2022 ASCO Annual Meeting: Targeted Therapy for Advanced HR-Positive, HER2-Negative Breast Cancer and Using Liquid Biopsy to Guide Treatment for Stage II Colon Cancer

2022 ASCO Annual Meeting; #ASCO22
June 4, 2022
Brielle Gregory Collins, ASCO staff

The theme of the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting is Advancing Equitable Cancer Care Through Innovation. From June 3 to 7 in Chicago, Illinois, and online, cancer researchers and clinicians from around the world will gather to discuss the latest research and how to ensure that all people receive the cancer care they need.

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Some of the notable research that will be presented today includes: 

Sacituzumab govitecan delays cancer growth for some people with advanced hormone receptor-positive, HER2-negative breast cancer

Who does this study affect? People with advanced hormone receptor-positive, HER2-negative breast cancer whose cancer has not been stopped by previous treatments.

What did this study find? The phase 3 TROPiCS-02 clinical trial found that the targeted therapy drug sacituzumab govitecan (Trodelvy) delayed cancer growth 34% longer than standard chemotherapy in people with advanced hormone receptor-positive, HER2-negative breast cancer whose cancer has grown despite previous treatments.

Hormone receptor-positive, HER2-negative cancer is the most common subtype of advanced breast cancer. The standard treatment for people with this type of cancer is hormonal therapy with or without targeted therapy until the cancer grows or spreads, at which point treatment options are limited to chemotherapy. In this study, researchers were evaluating whether treating patients at this stage with sacituzumab govitecan instead of chemotherapy would be better at delaying cancer growth or spread.

Sacituzumab govitecan is a type of targeted therapy called an antibody-drug conjugate. In this type of treatment, the antibody attaches to a cancer cell and then delivers the anticancer drug it carries to start destroying the cancer cell. Sacituzumab govitecan is currently approved for the treatment of people with metastatic triple-negative breast cancer who have already received at least 2 treatments.

This study included 543 people with hormone receptor-positive, HER2-negative breast cancer that was either metastatic or locally advanced but could not be treated with surgery. All patients had previously received treatment with hormonal therapy, targeted therapy, and 2 to 4 lines of chemotherapy. The patients were randomly assigned to receive either sacituzumab govitecan (272 patients) or standard chemotherapy (271 patients).

The study found that sacituzumab govitecan delayed cancer growth longer than chemotherapy, with a median delay of 5.5 months compared with 4 months for those receiving chemotherapy. The median is the midpoint, meaning that half of the participants experienced delayed growth for longer than 5.5 or 4 months, respectively, and half experienced a shorter period of delayed growth. At 6 months of follow-up, nearly half (46%) of the participants treated with sacituzumab govitecan had not had their cancer grow or spread, compared to about a third (30%) of participants in the chemotherapy group. These percentages remained higher at 1 year for those in the sacituzumab govitecan group (21% of participants) than those in the chemotherapy group (7% of participants).

Additionally, the percentage of participants whose tumors shrank following treatment was higher in the sacituzumab govitecan group (21% of participants) than in the chemotherapy group (14% of participants), as was the percentage of those whose tumors either shrank or did not grow for at least 6 months (34% versus 22%, respectively). Finally, the length of time that the cancer responded to treatment without growing or spreading was longer in those treated with sacituzumab govitecan (7.4 months) than in those treated with chemotherapy (5.6 months). There was not a significant difference in overall survival between the 2 groups.

Side effects from treatments occurred in both groups, though side effects occurred more frequently in the sacituzumab govitecan group (74% of participants) than in the chemotherapy group (60% of participants). The most common side effects in both groups were low white blood cell counts and diarrhea. However, few people in both groups experienced side effects serious enough to have to stop treatment.

What does this mean for patients? For people with advanced hormone receptor-positive, HER2-negative breast cancer that has not been stopped by previous treatments, sacituzumab govitecan may provide an alternative to chemotherapy in delaying cancer growth and spread.

