Etoposide (trade name Etopophos) is a semisynthetic derivative of podophyllotoxin that exhibits antitumor activity. It has been in clinical use for more than two decades and remains one of the most highly prescribed anticancer drugs in the world. The primary cytotoxic target for etoposide is topoisomerase II. This ubiquitous enzyme regulates DNA under- and over winding, and removes knots and tangles from the genome by generating transient double-stranded breaks in the double helix. Etoposide kills cells by stabilizing a covalent enzyme-cleaved DNA complex (known as the cleavage complex) that is a transient intermediate in the catalytic cycle of topoisomerase II. The accumulation of cleavage complexes in treated cells leads to the generation of permanent DNA strand breaks, which trigger recombination/repair pathways, mutagenesis, and chromosomal translocations. If these breaks overwhelm the cell, they can initiate death pathways. Thus, etoposide converts topoisomerase II from an essential enzyme to a potent cellular toxin that fragments the genome. Although the topoisomerase II-DNA cleavage complex is an important target for cancer chemotherapy, there also is evidence that topoisomerase II-mediated DNA strand breaks induced by etoposide and other agents can trigger chromosomal translocations that lead to specific types of leukemia. Etopophos (etoposide phosphate) is indicated in the management of the following neoplasms: Refractory Testicular Tumors-and for Small Cell Lung Cancer. The in vitro cytotoxicity observed for etoposide phosphate is significantly less than that seen with etoposide, which is believed due to the necessity for conversion in vivo to the active moiety, etoposide, by dephosphorylation. The mechanism of action is believed to be the same as that of etoposide.

P-32 is a radioactive isotope of phosphorus with a half-life of 14.29 days. Radioactive decay of P-32 produces beta-particles (electrons) which are able to penetrate tissue at a range of 3-8 mm. Phosphate ion P-32 has many applications in medicine and biology. P32 sodium phosphate was approved by the FDA for the treatment of polycythemia vera, chronic myelocytic leukemia, and chronic lymphocytic leukemia. P32-phosphate may also be used in the palliative treatment of selected patients with multiple areas of skeletal metastases. As metabolic uptake of phosphorus is selectively increased in malignant tissues, P-32 was also used for cancer diagnostics.

Phosphate is a major intracellular anion in mammals. Hydrogen phopshate is a protonated form of phosphate. In serum, phosphate exists in two forms, dihydrogen phosphate (H2PO4) and its salt, mono-hydrogen phosphate (HPO4). At the physiologic pH of 7.40, the pK of H2PO4 is 6.8 and the ratio of HPO4 to H2PO4 is 4:1. Altered level of phosphate can be an indicator of various disorders, such as chronic renal failure, hypoparathyroidism, familial intermittent hyperphosphatemia, endocrine disorders, hyperthyroidism, acromegaly, juvenile hypogonadism, etc. These disorders may lead to either hyper- or hypophosphatemia, which can be caused by cellular shifts of phosphate. Patients with hypophosphatemia can be treated with dietary phosphate supplements (potassium phosphate, for example).