Reviewers: John Han-Chih Chang, MD
Source: Lancet 1998; volume 352: pages 93 - 97
Thirteen thousand four hundred and nineteen women were recruited, but 8011 patients were not randomized secondary to refusal, ineligible or lost to follow-up. Five thousand four hundred and eight were randomized to either daily placebo or tam (20 mg per day x 5 years). This multicenter trial had 51 participating centers in Italy, 3 inSouth America and one in Greece.
One thousand four hundred and twenty-two have dropped out (placebo 670 and tam 752). A little over one thousand dropped out on their own accord. The others didsecondary to some adverse event. The most common cause of voluntary withdrawal from the trial was side effects. Over half withdrew in the first year. There were 15 deathsin patients on the trial (9 in the placebo arm and 6 in the tam arm). These were not attributable to breast cancer.
Forty-one cases of breast cancer were recorded. There were 19 cases in the tam arm and 22 in the placebo treated group. Thirty-three occurred while treatment was ongoing(tam 14 and placebo 19). Among women who finished at least one year of treatment, 19 breast cancers were diagnosed in the placebo group and 11 in the tam group (p =0.16 not statistically significant). Of those that received hormone replacement therapy, 8 developed breast cancer in the placebo arm (390 patients) and only one did in thetam arm (362 patients)
The breast cancer characteristics were not different in the two arms. Specifically, no difference was seen in estrogen or progesterone receptor positivity, size, grade,peritumoral invasion, axillary involvement or in-situ disease. A significant increase in the vascular events seen with the addition of tam. Thirty-eight had thrombophlebitis,phlebothrombosis or embolus in the tam arm contrasted to only 18 in the placebo group (p = 0.0053). Likely underestimates, but hypertriglyceridemia was seen in 15 ofthe tam patient and 2 of the placebo group.
Two other trials of note in the area of chemoprevention for breast cancer are also important: Royal Marsden Hospital from the United Kingdom and NSABP P1 trial.The trial from UK took patients who had a strong family history of breast cancer and randomized them to tamoxifen or placebo. The frequency of breast cancer wasthe same in both groups. The NSABP trial randomized patients with high risk based on age, lobular carcinoma in-situ, and other risk factors. The benefit was reduction in theoccurrence of invasive breast cancer by 49% (43.4/1000 versus 22/1000) and in-situ carcinoma by 50%. The incidence of estrogen-receptor positive tumors were reduced by 69% with tam.
Thus, the benefits of tamoxifen as a chemo-protectant against breast cancer is still to be defined. The studied patients in the NSABP high risk group derived a benefit. TheItalian study seems to have targeted a group with an overall lesser risk than the general population. The fact that the results are too preliminary and the poor compliancewith assigned treatment make this a questionable study to evaluate the chemoprevention.
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