Second Primary Cancer

Women with a history of breast cancer, in addition to being at risk for a recurrence of their original cancer, are at risk of developing another cancer, independent of the first occurrence. The risk of developing these so-called “second primary cancers” depends not only on an individual’s inherent predisposition, but also on the treatments used for the initial cancer. The underlying risk of developing a second primary cancer in the contralateral breast is estimated to be 0.5 to 1 percent per year and is greater in women whose first cancer was diagnosed at a younger age and women with heritable or familial breast cancer (Burstein and Winer, 2000). Radiation therapy contributes to a higher risk of cancer in exposed areas (e.g., soft-tissue sarcomas of the thorax, shoulder, and pelvis; lung cancer) (Matesich and Shapiro, 2003; Levi et al., 2003). Adjuvant chemotherapy, including alkylating agents and topoisomerase II inhibitors (e.g., anthracyclines), can increase the risk for acute myelogenous leukemia (Mrozek and Shapiro, 2005). Little is known about long-term side effects of a class of drugs called taxanes (i.e., paclitaxel, docetaxel)6 due to their relatively recent introduction into standard practice in the adjuvant setting (Mrozek and Shapiro, 2005).

Tamoxifen is usually administered for 5 years to women with estrogen receptor- (ER-) positive tumors.7 While providing survival benefits, serious medical risks associated with tamoxifen include endometrial cancer, strokes, and blood clots. Women taking tamoxifen have a two- to threefold increase in the risk of developing endometrial cancer (about 80 excess cases per 10,000 treated women at 10 years) (Matesich and Shapiro, 2003). This increase occurs primarily in women over the age of 50. Most of the endometrial cancers that develop are early-stage and low-grade tumors that can be successfully treated (Burstein and Winer, 2000). Women taking tamoxifen are advised to undergo an annual pelvic examination while taking tamoxifen, and to see a gynecologist if they have irregular bleeding (Shapiro and Recht, 2001).8

Two small groups of breast cancer survivors face relatively high risks of

6  

Taxanes are effective when used to treat women with metastatic breast cancer. More recently taxanes have been shown to improve outcomes when used in addition to other adjuvant chemotherapy for women with node-positive breast cancer (Henderson et al., 2003; Stearns and Davidson, 2004).

7  

Tamoxifen is a drug that acts like estrogen on some tissues, but blocks the effect of estrogen on other tissues (it is in a class of drugs called selective estrogen receptor modulators).

8  

Routine endometrial surveillance using biopsy or transvaginal ultrasound is not warranted, according to findings from clinical trials of their effectiveness in identifying early uterine cancer among breast cancer survivors (Emens and Davidson, 2003).



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