Based on its analgesic and anti-inflammatory activities, shark cartilage has been used to relieve symptoms in OA. To date, no clinical studies are available to determine its effectiveness; however, positive results have been obtained in several clinical studies for one of its constituents, chondroitin sulfate (see Chondroitin monograph for details).
Shark cartilage is a popular supplement with cancer patients (Bernstein & Grasso 2001), although results from the few clinical trials conducted using shark cartilage in people with advanced cancers have generally produced negative findings.
One study of 60 people with advanced, previously treated cancer (breast, colorectal, lung, prostate, non-Hodgkin's lymphoma, brain) failed to demonstrate an effect for orally administered shark cartilage (1 g/kg) on tumour growth or QOL (Miller et al 1998). A larger study of 83 patients with advanced breast and colorectal cancers, which was published in 2005, also found that shark cartilage failed to improve survival or QOL (Loprinzi et al 2005). This study was a two-arm, randomised, > 2007 Elsevier Australia
placebo-controlled, double-blind, clinical trial. Of note, there was a high drop-out rate as only half the patients receiving shark cartilage powder continued with treatment beyond 1 month and only 10% were still using the treatment by 6 months. It was thought that gastrointestinal symptoms may have contributed to the poor patient compliance.
Several smaller preliminary studies have produced positive results, with some patients experiencing less tumour progression and weight loss, improved appetite or decreased pain (Couzin et al 2003). Unfortunately, details of these studies are difficult to locate and much remains unanswered, such as doses used, time frames for use and criteria for improvement.
Investigation with Neovastat (AE-941), a standardised shark cartilage extract, has produced more promising results and demonstrated inhibitory effects on the growth and metastasis of tumors; however, research has mainly been conducted in animal models (Hassan et al 2005). One clinical study conducted with Neovastat did report a significant survival advantage for the patients with unresectable stage IIIA, IIIB, or IV non-small-cell lung cancers receiving treatment (Hassan et al 2005).
Clinical note — Angiogenesis and tumour growth
Angiogenesis is defined as the formation of new capillary blood vessels from existing microvessels and is a process regulated by inducers and inhibitors. It is critical for development, reproduction and repair and dominates many pathological conditions (Folkman 2003). In 1971, the hypothesis that tumour growth is angiogenesis-dependent was first proposed and since then, the study of angiogenesis inhibitors in cancer research has developed. It has now been demonstrated that solid tumours secrete angiogenic substances to set up an internal network of blood vessels to support further growth and there is a correlation between tumour microvessel density and the risk of metastases. In the absence of angiogenesis, tumour growth is restricted to a microscopic size and tumour cells do not shed into the circulation. Several clinical studies have been conducted with various anti-angiogenic therapies, generally indicating that despite an initial increase in tumour blood flow, long-term treatment causes total tumour blood flow to reach a steady state or to gradually decrease.
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