Incidental findings on LDCT are worth working up

By Kate Madden Yee, AuntMinnie.com staff writer

October 14, 2020 -- Low-dose CT (LDCT) for lung cancer screening occasionally finds other malignancies outside the lungs, according to a study published October 12 in the Journal of the American College of Radiology.

And the benefit of working up these findings seems to outweigh the harms, wrote a team led by Dr. Wariya Chintanapakdee of Massachusetts General Hospital in Boston.

"Although there is cost and potential harm [due to radiation exposure] associated with the workup of incidentally detected extrapulmonary lesions during lung cancer screening, there is potential benefit in detecting [these] malignancies at early stages, which have more favorable outcomes," the group wrote.

The strengths of lung cancer screening with LDCT have been validated by many studies, and its cost-effectiveness is considered reasonable when it is offered to appropriate patient populations. But sometimes LDCT used for lung screening identifies other malignancies, and the cost of working up these incidental findings has remained unclear, the team noted.

Chintanapakdee's group conducted a study that included 7,414 LDCT exams performed between June 2014 and December 2019 on 4,160 patients as part of a lung cancer screening program, identifying any patients with indeterminate extrapulmonary lesions and tracking the diagnostic workup, management, and outcomes of these findings. The team then estimated costs related to evaluating these incidental findings using 2020 total facility relative value units and the 2020 Medicare conversion factor.

The data showed 20 extrapulmonary malignancies among 241 indeterminate lesions, for a prevalence of 0.48% (20 out of 4,160 patients). Most of these lesions (80.1%) prompted further imaging; 20% were biopsied. Of these indeterminate findings, the majority were detected in the thyroid, kidneys, adrenal glands, and breasts.

Of 20 malignant lesions, 13 (65%) were early-stage cancers. The positive predictive value (PPV) for malignancy for LDCT for lung cancer screening was highest in the chest wall and axilla and the bone.

4 most common organ groups and highest PPV for incidental findings identified on LDCT for lung cancer screening
Measure Percentage
Organ group
Thyroid 23.7%
Kidney 20.8%
Adrenal gland 10.8%
Breast 10%
PPV for malignancy
Chest wall and axilla 36.4%
Bone 25%
Breast 12.5%
Kidney 12%

The total cost of working up all the incidental lesions among all patients was $26,321, with an average cost of diagnostic workup per additional malignancy of $1,316. Investigation of thyroid cancer was the most expensive, followed by upper abdominal cancers.

<
4 highest workup costs for incidental malignancies found on LDCT for lung cancer screening
Lesion location Cost per malignancy (consultation, imaging, and biopsy)
Thyroid $2,783.50
Upper abdomen $2,019.22
Mediastinum $908.02
Kidney $824.84

The cost/benefit analysis of extra imaging and extra cost for evaluating incidental lesions found on lung cancer screening would appear to lean toward the beneficial, according to the authors.

"Early detection and treatment of these incidental extrapulmonary malignancies could theoretically contribute to the reduction of all-cause mortality," they concluded.


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