Background: Taxane-induced peripheral neuropathy (TIPN) is a common and distressful side effect. Little is known on how long TIPN persist and its effect on health-related quality of life (HRQL). The overall aim of this thesis was to study the prevalence and severity of persistent TIPN, to investigate its impact on HRQL and to explore the clinical and genetic risk factors for TIPN among early-stage breast cancer survivors (ESBCS).   

Methods: A population-based cohort of 884 recurrence-free ESBCS diagnosed 2010-2015 in the Southeast Health Care region, Sweden and 1768 control women without prior cancer, who received a postal questionnaire including EORTC chemotherapy-induced peripheral neuropathy (CIPN20) and QLQ-C30 instruments. Prevalence of TIPN symptoms and clinical risk factors were explored. Adjusted relative risks (RR) were estimated for ESBCS compared to control women. For impact on HRQL, adjusted mean scores of QLQ-C30 scales among ESBCS with and without TIPN were calculated. Blood samples from 362 ESBCS were whole-exome sequenced. We leveraged logistic regression models to develop and validate polygenic prediction models to estimate the risk of persistent PN symptoms in a training and test cohort.   

Results: The response rate was 79% for ESBCS and 59% for controls. The median time post-taxane was 3.6 years. The adjusted RR for ESBCS vs. controls was highest (RR 1.8) for tingling in feet and numbness in feet. Individual sensory symptoms occurred in 9%-48% and motor symptoms in 7%-61% of ESBCS. The most prevalent symptoms were difficulty opening jar and cramps in feet. Paclitaxel, older age, overweight, diabetes mellitus, vibrating hand tools, smoking and autoimmune disease were independent risk factors (Study I). All 13 sensory and motor TIPN symptoms at increased risks among ESBCS had a significant impact on global health status, which worsened with increased severity of TIPN. Between 30%-93% of ESBCS with moderate-severe TIPN reported a clinically important impairment of functioning and personal finances. Moderate-severe difficulty climbing stairs and problems standing/walking were associated with medium-large clinically important differences (Study II). In the explorative sub-study, two of five prediction models based on genetic and clinical risk factors obtained AUC results above 60% in the test cohort. Using the model for numbness in feet (35 SNVs) in the test cohort, 73% survivors were correctly predicted. For tingling in feet (55 SNVs) 70% were correctly predicted (Study III).

Conclusions: Most sensory and motor symptoms are more common among taxane-treated ESBC survivors than in women from the general population, many symptoms persist ≥3.6 years. Persistent TIPN symptoms are associated with clinically relevant impairment of HRQL. Polygenic prediction models including clinical risk factors may be used to estimate the risk of persistent taxane-induced numbness in feet and tingling in feet.