DOI:10.2214/AJR.06.5075.1
AJR 2006; 187:W449-W450
© American Roentgen Ray Society
Reply
Ki Keun Oh,
Jeong Seon Park and
Eun-Kyung Kim
Department of Diagnostic Radiology College of Medicine Yonsei
University Seoul 135-720, Korea
WEB—This is a Web exclusive article.
Introduction
We appreciate the very interesting and important comments from Drs.
Mihmanli and Kantarci with regard to our recent AJR article
[1]. They posed several good
questions:
- Why did we perform screening thyroid sonography in patients after breast
sonography?
- Is screening thyroid sonography cost-effective in breast screening patients
with an asymptomatic thyroid?
- Was previous radiation exposure a factor in the patients with thyroid
cancer who also were in the breast cancer group in our study?
- Would overuse of thyroid sonography and sonography guided fine-needle
aspiration biopsy produce anxiety in women who also have undergone screening
breast sonography?
Discussion
According to the literature, the prevalence of thyroid cancer is variable
depending on patient screening
[1,
2] versus autopsy findings
[3], retrospective
[2] versus prospective analysis
[4], presence versus absence of
previous radiation to the neck or the chest wall
[4,
5], and ethnic background. Our
study focused on prospective sonographic screening for a relationship between
breast cancer and thyroid cancer, and the difference of incidence between the
cancer group and noncancer group of patients
[1]. We found there was a
statistically different incidence between the cancer group (1.9%, 13/685) and
noncancer group (0.6%, 29/4,864)
[1]. A similar screening study
[2] has been published with a
retrospective analysis of nonsymptomatic and nonpalpable lesions detected by
thyroid sonography (n = 1,140) and screening thyroid examination
following breast sonography (n = 1,057). Of the 155 detected solitary
and nonpalpable thyroid nodules between the size of 3-28 mm (mean = 7.5 mm),
49 nodules were confirmed histologically as malignant, which showed typical
findings of microcalcifications (59%), an irregular or microlobular margin
(55%), marked hypoechogenicity (27%), and were more tall than wide (32%)
[2]. However, the data in this
study by Kim et al. [2]
included men or only a thyroid sonogram without a concurrent breast sonogram
in women. Furthermore, Brander et al.
[4] reported that follow-up
thyroid sonographic screening was useless without detection of malignancy in
both men and women and that random thyroid screening is clinically
unimportant. However, the purpose of our study was to confirm the importance
of early detection and epidemiology and to establish whether there was any
relationship between thyroid malignancy and breast malignancy in women
because, in Korea, the incidence of breast cancer as well as thyroid cancer
has been increasing recently. In our study, we recognized that the incidence
of thyroid cancer was higher in the breast cancer group than in the non-breast
cancer group [1].
As noted by Drs. Mihmanli and Kantarci, radiation exposure is a known risk
factor for developing thyroid cancer
[5-7].
This adverse effect emerges 1 to 2 years after radiation to the chest wall or
supraclavicular area so that the diagnosis of thyroid cancer usually increases
with the passage of time [6].
To determine whether the postoperative radiation to the chest wall and
supraclavicular area influenced the development of thyroid cancer in our
hospital, we prospectively researched and followed the patients' thyroid for 3
years; none of these patients developed thyroid cancer. Patients did develop
postoperative thyroid edema during the first year, thyroid heterogenicity in
the second year, and thyroid shrinkage with increased sonographic echogenicity
due to histologic fibrosis [5].
We therefore concluded that postoperative radiation could be a long-term
causative factor for developing thyroid malignancy, but definitely not within
3 years after postoperative exposure to radiation
[5]. In the study we published
in AJR, we performed sonographic screening of the thyroid gland in
women undergoing breast sonography
[1]. Before surgery and
radiation therapy, we also performed sonography guided fine-needle aspiration
biopsy with histologic confirmation when we detected thyroid nodules. Thirteen
(1.9%) of the 685 breast cancer group patients were diagnosed with thyroid
cancer in conjunction with breast cancer; six (46.2%) of the 13 thyroid
cancers were already in existence at the time of the initial breast cancer
diagnosis by sonography, and seven of the 13 thyroid cancers were detected
within 6 to 14 months (mean, 9.4 months) after initial breast surgery. Four of
the seven patients with thyroid cancers detected postoperatively (40%, 4/7)
received additional postoperative radiation therapy (mean dose of 5,940 cGy).
They received radiation to the chest wall (4/4) and supraclavicular fossa
(2/4) [1].
The four thyroid cancers were all detected within 1 year after surgery and
ranged in size from 1 mm (6 months postoperative), 0.2 mm (6 months
postoperative), 0.1 mm (11 months postoperative), and 0.5 mm (11 months
postoperative). Theoretically and in our experience, the interval between
radiation exposure and the development of the thyroid cancer in these patients
was too short to attribute to a postoperative oncogenic effect of exposure to
the radiation [5].
We suggested that the use of thyroid sonography in addition to breast
sonography is a good screening method for asymptomatic thyroid nodules.
However, if abnormal thyroid nodules are detected by thyroid sonography,
sonographic guided fine-needle aspiration biopsy is necessary for confirmation
of the cancer [1,
2,
8]. There are considerable
controversies about the management of occult thyroid cancer
[2,
8]. Although the survival rate
for patients with differentiated thyroid carcinoma is generally excellent,
many studies have evaluated the factors that help predict which patients will
have poor prognosis. The reported factors include a patient's age (> 50
years old) and extrathyroidal metastasis of the cancerous lesion and the size
of the lesion [4,
5]. In our study, even
screening-detected thyroid cancers had some extracapsular invasion (13/42,
31.0%) or lymph node metastasis (15/42, 35.7%)
[1].
We agree that the cost-effectiveness of thyroid screening has not yet been
established, but we have been performing breast and thyroid sonography at no
extra charge because additional longitudinal and transverse scanning is easy
and quick to do after completion of breast sonography. The incidence of
thyroid cancer is increasing recently among women in Korea and, therefore,
they are happy to be examined by a specialist at no additional charge. We have
not received any patient complaints about the performance of thyroid
sonography or sonographically guided fine-needle aspiration biopsy of the
thyroid. We believe that further investigations regarding occult thyroid
cancer will lead to improved methods for clinically managing these
incidentalomas, but their management now remains controversial. We will
continue to follow the patients in our study population who received
postoperative radiation therapy for several years.
References
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Introduction
Discussion
