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LETTER TO THE EDITOR
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Year : 2015  |  Volume : 52  |  Issue : 4  |  Page : 652--653

Role of PET-CT versus MRI in carcinoma breast: Which one is indicated for detecting the primary?

Anirudh V Nair, CJ Sandya, S Moorthy, PV Ramachandran 
 Department of Radiology, Amrita Institute of Medical Science, Kochi, Kerala, India

Correspondence Address:
C J Sandya
Department of Radiology, Amrita Institute of Medical Science, Kochi, Kerala
India




How to cite this article:
Nair AV, Sandya C J, Moorthy S, Ramachandran P V. Role of PET-CT versus MRI in carcinoma breast: Which one is indicated for detecting the primary?.Indian J Cancer 2015;52:652-653


How to cite this URL:
Nair AV, Sandya C J, Moorthy S, Ramachandran P V. Role of PET-CT versus MRI in carcinoma breast: Which one is indicated for detecting the primary?. Indian J Cancer [serial online] 2015 [cited 2020 Aug 4 ];52:652-653
Available from: http://www.indianjcancer.com/text.asp?2015/52/4/652/178393


Full Text

Sir,

A 46-year-old woman presented with a left axillary swelling of 2 months duration. She has consulted a local hospital 2 weeks earlier, where a conventional mammography was done [Figure 1], which did not reveal any suspicious lesion. Biopsy of an enlarged axillary lymph node was done, which revealed metastatic adenocarcinoma, following which she was referred for further evaluation and management.{Figure 1}

Positron emission tomography-computed tomography (PET-CT) scan was done, which showed focal abnormal increased 2-(fluorine-18)fluoro-2-deoxy-D-glucose (FDG) uptake in discrete left axillary lymph node [standard uptake value (SUV) 4.3 max] suggestive of metabolically active left axillary lymph nodal metastasis [Figure 2], with no evidence of any other FDG avid lymph nodal or distant metastasis. No FDG avid possible site of primary malignancy could be detected in PET-CT survey.{Figure 2}

Magnetic resonance imaging (MRI) breast showed enhancing lesion measuring 2.5 × 1.8 cm in the lower outer quadrant of left breast (4 o' clock position) with irregular margins and type II enhancement curve on kinematic analysis, suggesting a primary breast malignancy [Figure 3]. The patient was subsequently taken up for modified radical mastectomy, and histopathology was reported as mixed ductolobular carcinoma, grade II with lymph nodes positive for malignancy.{Figure 3}

 Discussion



Breast cancer is the most common malignancy and the second leading cause of death in women in the western countries. Early detection and treatment still remains the main stay of reducing the mortality associated with breast cancer. Conventional mammography remains the screening modality for tumor detection in females aged more than 40 years [1] and ultrasonography for females younger than 40 years. PET-CT and MRI have been recently proposed for diagnosis and staging of patients with breast cancer.

Role of PET scan/PET-CT in detection of breast primary

Breast cancer detection requires the ability to demonstrate nonpalpable, small (<1.0 cm), invasive, in situ malignancies. These requirements are beyond the capability of current wholebody FDG-PET, and thus it is not used for primary breast cancer detection.[2]

FDG-PET is 88% sensitive and 80% specific for breast cancer with false-negative results in 12% of cancer cases.[3] FDG-PET of breast cancer typically do not reveal nonpalpable other imaging-detected cancers, which are the critical segment of the biopsy population. Currently, there is widespread agreement that wholebody FDG-PET does not have a clinical role in detecting primary breast cancer, nor is it an alternative to histologic sampling to establish or exclude primary breast cancer because of the well-documented inability of FDG-PET to consistently demonstrate small and low-grade lesions. However, PET-CT has been shown to be most helpful in staging recurrent or metastatic breast cancer and in evaluating the response of locally advanced and metastatic breast cancer to treatment.[4],[5],[6]

Overall accuracy, sensitivity, and specificity of single time point PET/CT for lesion greater than 10 mm were 77%, 75%, and 100%, respectively. For lesions smaller than 10 mm, single time point PET-CT showed an overall accuracy, sensitivity, and specificity of 55%, 31%, and 100%.[7] SUV threshold of 2.5 is regarded as the optimal threshold to differentiate benign from malignant tumors.[6] Most inflammatory lesions fall below this threshold, whereas most malignant lesions have SUV values that are greater than 2.5.

Role of MRI in detection of breast primary

The advantage of MRI for diagnostic evaluation of breast cancer include high soft tissue contrast, multiplanar sectioning that permits the acquisition of contiguous thin sections, enabling a full three-dimensional representation of one or both breasts, and the absence of ionizing radiation. Although, mammography is the basic screening modality, breast MRI is preferred for local staging of breast cancer. MRI allows most accurate delineation of size and local extent of cancer. MRI offers highest sensitivity for showing intraductal extension around invasive cancers.[8]

For lesions larger than 10 mm, MRI has a reported overall accuracy of 97%, with sensitivity and specificity of 100% and 67%, respectively. For lesions smaller than 10 mm, MRI has an overall reported accuracy of 90%, with sensitivity and specificity of 92% and 86%, respectively.[7]

 Conclusion



MRI as compared with PET-CT has an overall high accuracy, sensitivity, and specificity for detecting breast primary as well as nonpalpable lesions smaller than 10 mm.

PET-CT cannot be reliably used as a routine imaging procedure for patients with suspected breast cancer and cannot significantly reduce the necessity of invasive procedure in patients suspected with a breast primary.

References

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3Samson DJ, Flamm CR, Pisano ED, Aronson N. Should FDG PET be used to decide whether a patient with an abnormal mammogram or breast finding at physical examination should undergo biopsy? Acad Radiol 2002;9:773-83.
4Rosen EL, Eubank WB, Mankoff DA. FDG PET, PET/CT, and Breast cancer imaging. Radiographics 2007;27:S215-29.
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