Friday, December 10, 2004

Tamoxifen Versus Arimidex....
From the New York Times and The Lancet:Certain Type of Breast Cancer Drug Shows Better Result in Study:
A class of hormone-blocking drugs called aromatase inhibitors was more effective in preventing breast cancer recurrence in women past menopause than was tamoxifen, a medication now prescribed by many doctors, researchers reported yesterday.

The authors of the study, published online in the British medical journal The Lancet, said the findings suggested that aromatase inhibitors should replace tamoxifen as the first line of treatment for postmenopausal women with breast cancer.

But other experts said it was too early to tell if treating women with aromatase inhibitors from the outset was better than using tamoxifen first, followed by the newer drugs.
Here is the summary:
The standard adjuvant endocrine treatment for postmenopausal women with hormone-receptor-positive localised breast cancer is 5 years of tamoxifen, but recurrences and side-effects restrict its usefulness. The aromatase inhibitor anastrozole was compared with tamoxifen for 5 years in 9366 postmenopausal women with localised breast cancer. After a median follow-up of 68 months, anastrozole significantly prolonged disease-free survival (575 events with anastrozole vs 651 with tamoxifen, hazard ratio 0·87, 95% CI 0·78-0·97, p=0·01) and time-to-recurrence (402 vs 498, 0·79, 0·70-0·90, p=0·0005), and significantly reduced distant metastases (324 vs 375, 0·86, 0·74-0·99, p=0·04) and contralateral breast cancers (35 vs 59, 42% reduction, 12-62, p=0·01). Almost all patients have completed their scheduled treatment, and fewer withdrawals occurred with anastrozole than with tamoxifen. Anastrozole was also associated with fewer side-effects than tamoxifen, especially gynaecological problems and vascular events, but arthralgia and fractures were increased. Anastrozole should be the preferred initial treatment for postmenopausal women with localised hormone-receptor-positive breast cancer.
The greatest benefit was seen in receptor-positive patients for all of the measured outcomes (disease-free survival, time-to-recurrence, time-to-distant-recurrence, overall survival, time to breast cancer death, and contralateral breast cancer). The biggest impact was seen in the reduction of contralateral breast cancer. Arimidex seemed to be more well tolerated than the Tamoxifen.
The paper in its' PDF form is here.
Some problems I have with the study:
The usual amplification of benefits provided by relative risk rather than absolute risk. While the absolute benefit of Arimidex over Tamoxifen was about two percent, the relative benefit was 12 percent.
There appears to be no information on staging or indications that there was stage parity between the groups.
The authors were on the payroll of AstraZeneca, the manufacturer of both Tamoxifen and Arimidex. What's the big deal? you may ask, aren't they just robbing Peter to pay Paul? Not exactly:
About half a million American women use tamoxifen, sold under the brand name Novaldex by AstraZeneca and by other companies in generic form. But a growing body of evidence that aromatase inhibitors can more effectively prevent cancer from returning may have prompted tamoxifen's sales to plummet in recent years. Annual sales of all forms of tamoxifen fell to $52.3 million as of October 2004 from $177.9 million in 2003, according to IMS Health, a pharmaceutical information and health care company.
Is there a sinister plot to devalue the drug that is no longer under patent in favor of a branded product?
I report, you decide.
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