Dr. Tanya Dorff is a medical oncologist who serves as associate clinical professor in the Department of Medical Oncology & Therapeutics Research and the Head of the Genitourinary Cancers Program at City of Hope, a research and treatment center for cancer based in Duarte, California.
Dr. Dorff’s research interests in prostate cancer range from clinical trials in PSA-recurrent prostate cancer to the role of fasting in chemotherapy tolerability to CAR T cells that are primed to target prostate cancer tissue.
She leads one of the largest clinical trial portfolios in genitourinary cancers.
Dr. Dorff spoke with Prostatepedia about chemotherapy for prostate cancer.
Why did you become a doctor?
Dr. Tanya Dorff: When I was around three years old, I decided that what I wanted to do with my life was help people. And being a concrete thinker as a three-year-old, I felt like being a doctor was the only way to do that.
Have you had any patients over the years who have changed how you view the art of medicine or how you view your own role?
Dr. Dorff: There are so many who have influenced me. My mom had a rare form of leukemia when I was in college. It was uniformly fatal. But they had recently developed a new treatment with the discovery of a specific translocation of the retinoic acid receptor for acute promyelocytic leukemia (APL). All-trans retinoic acid was developed, and she received it as experimental (at the time) through compassionate access. She was cured, and she’s still alive today. That influences how I feel about clinical trials and translational science. If we hadn’t understood that biology, we couldn’t have designed the overwhelmingly effective treatment.
How is chemotherapy used today for men with prostate cancer?
Dr. Dorff: When I started treating prostate cancer, chemo was pretty much our only tool besides standard hormone therapy. It worked, but it was sort of end-of-the-line. People didn’t tolerate it very well, in part, because we used it in really advanced cases. Then, the drugs like Zytiga (abiraterone) and Xtandi (enzalutamide) came out, dramatically improved the situation for prostate cancer patients, and chemotherapy got pushed later and later.
The CHAARTED study was presented five years ago. That study showed that using chemotherapy early with the initiation of hormone therapy dramatically improved survival, above and beyond using it later. About 75% of the patients on the control arm got the chemo when they became resistant, so it was a pretty good experiment of now versus later, and not now versus never. To see that just using it early added an extra year or more of life for these men was really profound. That reinforced the strong role chemotherapy has in this disease.
With which other kinds of agents is chemotherapy frequently combined?
Dr. Dorff: Combinations with Taxotere (docetaxel) have never yet been successful in prostate cancer. There was Taxotere (docetaxel) with a high-dose Vitamin D, which was not only negative in that it failed to improve outcomes, but patients who received the combination actually fared worse. There was Taxotere (docetaxel) with Revlimid (lenalidomide), Taxotere (docetaxel) with atrasentan, Taxotere (docetaxel) with GVAX… All of these combinations have failed.
One of the ASCO presentations that prostate cancer physicians might remember most vividly is a slide presented by David Quinn in his presentation of the negative results of the SWOG S0421, the study of Taxotere (docetaxel) alone or with atrasentan. He showed a slide of a graveyard, implying that any drug tried in combination with Taxotere (docetaxel) is doomed to fail.
Why do you think that is? Is it just that the combination is too toxic?
Dr. Dorff: I don’t know. I don’t think it’s too toxic. All of these combinations go through safety before they go into Phase III, and you can combine them safely. I do not understand why combinations fail. Maybe it goes back to biology. Why would the combination succeed? You want something that makes the chemo work better, or you want the chemo to make the drug work better. That’s where we should probably start when planning combination studies. Even then, things that look good in early testing can fail in Phase III, so in some cases it may be that we need to sub-classify patients in order to design more successful trials.
Maybe a more interesting question when we’re talking about combinations is: how do we get the best use of the chemo and do the least damage to the patients?
At University of Southern California, we started a study looking at a fasting-mimic diet to make the Taxotere (docetaxel) better. We found preliminary evidence that fasting prior to chemotherapy reduced toxicity, and I envision that could have two specific benefits in men with prostate cancer who might get Taxotere (docetaxel).
One might be that if we could mitigate toxicity, more men would actually receive it. There was a lot of therapeutic nihilism out in the community about how chemotherapy doesn’t work so well for prostate cancer, or that these older patients can’t handle it. If we could ratchet down the toxicity, maybe more prostate cancer patients would actually get chemo.
The second benefit might be that if we could reduce toxicity to normal host cells, we would be more likely to get in full doses on time, which might make it work better against the cancer versus what happens now, which is that we frequently dose-reduce and dose-delay because of toxicities. The fasting-mimic diet study is still ongoing but these are the outcomes I was hoping for when designing it.
How long are they fasting before they start the chemo? What does that look like?
Dr. Dorff: They fast for 48 hours on a fasting mimic diet, which means they get vegetable broth and an energy drink. So, it’s a liquid, low calorie diet. It’s hard, so that’s part of why the study is still ongoing.
