Advanced breast cancer: diagnosis and treatment

The committee considered the evidence and their own experience on FDG PET-CT and contrast-enhanced CT (CECT) and agreed that both imaging methods can be suitable for detecting distant metastases in most people with suspected advanced breast cancer (including people with and without a previous diagnosis of breast cancer). Moderate to very low certainty evidence suggested that both FDG PET-CT and CECT have high specificity, meaning they are reliable for ruling in distant metastases. FDG PET-CT may also have high sensitivity, with fewer missed cases of distant metastases, while CECT may have slightly lower sensitivity, potentially missing more cases. The committee discussed the importance of clinical judgement in deciding between FDG PET-CT and CECT, including about whether the possible additional sensitivity of FDG PET-CT is likely to be useful, or whether CECT is likely to be sufficient.

The committee noted that, in practice, the same type of scan is usually used for diagnosis and monitoring. Health economic modelling results suggested that FDG PET-CT, while more expensive than CECT, was cost effective when used for both diagnosis and monitoring because of this higher level of diagnostic accuracy. Although the tracer used for an FDG PET-CT involves radiation, radiation exposure was considered similar for both tests, and the committee acknowledged ongoing efforts to reduce dose levels.

The committee noted that CECT is currently the most commonly used imaging test for diagnosing distant breast cancer metastases and is widely available. FDG PET-CT is not available in all areas, making it less easily accessible for many people. While the committee agreed people should not be denied the opportunity to access FDG PET-CT imaging, they recognised it may not be suitable for all as someone may not wish to, or be able to, travel to other centres to access it. In addition, there may not currently be capacity in the system (based on the availability of machines and radiologists to interpret the scans) for large numbers of people to access FDG PET-CT without increasing their waiting time, and in doing so potentially delaying diagnosis. For these reasons, the committee agreed that either CECT of the chest, abdomen and pelvis or FDG PET-CT can be used to diagnose the presence and extent of distant metastases.

The committee were aware that FDG PET-CT may be unsuitable or less useful for detecting metastases of certain types of breast cancer. Lobular breast cancer can be more difficult to detect on imaging than other types of breast cancer, and some lobular or low-grade breast cancers may not take up the tracer used in FDG PET-CT very well, making scans harder to interpret. The committee noted that information about grade and cancer type may not always be available before scans to diagnose distant metastases, and clinical judgement is needed when deciding whether to offer additional imaging, and what type of imaging that should be.

There was a small amount of evidence about the diagnostic accuracy of FDG PET-CT for people with lobular breast cancer, which showed the diagnostic accuracy was poor compared to those for people with non-lobular breast cancer. Despite the lack of diagnostic accuracy evidence for CECT for people with lobular breast cancer, the committee agreed that, in their experience, the accuracy is likely to be similar to FDG PET-CT. Because of the lack of evidence, the committee made a recommendation for research to investigate imaging modalities for diagnosing distant metastases in this group.

Alternate imaging options from the previous version of the guideline were retained and listed to address situations where there is uncertainty after the initial imaging or where further characterisation is needed (for example, to look for bone metastases using bone scintigraphy or to assess the risk of bone fractures).

The committee were aware of detailed guidance relating to the diagnosis of brain metastases and spinal cord metastases in other NICE guidance, and included cross references to this content.

Full details of the evidence and the committee's discussion are in evidence review B: FDG PET-CT and contrast-enhanced CT for diagnosing and monitoring distant metastases.

There was no direct evidence on the effects of using CECT or FDG PET-CT to monitor disease status in people with advanced breast cancer. However, based on their experience, the committee agreed that these scans are likely to perform similarly for monitoring as they do for diagnosing distant metastases. They therefore considered the evidence on diagnosing distant metastases, as well as their own experience and the results of the economic model, when making these recommendations.

The economic model showed that, regardless of whether CECT or FDG PET-CT was used for diagnostic imaging, using FDG PET-CT for monitoring would be the most cost-effective modality. However, there was significant uncertainty around this result given the lack of identified evidence for diagnostic test accuracy in monitoring and its impact on treatment choices and health outcomes. Consequently, the committee opted against recommending one imaging modality in preference to the other for monitoring.

Based on their experience, the committee noted that using the same type of scan for both diagnosis and monitoring helps clinicians interpret changes more accurately and make clearer decisions about treatment. Differences in scan type could make it harder to tell whether any changes are from treatment, or just differences in imaging. However, they agreed that clinical judgement should be used to decide on imaging modality for monitoring based on what specific clinical question is being asked of the scan: for example, whether the clinician is aiming to identify changes to specific areas only, and how clearly these areas were visible on earlier imaging.

Full details of the evidence and the committee's discussion are in evidence review B: FDG PET-CT and contrast- enhanced CT for diagnosing and monitoring distant metastases.