<prompt> Which of the following is best for treating ER positive Ca breast?RaloxifeneExemestaneLeuperideBicalutamide  <response>: Ans. A. Raloxifene. Ref. Harrisons Medicine 18thTable. 90-4.Tamoxifen, raloxifene:MechanismSelective estrogen receptor modulators SERMs -- receptor antagonists in breast and agonists in bone. Block the binding of estrogen to ER cells.UseBreast cancer treatment tamoxifen only and prevention. Raloxifene also useful to prevent osteoporosis.SETamoxifen--partial agonist in endometrium, whichthe risk of endometrial cancer; hot flashes.Raloxifene--noin endometrial carcinoma because it is an endometrial antagonist.The choice of endocrine therapy in Rx of breast cancer In most patients, the initial endocrine therapy should be an aromatase inhibitor rather than tamoxifen. For the subset of postmenopausal women who are estrogen receptor-positive but also HER2neu positive, response rates to aromatase inhibitors are substantially higher than to tamoxifen. Newer pure antiestrogens that are free of agonistic effects are also effective. Cases in which tumors shrink in response to tamoxifen withdrawal as well as withdrawal of pharmacologic doses of estrogens have been reported. Endogenous estrogen formation may be blocked by analogues of LHRH in premeno- pausal women. Additive endocrine therapies, including treatment with progestogens, estrogens, and androgens.Endocrine Therapies for Breast CancerTherapyCommentsCastrationSurgicalLHRH agonistsFor premenopausal womenAntiestrogens TamoxifenPure antiestrogensSurgical adrenalectomyAromatase inhibitorsHigh-dose progestogensHypophysectomyAdditive androgens or estrogensUseful in pre- and postmenopausal womenResponses in tamoxifen-resistant and aromatase inhibitor-resistant patientsRarely employed second-line choiceLow toxicity; now first choice for metastatic diseaseCommon fourth-line choice after Als, tamoxifen and fulvestrantRarely usedPlausible fourth-line therapies; potentially toxicAlso know:A trial comparing tamoxifen with another selective estrogen receptor modulator, raloxifene, showed that raloxifene is comparable to tamoxifen in cancer prevention. This trial only included postmenopausal women. Raloxifene was associated with more noninvasive breast cancer than tamoxifen; the drugs are similar in risks of other cancers, fractures, ischemic heart disease, and stroke. Because the aromatase inhibitors are even more effective than tamoxifen in adjuvant breast cancer therapy, it is hoped that they would be more effective in breast cancer prevention. 