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Phosphocol

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Phosphocol

Indications
Dosage
How Supplied

INDICATIONS

Phosphocol P 32 is employed by intracavitary instillation for the treatment of peritoneal or pleural effusions caused by metastatic disease, and may be injected interstitially for the treatment of cancer.

DOSAGE AND ADMINISTRATION

The suggested dose range employed in the average patient (70 kg) is:

Intraperitoneal instillation: 370 to 740 megabecquerels (10 to 20 millicuries)

Intrapleural instillation: 222 to 444 megabecquerels (6 to 12 millicuries)

Doses for interstitial use should be based on estimated gram weight of tumor, about 3.7 to 18.5 MBq/gm (0.1 to 0.5 mCi/gm).

The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration.

Physical Characteristics

Phosphorus P 32 decays by beta emission with a physical half-life of 14.3 days.1 The mean energy of the beta particle is 695 keV.

Table 1. Principal Radiation Emission Data

Radiation Mean Percent/ Disintegration Mean Energy (keV)
Beta-1 100.0 694.9

The range of the phosphorus P 32 beta particle, which has a maximum energy of 1.71 MeV, is 2.9 mm of aluminum.

To correct for physical decay of this radionuclide, the percentages that remain at selected time intervals before and after the day of calibration are shown in Table 2.

Table 2. Physical Decay Chart; Phosphorus P 32, Half-life 14.3 days

Days Fraction Remaining Days Fraction Remaining Days Fraction Remaining
-15 2.07 2 0.908 35 0.183
-10 1.62 5 0.785 40 0.144
-5 1.27 10 0.616 45 0.113
-2 1.10 15 0.483 50 0.089
-1 1.05 20 0.379 55 0.070
0* 1.00 25 0.298 60 0.055
1 0.953 30 0.234 65 0.043
*Calibration Day

Radiation Dosimetry

The effective half-life of phosphorus P 32 is considered to be equal to its physical half-life, with a residence time of 495 hours.

The radiation dose from a uniformly distributed concentration of 37 kilobecquerels (1 microcurie) per gram within a 16-gram prostate is estimated to be equivalent to about 7.3 grays (730 rads)2. Table 3 shows the estimated radiation doses to the prostate and the pleural or peritoneal surfaces3 of an average patient (70 kg) from a dose of 740 megabecquerels (20 millicuries) of phosphorus P 32.

In comparison to the distribution in the prostate, the distribution of phosphorus P 32 on the pleural and peritoneal surfaces is non-uniform, with great extremes in local doses. To obtain an estimate of the average dose, the surface area of the pleural and peritoneal cavities can be assumed to amount to 4,000 and 5,000 cm2, respectively. The estimated radiation doses to an average patient (70 kg) with 90% retention of a dose of 740 megabecquerels (20 millicuries) of phosphorus P 32 distributed uniformly over these areas are shown in Table 3. The decreases of the averaged radiation doses at various tissue depths away from the surfaces of the pleural and peritoneal cavities are also tabulated.

Table 3. Estimated Radiation Doses

Surface/Organ Pleural Peritoneal Prostate
% Retention Area/wt 90
4000 cm2
90
5000 cm2
100
16 gm
Depth in tissue (cm) Dose Rate Tissue Dose/74 0 MBq (20 mCi)
mGy-cm2 MBq-s rad-cm2 ÁCi-h grays rads grays rads grays rads
0.006 0.75 10 178 17800 134 13400 9180 918000
0.018 0.53 7 125 12500 94 9360    
0.03 0.42 5.6 100 10000 74.9 7490    
0.12 0.15 2 36 3570 26.7 2670    
0.21 0.064 0.85 15 1520 11.4 1140    
0.3 0.023 0.31 5.5 550 4.1 410    
0.4 0.0047 0.062 1 110 0.83 83    

HOW SUPPLIED

Catalog Number 470

Phosphocol P 32 - Chromic Phosphate P 32 Suspension (NDC No. 0019-N470-P0) is available in 10 milliliter vials containing 555 megabecquerels (15 millicuries) with a concentration of 185 megabecquerels (5 millicuries) per milliter. The radiopharmaceutical is manufactured with a specific activity of 122 megabecquerels (3.3 millicuries) per milligram Chromic Phosphate at the time of standardization.

The U.S. Nuclear Regulatory Commission has approved distribution of this radiopharmaceutical to persons licensed to use byproduct material listed in Section 35.300, and to persons who hold an equivalent license issued by an Agreement State.

Storage And Handling

Store at controlled room temperature 20 to 25°C (68 to 77°F).

REFERENCES

1 Stabin MG, da Luz CQPL. New Decay Data for Internal and External Dose Assessment, Health Phys. 83(4):471-475, 2002.

2 Stabin MG. A Model of the Prostate Gland for Use in Internal Dosimetry. J Nucl Med 35(3):516-520, 1994.

3 Watson EE, Stabin MG, Davis JL and Eckerman KF. A Model of the Peritoneal Cavity for Use in Internal Dosimetry. J Nucl Med 30:2002-2011, 1989.

Revised 020308. Mallinckrodt Inc. Hazelwood, MO 63042 U.S.A.

Last reviewed on RxList: 6/17/2009
This monograph has been modified to include the generic and brand name in many instances.

Indications
Dosage
How Supplied

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