CHALLENGING THE THRESHOLD FOR INTERVENTION IN BREAST CANCER RELATED LYMPHOEDEMA IN A LOW RESOURCE SETTING

Ness D.¹, Maharaj S.¹, Buccimazza I.², Sartorius B.³

¹UKZN, Health Sciences/Physiotherapy, Durban, South Africa, ²Melson Mandela School of Medicine, General Surgery, Durban, South Africa, ³UKZN, Discipline of Public Health, Bio-Medical and Statistics, Durban, South Africa

Background: Breast Cancer Related Lymphoedema (BrCa Ly) is clinically diagnosed when a 2cm circumferential difference is measured between the affected and unaffected limb, equating to 200ml limb volume difference (LVD) using conversion calculations/software. This is considered one of the main sign of lymphatic failure. Bioimpedance Spectroscopy (BIS) measures subcutaneous electrical impedance as a sign of Lymphatic failure, earlier than circumferential measurement changes.

Purpose: 1. To determine at what limb volume difference (LVD) the lymphatic system starts to fail (pre-clinical) by using Bioimpedance Spectroscopy (BIS).
2. To determine whether this BIS volume equivalent correlates with circumferential/LVD measurement.
3. Determine the prevalence of Br Ca Ly in this cohort using both methods.

Methods: This was a prospective study comprising 60 consenting, female BrCa survivors, post cancer therapy at the Provincial Oncology Clinic kwaZulu Natal. We included all consenting women up to 18 months post radiation and excluded patients with bilateral BRCA or other primary cancers, previous mantle field radiation. Data collected included epidemiological information extracted from the patient files, circumferential limb measurements with a tape measure were converted into volume difference using the LVP-5 software and electrical impedance in the subcutaneous space using the LDEX-U400 BIS unit.

Results: BRCA Ly cut off at ≥200ml performed fairly well as a diagnostic tool for true abnormality based on BIS sensitivity of 67% and specificity of 93% (AUC 0.8). Using a cut off of ≥100ml based on BIS abnormality scores, performed better with sensitivity but specificity was reduced to 69% (AUC 0.84). Optimal break point in actual continuous volume at169ml performed best in terms of diagnostic capability for abnormal/normal BIS, with sensitivity of 80%, Specificity of 89% (AUC 0.93). The Positive Predictive value (PPV) and negative predictive value (NPV) were calculated, on this new threshold, using the clinically accepted incidence of Br Ca Ly as 25%. At the threshold of 169ml LVD, the PPV was 71% and NPV was 93% with a confidence Index of 0.86-0.99. In this cohort( n=60), the incidence of BrCa Ly, using circumferential measurement, and a threshold of 169ml LVD for presence of Ly, the prevalence was 17/60 ( 28%), using BIS abnormality scores as a sign of a failing Lymphatic system and impending BrCa Ly, the prevalence was 15/60 (25%).

Conclusion(s): This study shows that the lymphatic systems optimal breakpoint for lymphatic system failure is 169ml LVD, which corresponds significantly to abnormal BIS readings. The prevalence of BrCa Ly using BIS abnormality scores was 3 % lower (25%) than the circumferential measurement (28%), for diagnosis of BrCa Ly using the new threshold of 169ml.

Implications: In a low resource setting, where there is no access to BIS or equivalent tools, using converted circumferential measurements can assist Physiotherapists to address lymphatic failure earlier. This will improve quality of life for patients and reduce treatmetn costs for patients and healthcare stakeholders.

Funding acknowledgements: This is part of a self funded part time PhD by research, as such, no disclosures are applicable.

Topic: Oncology, HIV & palliative care

Ethics approval: The study was approved by the UKZN Bio-ethics Research Committee BE250/010.

All authors, affiliations and abstracts have been published as submitted.