(just) one study showing radiation therapy not helping reduce distant mets in her2+pt

[Lani]

small study, based on IHC rather than FISH, Denmark known for long delays in treating patients with radiation therapy...but...here is the abstract:



Citation: European Journal of Cancer Supplements Volume 4, No. 2, March 2006, page 112

M. Kyndi12, F.B. Sørensen2, H. Knudsen3, M. Overgaard4, H.M. Nielsen1, J. Overgaard1

1Århus University Hospital, Dept. of Experimental Clinical Oncology, Århus C, Denmark
2Århus University Hospital, Dept. of Pathology, Århus C, Denmark
3Herlev Hospital, Dept. of Pathology, Herlev, Denmark
4Århus University Hospital, Dept. of Oncology, Århus C, Denmark

The study was conducted on behalf of the Danish Breast Cancer Cooperative Group DBCG
Purpose: The DBCG82bc study showed that adjuvant radiotherapy (RT) improved survival in high-risk pts treated with mastectomy and systemic therapy. So far, pts and tumors have been described by classical clinical factors only (e.g. nodal status, tumor size) not by biological markers. However, the disease is heterogeneous and biological markers might describe the response to RT more precisely. The aim of this study was to evaluate the importance of adding information on markers such as estrogen receptor (ER), progesterone receptor (PR), and HER2.
Material: DBCG82bc included 3083 high-risk breast cancer pts, characterized by positive nodes and/or tumor size > 5 cm and/or invasion to skin or fascia. The present analysis included 1241 pts with 8+ lymph nodes removed. Based on paraffin embedded tumor samples, tissue microarrays have been constructed for 918 pts, so far. Successful immunohistochemical staining for ER was obtained in 892 pts, PR in 894 pts and HER2 in 870 pts. Endpoints were loco-regional recurrence as first event (LR), distant metastases (DM) and survival.
Results: Of the 918 pts, 468 pts were randomized to no RT and 450 to RT. LR was found in 134 pts and DM in 516 pts. Overall, RT resulted in a significant reduction in LR (Odds Ratio 0.14 (0.08–0.22, 95% cf.l.)), in DM (OR 0.73 (0.56–0.94)), and death (OR: 0.73 (0.55–0.97)). When combining ER and PR, 658 pts were either ER or PR positive (receptor positive) and 245 pts were both ER and PR negative (receptor negative). HER2 positivity (3+) was observed in 149 pts. Significantly fewer DM were found in pts randomized to RT as compared to no RT, for receptor positive pts (OR: 0.66 (0.49–0.90)) and HER2 negative pts (OR: 0.68 (0.51–0.92)). No difference in DM as a function of RT was seen for the receptor negative pts (OR: 0.97 (0.58–1.63)) and the HER2 positive pts (OR: 1.02 (0.52–2.02)). Cox multivariate analyses of the separate prognostic subgroups showed that RT was not significant for survival in pts with HER2 positive and/or receptor negative tumors, whereas it was important in pts with HER2 negative and receptor positive tumors (P = 0.03).
Conclusion: Postmastectomy RT caused a significant reduction in DM for pts with HER2 negative and receptor positive tumors. This reduction was, however, not found for pts with the poorest prognosis i.e. receptor negative and/or HER2 positive. More exploration in other biologically markers is needed to confine the indication for RT in high-risk breast cancer.