Surgeon Giorgos Karakousis, MD, has studied and treated sarcomas for much of his career at the Abramson Cancer Center and Penn Medicine, where he is a Professor of Endocrine and Oncologic Surgery.
Soft tissue sarcomas are among the rarest of cancers, but those of the retroperitoneum are particularly uncommon (~2.7 cases per million population), and particularly complex.
"There are more than 70 histologic subtypes of sarcoma, including many subtypes of retroperitoneal sarcoma (RPS)," Dr. Karakousis observes. Among the most common of these are the liposarcomas and the leiomyosarcomas. The liposarcomas arise from fatty tissue in the back of the abdomen; leiomyosarcomas originate at smooth muscle cells. More rare than these, Dr. Karakousis adds, are such subtypes as the IVC leiomyosarcomas, which arise in the smooth muscle lining the walls of major venous structures.
Symptoms are often a late manifestation of retroperitoneal sarcomas, says Dr. Karakousis, and about half are high-grade at diagnosis. "The tumors are often insidious in their presentation and they tend to be displacive (pushing nearby structures to the side as they grow), rather than invasive, which means that symptoms usually occur only after the cancer has reached fairly large dimensions and often discovered by a palpable mass in the abdomen."
Once symptoms arise, two critical elements can determine the course of management. The first concerns imaging to accurately assess the extent and dimension of the cancer. The second, given the exceptional rarity of the cancer, is where treatment actually takes place.
"It's very important that RPS patients get referred as early as possible to a center like the Abramson Cancer Center for treatment," Dr. Karakousis says. "We know that expertise plays a role at every step in the management of these cancers, from the initial biopsy onward, and that outcomes can vary on the basis of treatment expertise."
Multidisciplinary Approach to Retroperitoneal Sarcoma Treatment at Penn Medicine
The Sarcoma Program at Penn Medicine is situated at the Abramson Cancer Center, a designated NIH comprehensive cancer care center and one of only nine Sarcoma Alliance for Research through Collaboration (SARC) Core Centers on the East Coast.
Care of RPS and other soft tissue sarcomas at the Abramson Cancer Center involves the close interaction of a team of specialists whose approach to management is informed by the histologic grade and extent of the cancer on diagnosis, the treatments available in the light of these findings, and whether metastases or recurrence are factors. CT and MRI are critical to the diagnosis of RPS and defining its extensiveness.
Surgery
Surgery with microscopically negative margins is the standard approach in patients with localized primary RPS.
"It is a fundamental approach, but when surgery is feasible, it's by far the best treatment for these tumors," says Dr Karakousis. "The surgery can be extensive, and involves removing the tumor in its entirety, and en bloc resection of any contiguously involved organs."
Extent and completeness of resection are robust predictors of disease-specific survival. However, given the histological complexity of RPS, locoregional recurrence is common. For this reason, other therapies, and other specialists, are often applicable in therapy.
Adjunct Modalities
Some sources suggest that younger patients with RPS whose histologies have a higher propensity for local recurrence may benefit from radiation therapy, though there are reservations for standard photon radiotherapy.
"It's hard to spare abdominal organs from off-target photon radiation after surgery because the abdominal organs tend to shift," Dr Karakousis notes. "We're fortunate here at Penn, however, to have proton therapy, which can focus radiation to specific areas and possibly spare collateral damage to the kidney, colon, and other nearby organs and tissues." Decisions for radiotherapy (which typically are used in the neoadjuvant setting for RPS) are made on a case-to-case basis at the Abramson Cancer Center on the basis of histology, tumor size, location, and other essential factors.
Chemotherapy is an option at the Abramson Cancer Center as neoadjuvant therapy in tumors for which complete resection is either impossible or untenable. The object of chemotherapy in these instances is to shrink the tumors if possible to make the surgery more feasible, while also providing treatment for possible clinically occults distant disease.
Clinical Decision-Making
The role of decision-making in the management of RPS, particularly in recurrent disease, cannot be underestimated, Dr. Karakousis says.
"The Penn Medicine Abramson Cancer Center has an outstanding team of clinical specialists whose role involves a deep and comprehensive understanding of these rare cancers and the ways that they behave. And these individuals all take part in the decision-making process that determines treatment."
Outside of their practical roles, these disciplines — including vascular surgeons, plastic surgeons, oncological surgeons, radiologists, radiation oncologists, pathologists, and medical oncologists — participate in boards and meetings where every aspect of a patient's cancer, from initial pathology and imaging reports to pre- and post-treatment concerns, are reviewed and deliberated to ascertain a direction forward.
"What sets us apart," Dr. Karakousis concludes, "is our capacity to provide total care for sarcoma in an environment in which the decisions being made for every patient originate with specialists whose clinical focus is sarcoma. It's what makes Penn Medicine and the Abramson Cancer Center unique."