984 – Photodynamic therapy for cutaneous recurrence of breast cancer: a potential palliative alternative

Abstract

Cutaneous recurrence of breast cancer represents a clinically challenging condition, frequently associated with pain,
ulceration, bleeding, and reduced quality of life, particularly in advanced stages when effective local treatment options
are limited. In this context, minimally invasive therapies capable of achieving local tumor control are highly desirable for
palliative management. Photodynamic therapy (PDT) has emerged as a promising strategy due to its localized cytotoxic
effects mediated by reactive oxygen species following activation of a photosensitizer. This in vitro study aimed to evaluate the cytotoxic effects of PDT using a nanoemulsion containing chloroaluminum phthalocyanine (ClAlPc/Ne) in breast
cancer cell lines, with emphasis on triple-negative breast cancer (TNBC), a subtype associated with aggressive clinical
course and limited therapeutic options. MCF-7 (luminal A) and MDA-MB-231 (TNBC) cells were incubated with ClAlPc/
Ne for 24 hours, followed by photoactivation at increasing light doses (1, 4, and 16 J/cm²) and subsequent viability assessment using the MTT assay. Control conditions included nanoemulsion without photosensitizer and non-irradiated cells.
ClAlPc/Ne-mediated PDT induced dose-dependent phototoxicity in both cell lines, with greater sensitivity observed in
MDA-MB-231 cells compared to MCF-7 (p<0.05). IC50 values for TNBC cells decreased from 1.96 μM (1 J/cm²) to <0.01 μM
(16 J/cm²), indicating enhanced susceptibility to oxidative stress. In contrast, MCF-7 cells demonstrated comparatively
lower sensitivity at equivalent conditions. These findings indicate that PDT with ClAlPc/Ne promotes selective cytotoxicity in TNBC cells and supports its potential as a localized therapeutic strategy. Although limited to an in vitro model,
these results highlight its relevance as a candidate approach for the palliative management of cutaneous recurrence of
breast cancer, aiming to improve local control and patient quality of life.
Ethics: In vitro study.