Received: 12 December 2017
Accepted: 12 December 2017
Can PET/CT help manage ground glass nodules?
“When you can measure what you are speaking about, and
express it in numbers, you know something about it, when
you cannot express it in numbers, your knowledge is of a
meager and unsatisfactory kind; it may be the beginning of
knowledge, but you have scarcely, in your thoughts
advanced to the stage of science.” − Lord Kelvin
In this issue of the JournalofSurgicalOncology, Son et al report that the
maximum standardized uptake value (SUVmax) of preoperative PET/CT
scanmaypredictthedegreeofinvasive lung cancer within ground-glass
nodules (GGN) with and without solid components that are associated with
the spectrum of early adenocarcinoma lesions. This includes adenocarci-
noma in situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive
adenocarcinoma (IA). They studied 190 patients who had undergone
resection for lung adenocarcinoma within GGN over an 11-year period.
A GGN on a CT scan is a frequent incidental clinical finding that can
challenge health care providers. MIA and AIS frequently presents as a
GGN, and may lie dormant or grow slowly over many years.
A part-solid component raises the probability of an IA to 93%.
This knowledge supports the finding of Son et al that the mean
SUVmax increased from 0.53 in the 13 non-solid GGN to a mean of
1.32 in the 177 part-solid GGN. Furthermore, the mean SUVmax
increased from 0.86 for the 38 patients with MIA to 1.32 for the 152
patients with IA. Following known adenocarcinoma, using the findings
of these authors may prove helpful in optimizing the timing for surgery
and other treatments for lung cancer based upon increase in dose-
uptake ratio. This is represented by an increase of in SUVmax by 0.4,
found by Son et al, for part solid lung adenocarcinoma when solid
component reaches 50%. Setting an expected range for SUV due to
part-solid adenocarcinoma and understanding how that range relates
to tumor activity as well as density may, in the future, help thoracic
surgeons to select specific lesions for resection.
The authors excluded competing causes of findings in order to find
the small difference in relatively low FDG avidity that corresponds with
increasing solid component in adenocarcinoma of lung. In our opinion, the
correlation with invasiveness is intuitive, and may currently be better
served by diagnostic CT that can more accurately quantify solid
component dimension and identify additional features of early adenocar-
cinoma. This includes extension to pleural surface and is often associated
with focal pleural thickening, termed by the authors as a pleural dimple.
The resulting ROC curve demonstrates minimal improvement over
chance in the absence of the full range of pathologic possibilities that
often require consideration at the time of PET/CT scanning prior to
pathologic diagnosis of adenocarcinoma of lung. The exclusion of GGN
inflammatory lesions is largely responsible for the statistical signifi-
cance achieved given the small difference between the mean SUVmax
The difference in SUVmax values appear to closely follow the
extent of solid component as would be expected for more active
tumor, suggesting attention to increases in SUVmax over time may
help to separate benign from malignant causes of GGN. The authors
have thereby provided a reference point for consideration in low FDG
avidity lesions, similar to the identification of a range within low avidity
lesions to support diagnosis of atelectasis by Gerbaudo et al.
We are left to wonder if PET/CT scans have a major contribution
in the management of GGN or part-solid GGN. A part-solid GGN
corresponds to a very high probability of an IA, and the patient should
be treated accordingly. Although there is value in gaining understand-
ing about non-solid GGN with this study that quantified SUVmax, this
may not justify the routine use of PET/CT to evaluate these patients.
PET/CT has proven disappointing for diagnosis of early adenocarci-
noma of lung in which utilization of glucose is not significantly greater
than that of normal lung. PET/CT is valuable for identification of
significant occult extrathoracic primary and metastatic tumors.
Further studies should aim to explore the utility of PET/CT in the
identification of disease spread, as well as clarification between
inflammatory disease and malignant conditions. The authors
concluded that SUVmax is beneficial in identifying whether a tumor
with a GGN was either MIA or IA. For the vast majority of these
patients, this pre-surgical knowledge does not change the surgical
therapy. Perhaps it can convince a reluctant patient to consider
Jeffrey N. Tarascio http://orcid.org/0000-0002-5380-7655
Francine L. Jacobson MD, MPH
Jeffrey N. Tarascio
Sam W. Fox
Brigham and Women's Hospital,
75 Francis St, Boston, Massachusetts 02115
Jeffrey N. Tarascio, Brigham and Women's Hospital,
75 Francis St, Boston, MA 02115.
J Surg Oncol. 2018;117:457–458. wileyonlinelibrary.com/journal/jso © 2018 Wiley Periodicals, Inc.