Objective: To examine the development of persistent pain after treatment for breast cancer and to examine risk factors associated with continuing pain.

Design: Repeated cross sectional study in a previously examined nationwide cohort. All eligible women who underwent surgery for primary breast cancer in Denmark in 2005 and 2006 and were examined in 2008 were surveyed again with the same questionnaire.

Setting: Surgical centres in Denmark.

Main outcome measures: Prevalence, location, and severity of persistent pain after treatment for breast cancer in well defined treatment groups and changes in pain reporting and sensory disturbances from 2008 to 2012.

Participants: In 2012, 2828 women were eligible in our database, and 108 were excluded. Exclusion criteria were death; new, recurrent, or other cancer; reconstructive breast surgery; and emigration.

Results: 2411 (89%) women returned the questionnaire. Prevalence of persistent pain after treatment for breast cancer ranged from 22% to 53% depending on treatment. In 2012, 903 (37%) women reported such pain, a fall from 45% in 2008. Of these, 378 (16%) reported pain of ≥ 4 on a numerical rating scale (scale 0-10), a fall from 19%. Among women reporting pain in 2008, 36% no longer reported it in 2012. In contrast, 15% of the women who did not report pain in 2008 reported it in 2012. Risk factors for having pain were axillary lymph node dissection rather than sentinel lymph node biopsy (odds ratio 2.04, 95% confidence interval 1.60 to 2.61; P<0.001) and age ≤ 49 (1.78, 1.25 to 2.54; P<0.001). No particular method of treatment or age was associated with an increase in pain from 2008 to 2012.

Conclusions: Persistent pain after treatment for breast cancer remains an important problem five to seven years later. The problem is not static as it can either progress or regress with time.