Hello welcome back. This is the final section of this lecture and we're going to talk about the theory of oligometastasis and how treatment is supported by imaging. In an earlier lecture which was titled metastasis the real killer, we learned that in patients with cancer who die, it's usually the metastasis that kills them. This was shown in a five year survival table, which compared those with, and without metastasis. In every type of cancer those with metastasis had a significantly worse five year survival rate. However, interestingly, and historically, there have always been occasional reports of patients with limited metastatic cancer, who were treated and cured. In 1994 this was defined as a state of limited metastatic potential and it was termed oligometastasis. Since 1994 due to improved imaging techniques and novel treatment options, many patients have been designated as oligometastatic. Here we're going to talk a little bit about the biology of oligometastasis which is a theory. So therefore, we don't know exactly how it works, but we have proposed mechanisms. There is a spectrum In which metastasis occurs. And within that spectrum, it's believed that there is a place where metastasis is more laid back and not as aggressive. And that's oligometastasis. Here, I have a figure which was taken from an earlier lecture, which explained metastasis. But I've shown areas in the figure where perhaps the mechanism might be slightly different to explain this different type of metastasis. On the top right part of this figure you can kind of see the tumor which has formed the primary tumor and it's breaking through the basement membrane. You can see it's reaching down into the blood vessel. And in the earlier lecture we talked about how that happens because the conditions in the tumor become so harsh that cells begin to leak. What we think about oligometastasis is perhaps the conditions in the primary tumor aren't so bad. Some cancer cells have sloughed off and they're not that aggressive. So they're CTCs, circulating tumor cells, but they're not as aggressive. The second thing that might explain oligometastasis is that there are fewer sloughed off circulating tumor cells. They are less aggressive so less of them will survive in circulation. And then the third proposed mechanism is that in oligometastasis, when the circulating tumor cells do go to a new organ, they may find that the new organ is not very hospitable to them. So they're not able to really thrive as compared to the other form of metastasis where the organ is more receiving of the circulating tumor cell. And it allows it to become a disseminated tumor cell. As mentioned earlier, increasingly, more patients are being designated as being oligometastatic due to better imaging and more treatment options. So, this is very exciting in the clinic because it raises the possibility that maybe some more patients then we thought before with metastatic cancer can be curable. In the clinic, oligometastasis can be diagnosed during the regular staging that would be done with imaging. For example here we have if a patient were diagnosed with prostate cancer, they underwent the usual staging imaging to look for metastases in likely sites. On the right you'll see a scenario with a bone scan with two lesions. And then below it, its not shown, but the same person perhaps would have had a CAT scan with no lesions. That's in comparison to the far right where you see a scenario where the bone scan has many lesions and the CAT scan was reported to have many lesions. So the first scenario will be an example of a patient with oligometastatic disease. To conclude then, much work has to be done to better characterize oligometastatis on a molecular level, on the pre-clinical level, and in the clinic. However, imaging is playing a strong role in moving this theory into the clinic. That concludes our lecture on imaging on oncology. We've covered the basics of imaging, the different types of imaging. Why it's important on oncology and actually how imaging can be used in novel therapies in oncology or diagnoses that we're not even certain exist but that do exist theoretically. Finally, I would like to say I hope that you've learned from this or gleaned from this that fighting cancer is best fought with a very diverse team, everyone has something different to bring to the table. In this series that we've done, introduction to cancer biology, the group of us that have presented this are a physician and three scientists of various different backgrounds who ended up in Dr. lab and myself and there's practitioner. Certainly, we could've expanded on the series and improved upon it with other people on the team. [MUSIC]