Harvard Women's Health Watch

In the journals: Some side effects of breast cancer treatment may be a good sign

In the journals

Some side effects of breast cancer treatment may be a good sign

Side effects are one of the worst aspects of breast cancer treatment. The harsh effects of standard chemotherapy are notorious, but even gentler endocrine treatments, such as tamoxifen, can cause distressing symptoms. These therapies work by interfering with the activity of estrogen, which can fuel the growth of certain tumors. Not surprisingly, the side effects resemble those associated with menopause, when ovarian production of estrogen declines — especially hot flashes, night sweats, and joint pain and stiffness. But as bothersome as such side effects can be, there may be an upside: a study published online and in the Oct. 30, 2008, Lancet Oncology suggests that in some cases they may be a sign that the treatment is working.

In a retrospective analysis of data on 3,964 women treated for early-stage breast cancer in the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial, researchers from the University of London studied the recurrence rate of breast cancer in women who complained of joint pain or vasomotor symptoms (hot flashes, night sweats, and cold sweats) during treatment with either tamoxifen or anastrozole (Arimidex). Tamoxifen works by blocking estrogen at receptor sites on the tumor; anastrozole works by blocking the activity of aromatase, an enzyme important in the production of estrogen in fat and other tissues — the main sources of estrogen in postmenopausal women.

Nearly 40% of the women had vasomotor symptoms, and 31% had joint symptoms. After nine years, women who experienced both had an 11.4% lower risk of recurrence than those reporting no side effects. Women who experienced only joint pain had a 10% lower risk of recurrence, and those who reported only vasomotor symptoms had a 6% lower risk. This study confirmed earlier research linking tamoxifen-induced vasomotor symptoms with lower recurrence rates. This study adds joint symptoms to the relevant side-effects list and indicates that side effects from anastrozole also correlate with a reduced rate of recurrence.

To continue reading this article, you must login.
  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise
Learn more about the many benefits and features of joining Harvard Health Online »