Adjuvant Chemotherapy May Benefit Subset Of Small, Node-Negative Breast Cancer Patients

A subgroup of breast cancer patients with tumours less than 1 cm in size and no nodal disease who may benefit from adjuvant chemotherapy has been identified

  • Date: 18 Sep 2017
  • Author: Lynda Williams, Senior medwireNews Reporter
  • Topic: Breast Cancer

medwireNews: Small tumour size does not equate to lack of aggression, caution researchers who found that one in four women with a node-negative breast cancer less than 1 cm in diameter were at risk of relapse and distant metastases.

“Our results challenge the assumption that all small tumours are less serious and do not need adjuvant chemotherapy”, emphasized lead investigator Konstantinos Tryfonidis, from the EORTC in Brussels, Belgium, in a press release.

He presented substudy data at the ESMO 2017 Congress, held in Madrid, Spain, for the 826 participants of MINDACT who had pT1a–b N0 disease and the 4461 participants who had T1c–T3 N0 disease. The patients were all assessed for clinical risk using an online tool and for genomic risk using a 70-gene signature.

The randomised phase III study previously demonstrated a 5-year distant metastases-free survival (DMFS) rate of 94.7% for patients with high clinical risk and low genomic risk who were randomly assigned to not receive adjuvant chemotherapy. Thus, the 46% of patients at high clinical risk who are determined have a low genomic risk are “able to safely forgo adjuvant chemotherapy”, Konstantinos Tryfonidis told delegates.

The current presentation showed that most (75.5%) of the patients with pT1a–b N0 disease were at low clinical and genomic risk, while 23.7% had low clinical and high genomic risk. This compared with 43.6% and 8.5%, respectively, of the participants with tumours larger than 1 cm, with a further 18.2% of this group classified as being at high clinical and low genomic risk and 29.7% at high risk for both markers.

For the whole population of patients who were classified as having low clinical and low genomic risk, DMFS, disease-free survival (DFS) and overall survival (OS) did not significantly differ between patients with tumours of less than or more than 1 cm, at 98.1% versus 97.4%, 92.3% versus 92.8%, and 98.6% versus 98.3%, respectively.

But among patients with tumours less than 1 cm, patients low for both clinical and genomic risk had a trend towards better outcomes than those with low clinical, high genomic risk, at 98.1% versus 94.5%, 92.3% versus 88.6%, and 98.6% versus 97.2%, respectively.

And among pT1a–b N0 disease patients with low clinical, high genomic risk, 5-year DMFS was 97.3% for the patients given adjuvant chemotherapy versus 91.4% for those who did not receive this treatment. By contrast, for patients with larger tumours, the rates were a comparable 94.3% versus 95.7%.

Similarly, 5-year DFS in the pT1a–b N0 disease group with low clinical, high genomic risk was higher among the chemotherapy-treated patients than controls (92.3 vs 84.5%) but did not differ between the chemotherapy and no chemotherapy treatment groups for patients with larger tumours (90.4 vs 91.8%).

The same pattern was true for OS findings in the patients with sub-centimetre tumours when stratified by chemotherapy use (98.5 vs 95.8%) and for those with larger tumours (96.1 vs 98.2%).

The presenter emphasized that the exploratory analysis was conducted in a small number of patients over a small number of events and further OS follow-up is required to confirm these findings.

Nevertheless, Konstantinos Tryfonidis concluded that patients with low clinical and genomic risk have an “overall excellent outcome irrespective of tumour size, confirming the results of the main MINDACT study.”

DMFS and DFS for patients with T1a–b N0 disease are better for patients with low versus high genomic outcome and in this subgroup, patients with high genomic risk appear to derive survival benefit from adjuvant chemotherapy. A similar outcome was seen in a subanalysis of patients with hormone receptor-positive tumours judged at clinical low, genomic high risk, he added.

The presenter concluded: “Decision-making in patients with T1ab/node negative [disease] must take into account biology of the disease as well as other factors, such as performance status/comorbidity, age and patient preferences.”

Reference

Tryfonidis K, Poncet C, Slaets L, et al. 150O_PR – Not all small node negative (pT1abN0) breast cancers are similar: Outcome results from an EORTC 10041/BIG 3-04 (MINDACT) trial substudy. ESMO 2017 Congress; Madrid, Spain, 8–12 September.

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