Roche said on Wednesday its experimental oral drug giredestrant reduced the risk of breast cancer recurrence by 30% compared with standard endocrine therapy, in what it said marked the first big advance in hormonal treatment for the disease in over 20 years.

The Swiss drugmaker said detailed results from the phase III lidERA trial showed at three years, 92.4% of patients in the giredestrant arm were alive and disease-free versus 89.6% in the standard-of-care arm.

The company had last month published only a brief summary of the results, saying the primary goals were met.

"When you talk about a 30% increase in disease-free survival, you're basically saying 30% of these patients who in standard of care would still have gone on to recur - you're getting 30% fewer of those patients recurring," Levi Garraway, Roche's Chief Medical Officer, said in an interview.

The results address a critical unmet need in ER-positive breast cancer, which accounts for approximately 70% of all breast cancer cases. Despite current treatments, up to a third of patients with early-stage breast cancer eventually experience recurrence.

The data positions giredestrant as a potential new standard of care in adjuvant endocrine therapy, though questions remain about which patients may still need additional treatment with drugs from the class of CDK4/6 inhibitors, like Novartis' Kisqali.

Garraway emphasized that giredestrant's safety profile was favorable, with numerically fewer patients discontinuing treatment due to side effects compared with those who received standard care.

JPMorgan analysts previously estimated the adjuvant indication could generate about $5 billion in annual revenue if approved.

The results will be presented at the San Antonio Breast Cancer Symposium on Wednesday. Giredestrant belongs to a class of drugs called oral selective estrogen receptor degraders, or SERDs.