Oncology patients undergoing radiation treatment and chemotherapy routinely use prescription and/or over‐the counter medications either as part of pre‐existing comorbid conditions or in the context of conventional treatment management. A growing amount of data suggest that commonly used pharmaceuticals possess antioxidant properties, which may also partially explain some of their therapeutic efficacy. Clinical research is continuing on how such agents interact during chemotherapy and radiation when oxidative mechanisms of action are involved. Historically, such discussions centered on the category of dietary supplements, natural health products, fruits and vegetables, along with established protectant medications. Evidence confirms that some pharmaceutical agents exhibit antioxidant properties similar to dietary supplements, protectants, and may hence hinder the efficacy of chemotherapy and radiation treatment. Awareness by both healthcare providers and patients in this area is often lacking. After reviewing some of the more common and well‐established pharmaceuticals, which include those prescribed during cancer treatment, caution needs to be advised especially in regards to the use of corticosteroids, as long‐term randomized outcome studies ensuring safety in this area are still outstanding.

A 66-year-old patient presented with acute recurrent metastatic estrogen and progesterone receptor–positive, Her-2/neu-negative breast cancer, bone lesions (lumbar spine, pelvis), pulmonary nodules, hepatic metastasis, elevated cancer antigen 15 and liver enzymes, dyspepsia, and diarrhea. The patient had been taking raloxifene for approximately 8 years. After discontinuation, clinical parameters and symptoms improved rapidly without oncological therapy or other forms of treatment. Three months after raloxifene discontinuation, capecitabine was initiated by the treating oncologist who deemed an anti-estrogen withdrawal effect (AEWE) implausible. However, the lasting regression was more indicative of a raloxifene rebound effect than chemotherapy or other interventions. Today, the patient is asymptomatic with a good performance status. Hepatic metastatic regression has been confirmed, without any oncological treatment administered in the past 16 months and approximately 23 months following the withdrawal of raloxifene. This case highlights the need to screen breast cancer patients for the possibility of an AEWE if they are using raloxifene and possibly similar selective estrogen receptor modulators (SERMs) which includes tamoxifen, when diagnosed with advanced breast cancer, especially in the recurrent disease setting.

Here we present an observational case report of a 49-year-old female, non-smoker, having a poor performance status with non-small-cell lung cancer and leptomeningeal carcinomatosis (LMC), who upon introduction of oral dichloroacetate (DCA) survived approximately 64 weeks (454 days) following palliative whole brain radiation without the need for chemotherapy or further targeted therapy to specifically address the LMC. To our knowledge, this is the first case report incorporating the use of DCA in LMC. Our findings are discussed in the context of previously reported applications of DCA in malignancies of the central nervous system.