PracticeUpdate: Haematology & Oncology

CONFERENCE COVERAGE

10

After 10 years, postmastectomy radiation is shown to improve local control but not overall survival in women with breast cancer and one to three positive nodes After 10 years of follow-up, postmastectomy radiotherapy improved local control but not overall survival in women with breast cancer and one to three positive lymph nodes, even after controlling for poorer prognostic features. M oses M. Tam, MD, of New York University Langone Medical Center, New York, not overall survival in women with one to three positive lymph nodes, even after controlling for poorer prognostic features. Future directions will involve a larger cohort of patients to help answer the question of whether radiation therapy impacts overall survival in the era of modern systemic therapy.

mammary nodes (27%). Women receiving postmastectomy radio- therapy were significantly younger, had more positive nodes, and had more advanced T stage than patients who did not receive the treatment. Postmastectomy radiotherapy im- proved 10-year local control (99% vs 94%, P = 0.006) significantly versus patients who did not receive postmastectomy radiotherapy. The therapy did not improve 10-year distant metastases (20% vs 17%) or overall survival (86% vs 84%) versus patients who did not receive post- mastectomy according to the use of propensity score analysis. A trend toward locoregional control was observed (95% vs 92%, P = 0.08). Subgroup analysis including larger tumours, poorly differentiated dis- ease, two or three positive lymph nodes, or premenopausal status did not identify a patient cohort in which postmastectomy radiother- apy predicted for improved overall survival. Dr Tam concluded after 10 years of follow-up, postmastectomy radio- therapy improved local control but

explained that the role of postmas- tectomy radiation in women with breast cancer and one to three positive lymph nodes in the set- ting of modern systemic therapy is controversial. “I wanted clarification,” Dr Tam said, “on the controversy regarding the need for postmastectomy radia- tion therapy in patients with one to three positive nodes. In fact, just last week, the ASTRO/American Society of Clinical Oncology/Soci- ety of Surgical Oncology released a consensus statement on this subject. They stated that postmastectomy radiation therapy confers a clear disease control and survival benefit in patients with T1–T2 disease and one to three positive nodes.” He continued, “Subsets of pa- tients may be at such low risk of disease recurrence that potential toxicities may outweigh the ben- efit of postmastectomy radiation therapy. Our analysis evaluated one of those patient subsets, essentially,

“We found,” he commented, “that patients treated with modern sys- temic therapy experienced excellent outcomes in local control and over- all survival, regardless of whether they received radiation therapy. We also found, however, that radiation therapy provides a clear local control benefit and a trend toward improved locoregional control once we ad- justed for imbalances in underlying patient characteristics.” He continued, “On multivariate analysis, we identified younger age (<40 years) and higher-grade disease were associated with higher risk of locoregional recurrence and death. These patients, therefore, may be more likely to benefit from radiation therapy.” “Future directions will involve a larger cohort of patients to help answer the question of whether ra- diation therapy impacts overall sur- vival in the era of modern systemic therapy.”

Adjuvant hormonal therapy was given in hormone-positive disease. Primary analysed outcomes in- cluded local control, locoregional control, distant metastasis, and overall survival. Statistical analysis of categorical data was performed with X2 test. Survival curves were plotted using the Kaplan-Meier method, and sur- vival estimates were obtained using log-rank test and Cox’s proportional hazard model using SPSS statistical software. A propensity score analy- sis was performed with R statistical package. Five hundred twenty-three women underwent mastectomy with one to three positive lymph nodes. Thirty-nine percent received postmastectomy radiotherapy, which included the chest wall, supracla- vicular field (71%), and internal

those who received modern systemic therapy.” Dr Tam and colleagues set out to investigate the effect of postmastec- tomy radiotherapy on breast cancer outcomes at 10-year follow-up in women enrolled on Breast Cancer International Research Group 005, a phase 3 trial of doxorubicin/cy- clophosphamide with concomitant versus sequential docetaxel. Individual patient data at 10-year follow-up were analysed for 1649 women treated on the control arm (sequential docetaxel). All women were node positive, HER-2 nonam- plified. They underwent mastectomy or lumpectomy with negative mar- gins followed by axillary lymph node dissection with at least six lymph nodes removed. Postmastectomy radiotherapy was given at the investigator’s discretion.

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