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Research Moving Toward Personalizing Breast Cancer Treatment (dateline January 4, 2008)

Recent research suggests that analyzing individual characteristics of breast cancer tumors can provide a more effective treatment while avoiding unnecessary therapies with often serious side effects. For example, a study presented at a large breast cancer conference in December discussed results of a genetic test called Oncotype DX, which can help predict the likelihood of a breast cancer recurrence, and in doing so, provide information as to whether chemotherapy would be helpful in women whose breast cancer has spread to the lymph nodes. The test works by analyzing genes in a breast cancer tumor and rating the chances that the breast cancer will return.

The Oncotype DX test, made by Genome Health, Oncotype is a multi-gene expression test that can be used to help predict:

  • the likelihood of breast cancer recurrence
  • the likelihood of patient survival within 10 years of diagnosis
  • the likelihood of chemotherapy benefit

In research presented at the San Antonio Breast Cancer Symposium, researchers used the Oncotype DX test on 370 women with breast cancer. Some of the women had been treated with chemotherapy and the drug tamoxifen while others had only received tamoxifen. The test works by analyzing 21 genes in breast cancer tumor cells and predicting, on a scale of 1 to 100, the chances that breast cancer will return after treatment. A low score suggests that breast cancer is not likely to return while a higher score suggests a stronger likelihood of a recurrence.

The researchers found that some women who were treated with both chemotherapy and tamoxifen had low Onocotype DX scores, suggesting that they might not have needed to be treated with chemotherapy, as their scores were similar to other women in the study who had been treated only with tamoxifen.

Chemotherapy can cause serious side effects. The most common temporary effects include nausea and vomiting, hair loss, and fatigue. Other possible side effects include:

  • Infection
  • Mouth sores
  • Taste changes
  • Decreased appetite
  • Diarrhea or constipation
  • Tingling or burning sensations
  • Numbness in hands and/or feet
  • Skin irritations (redness, itching, peeling, or acne)
  • Dark, brittle, or cracked fingernails or toenails
  • Kidney/bladder infections
  • Flu-like symptoms after chemotherapy sessions
  • Fluid retention

However, the test also showed that some women with high Oncotype DX scores likely benefited from chemotherapy, as their cancers were less likely to return after treatment.

While researchers will continue to explore the potential uses of tests such as the Oncotype DX, they represent a shift toward a more individualized approach to treating cancer. Research has been focusing more on "targeted" cancer therapies, such as the drug Herceptin, which is beneficial only in women who have certain types of breast cancers that carry extra copies of the HER2 gene. Similarly, the most widely used drug to treat breast cancer, tamoxifen, has been shown to only be beneficial in women whose breast cancers are estrogen dependent.

By examining the individual characteristics of a patient's cancer, physicians are more likely to be able to design a treatment that is most beneficial to the patient and avoid unnecessary therapies which can have serious side effects.

Additional Resources and References