When Brownie, an adorable, four-year-old Chihuahua mix, was rescued by PAWS from Animal Control, they quickly realized she had mammary masses. The team at PAWS knew exactly who to call.

Karin Sorenmo, DVM, DACVIM, chief of medical oncology at Penn Vet’s Ryan Hospital, founded the Penn Vet Shelter Canine Mammary Tumor Program in 2009. This unique program provides care to shelter dogs with mammary tumors that are homeless and without access to the treatment they need to survive. Brownie became the 100th dog to join the program, which covers surgery and follow-up care costs and helps facilitate adoption, all while advancing knowledge of both canine and human breast cancer.

“We believe that by studying dogs with mammary tumors, we can improve our understanding of how cancer develops, and through this understanding, find better and more efficient drugs to treat and prevent this potentially lethal disease,” says Dr. Sorenmo.

Since the incidence of mammary tumors in unspayed female dogs is at least four times greater than in spayed dogs, shelter dogs serve as an ideal population for studying mammary tumors. Only 10 percent of animals received into shelters have been spayed or neutered.

In addition, mammary tumors in dogs and breast cancer in women have many similarities, both in terms of risk factors and biology. Many of the dogs have multiple tumors, often in different stages of malignant transformation, and therefore provide a unique opportunity to study cancer progression.

“The dog is such a good model for this kind of comparative oncology because we see so many different tumors in the same dog,” explains Dr. Sorenmo. “Many times when you look at genetics in human cancer, it’s difficult to compare a benign and a malignant tumor between two different patients. With dogs, you have a snapshot of the progression from benign to malignant in the same patient.”

Dr. Sorenmo collaborates with Dr. Troyanskaya and her group at the Lewis-Sigler Institute for Integrative Genomics and Department of Computer Science at Princeton University. They will perform the molecular analysis to identify the molecular alterations associated with progression from benign to malignant.

The first results of this study will be available later this summer. Comparison to human breast cancer data will then be performed in collaboration with Drs. Robert Vonderheide and Susan Domchek of Penn Medicine’s Abramson Cancer Center.

“So many of us have been touched by breast cancer. It’s really devastating,” adds Dr. Sorenmo. “If the dogs can be a link to help advance our knowledge and treatment of breast cancer, it will be a true win-win situation.”

The Penn Vet Shelter Canine Mammary Tumor Program is also rewarding, says Dr. Sorenmo, “in that we are attaining such important knowledge while actually saving the lives of some of the most vulnerable members of animal shelter populations.”

Many of the dogs in the program have had difficult, heartbreaking pasts. “It’s so gratifying to make something positive out of such a terrible situation,” adds Dr. Sorenmo. “These dogs certainly deserve something good in their lives.”

Brownie is currently in foster care with a PAWS volunteer, while waiting for her forever home. For more information about Brownie, contact PAWS at dogs@phillypaws.org. Please note that Brownie’s owners must be willing to keep her in Penn Vet’s Shelter Canine Mammary Tumor Program.