Lung cancer screening
As a component of the Centers for Medicare & Medicaid Services’ requirements for lung cancer screening payment, institutions performing screening must use low-dose techniques and participate in a dose registry. The American College of Radiology (ACR) recommends the dose levels per CT slice (CTDIvol; 3 mGy or lower) and the effective dose (ED; 1 mSr or lower) that would qualify an examination as “low dose,” thereby hoping to minimize the risk of radiation-induced cancers.
Joshua Demb, PhD, and colleagues prospectively collected lung cancer screening examination dose metrics at U.S. institutions in the University of California, San Francisco, International Dose Registry (JAMA Intern Med. 2019 Sep 23. doi: 10.1001/jamainternmed.2019.3893). Only U.S. institutions that performed more than 24 lung cancer screening scans from 2016-2017 were included in the survey (n = 72, more than 12,500 patients). Institution-level factors were collected via the Partnership for Dose trial, including how CT scans are performed and how CT protocols are established at the institutional level.
In a data-dense analysis, the authors found that 65% of institutions delivered, and more than half of patients received, radiation doses above ACR targets. This suggests that both the potential screening benefits and the margins of benefits over risks might be reduced for patients at those institutions. Factors associated with exceeding ACR guidelines for radiation dose were using an “external” medical physicist, although having a medical physicist of any type was more beneficial than not having one; allowing any radiologist to establish or modify the screening protocol, instead of limiting that role to “lead” radiologists; and updating CT protocols as needed, compared with updating the protocols annually.
How these results influence clinical practice
As with the ASTRO 2019 presentation, the law of unintended consequences applies here. Whenever potentially healthy people are subjected to medical procedures to prevent illness or detect disease at early stages, protecting safety is paramount. For that reason, National Comprehensive Cancer Network (NCCN) guidelines are explicit that all lung cancer screening and follow-up scans should use low-dose techniques, unless evaluating mediastinal abnormalities or adenopathy.
The study by Dr. Demb and colleagues critically examined the proportion of lung cancer screening participants receiving guideline-concordant, low-dose examinations and several factors that could influence conformance with ACR guidelines. The results are instructive despite some of the study’s limits including the fact that the database used did not enable long-term follow-up of screened individuals for lung cancer detection or mortality, the survey relied on self-reporting, and the institutional level data was not solely focused on lung cancer screening examinations.
The survey reminds us that the logistics, quality control, and periodic review of well-intentioned programs like lung cancer screening require the thoughtful, regular involvement of teams of professionals who are cognizant of, adherent to, and vigilant about the guidelines that protect the individuals who entrust their care to us.
Dr. Lyss has been a community-based medical oncologist and clinical researcher for more than 35 years, practicing in St. Louis. His clinical and research interests are in the prevention, diagnosis, and treatment of breast and lung cancers and in expanding access to clinical trials to medically underserved populations.