Dr. Kanwal Raghav is a medical oncologist at MD Anderson Cancer Center in Houston, where he specializes in peritoneal mesothelioma and studies new therapies for advanced cases.
His patients often have many questions after a diagnosis. While surgery is the standard recommendation for peritoneal mesothelioma, not everyone qualifies. Fortunately, chemotherapy, immunotherapy, and clinical trials are expanding options for people facing this rare cancer.
Dr. Raghav recently sat down with Mesothelioma Hope to answer questions about these therapies and more. Keep reading for his insights on treatment decision-making, the latest developments in immunotherapy research, and why he encourages patients to ask about clinical trials early in their care journey.
What treatments are available for patients with peritoneal mesothelioma today?
I think cytoreductive surgery and HIPEC are clearly the mainstays of treatment, but they’re generally more successful in patients with a limited amount of disease. A lot of our patients don’t fall into that category, so we often take a multidisciplinary approach that combines systemic therapy with surgery.
For systemic therapy, much of the available data has been extrapolated from pleural mesothelioma, although there’s also data specific to peritoneal mesothelioma. We generally use platinum and pemetrexed-based chemotherapy, along with immunotherapy.
How we apply immunotherapy in peritoneal mesothelioma is still being defined, but we commonly use dual immune checkpoint inhibitors or atezolizumab (Tecentriq®) with bevacizumab (Avastin®), which we evaluated in our phase II study. We’ve seen encouraging responses with that regimen.
Beyond those options, we prefer to enroll patients in clinical trials whenever possible. There are also other cytotoxic agents, such as vinorelbine (Navelbine®) and gemcitabine (Gemzar®), that are sometimes used, although there’s much less evidence supporting their use in peritoneal mesothelioma.
Why is it important for peritoneal mesothelioma patients to visit a specialized treatment center?
Community oncologists do a phenomenal job treating common cancers like breast, colon, and lung cancer. That’s where they see the majority of their patients and where they have tremendous experience.
But peritoneal mesothelioma is different. Because it’s so rare, many physicians may only see one or two cases during their careers. It’s completely understandable that they won’t have the same level of experience treating this disease.
From a provider’s perspective, my recommendation is that whenever you encounter a rare tumor, it’s always better to have more than one brain involved in managing the patient.
From a patient’s perspective, if you’re diagnosed with a rare cancer, seek out a center that has experience treating it. These treatment centers bring together specialists from multiple disciplines and can also provide access to clinical trials that may not be available elsewhere.
How do you decide whether someone qualifies for peritoneal mesothelioma surgery?
This is a very multidisciplinary decision. The key is having strong communication between surgeons, pathologists, and radiologists, because peritoneal mesothelioma can be difficult to diagnose, and imaging is sometimes suboptimal.
At MD Anderson, we have a large group that reviews these cases before we formalize a management approach. We consider the amount of disease, the patient’s overall health and other medical conditions, and whether the location of the disease makes surgery less effective.
We also look at the biology of the disease, including how quickly it’s growing, how it responds to neoadjuvant therapy (treatment before surgery), and certain molecular features.
Can chemotherapy or immunotherapy improve patient outcomes when combined with surgery?
Yes. We frequently use neoadjuvant therapy at MD Anderson, and any degree of cytoreduction you can achieve with chemotherapy or immunotherapy can be helpful for surgery and surgical outcomes.
Whether we use chemotherapy or immunotherapy depends on a variety of factors, including the histologic (cell) type, molecular profile, PD-L1 expression, kidney function, and the patient’s overall health.
Because this is a rare cancer, treatment has to be individualized. We still don’t have enough insight into the disease for a standardized precision-medicine approach, so treatment decisions have to be tailored to each person’s situation.
Why do some patients respond better to immunotherapy than others?
When you look at the available data, it’s clear that immunotherapy isn’t the solution for all our patients. Even in pleural mesothelioma, there’s a distinct signal showing that patients with sarcomatoid disease respond very well to immunotherapy, while outcomes for epithelioid disease remain more comparable to chemotherapy.
I think we need better biomarkers than we currently have. That’s going to be one of the most important advances because it will help us identify which patients are most likely to benefit from immunotherapy.
Can you tell us about your phase II trial evaluating atezolizumab and bevacizumab?
This was one of the first prospective trials evaluating immunotherapy combined with targeted therapy specifically for peritoneal mesothelioma. The treatment combined bevacizumab, a VEGF (vascular endothelial growth factor) inhibitor, with atezolizumab, an immune checkpoint inhibitor.
The study enrolled 20 patients whose disease had progressed after platinum and pemetrexed-based chemotherapy or who couldn’t tolerate prior chemotherapy. Overall, the treatment was very well tolerated, and side effects were minimal.
We observed a confirmed objective response rate of nearly 40%, which is among the highest reported in this disease. Many of those responses were durable, with a median duration of response of 12.8 months.
Six patients maintained their responses for longer than 10 months, which is quite unprecedented in peritoneal mesothelioma. Overall, I think the study showed this is a very promising treatment approach.
Why should patients consider clinical trials?
At MD Anderson, we’re firm believers that clinical trials are the key to improving outcomes, not only for today’s patients but for future patients as well. Every treatment that’s now considered standard of care was once available only through a clinical trial.
We still don’t have a treatment that’s a home run, so we want to give patients as many options as possible. Clinical trials provide access to promising therapies that aren’t otherwise available.
I also encourage patients to ask about clinical trials early. One reason enrollment can be challenging is that patients are often referred after they’ve already received multiple treatments. Clinical trials have strict eligibility criteria, so changes in kidney function, blood counts, or other treatment-related side effects can sometimes prevent patients from participating later.
What advances in peritoneal mesothelioma treatment are you most excited about?
There are so many different approaches being studied right now that it would probably take another conversation to discuss all of them.
More than any individual drug, though, I’m excited about continued participation in clinical trials.
Every patient deserves the opportunity to consider a clinical trial before moving through all of the standard treatments. That’s how we’ll continue making progress and improving care for future patients.
Find a Peritoneal Mesothelioma Specialist
Choosing where to get treatment for peritoneal mesothelioma is an important decision. Seeing a mesothelioma specialist at a major cancer center gives you the opportunity to review your diagnosis, explore your options, and understand the benefits and risks of various treatments.
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