Timing of radiotherapy and outcome in patients receiving adjuvant endocrine therapy.
OBJECTIVE
To evaluate the association between the interval from breast-conserving surgery (BCS) to radiotherapy (RT) and the clinical outcome among patients treated with adjuvant endocrine therapy.


METHODS
Patient information was obtained from three International Breast Cancer Study Group trials. The analysis was restricted to 964 patients treated with BCS and adjuvant endocrine therapy. The patients were divided into two groups according to the median number of days between BCS and RT and into four groups according to the quartile of time between BCS and RT. The endpoints were the interval to local recurrence, disease-free survival, and overall survival. Proportional hazards regression analysis was used to perform comparisons after adjustment for baseline factors.


RESULTS
The median interval between BCS and RT was 77 days. RT timing was significantly associated with age, menopausal status, and estrogen receptor status. After adjustment for these factors, no significant effect of a RT delay ≤20 weeks was found. The adjusted hazard ratio for RT within 77 days vs. after 77 days was 0.94 (95% confidence interval [CI], 0.47-1.87) for the interval to local recurrence, 1.05 (95% CI, 0.82-1.34) for disease-free survival, and 1.07 (95% CI, 0.77-1.49) for overall survival. For the interval to local recurrence the adjusted hazard ratio for ≤48, 49-77, and 78-112 days was 0.90 (95% CI, 0.34-2.37), 0.86 (95% CI, 0.33-2.25), and 0.89 (95% CI, 0.33-2.41), respectively, relative to ≥113 days.


CONCLUSIONS
A RT delay of ≤20 weeks was significantly associated with baseline factors such as age, menopausal status, and estrogen-receptor status. After adjustment for these factors, the timing of RT was not significantly associated with the interval to local recurrence, disease-free survival, or overall survival.
Karlsson
Per
P
Department of Oncology, Sahlgrenska University Hospital, Gothenburg, Sweden. per.karlsson@oncology.gu.se
Cole
Bernard F
BF
Colleoni
Marco
M
Roncadin
Mario
M
Chua
Boon H
BH
Murray
Elizabeth
E
Price
Karen N
KN
Castiglione-Gertsch
Monica
M
Goldhirsch
Aron
A
Gruber
Günther
G
D000367:Age Factors; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000737:chemistry / Q000188:drug therapy / Q000401:mortality / Q000517:prevention & control / Q000532:radiotherapy* / Q000601:surgery; D017024:Chemotherapy, Adjuvant / Q000379:methods; D003131:Combined Modality Therapy / Q000379:methods; D003520:Cyclophosphamide / Q000008:administration & dosage; D018572:Disease-Free Survival; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D015412:Mastectomy, Segmental; D008593:Menopause; D008727:Methotrexate / Q000008:administration & dosage; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control; D016016:Proportional Hazards Models; D011960:Receptors, Estrogen / Q000032:analysis; D012044:Regression Analysis; D013629:Tamoxifen / Q000627:therapeutic use*; D013997:Time Factors
D018931:Antineoplastic Agents, Hormonal; D011960:Receptors, Estrogen; D013629:Tamoxifen; D003520:Cyclophosphamide; D005472:Fluorouracil; D008727:Methotrexate