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Since its opening in July, 2004, the New City Osaki Clinic has been providing “highly active NK (natural killer) cell therapy” to more than 800 cancer patients. The most frequent type of cancer was pancreatic cancer, followed by lung cancer, colorectal cancer, gastric cancer, and hepatoma.
It is very exciting to see cancer shrinking or disappearing during the treatment. One of the evaluation methods for the therapeutic efficacy of anticancer agents is the method according to the RECIST guideline, which is recognized worldwide. This guideline focuses on the change in size of cancer and has the advantage of being able to rate the efficacy in a short time in the form of response rates. It is generally considered, however, that “overall survival time” or “survival rate” rather than a change in the size of cancer should be examined in order to precisely evaluate the therapeutic efficacy. At our clinic, we believe that the most important criterion for efficacy is how long patients can live in a good condition with cancer.
Among many types of cancer, pancreatic cancer is known to have an especially low five-year survival rate worldwide (see “International comparison of cancer survival rate by site” on the website of the National Cancer Center).
Pancreatic cancer is indeed considered to be the most difficult to treat. We think that, if we examine the efficacy of highly active NK cell therapy of the New City Osaki Clinic for the treatment of pancreatic cancer, we would be able to speculate the efficacy for other types of cancer.
Not the shrinking of cancer, but survival time (that is to say, how much the therapy prolonged life) most precisely represents the therapeutic efficacy for cancer. Therefore, we followed up 27 patients with pancreatic cancer who received immune therapy at least four times at our clinic and examined the survival time from the time of diagnosis of pancreatic cancer to the present. Let’s compare the results with the published data on the treatment of pancreatic cancer only with anticancer agents.
In general, when we look at survival time, we often use the median survival time (how long half of the patients survived after the start of treatment), but here we will review a one-year survival rate (the proportion of patients who survived for a year after the start of treatment), which is relatively easy to understand.
Clinical studies of anticancer agents are conducted in patients with inoperable locally advanced or metastatic cancer in good overall condition—those who can perform light work (PS 0-1), for example. This is because, if patients have to lie down and rest occasionally and it is difficult to even go out for shopping (PS 2-3), the side effects and other factors would affect the treatment outcome.
(*PS = performance status, staging of general condition)
“Gemzar (name of the compound: gemcitabine)” was launched for the treatment of pancreatic cancer for which not many anticancer agents before this agent were effective. The efficacy of Gemzar in prolonging survival and alleviating pain was demonstrated in clinical studies and this agent became the world’s first anticancer agent for pancreatic cancer.
The one-year survival rate in the treatment with Gemzar is still as low, however, at around 20%. The high efficacy of the combination of Gemzar and Tarceva (name of the compound: erlotinib) attracted attention in 2006 as it was shown to increase the one-year survival rate to 24% compared with 17% in treatment with Gemzar alone, but in terms of the median survival time, the improvement was only by two weeks.
In Japan, TS-1 was approved and began to be used as the second anticancer agent for the treatment of pancreatic cancer. Its efficacy was reported to be equivalent or superior to that of Gemzar. Currently, a clinical study on the simultaneous use of Gemzar and TS-1 is underway.
As shown in the above graph, according to the reports from the National Cancer Center, which is a representative hospital specializing in cancer in Japan, and from overseas, the one-year survival rate of patients with pancreatic cancer ranges from 20% to 30%. This rate is still not satisfactory compared with the rates for other types of cancer.
Please look at the survival time of the patients with pancreatic cancer who received highly active NK cell therapy at least four times (27 patients). (Patients who received this therapy for three times or less are not included because it is difficult to evaluate the efficacy if the number of dosing is too small.)
We recommended simultaneous use of anticancer agents, which is expected to produce synergistic effect, and therefore, about 80% of the patients concomitantly used anticancer agents.
The one-year survival rate in these 27 patients was 63%. As shown in the graph, the treatment outcome was two or three times better than that of the treatment with only anticancer agents, indicating a synergistic effect in the combined use. The general condition of 12 of these patients was already poor, rated as PS 2-3, at the start of the treatment, so this result was obtained under worse conditions than those of the above-mentioned clinical studies on anticancer agents.
Even if we exclude the eight patients whose pancreas had been removed (who came to our clinic for the treatment of recurrence or distant metastasis after resection) and examine the remaining 19 patients whose pancreas was unresectable (because the rate after resection of the pancreas is known to be as high as 50 to 70%), our therapy turns out to be effective, having a one-year survival rate of 58%. In addition, the one-year survival rate of patients with distant metastasis and those with relatively poor general condition rated as PS 2-3 is 63% and 58%, respectively. These data demonstrate that we can expect a substantial increase in the one-year survival rate in the combined use of anticancer agents and highly active NK cell therapy over the treatment with anticancer agents alone, even in patients with advanced metastatic cancer, or those with relatively poor general condition, who have to lie down and rest occasionally.
These results indicate a marked extension of survival when compared with the median survival time in the current treatment in general, which is around ten months. When we examined the immunity of these patients over time, it was characterized by an early several-fold increase in the NK cell count, NK activity, and NKG2D-positive lymphocyte count resulting from repeated highly active NK cell therapy and long-term maintenance of such increase. Thus, the therapy which makes the best use of the “quantity and quality” of the administered NK cells proved successful.
Pancreatic cancer progresses rapidly, and it is one of the most difficult-to-treat cancers. However, combined use of anticancer agents and highly active NK cell therapy has an efficacy that cannot be obtained in the treatment with anticancer agents alone. It should now be clear that major enhancement of the body’s immunity and its maintenance are crucial components of cancer treatment.