Oncotype Score Helps Avoid Unnecessary Radiation in DCIS

There’s a long-standing concern among oncologists that many women with ductal carcinoma in situ (DCIS), a potential precursor to invasive breast cancer, receive more treatment than they need. The potential for overtreatment largely revolves around the extent of surgery and the use of radiation.

Using the Oncotype DX Breast DCIS Score test, a laboratory test that estimates DCIS recurrence risk, may help identify patients with low-risk DCIS who can safely avoid adjuvant radiation after surgery, according to new research (abstract GS03-01) presented on December 8 at the 2023 San Antonio Breast Cancer Symposium. 

Researchers found that the Oncotype DX score helped identify patients who are at low and high risk for DCIS recurrence. Low-risk patients who skipped adjuvant radiotherapy after breast-conserving surgery demonstrated similar 5-year recurrence rates compared with high-risk patients who received adjuvant radiotherapy.

This is the first prospective study to evaluate radiation decisions among patients with DCIS. 

Lead author Seema Khan, MD, who presented the research, called the findings “reassuring.”

However, “we need larger and better trials” as well as longer follow-up to confirm this less-is-more approach, said Khan, a breast cancer surgeon and researcher at Northwestern University, Chicago. 

Virginia Kaklamani, MD, who moderated the presentation, noted that it is good to finally have prospective data on this topic. And although they are not definitive, “I personally think these results should be used” for counseling, said Kaklamani, leader of the breast cancer program at UT Health San Antonio. 

To reduce the risk for DCIS recurrence or progression to invasive breast cancer, most patients with DCIS undergo breast-conserving surgery followed by adjuvant radiotherapy, Khan explained. Instead of breast-conserving surgery, about 1 in 4 patients opt for mastectomy.

Earlier results from this trial revealed that MRI helped identify patients who can safely receive breast-conserving surgery instead of mastectomy.

The current results assessed whether the Oncotype DX score can guide radiation treatment decisions. 

The study included 171 patients with DCIS who had wide local excisions after MRI confirmed that they could forgo more extensive surgery. 

Surgical specimens were then sent for testing to determine the DCIS score using the 12-gene Oncotype DX test.

Women who scored < 39 points on the 100-point Oncotype DX scale were considered to be at low risk for recurrence and were advised to skip radiation. Women who scored > 39 were advised to undergo radiation. Overall, 93% of the patients followed the radiation recommendations: 75 of 82 patients (91.4%) deemed as low risk skipped adjuvant radiotherapy and 84 of 89 patients (94.4%) deemed as high risk had radiotherapy. 

At a median follow-up of 5 years, 5.1% (four of 82) of low-risk patients experienced a recurrence vs 4.5% (four of 89) of higher-risk patients. 

Recurrence rates among patients who followed the radiation recommendations mirrored these overall findings: 5.5% of 75 patients with low-risk DCIS who skipped radiotherapy experienced disease recurrence vs 4.8% of 84 patients with high-risk DCIS who received radiotherapy.

Age did not appear to impact the outcomes. Among the 33 women younger than 50 years, two experienced a recurrence (4%), both invasive. One occurred in the low-risk group and the other in the higher-risk group. Among the 138 older women, six had recurrences, three in each group, and one recurrence in each was invasive.

In short, “women who skipped radiation based on this score did not experience an excess risk of” ipsilateral recurrence over 5 years, said Khan. 

Overall, the study offers “strong evidence” that the DCIS score might help “prevent excessive treatment for some patients,” she concluded, adding that 10-year outcomes will be reported. 

The work was funded by the National Cancer Institute. Khan has no conflicts of interest. Kaklamani has extensive industry ties, including being a speaker for Pfizer, Genentech, Novartis, and AstraZeneca.

M. Alexander Otto is a physician assistant with a master’s degree in medical science and a journalism degree from Newhouse. He is an award-winning medical journalist who worked for several major news outlets before joining Medscape. Alex is also an MIT Knight Science Journalism fellow. Email: [email protected]