Certain Lumen A Breast Cancers May Discontinue Radiation Therapy After Breast-Conserving Surgery

The results of a prospective LUMINA study (NCT01791829) show that patients aged 55 years and older with low-grade T1N0, luminal A breast cancer, and Ki67 expression of 13.25% or less are at no risk of increased disease recurrence after breast-conserving surgery. It was revealed that radiation therapy could be discontinued.According to the presentation at 2022 American Society of Clinical Oncology (ASCO) Annual Meeting..

A single-group cohort study excluded radiation therapy from the treatment of 500 women with low-risk luminal A breast cancer. Five years later, there were only 10 local recurrences and the cumulative local recurrence risk rate was 2.3% (90% CI, 1.3% -3.8%), below the 5% significant cutoff. According to lead author Timothy J. Welan, MD, FASCO, overall survival at 5 years was 97.2% (90% CI, 95.9% -98.4%), with only one breast cancer-related death.

“Women aged 55 years and older with T1N0 grade 1-2 luminal A breast cancer after breast-conserving surgery treated with endocrine therapy alone had a very low local recurrence rate at 5 years,” said a professor of oncology. Whelan said. A Canadian research chairman for breast cancer research at McMaster University and a radiation oncology scientist at the Durabinsky Cancer Center in Hamilton, Ontario, Canada, said at a press conference on the data. “The positive and controlled nature of this multicenter study confirms that such patients are candidates for the omission of radiation therapy.”

At 26 centers in Canada, the study enrolled 500 patients with hormone receptor-positive breast cancer, with estrogen receptor positive in more than 1% of cells and progesterone receptor in more than 20% of cells. .. All patients had HER2-negative disease. At baseline, the patient had undergone breast mass resection and started or was planning to start endocrine therapy.

Only those with 13.25% less Ki67 were included in the study. The Ki67 test was centrally completed using a systematic approach to counting cells in five random fields in three different locations across Canada. “The reliability test was greater than 0.90 and actually up to 0.98. I was very happy with the reliability test in this study,” Whelan said. “Ki67 is increasingly being used in many hospital laboratories to check for cancer growth and has recently been recommended by the FDA as an adjunct therapy with abemaciclib. [Verzenio].. “

The average age of patients in this study was 67 years, 40% were 55 to 65 years, 48% were 65 to 74 years, and 12% were 75 years or older. The mean tumor size at resection was 1.1 cm, with tumors smaller than 0.5 cm present in 8% of patients, 0.51 to 1.0 cm in 43% of patients, and 1.1 to 2.0 cm in 49% of patients. Tumor grades were 1 (66%) and 2 (34%), and the main endocrine therapies administered were tamoxifen (41%) and aromatase inhibitors (59%).

“In the last two decades, we have noticed a steady reduction in the risk of local recurrence, due to the detection of smaller cancers screened, better surgical treatment, and more effective hormone therapy. Welan explained. “Breast cancer was found to be composed of many different molecular subtypes, especially 4. The first subtype, lumen A, is characterized by estrogen receptor positivity and low Ki67, a measure of proliferation. This has the lowest risk of recurrence. “

Other efficacy endpoints supported the omission of radiation therapy for patients with luminal A breast cancer. In a 5-year analysis, there were only 8 cases of contralateral breast cancer and the risk of contralateral recurrence was 1.9% (90% CI, 1.1% -3.2%). Recurrences everywhere were experienced in 12 patients with an overall risk of recurrence of 2.7% (90% CI, 1.6% -4.1%). Disease-free survival, including recurrence, secondary cancer, and death from other causes, was 89.9% (90% CI, 87.5% -92.2%).

“Radiation therapy is an inconvenient treatment. It can last up to 5 weeks daily and it is a costly treatment. It is a lot. [adverse] effect [AEs]Including early [AEs]Like skin irritation and malaise, and slow [AEs]Breast pain and distortion can affect the appearance and overall quality of life of the breast, “Whelan said. “It is also associated with very rare and serious AEs such as heart disease and secondary cancer.”

In North America, Whelan says there are more than 300,000 diagnoses of invasive breast cancer annually. Due to this rate and the prevalence of luminal A subtypes, he predicted that these results could lead to the omission of radiation therapy in 30,000 to 40,000 patients annually.

“These exciting data are very encouraging and can affect many cancer patients who are very unlikely to have breast cancer recurrence without radiation therapy,” said radiation oncology. ASCO Expert Corey W. Speers, MD, PhD, Michigan Rogel Cancer Center, said. “These findings are the first of many recent breast cancer trials that are still commonly used but are considering reducing treatments that may not be needed for properly selected patients. . “

Study follow-up will be continued for a total of 10 years for each patient to better assess the effects of long-term recurrence rate, new primary cancers, and omission of radiation therapy on survival. The start date of the study was July 2013 (NCT01791829).

reference

Whelan TJ, Smith S, Nielsen TO, et al. Lumina: A prospective study omitting radiation therapy (RT) after breast-conserving surgery (BCS) in T1N0 luminal A breast cancer (BC). J Clin Oncol.. 2022; 40 (suppl 17): LBA501. doi: 10.1200 / JCO.2022.40.17_suppl.LBA501