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The Significance Of Incidental Findings On PET-CT
Poster Title: The Significance Of Incidental Findings On PET-CT
Submitted on 30 Oct 2020
Author(s): Dr. Ahmed Daud Khan, Dr. Abdulbasit Dhedhi, Dr. Asaad Osman, Dr. Yvette Griffin
Affiliations: University Hospitals of Leicester, Leicester Royal Infirmary, UK
Poster Views: 157
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Poster Information
Abstract: PET-CT is an integral part of oncological imaging as it offers increased accuracy in the diagnosis, staging and surveillance of many cancers.

In addition to cancer, FDG uptake can be encountered in a wide array of benign processes. As a result, radiologists frequently encounter indeterminate metabolic findings on these complex whole-body examinations.

Patients with a primary malignancy have a high rate of secondary malignancy compared to the general population. Dong et al found that 8.5% of 633,964 patients developed 2nd cancers during follow-up2.

Overall prevalence of incidental clinically significant lesions of malignant or premalignant pathology on FDG PET-CT is between 1.2-2.0%3.

Thus, it can be very challenging to determine the importance of incidental metabolic findings found on PET-CTs. Ideally, further evaluation of PET-CT incidentalomas should be an MDT decision. The potential clinical risk posed by these incidentomas should be balanced against the risks of investigation, patient’s comorbidity and overall life expectancy4.


1) 100% follow up for incidentalomas (unless reason given not to do so in MDT review code)
2) 100% follow up investigation within 3 months.


Data was collected retrospectively from 01/07/2019 – 19/08/2019 using PET-CT reports, PACS, CRIS and ICE. The first 50 consecutive patients, which were found to have incidentalomas on their FDG PET-CTs were reviewed.

Data collected:
Patient demographics (age, sex, hospital number).
Date and indication for PET-CT.
The nature of the incidentaloma.
If the incidentaloma or the follow up investigation was discussed at MDT.
If there was a follow up investigation.
The nature and modality of the investigation.
The date the investigation was performed and if it was within a 3 month time period.
The findings of the follow up investigation.


Total of 322 patients/scans reviewed.
- Total number of incidentalomas 57/322 – 17%
- 50 patients with incidentalomas (50/322) – 15.5%
- 19 female patients with incidentalomas
- 31 male
- Age range 30-85. Mean age 68
- 7 patients had more than one incidentaloma (max 3)

Follow up of incidentalomas:
- Total followed up 20/50 patients (40%)
- Total followed up within 3 months - 17/50 (34%)
- Those that were followed up and had imaging/investigation within 3 months - 17/20 (85%)
- Those that were followed up but imaging/investigation outside of 3 months - 3/20 (15%)
- Patients not followed up at all - 30/50 (60%)
- Had MDT review - 23/50 (46%)
- No mention of incidentaloma in MDT documentation - 27/50 (54%)
- Only 1 mention of mitigating certain circumstance to not have further imaging (frail patient not fit for any further intervention).
- Confirmed malignancy of incidentaloma - 4/50 (8%)
o RWES0137391 – Metastaic liver lesion
o RWES2021078 – Adenocarcinoma of the rectum.
o RWES0269150 – Prostate
o RWES2289277 – Hard palate sarcoma

- 4/322 PET-CT scans with incidental confirmed malignancies. (1.2% 2nd malignancy pick up rate – in keeping with the literature).
- 4/20 (20%) – Those that were followed up and were proven to be malignant.
- 16/20 (80%) – those that were followed up but were likely or proven benign.

Conclusion and Recommendations

Our results show that the current practice is well below the standard regarding timely follow up investigations for incidentalomas. Of the 20 scans with incidentalomas that were followed up, 16 were either likely or proven to be benign. Thus showing that there is a high rate of overcalling non-significant findings on PET-CT. Of the 50 scans with incidental findings, less than half were discussed in a formal MDT setting. This is likely to contribute to the poor compliance with follow up imaging. Therefore we mandate that all incidentalomas are reviewed at MDT meetings with decisions regarding follow up imaging clearly documented. Given that 4 out of the 20 followed up incidentalomas were proven to be malignant, we also mandate that follow investigations be performed within a 3 month period.
Summary: An incidentaloma is the term ascribed for incidentally found asymptomatic tumors.
The aim of this audit is to review the follow up and nature of unexpected incidental FDG-avid lesions on PET-CT.
References: 1. Chojniak R. Incidentalomas: managing risks. Radiol Bras. 2015;48(4):IX-X. doi:10.1590/0100-3984.2015.48.4e3
2. Dong, Chuanhui & Hemminki, Kari. (2001). Second primary neoplasms in 633,964 cancer patients in Sweden, 1958–1996. International Journal of Cancer. 93. 155 - 161. 10.1002/ijc.1317.
3. Ishimori T, Patel PV, Wahl RL. Detection of unexpected additional primary malignancies with PET/CT. JNM 2005;46(5):752-757
4. Liu Y, Ghesani NV, Zuckier LS. Physiology and pathophysiology of incidental findings detected on FDG PET scintigraphy. Semin Nucl Med 2010; 40:294-315.
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