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By 

Chief of Lung Radiation Oncology Service, Director of Clinical Innovation and Information Systems

Most families discover inherited genetic mutations after one member develops a health problem unusual to their age. This can prompt younger generations to get genetic testing.

But in the case of Cassie Munoz and her family, the scenario was reversed. Cassie was 29 years old in 2012 when she was diagnosed with a rare form of . Her mother would be diagnosed with the same cancer five years later.

After experiencing chest pains and collapsing at the Southlake elementary school outside of Dallas where she was teaching third grade, Cassie was transported to a nearby hospital. Scans showed a 3.5-inch tumor on her left lung. She was diagnosed with non-small cell lung cancer.

“The doctors there told me that I had few options,” Cassie said. “I felt devastated.”

But she didn’t give up. A parent of one of her students connected Cassie with , a pulmonary specialist at UT Southwestern. He ordered a  and a , which showed that the cancer appeared to be contained to her upper left lung. However, testing showed that multiple spots in Cassie’s right lung were at high risk of becoming cancerous. Despite the imaging results, Cassie said Dr. Abu-Hijleh was the first to offer her hope that treatment was possible.

Due to Cassie’s age and overall health, she was also recommended for genetic testing. Results revealed a T790M mutation – a rare variance found in about 1% of people with non-small cell lung cancer, the most common type of lung cancer.

Though these diagnoses shook Cassie’s family to the core, both mother and daughter are now thriving. And with the knowledge that they graciously shared through an extensive clinical study of their family, we know more about this mutation than ever before – and we’ll be ready to help more families face non-small cell lung cancer head on.

Tracking the T790M mutation

After Cassie’s genetic testing revealed the T790M mutation, Joan Schiller, M.D., the former UT Southwestern Division Chief of Hematology and Oncology and Deputy Director of the , recommended that other members of Cassie’s family also be checked for the mutation.

“I started asking around my family,” Cassie said. “That’s when I found out that there were relatives on my mother’s side who died from lung cancer.”

Testing showed that Cassie’s mother also had the T790M mutation, which activates the EGFR gene, making cancer cells grow out of control. The T790M mutation is associated with recurrence.

From there, Dr. Schiller invited the family to participate in  on their unique mutation. UTSW researchers tracked the gene change through five generations and collected blood samples from 17 family members. This research revealed that lung cancer was more common in never-smokers with the T790M mutation than in smokers without the mutation.

UTSW doctors began screening Cassie and her mother for signs of lung cancer. They received periodic intensive screenings by chest CT imaging, as they had precancerous lesions that needed additional monitoring. Through these frequent touch points, we found her mother’s lung cancer at an early stage in 2017, and Dr. Abu-Hijleh referred her for surgical resection that provided curative treatment.

Cassie’s journey was much more complicated.

Surgery to remove the tumor

After diagnosing Cassie’s cancer, Dr. Abu-Hijleh referred her to thoracic surgeon , to test 26 lymph nodes in her chest for signs that the cancer had spread. If any of the lymph nodes he tested were positive for cancer, he told Cassie, he would surgically remove either a section or the whole lobe of her right lung, depending on the metastasis.

"I wasn’t sure what news I would get when I woke up,” said Cassie, “but I trusted Dr. Kernstine to make the right decision.”

The cancer had not spread to her right lung, and Dr. Kernstine removed the upper left lobe of her lung where the original tumor was located. For the next five years, Cassie continued with routine checkups. Everything was steady until 2017, when another tumor was discovered – around the same time her mother was diagnosed with lung cancer.

Dr. Kernstine removed Cassie’s second tumor, and another developed in 2018. By this point, Cassie was exhausted. She’d been hospitalized for over two weeks after the second surgery, and while she didn’t want to give up, she didn’t want to go through aggressive treatment again.

Pivot to precise radiation therapy

As a radiation oncologist, I started treating Cassie during her third recurrence in 2018. We used  (SBRT), which is sometimes referred to as stereotactic ablative therapy (SABR). This advanced treatment is precise in targeting tumors with bursts of high-dose radiation. Compared with traditional radiation therapy, SABR requires fewer treatment sessions and, in many cases, can avoid side effects such as changes in lung function.

SABR plans are constructed based on 3D imaging, taking into account the location of the tumor and nearby normal tissues. Multiple beam angles are used to deliver a high dose to a target and a far lower dose to surrounding normal tissues.

Many studies, including several authored by UTSW physicians, have shown that SABR can achieve similar cancer control rates as surgery in early-stage lung cancer, with minimal or manageable side effects.

Over several weeks, Cassie’s tumor responded. Follow-up scans showed lung inflammation, as can often happen in this situation, making her imaging more challenging to interpret.

After some months of observation, it became clear that her inflammation was resolving. During these months of watching, Cassie’s care was tailored to her preferences – she wanted to be informed about her health but not overwhelmed.

“I don’t need to know every little detail of what’s on the scan,” she said, “I trust my doctors to give me the information I need.”

Radiation therapy

For decades, UT Southwestern has been at the forefront of radiation therapy. , Chair of Radiation Oncology, brought SBRT into widespread use in the U.S., and we have trained thousands of physicians in radiotherapy techniques.

In 2017, we opened a  as part of the Simmons Cancer Center to continue leading the advancement of radiation therapy techniques for cancer. We’ve accelerated our research in radiation therapy to include more precise and personalized techniques, including:

•  (PULSAR): Real-time imaging allows us to visualize the tumor between radiation doses and adjust the placement and dosage from session to session.
• Leverage the immune system: A  found that some patients create antibodies against their cancer between PULSAR treatment sessions. Today, in some cases, immunotherapy during or after radiation therapy can be more effective when “pulses” of radiation therapy are spaced out over a longer period of time than traditional treatment.
• Harnessing AI-powered imaging: The ability to adjust the machines within millimeters of a lesion allows for greater treatment precision.

Lung cancer genetic testing can be lifesaving

Cassie’s genetic lung cancer diagnosis changed the trajectory of her life. But it also gave her family a wealth of knowledge they’ve used to be proactive about their health.

As of early 2025, Cassie and her mother are both in remission. In 2015, Cassie gave birth to a son, Jaden, with support from the  team at .

“My doctors initially told me I might not have a child,” Cassie said. “There wasn’t much research at the time on the possible side effects on fertility from lung cancer treatment. But with customized, attentive care from my UT Southwestern team, I got to be a mom, and my bonus son, Trevor, got a brother.”

Cassie’s successful outcomes are directly attributed to her dedication to listening to her body and trusting her care team, which has included the expertise from multiple disciplines at UT Southwestern over the years. If she ever has another recurrence, we’re confident that we’ll be able to catch it early.

"The people at UTSW have been instrumental and irreplaceable in my cancer journey,” said Cassie, who’s now 42. “The connections I’ve made with doctors, the team that makes me feel like I matter, the ones whispering words of wisdom and hope, the many people behind the scenes researching genetic mutations, targeted therapies, innovative ways to detect new cancer cells - all so I can have the gift of more time. I learned how to live and now have a very full life after my cancer diagnosis because of the doctors and treatment I received at UTSW."