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PRIME II RT Omission — SCE Medical Oncology MCQ

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ModerateBreast CancerPRIME II RT OmissionSCE Medical Oncology

A 72-year-old woman with early ER+/HER2- breast cancer (T1c N0, grade 1, Ki-67 5%) asks whether she can safely omit radiotherapy after BCS. The PRIME II trial addressed this question. What were its findings?

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Correct answer: C — PRIME II showed that in women ≥65 with low-risk ER+ breast cancer (T1-2 ≤3 cm, N0, grade 1-2) on adjuvant endocrine therapy, omitting RT increased ipsilateral recurrence modestly (~5% at 10 years vs ~1%) without OS difference — RT omission is reasonable after informed discussion

PRIME II randomised women ≥65 with low-risk ER+ early breast cancer (BCS, T1-2 ≤3 cm, N0, grade 1-2, clear margins) to WBRT vs no RT (all received ET). At 10 years, local recurrence was modestly higher without RT (~5% vs ~1%) but no OS difference was seen. This supports informed discussion about RT omission in selected elderly patients, weighing the small absolute recurrence risk reduction against RT inconvenience and toxicity. NICE NG101 acknowledges this option for appropriate patients.

Reference: NICE NG101; PRIME II Kunkler et al NEJM 2015; ESMO 2024