Background: chronic postsurgical pain (CPSP) after breast cancer surgery is associated with reduced quality of life, unemployment, and increased healthcare costs. Hundreds of observational studies have been published for CPSP; however, the lack of standardized definitions and measurement of CPSP makes the reported prevalence vary widely, from 10% to 90%.
Objectives: we conducted a systematic survey of observational studies that reported CPSP in breast cancer survivors to explore the variation in definition, measurement, and reporting of CPSP.
Methods: we searched MEDLINE, Embase, CINAHL, and PsycINFO from inception to October 2018, to identify observational studies with at least 100 patients that reported the prevalence and intensity of CPSP after breast cancer surgery. We performed random-effects meta-analysis with Freeman-Tukey transformation for CPSP prevalence, and pooled pain intensity after converting all pain scales to the 10 cm visual analogue scale (VAS).
Results: we included 188 observational studies with 300,906 patients that have published in 89 medical journals since 1986, with 90% published after 2000; of these,165 studies (88%) were conducted in high-income countries, 23 (12%) in middle-income countries and none in low-income countries. The average sample size was 1601 for each study with a median of 300 and interquartile range (IQR) of 178 to 520. The length of follow-up ranged from 3 months to more than 10 years. Of the 188 eligible studies, 155 (82%) used representative samples, 178 (95%) used patient-reported pain, and 129 (69%) used valid pain measures. Only 22 (12%) studies used a rigorous definition of CPSP (distinct from pain before surgery, associated with the site of surgery, and not explained by other reasons). Most studies (n = 150) reported pain prevalence, with 22 (15%) using a high threshold (more than mild pain) from pain instruments, 128 (85%) using low threshold (pain present or not). A total of 126 studies reported pain intensity using 63 different pain instruments or questionnaires, with pain scales ranged from 0 to 3, to 0 to 500. Due to the variations in pain definitions, measures, populations, the median prevalence of CPSP was 36.0% (IQR 20.1% to 46.8%); and median of mean pain intensity was 2.9 (IQR 1.9 to 4.0) on a 10 cm VAS. The pooled prevalence of CPSP was 34.2% (95%CI 30.9% to 37.6%); and pooled pain intensity on a 10 cm VAS was 3.0 (95% CI 2.7 to 3.4). We found significant subgroup effects between the use of 'any pain' (41.9%, 95%CI 38.3% to 45.5%) versus localized pain (29.2%, 95%CI 25.1% to 33.4%) to measure CPSP, and between low (36%, 95% CI 32.2% to 39.9%) versus high (24.3%, 95% CI 18% to 31.3%) threshold pain.
Conclusions: CPSP after breast surgery affects between 24% to 41.9% of women, depending on how pain is measured. Future studies require standardizing the definition of CPSP and using a validated instrument to measure pain intensity.
Patient or healthcare consumer involvement: no.