Peteosthor - a medical disaster due to Radium-224A personal recollection

Estimating the Risk for Secondary Cancer After Targeted α-Therapy with 211At Intraperitoneal Radioimmunotherapy

Intraperitoneal ²¹¹At-based targeted α-therapy (TAT) may hold great promise as an adjuvant therapy after surgery and chemotherapy in epithelial ovarian cancer to eradicate any remaining undetectable disease. This implies that it will also be delivered to patients possibly already cured by the primary treatment. An estimate of long-term risks is therefore sought to determine whether the treatment is justified. Methods: Baseline data for risk estimates of α-particle irradiation were collected from published studies on excess cancer induction and mortality for subjects exposed to either ²²⁴Ra treatments or Thorotrast contrast agent (25% ThO₂ colloid, containing ²³²Th). Organ dosimetry for ²²⁴Ra and Thorotrast irradiation were taken from the literature. These organ-specific risks were then applied to our previously reported dosimetry for intraperitoneal ²¹¹At-TAT patients. Results: Risk could be estimated for 10 different organ or organ groups. The calculated excess relative risk per gray (ERR/Gy) could be sorted into 2 groups. The lower-ERR/Gy group, ranging up to a value of approximately 5, included trachea, bronchus, and lung, at 0.52 (95% CI, 0.21-0.82); stomach, at 1.4 (95% CI, -5.0-7.9); lymphoid and hematopoietic system, at 2.17 (95% CI, 1.7-2.7); bone and articular cartilage, at 2.6 (95% CI, 2.0-3.3); breast, at 3.45 (95% CI, -10-17); and colon, at 4.5 (95% CI, -3.5-13). The higher-ERR/Gy group, ranging from approximately 10 to 15, included urinary bladder, at 10.1 (95% CI, 1.4-23); liver, at 14.2 (95% CI, 13-16); kidney, at 14.9 (95% CI, 3.9-26); and lip, oral cavity, and pharynx, at 15.20 (95% CI, 2.73-27.63). Applying a typical candidate patient (female, age 65 y) and correcting for the reference population mortality rate, the total estimated excess mortality for an intraperitoneal ²¹¹At-monoclonal antibody treatment amounted to 1.13 per 100 treated. More than half this excess originated from urinary bladder and kidney, 0.29 and 0.34, respectively. Depending on various adjustments in calculation and assumptions on competing risks, excess mortality could range from 0.11 to 1.84 per 100 treated. Conclusion: Published epidemiologic data on lifelong detriment after α-particle irradiation and its dosimetry allowed calculations to estimate the risk for secondary cancer after ²¹¹At-based intraperitoneal TAT. Measures to reduce dose to the urinary organs may further decrease the estimated relative low risk for secondary cancer from ²¹¹At-monoclonal antibody-based intraperitoneal TAT.

The risk of cancer following high, and very high, doses of ionising radiation

It is established that moderate-to-high doses of ionising radiation increase the risk of subsequent cancer in the exposed individual, but the question arises as to the risk of cancer from higher doses, such as those delivered during radiotherapy, accidents, or deliberate acts of malice. In general, the cumulative dose received during a course of radiation treatment is sufficiently high that it would kill a person if delivered as a single dose to the whole body, but therapeutic doses are carefully fractionated and high/very high doses are generally limited to a small tissue volume under controlled conditions. The very high cumulative doses delivered as fractions during radiation treatment are designed to inactivate diseased cells, but inevitably some healthy cells will also receive high/very high doses. How the doses (ranging from <1 Gy to tens of Gy) received by healthy tissues during radiotherapy affect the risk of second primary cancer is an increasingly important issue to address as more cancer patients survive the disease. Studies show that, except for a turndown for thyroid cancer, a linear dose-response for second primary solid cancers seems to exist over a cumulative gamma radiation dose range of tens of gray, but with a gradient of excess relative risk per Gy that varies with the type of second cancer, and which is notably shallower than that found in the Japanese atomic bomb survivors receiving a single moderate-to-high acute dose. The risk of second primary cancer consequent to high/very high doses of radiation is likely to be due to repopulation of heavily irradiated tissues by surviving stem cells, some of which will have been malignantly transformed by radiation exposure, although the exact mechanism is not known, and various models have been proposed. It is important to understand the mechanisms that lead to the raised risk of second primary cancers consequent to the receipt of high/very high doses, in particular so that the risks associated with novel radiation treatment regimens-for example, intensity modulated radiotherapy and volumetric modulated arc therapy that deliver high doses to the target volume while exposing relatively large volumes of healthy tissue to low/moderate doses, and treatments using protons or heavy ions rather than photons-may be properly assessed.

Treating infections with ionizing radiation: a historical perspective and emerging techniques

Background

Widespread use and misuse of antibiotics have led to a dramatic increase in the emergence of antibiotic resistant bacteria, while the discovery and development of new antibiotics is declining. This has made certain implant-associated infections such as periprosthetic joint infections, where a biofilm is formed, very difficult to treat. Alternative treatment modalities are needed to treat these types of infections in the future. One candidate that has been used extensively in the past, is the use of ionizing radiation. This review aims to provide a historical overview and future perspective of radiation therapy in infectious diseases with a focus on orthopedic infections.

Methods

A systematic search strategy was designed to select studies that used radiation as treatment for bacterial or fungal infections. A total of 216 potentially relevant full-text publications were independently reviewed, of which 182 focused on external radiation and 34 on internal radiation. Due to the large number of studies, several topics were chosen. The main advantages, disadvantages, limitations, and implications of radiation treatment for infections were discussed.

