Studies Highlight Optimizing Therapy in Colon and Breast Cancer
Getting the right treatment to the right patient at the right time with the least amount of toxicity is a driving force behind the latest advances in cancer research. Two studies focusing on this concept are making headlines at the 2022 American Society of Clinical Oncology Annual Meeting.
The first focuses on stage 2 colon cancer patients who receive surgery. Current standard of care recommends chemotherapy post-surgery to kill any remaining cancer cells. However, new data from the phase 2 DYNAMIC clinical trial suggest circulating tumor DNA testing post-surgery could help oncologists decide if chemotherapy is necessary.
Circulating tumor DNA testing is still relatively new in oncology. The test examines the blood to detect DNA fragments shed from cancer cells. Cancer cells are constantly dying and making new cells to grow. And as a tumor grows, the amount of circulating tumor DNA may be higher.
The DYNAMIC study is a randomized trial, meaning the 455 enrolled participants were randomly assigned to one of two study arms:
- Standard of care — surgery with adjuvant chemotherapy
- Circulating tumor DNA testing — surgery followed by circulating tumor DNA testing to determine future course of treatment
Dr. Richard Kim, Service Chief, Medical Gastrointestinal Oncology
In the circulating tumor DNA-guided arm, patients who tested positive were given adjuvant chemotherapy while those with negative results were not, almost halving the total number of patients who needed post-surgical chemotherapy compared to standard of care. Patients with a negative circulating tumor DNA result, who did not receive post-surgical chemotherapy, had a very low risk of recurrence.
“The DYNAMIC trial results are encouraging. The goal of surgical resection for colon cancer is to remove the tumor and sometimes we give adjuvant chemotherapy to kill any cancer cells left behind. But it is unclear if everyone will benefit from adjuvant chemotherapy. Utilizing circulating tumor DNA testing could help better guide whether a patient needs adjuvant chemotherapy,” said Dr. Richard Kim, the service chief of Medical Gastrointestinal Oncology at Moffitt Cancer Center.
Antibody-Drug Conjugate for Breast Cancer
The second study looking at a more targeted approach to therapy involves patients with ER+/HER2- breast cancer, the most common type of the disease accounting for 70% of all cases. First-line therapy for ER+ breast cancer includes endocrine therapy and CDK4/6 inhibitors. However, patients often fail this treatment course and move on to different chemotherapy agents.
The phase 3 TROPiCS-02 clinical trial evaluated using sacituzumab govitecan in hormone receptor (ER) positive HER2- breast cancer patients who have progressed on endocrine therapy, CDK4/6 inhibitors or different chemotherapy agents. Sacituzumab govitecan is an antibody-drug conjugate, meaning an antibody is chemically linked to the drug. That antibody helps the medication, in this case a type of chemotherapy, find and enter the tumor, where it kills cancer cells. Sacituzumab govitecan specifically is a Trop-2 directed antibody, which lends to the clinical trial’s name: TROPiCS-02.
Dr. Hatem Soliman, Medical Oncologist, Breast Oncology and Immunology Departments
For this phase 3 trial, 543 patients were randomized into two arms: standard of care (chemotherapy) or sacituzumab govitecan. Trial results showed that use of sacituzumab govitecan resulted in a 34% improved median progression free survival compared to standard chemotherapy. The median duration of response, which is the length of time that a tumor continues to respond to treatment without the cancer growing or spreading, was also better for sacituzumab govitecan compared to standard chemotherapy (7.4 vs. 5.6 months).
“The results of the TROPiCS-02 trial are promising and could be practice changing. We have seen this therapy perform well in triple-negative breast cancer, and the data suggest this could be a better option for heavily pre-treated, endocrine therapy resistant HER2+ cancer patients who have exhausted other treatment options,” said Dr. Hatem Soliman, medical director of the Clinical Trials Office and medical oncologist in the Breast Oncology and Immunology departments at Moffitt.
