The role of chemotherapy in breast cancer treatment

It’s impossible to think about chemotherapy as a treatment for breast cancer without concurrently thinking:

The treatment should not be worse than the disease

Writing in Tripping Over the Truth: How the Metabolic Theory of Cancer is Overdue, Travis Christofferson documents the origins of chemotherapy: “a substance designed to main and break the will of enemies in a cloud of slow-moving death.” Yes, we’re talking about mustard gas and WII.

The cost of cancer drugs, Christofferson continues, has escalated. Before 2000, the average cost per treatment course was $5,000. In 2005, the average cost had increased eightfold, to $40,000. In 2012, “almost every new drug was priced at more than $100,000 in the United States.”

We spend twice as much on medical care as 12 other high-wealth nations “while seeing the lowest life expectancy and some of the worst health outcomes among this group.”

Chemotherapy and breast cancer

Chemotherapy may be recommended for breast cancer patients before surgery (neoadjuvant) or after surgery (adjuvant).

  • Patients who undergo chemo before surgery are doing so to attempt to shrink the tumor so that less breast tissue must be removed.
  • Patients who undergo chemo after surgery are doing so to attempt to kill any remaining cancer cells in the body.
  • Patients with metastatic cancer may undergo chemo to  shrink the tumor.

Because it is a systemic treatment, chemotherapy drugs travel throughout the entire body, subjecting all cells to the drug’s toxicity.

Chemo works on the theory that cancer cells are dividing rapidly. But we have normal cells that also divide rapidly: in our blood, hair, intestinal tract, mouth, nails, nose, and vagina. The hope is that normal cells recover from the toxicity while cancer cells succumb.

Common side-effects of chemo include:

  • Reduced numbers of red and white blood cells
  • Hair loss
  • Intestinal/digestive tract distress
  • Tingling or numbness (neuropathy)

Chemo is less effective with slow-growing cancer than with fast-growing (aggressive) cancer. Every cancer responds differently, and cancer cells which survive chemo may mutate and become more aggressive/harder to treat.

Should you undergo chemo?

One of the side-effects of chemotherapy is an increased risk of cardiovascular disease. Researchers have developed a decision matrix to weigh trade-offs of chemotherapy treatment for breast cancer. They reported the results of three scenarios in a paper published in July:

  • no chemotherapy treatment
  • anthracycline (AC)-based adjuvant chemotherapy (more effective but more cardio-toxic)
  • non-AC-based adjuvant chemotherapy

They relied on results from clinical trials to measure 10-year mortality; cause of death; life years (LYs); and quality-adjusted LYs. Their conclusion:

Patients with low risk of metastatic recurrence are better off without adjuvant chemotherapy regardless of the outcome considered (i.e., the risks of cardiac toxicity from chemotherapy outweighed the benefits)… The choice of adjuvant treatment must consider the patient’s risk of distant recurrence and the quality of life associated with different health outcomes.

Two research papers, one in 2012 and one in 2017, specifically examined the effectiveness of chemotherapy on invasive lobular breast cancer. From 2012:

Adjuvant chemotherapy seems to confer no additional beneficial effects in postmenopausal patients with pure or mixed type lobular breast cancer receiving hormonal therapy.

The 2017 research echoed the earlier results: adjuvant chemotherapy was not associated with improved outcomes (10-year survival) for patients with ER+, HER2-, stage I/II invasive lobular cancer.

The 2017 research noted that chemotherapy extended 10-year survival rates for invasive ductal cancer. Patients with IDC undergoing chemo were 17% less likely to die in 10 years. Researchers are 95% confident that the true hazard is between 8% and 26% (hazard ratio, 0.83; 95% confidence interval, 0.74-0.92; what is a hazard ratio).

A 2012 report in Science Daily talked to Julie Gralow, M.D., director of breast medical oncology at Seattle Cancer Care Alliance. When thinking of ER+/HER2- cancer patients, “estrogen-blocking therapies often will work better than traditional chemotherapy.”

Can tests help me make a decision?

Researchers have developed genomic tests that predict how cancer might behave and respond to treatment.

The Oncotype DX breast cancer assay is used to help guide treatment decisions for early stage, hormone-positive, HER2-negative breast cancer. An analysis published in January 2017 demonstrated that lobular breast cancer differs “significantly from that in ductal carcinoma. Consequently, the clinical usefulness and cost-effectiveness of the Oncotype DX in guiding treatment for ILC should be further investigated.”

What is considered “high risk”?

The 13th St Gallen International Breast Cancer Conference (2013) Expert Panel defines patients with “high risk” of recurrence as having these characteristics (the more, the higher risk):

  • patient age < 35 years
  • tumor size >2 cm
  • tumor grade III
  • presence of extensive peritumoural vascular invasion
  • estrogen receptor (ER) and/or progesterone receptor (PR) negative
  • HER2 positive
  • high Ki67 expression (in grade II tumours)
  • >3 positive lymph nodes.

 

 

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