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Switching from One Chemo Drug to Another

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Dr. Emmanuel Antonarakis is an Associate Professor of Oncology and Urology at the Johns Hopkins University Sidney Kimmel Comprehensive Cancer Center.

Prostatepedia spoke with him recently about his work on the benefit of switching men from Taxotere (docetaxel) to Jevtana (cabazitaxel)— or vice versa—if his PSA doesn’t go down by 30% in the first twelve weeks of treatment.

You’ve published a paper on switching patients from Taxotere (docetaxel) to Jevtana (cabazitaxel) and vice versa. What is the thinking behind switching chemotherapeutic agents? Why would you want to switch agents earlier as opposed to when the first chemotherapy drug stops working?

Dr. Emmanuel Antonarakis: The motivation behind this paper was that the FDA-approved recommended dosing schedule for both Taxotere (docetaxel) and Jevtana (cabazitaxel) is a course of ten doses, given three weeks apart. When patients begin FDA-approved Taxotere (docetaxel) or FDA approved Jevtana (cabazitaxel), they’re often told by their oncologists that they should expect to receive this chemotherapy once every three weeks for up to ten doses. A patient may not receive ten doses or might stop the therapy before he reaches ten doses because he cannot tolerate the therapy and has unmanageable side effects, or his cancer begins to progress before he ever get to dose number ten. If his PSA begins to increase again at dose six or seven or the tumors begin to grow again, his oncologist might ask him to stop chemotherapy.

We then wondered whether the ten doses was a reasonable time to wait or whether there could be an early indicator, or an early sign, of therapy resistance or therapy futility without having to go through six, seven, eight, nine or ten doses.

The idea that we had was to test an early intermediate marker of sensitivity or resistance to the chemotherapy. The best marker of early sensitivity or resistance that we could think of was whether or not a patient had a 30% PSA drop within the first four cycles of therapy. As you recall, if the therapy is given once every three weeks, four cycles basically means 12 weeks, which roughly equates to about three months.

The decision to use this intermediate endpoint was not arbitrary; it was based on some large retrospective meta-analyses that have shown that the strongest predictor of overall survival in patients receiving both Taxotere (docetaxel) and also separately Jevtana (cabazitaxel) was whether or not patients had a 30% PSA reduction after 12 weeks.

Patients who do achieve at least a 30% or greater reduction in the first 12 weeks have a survival that’s longer than patients who don’t achieve that endpoint. We thought, well if this endpoint is strongly correlated to survival, perhaps we can use it as a decision point. If after four doses of therapy or 12 weeks of therapy a patient don’t achieve a 30% reduction in PSA perhaps we should switch him to the other chemotherapy, rather than sticking with it and just waiting for either the toxicity to develop or the PSA or the radiographic disease to progress. That was the hypothesis.

We designed a relatively small study of about 63 patients. We used a 2:1 randomization so they were twice as likely to get Taxotere (docetaxel) compared to Jevtana (cabazitaxel). Approximately 41 patients got Taxotere (docetaxel) first. The other 22 patients, got Jevtana (cabazitaxel) first. Irrespective of which arm they were randomized to, they received the first four doses of chemotherapy in 12 weeks. We checked their PSA every three weeks.

At the end of the fourth dose, if the PSA level had dropped by 30% or more, the patients would continue on the same therapy on which they started. However, if patients did not achieve a 30% reduction or more, they would be switched to the other chemotherapeutic agent.

If a patient had a 25% reduction, we would switch him to the other agent because we thought that was not good enough. If someone received Taxotere (docetaxel), and their PSA dropped by 25%, even though it dropped by 25%, it did not meet that 30% threshold so they would then switch for the fifth dose to receive Jevtana (cabazitaxel) for the remainder of their chemotherapy. The inverse was also true. If the patient received Jevtana (cabazitaxel) first and also did not get a 30% reduction by week 12, in other words four doses, they would also switch to receive Taxotere (docetaxel). The interesting thing that we found in both treatment arms was that the chance that a patient had a favorable PSA response, which was defined as a 50% or more decrease, was higher than we had seen in historical trials using each drug by itself without switching. To put some numbers on that, we found that there was about a 54% chance that patients would have a 50% reduction in PSA if they had to the opportunity to switch from one chemotherapy to the other, compared to about a 45% chance of PSA reduction in the historical data where patients did not switch.

Did it matter if they got Jevtana (cabazitaxel) first or Taxotere (docetaxel) first?

Dr. Antonarakis: What we found out is a bit of a paradox: people could benefit from the switch in both down over time and the availability of non-chemotherapy agents is going up. A lot of these patients who may not have a 30% PSA reduction with one chemotherapy, might choose to do another hormone therapy, a radiopharmaceutical drug like Xofigo (radium-223), immunotherapy like Provenge (sipuleucel-T), or even a PD-1 inhibitor, or potentially a PARP inhibitor.

It might be difficult to convince a patient who has just failed one chemotherapy after four doses to go immediately to a second chemotherapy. I’m not 100% sure what the future will hold. I also don’t think this is a trial that we could have conducted today.

What would you say to a man reading it? That this is worth talking to his oncologist about or is this just something interesting for him to know about?

