# CALGB 9343

Source: https://onco.cc/trials/calgb-9343/  
OnCo record `calgb-9343` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

CALGB 9343 showed that older women with small hormone-sensitive breast cancers taking tamoxifen gain only a small reduction in local recurrence from radiotherapy and no survival benefit, opening the door to omitting it.

## Summary

CALGB 9343 randomised 636 women aged 70 or older with clinical stage I oestrogen receptor-positive breast cancer treated by lumpectomy to tamoxifen alone or tamoxifen plus radiotherapy. At ten years, locoregional recurrence was 10 percent without and 2 percent with radiotherapy, with no difference in mastectomy rates, distant disease or overall survival (Hughes and colleagues, New England Journal of Medicine 2004 and Journal of Clinical Oncology 2013). Guidelines now list radiotherapy omission as an option in this group.

## Fields

- Kind: Trial
- Status: positive
- Last checked: 2026-09-16
- Tags: radiation-wave2
- Phase: 3
- Setting: Women aged 70 or over with small oestrogen receptor-positive breast cancer after lumpectomy: tamoxifen alone versus tamoxifen plus whole-breast radiotherapy
- Sponsor: Cancer and Leukemia Group B (US)
- Enrolled: 636
- Result: 10-year locoregional recurrence 10% (tamoxifen alone) vs 2% (tamoxifen plus radiotherapy); no survival difference.
- Outcomes: Locoregional recurrence at 10 years: Tamoxifen alone 10% vs Tamoxifen plus radiotherapy 2%

## Sources

- NEJM 2004: https://doi.org/10.1056/NEJMoa040587
- JCO 2013 update: https://doi.org/10.1200/JCO.2012.45.2615

## Connected records

- cancers: [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/)
- technologies: [Active surveillance](https://onco.cc/technologies/active-surveillance/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/)
- drugs: [Tamoxifen](https://onco.cc/drugs/tamoxifen/)

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