Access to anticancer drugs: many evidence-based treatments are off-label and unfunded by the Pharmaceutical Benefits Scheme

BACKGROUND

The off-label use of a drug refers to a use outside the terms of its approval by the Therapeutic Goods Administration (TGA). It is also possible to prescribe unlicensed drugs under the TGA's special access scheme. A high rate of off-label prescribing has previously been reported in cancer. Our study aimed to document the disparity between evidence-based clinical guidelines for anticancer therapy, product approval and funding status of these agents within an academic tertiary/quaternary cancer centre.

METHODS

All chemotherapy protocols approved for use in our specialist oncology centre were assessed to determine if the drugs were off-label or unlicensed for that indication based on review of their current product information. The Pharmaceutical Benefits Scheme (PBS) funding status for each protocol was subsequently assessed.

RESULTS

A total of 448 protocols containing 82 different drugs across 15 tumour groups was identified. Overall, 189 (42.2%) of protocols were off-label, and three (0.7%) were unlicensed. This resulted in all 192 protocols being unfunded by the PBS. Of the 189 off-label protocols, 132 (69.9%) were based on established evidence-based treatment guidelines, and a further 39 (20.6%) was based on phase II or III clinical trial data.

CONCLUSION

Over 90% of off-label protocols are supported by established treatment guidelines or published peer-reviewed research even though the medications are not approved for that particular use by the TGA. However, these off-label protocols are unfunded by the PBS; this results in a marked inequality of access to appropriate medications for cancer patients across Australia.

Olfactory mitral cell integrity after freeze-fixation

The condition of freeze-fixed mitral cells from the main olfactory bulb of the rat brain was found to depend on the rat at which the tissue is frozen: at very slow rates, mitral cells swell and rupture; at faster rates, cell integrity is preserved. Cooling the tissue to just above its freezing point before rapid freeze-fixation helps to maintain cell integrity at depths well below the surface. When freeze-fixation must be used, as in the 2-deoxyglucose technique, rapid freezing rates should be used to minimize diffusion of isotope and increase autoradiographic resolution. After rapid freezing, better cell integrity was produced by freeze-drying and plastic embedding than by cryostat sectioning and thaw-mounting.

In vitro metabolism of 17beta-estradiol by human liver tissue

17beta-[6,7- 3H]Estradiol was incubated with adult human liver slices in Krebs-Ringer phosphate buffer containing glucose. Of the identified 3H recovered, 51-76 percent consisted of estrone-3-sulfate (E13S) and 17 beta-estradiol-3-sulfate (E23S). E13S was the main metabolite and was found in both tissue and medium. E23S was present only in the medium. Minor amounts of estrogen glucuronides were formed. When a human liver homogenate was incubated with [3H]E2 in a medium fortified with excess uridine diphosphate glucuronic acid only some 4 percent of conjugation with glucuronic acid was observed. It is suggested that human liver favors sulfurylation as the conjugating mechanism for E2 and E1.

In vitro synthesis of estrogen glucuronides and sulfates by human renal tissue

17beta-[6,7-3H]Estradiol (E2) was incubated with slices and homogenates of adult human renal tissue. The metabolites formed were identified by chromatography on DEAE-Sephadex, thin layer chromatography and crystallization with carrier steroids or steroid derivatives. The major metabolites formed by slices were estradiol-17-glucuronide (E217G), estrone sulfate and estradiol-3-sulfate. This is the first report of in vitro synthesis of estrogen sulfates by adult renal tissue. Minor quantities of the 3-glucuronides of estrone and estradiol were also found. An oxygen atmosphere appeared to stimulate the production of E217G. A time study with tissue slices showed similarities between the in vitro pattern of glucuronide synthesis and the excretion pattern of these compounds seen in earlier in vivo studies. Homogenates fortified with uridine diphosphoglucuronic acid formed the same pattern of glucuronide products but in lesser amounts. No sulfates were formed under these conditions. Testosterone did not act as a substrate in the experimental conditions used.

Intracellular distribution of steroid glycosidases of rabbit liver

The activity and intracellular distribution of several glycosidases in rabbit liver have been examined. Glycosides of the steroid estrogens, which have been shown to occur naturally in the rabbit, were used as substrates and the results were compared to those obtained when synthetic p-nitrophenyl glycosides were used. β-N-acetylglucosaminidase (EC 3.2.1.30) and β-glucuronidase (EC 3.2.1.31) activities were concentrated in the lysosomes and showed the latency typical of lysosomal acid hydrolases. β-D-Glucosidase (EC 3.2.1.21) activity was concentrated in the unsedimentable fraction of the liver homogenates and did not exhibit latency. No differences were found in the intracellular distribution of glycosidase activities towards the steroid and the p-nitrophenyl glycosides.