IR JUNIORS | The Future of Interventional Radiology
Precision Medicine & Interventional Radiology
By Dr Sagar Kulkarni
Precision or personalised medicine is an approach to healthcare that is driven by a patient’s unique characteristics, such as their genetics or environment. It is best understood by looking at one of the first examples of precision medicine, trastuzumab (also known as Herceptin), in the treatment of breast cancer.(1) Some patients with breast cancer over-express the protein HER2; trastuzumab, a monoclonal antibody, binds to HER2 in patients who express it to limit the spread of the cancer. As such, trastuzumab is a targeted therapy and demonstrates the basic idea of precision medicine. Other successes of precision medicine in oncology include imatinib for chronic myeloid leukaemia and rituximab for non-Hodgkin’s lymphoma.(1)
Interventional radiology (IR) will likely have a stake in precision medicine in the future. Randazzo et al.(2) identified three areas where IR could be more personalised: microbiological sampling of abscess cavities, molecular imaging-guided biopsies and metabolic imaging to assess tumour heterogeneity.
Microbiological Correlation in Lung Abscess Drainage
Lung abscesses (figure 1) are an infective cavitary process that can progress to critical illness and death without proper treatment. Frequently, blood and sputum culture are negative, and broad-spectrum antibiotic therapy fails. Duncan et al.(3) showed that lung abscesses produce positive blood cultures in zero (0%) cases and only 21% of cases were positive for sputum cultures. In contrast, cultures taken from IR percutaneous lung abscess catheter drainage of the abscess cavity isolated the causative organism in 95% of cases. As well as providing drainage of the abscess, isolating the organism enables targeted antimicrobial treatment to be delivered to combat the infection.
Figure 1: CT scan showing a left-sided lung abscess. Credit: Case courtesy of Dr Ahmed Abdrabou, Radiopaedia.org, rID: 24443
Intra-Procedural Molecular Imaging for Image-Guided Biopsies
Molecular imaging involves tagging particular molecules so that they show up on imaging. The most common molecular imaging technique is PET-CT, which tags glucose molecules to highlight tissues with high metabolic activity. This can highlight cancerous tumours, or within a tumour itself can highlight the most metabolically active portion. In some centres, during CT-guided biopsy of a tumour, the pre-procedural PET-CT image is overlaid onto the intra-procedural CT image (4). The operator can then focus on the most metabolically active part of the tumour to improve the yield of biopsy samples. A truly real-time PET-CT scanner (figure 2) also exists in the IR department of Memorial Sloan Kettering Cancer Center in New York City (5).
Figure 2: Non-contrast CT image of the liver (left). Intra-procedural PET-CT image showing an area of high radiotracer uptake for biopsy (right). Credit: Dr Stephen Solomon, MD, Memorial Sloan Kettering Cancer Center
Advanced MRI to Assess Tumour Heterogeneity
As cancer biology advances, there is now broad understanding that tumours are heterogenous; rather than being one homogenous mass of cells, a tumour is a collection of cells that have accumulated a cascade of mutations. As such, different lineages of cells within a tumour contain different mutations and may react differently to anti-cancer treatment. An emerging field, radiomics, attempts to capture this heterogeneity (and many other features) using imaging, most commonly MRI and MR spectroscopy (6). Although it is still experimental, in the future the technology could be used to direct the interventional radiologist to take multiple biopsies of different cell populations within the tumour, thus gaining information on the full gamut of oncogenic mutations that the patient possesses (7). Doing so would enable better delineation of targeted treatment and prognostication.
Conclusion
Whilst much of the technology is still experimental, precision IR shows great promise. The precision medicine global market is expected to grow to USD $738.8 billion by 2030.(8) Due to its presence in oncology, IR will likely be part of this development.
References
1. Issa AM. Personalized Medicine and the Practice of Medicine in the 21st Century. McGill J Med MJM. 2007;10(1):53. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2323540/
2. Randazzo W, Gade T, Nadolski G, Hunt S. The interventional radiologist’s role in precision medicine. J Vasc Interv Radiol. 2016 Mar 1;27(3):S217. Available from: http://www.jvir.org/article/S105104431501814X/fulltext
3. Duncan C, Nadolski GJ, Gade T, Hunt S. Understanding the Lung Abscess Microbiome: Outcomes of Percutaneous Lung Parenchymal Abscess Drainage with Microbiologic Correlation. Cardiovasc Intervent Radiol. 2017 Jun 1;40(6):902–6.
4. Tam AL, Lim HJ, Wistuba II, Tamrazi A, Kuo MD, Ziv E, et al. Image-Guided Biopsy in the Era of Personalized Cancer Care: Proceedings from the Society of Interventional Radiology Research Consensus Panel. J Vasc Interv Radiol. 2016 Jan 1;27(1):8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5056791/
5. Solomon SB, Cornelis F. Interventional Molecular Imaging. J Nucl Med. 2016 Apr 1;57(4):493. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5484794/
6. Lin G, Keshari KR, Park JM. Cancer Metabolism and Tumor Heterogeneity: Imaging Perspectives Using MR Imaging and Spectroscopy. Contrast Media Mol Imaging. 2017;2017. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5654284/
7. Abi-Jaoudeh N, Duffy AG, Greten TF, Kohn EC, Clark TWI, Wood BJ. Personalized Oncology in Interventional Radiology. J Vasc Interv Radiol. 2013 Aug;24(8):1083. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3742380/
8. Prescient & Strategic Intelligence. Precision Medicine Market Research Report [Internet]. 2021 Mar. Available from: https://www.psmarketresearch.com/market-analysis/precision-medicine-market-outlook