For decades, mesothelioma, a cancer almost always tied to asbestos, has been one of the most feared diagnoses linked to asbestos exposure. With few treatment options and a grim outlook, this aggressive cancer has offered little hope for the people living with it. But, in a promising turn of events, a recent clinical trial out of the UK may have opened the door to a new option that could give patients more time and a better quality of life. The drug, part of a class known as PARP inhibitors, isn’t new to cancer treatment. It’s already been used in breast and ovarian cancers. But now, for the first time, researchers have found evidence that it can also help people living with this particularly aggressive form of cancer[1].

The Silent Danger of Asbestos

Asbestos isn’t just a problem of the past. Although its use peaked during its heyday in the 20th century, the damage the deadly mineral causes is still showing up today. Once sought after for its heat resistance and durability, asbestos was added to everything from insulation and ceiling tiles to brake pads and cement. The problem? It would soon be discovered that all forms of asbestos can cause serious health issues, including asbestosis, lung and ovarian cancer, pleural plaques, other chronic respiratory conditions, and mesothelioma, a cancer that develops in the lining of the lungs, heart, or abdomen.

Latency: Asbestos cancers like mesothelioma can take 20-50+ years to appear.

One of the major challenges with asbestos exposure is the long delay between the exposure and the appearance of symptoms. It can take 20, 30, or even 50 years for a person who inhaled or ingested asbestos fibers to show signs of illness. This delay means people who worked with asbestos decades ago (like construction workers, mechanics, and veterans) are just now being diagnosed. It also means that many people don’t even realize they were exposed until it’s far too late to take preventive action.

What Makes Mesothelioma So Difficult to Treat

Mesothelioma is notoriously resistant to treatment. Unlike some cancers, it doesn’t respond well to surgery, radiation, or chemotherapy, especially once it has spread, which it almost always has once a diagnosis is received. It’s hard to detect early, and it grows along surfaces, rather than forming a distinct lump that can be easily removed. On top of that, asbestos fibers, once lodged in the body, are nearly impossible to get rid of. They can trigger long-term inflammation and scarring, which eventually leads to cancerous changes in cells.

Traditional treatments can help ease symptoms and slow the spread of the disease, but they rarely lead to long-term survival. The average life expectancy after diagnosis is just 12 to 21 months with only about 5% of people still living five years or more after being diagnosed. This grim reality has left researchers searching for new answers.

What Are PARP Inhibitors?

PARP inhibitors[2] are a class of targeted cancer therapies that work by blocking a protein in cells called PARP, which stands for poly (ADP-ribose) polymerase. This protein plays a key role in detecting and repairing single strand breaks in DNA. When DNA damage occurs, from normal cellular processes or from external stress like radiation or chemotherapy, PARP acts like a first responder, patching the breaks to maintain cell survival.

Helping the body help itself

In healthy cells, this repair mechanism is vital. It protects against mutations, preserves genetic stability, and prevents cell death. However, cancer cells exploit this same DNA repair system to survive treatment. When therapies like chemotherapy damage the DNA of rapidly dividing cancer cells, PARP steps in to help them recover, reducing the treatment’s effectiveness.

PARP inhibitors interrupt this repair process. By blocking the PARP protein, they prevent cancer cells from repairing damaged DNA, especially the kind caused by treatment. This leads to a collection of DNA errors in the cancer cells, ultimately causing them to die (a process known as “synthetic lethality”).

These drugs are particularly powerful in cancers with existing defects in other DNA repair genes, such as BRCA1 and BRCA2. These genes normally help fix double-strand DNA breaks through a process called homologous recombination. When BRCA is mutated, cells become more reliant on PARP to survive. So, when PARP is blocked in BRCA-mutated cells, they lose their last remaining repair option, making them highly vulnerable to death.

Inside the NERO Trial: A Ray of Hope

The NERO trial[3], led by researchers from the University of Leicester and the Cancer Research UK Southampton Clinical Trials Unit, set out to test whether a PARP inhibitor called niraparib could help people whose mesothelioma had come back after standard treatment. The trial included 88 patients from 11 hospitals across the UK. Most had pleural mesothelioma, which affects the lining of the lungs and had already gone through chemotherapy.

