedly reduce the value of the screening program. For example, a change from annual to biannual screening may cut the costs in half, but in turn can increase the frequency of higher stage cancer diagnoses, which then increases the cost of lung cancer treatment potentially offsetting the savings provided by the reduced frequency of screening.

In designing ELCAP, the decision to provide annual screening was based on the estimated growth rates of lung cancers 26 - 31. Growth rates were initially based principally on chest radiograph findings which did not allow for very accurate measurements. Typically reported volume doubling times VDTs of lung cancers were from 100 to 200 days. Since those early reports, studies have shown median growth rates of lung cancers to be about 120 to 180 days.

Indications for screening

Thus, a lung cancer with a doubling time of 122 days that is just becoming visible at 2 mm in diameter would grow to 4 mm in one year, and thus become readily detectable. To illustrate the importance of the doubling times, we give an example of an aggressive cancer and a much less aggressive one.

A 2 mm lung cancer with a doubling time of 30 days, a typical small-cell lung cancer, would grow from 2 to 30 mm in one year, and most likely will no longer be a potentially curable Stage I lung cancer 1132.

On the other hand, a 2 mm lung cancer with a 400 days doubling time would grow to measure 2. Some studies have looked into screening with different intervals between baseline and follow up scans, and screening intervals have a history of detecting lung cancer at desert radiologists modeled by Duffy et al. For example, the NELSON study 35 performed their first repeat screening one year after the baseline round, while the second and third scans were performed 2 and 2.

In the second and third rounds of screening, they reported a lower frequency of diagnoses of stage I lung cancer, along with a higher frequency of interim cancers. Interim cancers are cases of lung cancer prompted by symptoms and diagnosed in between rounds of screening. As the time between screening rounds increases, the frequency of interim cancers typically increases. As one can see, the discussion of screening frequency requires a balance between minimizing the cost of the screening and maximizing the detection of early, curable lung cancers.

Regimen of screening CT screening refers to the entire process of the pursuit of early, rule-in diagnoses of lung cancer.

It begins with the initial, baseline low-dose CT scan and continues with repeat screenings. A positive result of each round of screening is followed by diagnostics using a well-defined algorithm. As the frequencies of different cell-types of lung cancer in the baseline round are different from those diagnosed in repeat rounds of screening, the definition of a positive result and the subsequent algorithm are defined separately for the baseline and subsequent annual repeat rounds 36.

It is also understood that there may need to be occasional exceptions to the protocol based on clinical and imaging findings. When the algorithm is applied in each screening round and does not lead to the diagnosis of malignancy, the next repeat screening is scheduled at a preset time.

  1. Of note, in making the distinction between part-solid and nonsolid nodules, blood vessels within the nodule are not considered be considered to be solid components, despite their solid appearance. Frequency of screening There is a complex relationship between screening frequency and healthcare costs.
  2. Width, defined as the longest dimension perpendicular to the length, is measured on the same image.
  3. The recommendations for abnormal findings in all these organs and the workup also need to be interpreted in light of the fact that they are found in asymptomatic people at risk of lung cancer and not that they presented for clinical care because of symptoms.
  4. Regimen of screening CT screening refers to the entire process of the pursuit of early, rule-in diagnoses of lung cancer.
  5. Also, considerations need to be taken as to how the results are communicated to the referring physician and to the screening participant, typically with a lay summary provided to the latter. However, similarly to the NLST, it only recruited individuals 55 to 74 years of age.

While the regimen has been continuously updated and improved by integrating new technologies and knowledge based on accrued screening results, its basic structure has remained unchanged. The former used a defined algorithm, while the latter specifically stated that it did not specify one. The nodule definitions and size thresholds of positive results have been continually reevaluated and updated. In the initial CT screening study 23there was no size cutoff for positive results.

Since then, updated thresholds have been introduced because of new CT scanner technology and accumulating evidence. The threshold for positive results in baseline screening was changed to 5 mm 38and then eventually revised to 6 mm 38 - 40.

It was also shown that some solid and many subsolid pulmonary nodules resolved spontaneously, particularly new ones identified on repeat screening examinations 43.

Thus, follow-up imaging 3 months after baseline or 1 month after annual repeat screening is useful to avoid unnecessary diagnostic interventions, especially invasive diagnostic interventions. Image acquisition The low dose CT imaging technique remains consistent between baseline and repeat screenings. Given that there are a large variety of CT manufacturers and scanner models with high-resolution capabilities, the following are general guidelines for image production.

Scans should be acquired on MDCTs, ideally with scanners having more than 16 rows. Images should be acquired a history of detecting lung cancer at desert radiologists that scans can be reconstructed with a slice thickness of 1 mm or less.

Studies have shown that thinner slices are better for automated image processing and nodule detection. An alternative is to use dose-modulation, which should be established to correspond to approximately the same dose without modulation. Collimation and pitch also affect the dose, and these should be set to allow for the lowest possible dose while maintaining acceptable image quality.

Image reconstruction should be performed using a standard, non-edge enhancing kernel to minimize the effects of noise. However, additional reconstructions may also be obtained, including maximum intensity projection MIP images.