In our earlier trial, in which we did fasting with platinum chemo for up to 72 hours (48 before and 24 after the chemo dose), people really swore by it. They really felt like they had so much less toxicity compared to chemo cycles in which they didn’t fast.
With the fasting mimic diet (created by L-Nutra), because it’s not pure fasting, we extended it to three days before chemo. The first day is a fairly robust number of calories, just plant based and with specific amino acids left out, which is felt to be part of the effect. Then there’s the two days before chemo with lower calories, and one day after. After fasting or the fasting-mimic diet the body needs a bridging diet for the first meal, and the L-Nutra regimen also included supplements to replenish the body.
If someone reading this is interested in participating, can they contact you directly or should they contact someone else?
Dr. Dorff: Sure, they can contact me directly at firstname.lastname@example.org. But the trial is going on only at USC, so they may wish to contact the clinical trials office at USC or the medical oncology group at USC.
Are you combining diet with chemo instead of another agent?
Dr. Dorff: Yes.
What kinds of side effects can patients expect from chemotherapy? What are you hoping to reduce?
Dr. Dorff: One of the most concerning side effects is the peripheral neuropathy, which can become permanent, but I don’t want to scare any readers.
Can you explain what that is?
Dr. Dorff: It’s damage to the small nerves out in the fingers and toes that can manifest as numbness or pins and needles, burning kinds of discomfort. That can be permanent.
Is there anything patients can do before or during getting chemo to reduce the likelihood of that happening?
Dr. Dorff: Not that we know of.
There’s no way to predict who might suffer from that or not?
Dr. Dorff: It’s not a complete no. We know patients who already have some preexisting neuropathy, whose nerves are already damaged, are more susceptible, for instance patients with diabetic nerve damage. That’s one reason we might try to get them Jevtana (cabazitaxel) instead of Taxotere (docetaxel) because Jevtana (cabazitaxel) doesn’t impact the nerves in the same way. I’m not sure if that’s what patients worry about, but that’s one of my number one concerns because I’ve seen patients a few years after chemo who are still vexed by the neuropathy.
If Jevtana (cabazitaxel) doesn’t result in neuropathy, why wouldn’t you use that agent over Taxotere (docetaxel)?
Dr. Dorff: Because insurance typically won’t cover it. Head-to-head, they were compared in the FIRSTANA trial, and they were equally effective; one wasn’t much better than the other. So, insurance companies can say that Jevtana (cabazitaxel) is not more effective; it’s equally effective. Taxotere (docetaxel) is a fraction of the price because it’s off-patent, and Jevtana (cabazitaxel) is actually approved specifically in post-Taxotere (docetaxel) patients, so it’s off-label to use it first-line. You can make a case when you have a guy with neuropathy, but even if you have a guy without neuropathy, you sure would like to leave him without neuropathy at the end of his treatment.
We start to see the neuropathy around dose five. If you stop, it’s more reversible, but if you keep going, that’s where it can become permanent, and so again, when we’re getting to how we can enhance the efficacy, if we could get more doses in without being limited by neuropathy, maybe we would do better with the drug, or maybe we just avoid the neuropathy, have equal efficacy and patients suffer less. There’s two ways we can win.
Equal efficacy and side effects are a huge issue for men.
Dr. Dorff: Patients really worry about hair loss. I don’t think we’re impacting that with the diet, unfortunately. That is reversible. They also complain about the taste changes and mouth sensitivity because that really impacts eating.
Does that go away once chemotherapy is finished, or does that linger after?
Dr. Dorff: That goes away.
It’s just while they’re getting chemo that they lose sense of taste?
Dr. Dorff: Yes, but it’s a long time to not be able to taste.
And the hair loss only happens while they’re getting chemo, too? It comes back?
Dr. Dorff: Yes, it grows back.
What combinations with Taxotere (docetaxel) do you think will work best?
Dr. Dorff: The ongoing combinations that I think people are still interested in are platinum with taxane and carboplatin with Jevtana (cabazitaxel). That’s an important combination for the more aggressive variants.
Part of how we think Taxotere (docetaxel) chemotherapy works is that it interferes with antigen receptor (AR) translocation in the cell to the nucleus, because the microtubules are needed for that. It still may be more for patients whose cancer is using a lot of AR signaling whereas platinum is more for cancer that might not be as dependent on that mechanism. That combination is pretty important.
There are some other biologics being studied together with Taxotere (docetaxel), but I’m not sure that those will be successful. There’s Taxotere (docetaxel) with immunotherapy, but we have the negative GVAX trial that tried combining vaccines with Taxotere (docetaxel). We are also combining it with Xofigo (radium-223), which is a little interesting, but I don’t know why those agents would necessarily help each other. Again, when you’re looking at a combination, it’d be nice if there were a reason to expect synergy.
What about favorite sequences?