Participants were split into two groups: one received standard symptom control, and the other received symptom control plus niraparib. The goal was to see if the drug could delay the progression of the cancer.

The results were promising. Patients who received niraparib had an average of 1.5 extra months before their cancer got worse: 4.14 months versus 2.76 months in the standard treatment group. While that might not seem like a lot, it represents a 27% reduction in the risk of the cancer worsening or leading to death. Some patients, like James Fox, a retired architect exposed to asbestos decades ago, have seen much longer benefits.

Why This Matters

This study is the first to show that PARP inhibitors can work against mesothelioma in a large, controlled trial. Researchers still don’t fully understand why the drug works better in some patients than others, but early clues point to differences in immune system signaling and genetic factors.

One especially interesting finding involved interferon alpha, a protein involved in immune responses. Higher levels of interferon alpha activity were linked to better responses to the drug, even in patients who didn’t have the usual BRCA-related mutations. Scientists also found that certain genetic deletions in a region called 9p21.3 may influence how well the drug works. This information could eventually help doctors predict which patients are most likely to benefit from the treatment.

The Ongoing Legacy of Asbestos

Even though asbestos has been banned or restricted in many countries, its legacy lives on—meaning, so too will the devastating legacy of mesothelioma. Mesothelioma rates are expected to remain high for years to come, in fact, especially for those exposed on the job and their families. In the U.S., that includes construction and textile workers, auto mechanics, military veterans, shipyard workers, and others directly exposed. These people were often exposed without knowing the risks, and without the protection they needed. In fact, even when there was evidence that asbestos was causing severe respiratory conditions, employers often looked the other way in favor of making a profit, leaving their workforces exposed to the toxin much longer than they should have been.

To this day, these individuals and their families, including the next generation of their children, are developing life-threatening illnesses like mesothelioma. Asbestos also still lingers in many homes, schools, and public buildings. Left alone, it isn’t considered harmful, but when stirred up during renovations and demolitions, new risks emerge.

The High Cost of Treatment & Trust Funds

Receiving a cancer diagnosis can be devastating for everyone involved—not just the patient but their family, too. One issue that doesn’t get talked about enough is the financial strain that mesothelioma puts on families. Even with insurance, the cost of cancer treatment, including doctor visits, hospital stays, medications, lost wages, can be overwhelming. Medical bills are one of the leading causes of bankruptcy in the U.S., in general, and cancer treatment costs remain especially high.

Even with clinical advancements, treating mesothelioma is bound to be costly. Luckily there is a financial option that has been put into place to help families during this especially vulnerable time, especially those who were exposed to asbestos in the workplace. Trust funds were created by asbestos manufacturers amid bankruptcy proceedings—which resulted after they were hit with a wave of lawsuits for exposing their workers. And there are still funds available waiting to be claimed.

Trusts allow victims (or their families) to apply for compensation without going through a full court case. This is particularly beneficial for mesothelioma patients as lawsuits can be time consuming and time is a resource that they generally don’t have. The process is often quicker than a lawsuit and helps cover medical bills, lost income, and other damages.

What’s Next?

The results of the NERO trial are an important step forward, but they’re not the final answer. Researchers are continuing to analyze the data to understand why some patients respond better than others. The goal is to figure out how to make these treatments even more effective, and ideally, tailor them to individual patients.

For now, patients and families facing a mesothelioma diagnosis can find newfound hope. It’s not a cure, and as with any medical solution, it’s not perfect. But in a field that’s seen too many dead ends, this small step could lead to something much bigger. Only time will tell.

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[1] American Cancer Society. (2023). “What is Mesothelioma?” Retrieved from https://www.cancer.org/cancer/malignant-mesothelioma/about/what-is-mesothelioma.html. 

[2] Lord, C. J., & Ashworth, A. (2017). PARP inhibitors: Synthetic lethality in the clinic. Science, 355(6330), 1152-1158. https://doi.org/10.1126/science.aam7344.

[3] Fennell, D. et al. (2025). “Efficacy and multiomic analysis of Niraparib in relapsed mesothelioma: NERO a randomized phase II trial.” Cancer Research 85 (8_Supplement_2): CT263. https://doi.org/10.1158/1538-7445.AM2025-CT263.