New Treatments for Endometrial Cancer. Part 5
Now for disseminated disease, we have the small percentage of patients who present with primary stage IVb disease, which is 3% of the total, that is disease outside the pelvis and we also have those who recur after initial treatment. The mainstay of management here has been systemic therapy, either hormonal therapy or chemotherapy – and we want to look at each of these areas since these tend to be more the province for medical oncologists. Hormonal therapy has been looked at for gestational agents, the most common agents used, the antiestrogens have also been studied. Now let’s look first at the progestational agents. Now if you read any of the older gynecologic texts what you will see in there is that patients with advanced endometrial cancer do extremely well on progestins and you ought to put them on progestins and just forget about it, because they are going to do great. There’s a lot of mythology associated with progestins so let’s look at the mythology. The first part of the mythology is that the frequency of response to progestins in very high. Here is what the older literature shows. Roughly a 33-34% response rate to several different progestational agents. That’s not what I would call extremely high. But it’s not bad either. Here’s what the more recent studies have shown; response rates that range from 16-21%. These are much better documented studies with much clearer definitions of what constitutes a response. These last two here were done with oral medroxyprogesterone acetate by the gynecologic oncology group. You can see there are a large number of patients involved here, 625 to be exact, with response rates that range from 17-21%. So those numbers are fairly firm.
The second part of the mythology is that the duration of response as well as survival on progestins is often very low. These people do extremely well for decades. Let’s look at what the fact is here, and we are going to take a little more detailed look at this patient population’s makeup. If you look at patients who develop recurrent disease and receive progestational agents as treatment, what we find is that about 1:5 will have grade I disease, 36% will have grade II disease and roughly 43% will have grade III disease. Note that the response to progestins correlates with grade. Grade I patients have a 39% response rate, grade II 25%, grade III 10%. There’s a reason for that. Grade also correlates with the presence of receptors as it does in breast cancer. Grade I patients have a frequency of estrogen and progesterone receptor positivity of 84%. Grade II, 50%. Grade III, 25%. That mirrors the response rate. The response rate is about half of those numbers for each of those grades. There is also a clear correlation between receptor status and response. This shows you a summation of the world’s literature to date, only 134 patients reported with receptors; 62% response rate in those patients who were positive for estrogen and progesterone receptors, and 8% response rate to progestational agents in those who were negative for both receptors. So an excellent correlation, but in the largest group of patients – this is the GOG study here – while there is still a correlation, the response rate to progestins in the receptor positive group is only 44%, which is significantly less than what we see in the rest of these with much smaller numbers; 12% in those who were receptor negative.
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This looks at survival figures according to receptor status. Patients who are receptor positive have a median progression free survival of 8.5 months and overall survival of 13.5 months. Those who are receptor negative, 2.5 months progression free survival, 9.5 months overall survival. But as far as the contention that these patients live for a long time and have durable responses, overall four month progression free survival, 10.5 month overall survival, progestins aren’t as good as they have been said to be in the older literature.