Machine-Learning Analysis of Serum Proteomics in Neuropathic Pain after Nerve Injury in Breast Cancer Surgery Points at Chemokine Signaling via SIRT2 Regulation.

BACKGROUND: Persistent postsurgical neuropathic pain (PPSNP) can occur after intraoperative damage to somatosensory nerves, with a prevalence of 29-57% in breast cancer surgery. Proteomics is an active research field in neuropathic pain and the first results support its utility for establishing diagnoses or finding therapy strategies. METHODS: 57 women (30 non-PPSNP/27 PPSNP) who had experienced a surgeon-verified intercostobrachial nerve injury during breast cancer surgery, were examined for patterns in 74 serum proteomic markers that allowed discrimination between subgroups with or without PPSNP. Serum samples were obtained both before and after surgery. RESULTS: Unsupervised data analyses, including principal component analysis and self-organizing maps of artificial neurons, revealed patterns that supported a data structure consistent with pain-related subgroup (non-PPSPN vs. PPSNP) separation. Subsequent supervised machine learning-based analyses revealed 19 proteins (CD244, SIRT2, CCL28, CXCL9, CCL20, CCL3, IL.10RA, MCP.1, TRAIL, CCL25, IL10, uPA, CCL4, DNER, STAMPB, CCL23, CST5, CCL11, FGF.23) that were informative for subgroup separation. In cross-validated training and testing of six different machine-learned algorithms, subgroup assignment was significantly better than chance, whereas this was not possible when training the algorithms with randomly permuted data or with the protein markers not selected. In particular, sirtuin 2 emerged as a key protein, presenting both before and after breast cancer treatments in the PPSNP compared with the non-PPSNP subgroup. CONCLUSIONS: The identified proteins play important roles in immune processes such as cell migration, chemotaxis, and cytokine-signaling. They also have considerable overlap with currently known targets of approved or investigational drugs. Taken together, several lines of unsupervised and supervised analyses pointed to structures in serum proteomics data, obtained before and after breast cancer surgery, that relate to neuroinflammatory processes associated with the development of neuropathic pain after an intraoperative nerve lesion.

Breast reconstruction after breast cancer surgery - persistent pain and quality of life 1-8 years after breast reconstruction.

OBJECTIVES: To assess the long-term outcome of breast reconstructions with special focus on chronic postsurgical pain (CPSP) in a larger cohort of breast cancer survivors. METHODS: A cross-sectional study on 121 women with mastectomy and breast reconstruction after mean 2 years 4 months follow up. The mean time from breast reconstruction to the follow-up visit was 4 years 2 months. We studied surveys on pain (Brief Pain Inventory, BPI and Douleur Neuropathique 4, DN4), quality of life (RAND-36 health survey), sleep (insomnia severity questionnaire, ISI), mood (Beck's Depression Index, BDI; Hospital Anxiety and Depression Scale, HADS), and a detailed clinical sensory status. Patients were divided into three groups: abdominal flap (Deep inferior epigastric perforator flap, DIEP; Free transverse rectus abdominis flap, fTRAM, and Pedicled transverse rectus abdominis flap, pTRAM), dorsal flap (Latissimus dorsi flap, LD and Thoracodorsal artery perforator flap, TDAP), and other (Transverse myocutaneous gracilis flap, TMG; implant). Clinically meaningful pain was defined ≥ 4/10 on a numeric rating scale (NRS). We used patients' pain drawings to localize the pain. We assessed preoperative pain NRS from previous data. RESULTS: 106 (87.6%) of the patients did not have clinically meaningful persistent pain. We found no statistically significant difference between different reconstruction types with regards to persistent pain (p=0.40), mood (BDI-II, p=0.41 and HADS A, p=0.54) or sleep (p=0.14), respectively. Preoperative pain prior to breast reconstruction surgery correlated strongly with moderate or severe CPSP. CONCLUSIONS: Moderate to severe CPSP intensity was present in 14% of patients. We found no significant difference in the prevalence of pain across different reconstruction types. Preoperative pain associated significantly with postoperative persistent pain.

Static mechanical allodynia in post-surgical neuropathic pain after breast cancer treatments.

Objectives Static mechanical allodynia (SMA), i. e., pain caused by normally non-painful static pressure, is a prevalent manifestation of neuropathic pain (NP). Although SMA may significantly affect the patient's daily life, it is less well studied in the clinical context. We aimed to characterize SMA in women with chronic post-surgical NP (CPSNP) after breast cancer surgery. Our objective was to improve understanding of the clinical picture of this prevalent pain condition. This is a substudy of a previously published larger cohort of patients with intercostobrachial nerve injury after breast cancer surgery (Mustonen et al. Pain. 2019;160:246-56). Methods We studied SMA in 132 patients with CPSNP after breast cancer surgery. The presence, location, and intensity of SMA were assessed at clinical sensory examination. The patients gave self-reports of pain with the Brief Pain Inventory (BPI). We studied the association of SMA to type of surgery, oncological treatments, BMI, other pains, and psychological factors. General pain sensitivity was assessed by the cold pressor test. Results SMA was prevalent (84%) in this cohort whereas other forms of allodynia were scarce (6%). Moderate-to-severe SMA was frequently observed even in patients who reported mild pain in BPI. Breast and the side of chest were the most common locations of SMA. SMA was associated with breast surgery type, but not with psychological factors. Severe SMA, but not self-reported pain, was associated with lower cold pain tolerance. Conclusions SMA is prevalent in post-surgical NP after breast cancer surgery and it may represent a distinct NP phenotype. High intensities of SMA may signal the presence of central sensitization. Implications SMA should be considered when examining and treating patients with post-surgical NP after breast cancer surgery.

