In much the same way that the nonradioactive congeners allowed us to have a new dawn in medicine, the radiolabeled congeners have offered a similar kind of intervention. These targeted drugs can make a difference, not only from a diagnostic but also from a therapeutic standpoint.

We are now in a position to specifically localize tumors with this technology. For example, we can use the extracorporal approach of scintigraphy. Or we can look at the gamma pen, a more invasive way of localizing where somatostatin receptor-enriched tissue may lie at the time of exploratory laparotomy.

Now, for tumors that may not respond or take up the indium-111 pentetreotide, there's another radiolabeled somatostatin analog called depreotide, and this is another analog that sees a different spectrum of the five different subtypes of the somatostatin receptor. Today we can utilize this technology to better understand what we're seeing from a clinical standpoint. If we're not seeing all the tumor masses with the indium pentetreotide, then technetium-99 depreotide might allow us to see things a little bit differently.

Where are we headed in this line of treatment? We've clearly made an impact for patients who have failed somatostatin analogs, biotherapy and potentially hepatic artery chemoembolization and surgical approaches. We have made an impact in controlling symptoms with the higher doses of the indium pentetreotide. We have found that, if we do a good job controlling symptoms, then we've not only restored a better quality of life with our patients, but have likely also increased the quantity of life.

It's interesting that the insulinomas, particularly, are very sensitive to the radiolabeled somatostatin analogs. I see over the next few years that these drugs will be used sooner in the management of these patients, after we have used our biopsy techniques to establish the disease and done primary medical therapy. Rather than subject these people to aggressive surgical therapy, we'll be using the radiolabeled drugs sooner in disease management. However, in other neuroendocrine tumors, such as the carcinoids, that may be wildly metastatic, we're not quite at the point where we want to use the yttrium-90 drug or even the indium-111 drug for therapies during the first several years of disease management.

New drugs that are coming along would encompass other radio emitters-not only yttrium-90, but iridium-188 with the depreotide molecule is being looked at. There's also lutecium-177 when it's bound to the somatostatin congener. We've got new congeners and new isotopes coming along. I think over the next five or ten years we'll certainly have more things to offer these patients as our experience increases.

Lowell Anthony MD