Dr. Antonarakis: Patients who are beginning their first chemotherapy should discuss this trial with their oncologist, and together with the oncologist decide in a joint fashion whether switching from one chemotherapy agent to another after four doses might be right for him, especially if he’s tolerating the chemotherapy well. If he tolerates the drug and his PSA has not dropped by 30% or is continuing to increase, then in my opinion rather than continue with the potentially futile therapy, a patient and his oncologist may wish to consider using this trial to guide or justify their choice of switching drugs earlier rather than later. directions. That was fascinating to us because, as we all know

Jevtana (cabazitaxel) was specifically approved by the FDA as a second-line curative therapy only indicated in men who have failed Taxotere (docetaxel) first. Based on that reasoning, one might expect Jevtana (cabazitaxel) to work better after Taxotere (docetaxel) but not Taxotere (docetaxel) after Jevtana (cabazitaxel).

This is not what we found.

We found that in both directions, both from the Taxotere (docetaxel) to Jevtana (cabazitaxel) switch, but also in the Jevtana (cabazitaxel) to Taxotere (docetaxel) switch, there was a significant amount of patients, approximately half, who were salvaged by the crossover therapy. By salvaged, I mean those who did not achieve a 30% PSA reduction with the first drug but did achieve a PSA reduction of 50% or more after crossing over to the second drug.

As I mentioned before, this occurred in both directions, both in patients receiving Jevtana (cabazitaxel) after Taxotere (docetaxel) and Taxotere (docetaxel) after Jevtana (cabazitaxel).

Are the side effects of Jevtana (cabazitaxel) a little bit easier to take than the side effects of Taxotere (docetaxel)?

Dr. Antonarakis: Interestingly, the side effects of Jevtana (cabazitaxel) in the published literature indeed appear to be slightly better. In this particular trial, which was very small obviously, they seemed comparable. In other words, we did not see any appreciable difference between the Taxotere (docetaxel) and the Jevtana (cabazitaxel) overall in terms of side effects. Taxotere (docetaxel) had a little bit more neuropathy nerve damage, which Jevtana (cabazitaxel) did not do. On the other hand, Jevtana (cabazitaxel) had a little bit more neutropenia, while the Taxotere (docetaxel) did not.

I would say that when patients receive these agents in a first-line setting, in other words, when they had not received another chemotherapy previously, their side effects were fairly comparable. I don’t think there was a clear signal in terms of one drug being clearly safer than the other.

Does it matter which you get first?

Dr. Antonarakis: From a side effect perspective, they’re both fairly equivalent in terms of tolerability, with slight differences in neutropenia, which is worse with Jevtana (cabazitaxel) and neuropathy, which is worse with Taxotere (docetaxel).

What is the next step? Are you going to run a similar trial with more patients?

Dr. Antonarakis: One question that arises is if this small randomized trial is enough to change practice. Should a community oncologist or urologist give Taxotere (docetaxel) for four doses and wait to see if the patient’s PSA drops by 30% or more? If it doesn’t drop to 30% or more, should he to switch to Jevtana (cabazitaxel)?

I have to admit that this is something that I have done in my practice a few times, but I really don’t believe that this is ready for clinical practice yet. Yes, in this trial, we showed that the PSA response rates could potentially be improved by this switch strategy. What we did not demonstrate was whether this improves overall survival.

The ultimate question is does switching chemotherapy agents after four doses improve survival, compared to just waiting until we see radiographic or clinical progression to switch agents. That would, as you mentioned, require a larger Phase III randomized study. The idea of study design would be to randomize patients to the switch strategy versus no-switch. We would randomize one group of patients to receive chemotherapy and switch if their PSA did not drop by 30%. The second group of patients would start chemotherapy but would not be given the opportunity to switch, even if their PSA did not drop by 30% or more. The randomization would not necessarily be the randomization to the chemotherapy, but would be randomization to a switch strategy versus a stick-with the first-chemotherapy strategy.

Sanofi, which makes both Jevtana (cabazitaxel) and Taxotere (docetaxel), have not been eager eager to respond to such a study because of financial considerations and also because the patent life of Taxotere (docetaxel) is over and the patent life of Jevtana (cabazitaxel) will be expiring soon.

Unfortunately, we might be left with a Phase II study that may, potentially, not translate into a Phase III study. I think individual patients and individual oncologists may look at these data and might be convinced that some patients might potentially benefit from a switch strategy, especially those who did not have any degree of PSA reduction after four cycles.

An added complexity is that the popularity of chemotherapy is going down over time and the availability of non-chemotherapy agents is going up. A lot of these patients who may not have a 30% PSA reduction with one chemotherapy, might choose to do another hormone therapy, a radiopharmaceutical drug like Xofigo (radium-223), immunotherapy like Provenge (sipuleucel-T), or even a PD-1 inhibitor, or potentially a PARP inhibitor.

It might be difficult to convince a patient who has just failed one chemotherapy after four doses to go immediately to a second chemotherapy. I’m not 100% sure what the future will hold. I also don’t think this is a trial that we could have conducted today.

What would you say to a man reading it? That this is worth talking to his oncologist about or is this just something interesting for him to know about?

Dr. Antonarakis: Patients who are beginning their first chemotherapy should discuss this trial with their oncologist, and together with the oncologist decide in a joint fashion whether switching from one chemotherapy agent to another after four doses might be right for him, especially if he’s tolerating the chemotherapy well. If he tolerates the drug and his PSA has not dropped by 30% or is continuing to increase, then in my opinion rather than continue with the potentially futile therapy, a patient and his oncologist may wish to consider using this trial to guide or justify their choice of switching drugs earlier rather than later.

Join us to read more conversations about chemotherapy for prostate cancer.

Author: Prostatepedia

Conversations about prostate cancer.

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