Douleur Neuropathique 4 (DN4) stratifies possible and definite neuropathic pain after surgical peripheral nerve lesion.

BACKGROUND: Douleur Neuropathique 4 (DN4) is a screening questionnaire to help identify neuropathic pain (NP) in clinical practice and research. We tested the accuracy of the DN4 questionnaire in stratifying possible NP (pNP) and definite NP (dNP) in patients operated for breast cancer. METHODS: We studied 163 patients from a longitudinal cohort of breast cancer operated patients 4-9 years after surgery. pNP or dNP were classified according to the NP grading system. Surgeon-verified intercostobrachial nerve resection was used as a confirmatory test for dNP. A receiver-operating characteristic (ROC) curve analysis was performed and the area under the curve (AUC) was calculated to test the diagnostic accuracy (sensitivity, specificity, positive and negative predictive values) of the DN4. Additionally, we studied clinical factors that associated with a positive screening outcome in the interview part of the DN4 (DN4i). RESULTS: DN4i and DN4 showed significant accuracy in stratifying patients with pNP or dNP with cut-off scores 3 and 4 resulting to sensitivity of 66.2% and 79.4% and specificity of 77.8% and 92.6%, respectively. pNP and dNP patients showed differences in sensory descriptors of pain according to DN4i items. Screening positive on DN4i associated with dNP and younger age. CONCLUSIONS: Full DN4 could stratify pNP and dNP patients in a chronic postsurgical NP patient group operated for breast cancer. Additionally, DN4i showed significant accuracy in stratifying pNP and dNP, but an examination is necessary to obtain proper accuracy. Demographic factors may have an impact on the screening outcome of DN4i. SIGNIFICANCE: DN4 stratifies possible and definite postsurgical peripheral neuropathic pain. DN4i may also show this, but full DN4 is more accurate. We confirm DN4i as a valid screening tool for NP.

What makes surgical nerve injury painful? A 4-year to 9-year follow-up of patients with intercostobrachial nerve resection in women treated for breast cancer.

Nerve injury during breast cancer surgery can cause neuropathic pain (NP). It is not known why some, but not all, patients develop chronic postsurgical neuropathic pain (CPSNP) after the same nerve injury. In this study, we examined 251 breast cancer survivors with surgeon-verified intercostobrachial nerve resection to identify factors that associate with CPSNP. The patients were recruited from a previous study of 1000 women treated for breast cancer in 2006 to 2010. This enabled us to analyze preoperative factors that associate with future CPSNP. The patients were re-examined in 2014 to 2016 to diagnose CPSNP using the revised NP diagnostic criteria. Preoperative assessments were pain in the area to be operated on, any chronic pain condition, depressive symptoms, anxiety, sleep, and experimental cold pain sensitivity using the cold pressor test (CPT). Follow-up assessments were CPT, psychological factors, sleep, any chronic pain, and basic laboratory tests. One hundred thirty-seven (55%) patients with intercostobrachial nerve resection fulfilled CPSNP diagnostic criteria after 4 to 9 years. Of them, 30 patients (22%) had moderate to severe pain in self-reports and 86 (63%) presented moderate to severe evoked pain at examination. Preoperative pain in the surgical area, other chronic pains, and breast-conserving surgery were associated with future CPSNP. Other chronic pains, increased psychological burden, and insomnia, both before surgery and at the follow-up, were associated with CPSNP. Preoperative CPT did not associate with future CPSNP. Patients with established CPSNP showed increased pain sensitivity in CPT and higher levels of inflammatory markers, suggesting that central sensitization and inflammation may associate with the maintenance of CPSNP.

Loss of Pax5 promotes plasma cell differentiation.

Pax5 is indispensable for the commitment of early lymphoid progenitors to the B cell lineage as well as for the development of B cells. To better understand the functional importance of Pax5 at the later stages of B cell differentiation, we established a Pax5-deficient DT40 B cell line. The Pax5(-/-) cells exhibited slower growth, decreased surface IgM expression, and total loss of B cell receptor signaling. Moreover, the expression of the plasma cell-characteristic transcription factors Blimp-1 and XBP-1 were significantly upregulated and the expression of Bcl-6 diminished in the Pax5(-/-) cells, and this alteration was normalized by restored Pax5 expression. The Pax5-deficient cells further manifested substantially elevated secretion of IgM into the supernatant, another characteristic of plasma cells. These results indicate that downregulation of Pax5 function promotes the plasma cell differentiation of B cells.