"It is very gratifying to see the benefit of sacituzumab govitecan for these patients who have had very limited treatment options. Longer follow-up is needed to determine the impact on overall survival, and additional prespecified analyses will help us understand the potential role of sacituzumab govitecan in a setting where there are currently no other targeted treatment options available.”

—lead study author Hope S. Rugo, MD, FASCO
University of California San Francisco Comprehensive Cancer Center
San Francisco, California

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Liquid biopsy may reduce the need for chemotherapy after surgery in some people with stage II colon cancer

Who does this study affect? People with stage II colon cancer who have had surgery.

What did this study find? The phase 2 DYNAMIC clinical trial found that using liquid biopsy was helpful in guiding treatment decisions after surgery for people with stage II colon cancer. If liquid biopsy found no cancer DNA in a person’s blood after surgery, they did not receive chemotherapy and this did not increase their risk of recurrence, sparing some patients from receiving unnecessary treatment.

Liquid biopsy uses a blood sample to assess the amount of cancer DNA, also called circulating tumor DNA (ctDNA), found in a person’s blood. Liquid biopsies are useful in detecting cancer cells that might be left in the body after surgery, which can help predict a person’s risk of recurrence, which is the chance of the cancer coming back, and guide decisions about further treatment. This study was evaluating whether liquid biopsy could help reduce the number of people with stage II colon cancer who needed chemotherapy after surgery without increasing their risk of recurrence.

This study included 455 people who had received surgery for stage II colon cancer. The participants were randomly assigned to receive post-surgery treatment using either guidance from liquid biopsy (302 participants) or standard care without liquid biopsy (153 participants). For those in the standard care group, doctors used criteria such as the stage of the disease and whether the cancer had spread to the lymph nodes or grown into the bowel wall to determine post-surgery treatment. Those in the liquid biopsy group who had cancer DNA found in their blood at 4 or 7 weeks after surgery received chemotherapy, while those with no cancer DNA found in their blood did not receive further treatment.

At a median follow-up of 37 months, the study found that the percentages of people without signs of the cancer returning after treatment (this is called recurrence-free survival) were similar between the liquid biopsy group and the standard care group. This is despite fewer people in the liquid biopsy group receiving chemotherapy. Overall, about half as many people in the liquid biopsy group needed chemotherapy (15.3% of participants) compared with those in the standard care group (27.9% of participants). At 2 years, 93.5% of people in the liquid biopsy group did not show signs of the cancer returning versus 92.4% of those in the standard care group. At 3 years, the recurrence-free survival rate was 91.7% in the liquid biopsy group and stayed the same for the standard care group at 92.4%.

People who received chemotherapy in the liquid biopsy group saw a benefit from the additional treatment, with a recurrence-free survival rate of 86% at 3 years. People in the liquid biopsy group with no ctDNA detected and who did not receive chemotherapy had a very low risk of recurrence (7.5%) at 3 years. People with no ctDNA, no post-surgery chemotherapy, and low-risk factors, such as no cancer in the lymph nodes, smaller tumor size, and other factors, had a 3.3% risk of recurrence. Even among participants in this group who had a tumor that had grown into the outer lining of the bowel but had not grown through it, the risk of recurrence was 5.8%.

What does this mean for patients? Liquid biopsy could help determine which people with stage II colon cancer will benefit most from chemotherapy after surgery to reduce their risk of recurrence, ultimately sparing some people from receiving chemotherapy that may be unnecessary.

"The DYNAMIC study results are very encouraging because previous data suggest that patients with a positive ctDNA score after surgery have a very high recurrence risk if no further treatment is given. Our findings show that with adjuvant treatment, ctDNA-positive patients derive considerable benefit from chemotherapy such as an oxaliplatin-based regimen.”

— lead study author Jeanne Tie, MD
Walter and Eliza Hall Institute of Medical Research and Peter MacCallum Cancer Centre
Victoria, Australia

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