Dr. Dorff: We know that after you’ve had Zytiga (abiraterone) or Xtandi (enzalutamide), you can induce the androgen receptor splice variants such as AR-V7. These are associated with less responsiveness to Zytiga (abiraterone) or Xtandi (enzalutamide). Patients might want to go from Zytiga (abiraterone) straight to Xtandi (enzalutamide), but we know there’s a lower likelihood of success, and we know AR-V7 is a big part of that. If we sequence in chemo, since they’ve shown that AR-V7 positive patients still benefit from chemo, I view the optimal sequence as Zytiga (abiraterone) or Xtandi (enzalutamide), followed by wiping out the AR-V7 population with a chemo drug, and then going to Zytiga (abiraterone) or Xtandi (enzalutamide) next. We don’t know for sure if that’s what happens when we use that type of sandwich approach, but it has theoretical appeal, and that’s how I talk to patients about it. The other way to go is a clinical trial, especially for combination with Zytiga (abiraterone) or Xtandi (enzalutamide).
What about the side effects profile when you do those kinds of sequencing?
Dr. Dorff: Hormone drugs like Zytiga (abiraterone) and Xtandi (enzalutamide) have much better side effect profiles, generally speaking, but the chemo side effects are largely reversible, and we tell patients that it’s not forever. There are good days and bad days, so it’s important to note that most people are not feeling bad every single day that they’re on the chemo. I don’t think the side effects vary based on sequence.
Some of my colleagues feel that when they use chemotherapy up front like in the CHAARTED study, they see more side effects if they start the chemo right away, but they see fewer side effects if they wait a month or two into the hormone therapy to add the chemo.
Is that because the patients become used to the side effects and learn how to manage them before you add something else?
Dr. Dorff: No, because the side effects are totally different between the two treatments. This is speculative, but I think you debulk. I think that part of the reason people get a lot of chemo side effects is that when we’re killing a lot of cancer there’s a big inflammatory reaction. You can feel sick from it, and we see that anecdotally in certain patients. If you can debulk the cancer a little bit with a couple months of hormone therapy, and then give the chemo, it might be better tolerated.
That’s interesting. So as the cancer’s dying, it throws off some kind of signal?
Dr. Dorff: It does. There’s a lot of dead stuff that has to be cleared by the body, and maybe that means it doesn’t have as much attention to do the healing that it needs to do with the chemo. I don’t know; that’s purely speculation.
Is there anything else you think men should know about chemotherapy for prostate cancer?
Dr. Dorff: First and foremost, chemo is effective. People downplay the role but CHAARTED really showed us that this is a good tool. We are working on tools that have fewer side effects. I’m working on whether diet can help mitigate side effects, and other people are looking at things like exercise, but the bottom line is that chemo is a good tool.
But still some patients draw a line in the sand and say they’ll never receive chemo because they’ve seen other patients getting chemo for other cancers. The chemo we use for other cancers is different than what we use for prostate, and every person’s reaction to chemo is different. Of course, you can’t erase that impression that’s made on you when you see someone who you care about struggling through chemo, but it doesn’t mean that’s what your experience is going to be.
Your doctor’s job, and your oncologist’s job, is to make it livable, to allow you to still do the things you want to do and to keep you safe and healthy through your chemo. There are tricks up our sleeves that we use to make that happen.
Sometimes patients are surprised to hear that they can actually feel better on chemo.
Why would that be?
Dr. Dorff: Because sometimes the cancer’s driving their side effects. It’s a catch-22. There are patients who might want to wait until they’re feeling better to get chemo, but if they’re feeling bad from the cancer, it’s really the chemo that’s going to make them feel better.
I have patients who’ve been unable to eat, in too much pain to really get out and do anything, and when they start chemo, they feel better, they eat better, they have more energy, and they can do more. If you take someone with no cancer symptoms, sure, the chemo’s going to make them feel worse. But if you take somebody with cancer symptoms, they may actually feel better.
That’s interesting because there’s this whole cultural perception of chemo as being catastrophic. The idea that chemo would make you feel better seems bizarre, but it makes sense the way you explain it.
Dr. Dorff: Yes, I think a lot of patients are shocked to hear it, and I think that’s a good thing to put out there.
Do you have any suggestions for men as to how to handle side effects before going into it?
Dr. Dorff: Communication with your doctor is the way to be successful in your chemo. A lot of people don’t want to bother the doctor, or they want to tough it out, but the earlier they tell the doctor that there’s a side effect, the easier it is for the doctor to intervene and reverse it. There’s no medal at the end of chemo for not having had to take a treatment for a side effect or not having called the doctor. Just pick up the phone and call. That’s how your doctor can do their best by you, and how you can be most successful with your treatment.
Aside from that, staying active is really important. Getting out and walking, even if you’re not exercising per se, but just moving around and not being sedentary is important for circulating the blood. We don’t want you to get a blood clot during chemotherapy because you’re not moving. It helps you expand your lungs, so maybe it can help keep your respiratory tract and heart healthier. Go into chemo as fit as possible, and try to maintain activity and mobility during treatment.