When surgical oncologist Dr. Kelvin Allenson came to Houston Methodist in 2022, he expected a large volume of colorectal, gastric, pancreatic and melanoma cancer cases, among the most common tumors in his line of work.

What he didn't expect was the number of complex sarcoma cases seen at the hospital system.

Although all sarcomas — cancers of the soft tissues or bone — are considered rare, two of Dr. Allenson's recent cases were especially unusual.

The first, a de-differentiated retroperitoneal liposarcoma, occurs in roughly three of every one million people per year.

"These are often the largest tumors we find in the human body, but this one was large, even among this group," Dr. Allenson explained.

The patient, a woman in her 60s, had an abdominal mass that measured 16.5 inches at its largest diameter and weighed 17 pounds upon resection.

"Due to its large size, the tumor required the removal of adjacent and involved organs, including one kidney, a portion of the colon, the tail of the pancreas and the spleen," Dr. Allenson said. "This obviously makes it a more complex resection and reconstruction due to its deep location in an anatomically complex area containing a number of vital structures."

Dr. Allenson's second rare complex sarcoma patient was diagnosed with a leiomyosarcoma of the inferior vena cava, a tumor located in the smooth muscle lining of the wall of the largest vein in the body. The vein carries blood from the lower extremities back to the heart.

"Less than 400 of these tumors have ever been reported — that's how rare they are," Dr. Allenson said. "Surgery is the only potentially curative therapy, but resecting the tumor and reconstructing the vein while maintaining the patency of major venous flow presents a considerable technical challenge."

Luckily, Dr. Allenson could call on skilled colleagues in the Houston Methodist DeBakey Heart and Vascular Center to help secure and reconstruct the critical blood vessel.

Recently, Leading Medicine sat down with the accomplished young surgeon — a former recipient of a prestigious National Institutes of Health T32 research fellowship — to discuss the complexities of the two complex sarcoma cases and how both patients found the multidisciplinary care they needed at Houston Methodist.

Q: How did the patient with the retroperitoneal liposarcoma present?

Dr. Allenson: The patient's primary care physician detected a large mass. By the time she was seen here, maybe a few weeks later, it was tangibly larger than it had been at the time of the first scan. That means it was growing very rapidly. We scanned it again and performed a needle biopsy, which showed that it was a de-differentiated liposarcoma — an aggressive, or high-grade, tumor which not only grows into the adjacent organs but also has a high potential to metastasize and spread throughout the body. One of the main complexities in these cases is balancing the use of nonsurgical treatments, including radiation and chemotherapy, with surgical treatments. First, the patient underwent radiation therapy every day for five weeks, and then we waited a month to perform the complex multivisceral resection.

Q: How did the resection surgery go?

Dr. Allenson: She did well. The mass and her abdominal girth did shrink during that period, so that helped, and we were able to remove the affected tissue and organs and reconstruct critical functions successfully.

Because she only has one kidney now, she has slightly worse kidney function than before, but otherwise she is doing really well. It's been around a year, and she doesn't have any evidence of disease recurrence, which is great considering how aggressive her tumor was initially.

Q: What are the chances it stays that way?

Dr. Allenson: There is a tool we use called the "sarculator" — a sarcoma calculator, if you will — that was developed by Dr. Alessandro Gronchi, a well-known sarcoma surgeon in Italy, and his colleagues. Although these tumors are rare, the clinical and pathologic factors from many individual sarcoma cases were compiled in this algorithm in order to predict their behavior. The calculator can predict a risk of recurrence, and we use that information to inform the use of chemotherapy, administered in order to reduce the risk of recurrence. In this case, our patient received chemotherapy. We were fortunate to see her when we did, because had much more time passed, given the rate of growth, the tumor may have become unresectable. With sarcomas, every case is unique. There are over 100 types of sarcoma, all of which have unique behavior patterns. In addition, the surgery must be tailored to account for various organs affected and what will be required for reconstruction. This was a very good outcome. Our patient had a successful surgery and recovery, and she's back to being healthy, with the same quality of life she was used to prior to the sarcoma diagnosis.

Q: Tell us about the leiomyosarcoma of the inferior vena cava. How did this patient present?

Dr. Allenson: This patient was also a woman in her 60s. She had been having abdominal pain, which prompted a CT scan revealing the tumor. She had seen a local surgeon in her community but wanted a second opinion after doing some research and discovering how rare these tumors are. I completely agree with her intuition. The National Comprehensive Cancer Network guidelines recommend that all patients with sarcoma should receive a full multidisciplinary evaluation at a cancer center. This patient — and all of our patients with sarcoma — have their pathology and radiology records reviewed at our multidisciplinary tumor boards. These tumor board meetings bring together the medical oncologists, radiation oncologists and surgical oncologists, collectively as a group, to provide a comprehensive assessment.

I like to tell my patients that I may be their individual doctor, but with our tumor board, all cancer specialists have seen your case. You're really receiving the opinion of 10 experts, not just one.

We discussed her case at the comprehensive tumor board and recommended that she undergo chemotherapy before surgery because neoadjuvant radiation, which is a standard for other types of retroperitoneal sarcoma, has not been shown to have a benefit for this type of tumor. She had a difficult time with chemotherapy and did require an inpatient hospitalization. We enrolled her in our prehabilitation program, run by Dr. Atiya Dhala, and she was able to regain her physical strength and undergo the surgery.

Q: How did the surgery go?

Dr. Allenson: The retroperitoneum is not readily visible when you make an incision on the abdominal wall, so you can't tell exactly what you're going to find until you get in there and move all the organs out of the way. We were relieved to see that the tumor was not connected to the intestines, but it definitely involved the vena cava. I reviewed and planned this case with Dr. Charudatta Bavare, one of our very experienced vascular surgeons. Together, we obtained proximal and distal control in order to access the blood vessels we needed to work on. We removed the tumor in its entirety and then Dr. Bavare put in a bovine pericardial patch, a biologic graft obtained from the processed lining of a cow's heart, to restore the integrity of the vena cava.

The patient recovered well and went home within a week. She has been doing very well ever since. She was already very fit, functional and active just a couple of months after surgery.

I think the case really highlights the importance of being at a major academic medical center, and how our oncology team, surgical oncology, prehabilitation and cardiovascular surgery program all come together to deliver the right kind of care.