Results

In the pre-antibiotic era, high mortality rates were seen in different infections such as pneumonia, gas gangrene and otitis media. In some cases, external radiation therapy decreased the mortality significantly but long-term follow-up of the patients was often not performed so long term radiation effects, as well as potential increased risk of malignancies could not be investigated. Internal radiation using alpha and beta emitting radionuclides show great promise in treating fungal and bacterial infections when combined with selective targeting through antibodies, thus minimizing possible collateral damage to healthy tissue.

Conclusion

The novel prospects of radiation treatment strategies against planktonic and biofilm-related microbial infections seem feasible and are worth investigating further. However, potential risks involving radiation treatment must be considered in each individual patient.

Administration of lower doses of radium-224 to ankylosing spondylitis patients results in no evidence of significant overall detriment

The use of low doses of radium-224 (224Ra) chloride for the treatment of ankylosing spondylitis was stopped following the discovery that patients treated with it had a higher than control incidence of leukaemia and other cancers. This was so even though the treatment resulted in decreased pain and increased mobility-both of which are associated with decreased mortality. It was decided to re-analyze the epidemiological data looking at all causes of death. The risk of leukaemia, solid cancer, death from non-cancer causes and from all causes in a study populations of men that received either the typical dose of 5.6 to 11.1 MBq of 224Ra, any dose of 224Ra or no radium were compared using the Cox proportional hazard model. For patients that received the typical dose of 224Ra agreed with the excess cancer was similar to that reported in previous studies. In contrast, these patients were less likely to die from non-cancer diseases and from all causes of death than the control patients. No excess mortality was also found in the population of all males that received the radionuclide. It is concluded that 224Ra treatment administered at low doses to patients with ankylosing spondylitis did not impact mortality from all causes. The study demonstrates the need to consider all causes of death and longevity when assessing health impacts following irradiation.

Primary standardization of 224Ra activity by liquid scintillation counting

A standard for activity of ²²⁴Ra in secular equilibrium with its progeny has been developed, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) counting. The standard was confirmed by efficiency tracing and 4παβ(LS)-γ(NaI(Tl)) anticoincidence counting, as well as by 4πγ ionization chamber and NaI(Tl) measurements. Secondary standard ionization chambers were calibrated with an expanded uncertainty of 0.62% (k = 2). Calibration settings were also determined for a 5 mL flame-sealed ampoule on several commercial reentrant ionization chambers (dose calibrators).

Incidence of leukaemia and other malignant diseases following injections of the short-lived alpha-emitter 224Ra into man

We performed an epidemiological study on 1,471 ankylosing spondylitis patients treated with repeated intravenous injections of the short lived alpha-emitter (224)Ra (excluding radiation therapy with X-rays) between 1948 and 1975. These patients have been followed together with a control group of 1,324 ankylosing spondylitis patients treated neither with radioactive drugs nor with X-rays. The mean follow-up time was 26.3 years in the exposed and 24.6 years in the control group. To date, causes of death have been ascertained for 1,006 exposed patients and 1,072 controls. Special emphasis was placed on the reporting of malignant diseases. Expected numbers of cases were computed for the age, sex and calendar year distribution of both groups using cancer registry incidence rates. In the exposed group 18 cases of kidney cancer (vs. 9.1 cases expected, P < 0.01) and 4 malignant thyroid tumours (vs. 1.2 cases expected, P = 0.03) were observed. In the control group the observed cases for these tumours were not significantly elevated. The most striking observation, however, were the 21 cases of leukaemia in the exposed group (vs. 6.8 cases expected, P < 0.001) compared to 12 cases of leukaemia in the control group (vs. 7.5 cases expected). Further sub-classification of the leukaemias demonstrated a high increase of myeloid leukaemia in the exposed group (12 cases observed vs. 2.9 cases expected, P < 0.001), and out of these, especially a high excess of acute myeloid leukaemias (7 cases observed vs. 1.8 expected, P = 0.003). In the controls the observed cases are within the expected range (4 myeloid leukaemias vs. 3.1 cases). This increase in total leukaemias as well as particularly in myeloid leukaemias is significant in direct comparison between the exposed and control groups too (P < 0.05). The enhanced leukaemia incidence in the exposed group is in line with the observation of increased leukaemia incidence in mice injected with (224)Ra.

Osteonecrosis of the jaw and bisphosphonates: a comparison with white phosphorus, radium, and osteopetrosis

INTRODUCTION

Recent reports of bisphosphonate-associated jaw osteonecrosis are reminiscent of earlier incidents in which a comparable syndrome was caused by occupational exposure to white phosphorus or radium. Osteonecrosis of the jaw is also caused by an inherited disease: osteopetrosis. This review analyzes the biomedical and social aspects of these four situations associated with jaw osteonecrosis.

RESULTS

Clinical evidence is contradictory but suggests aminobisphosphonates cause rare cases of jaw necrosis. In addition to jaw problems, generalized skeletal defects characterize osteopetrosis and exposure to phosphorus or radium and there is evidence of decreased bone resorption in these conditions and with bisphosphonate therapy.

CONCLUSION

Bisphosphonate-induced jaw necrosis appears to be an on-target toxicity as the same mechanism, inhibition bone resorption, probably underlies both the therapeutic and adverse effects. Since bisphosphonates are retained for long periods by bone the theoretical potential for skeletal toxicity is increased by using higher doses of potent aminobisphosphonates administered less frequently.

Osteochondromas and growth retardation secondary to externally or internally administered radiation in childhood

For over five decades, osteochondromas (exostoses) and associated growth retardation have been known to be caused by radiation damage to the growing skeleton. Patients can be divided into three exposure groups. Group I received external beam radiation therapy primarily for the treatment of childhood cancers (typical dose 3,500 cGy), and 6-20% developed osteochondromas and growth retardation within the radiation portal. Group II consists of recently described patients who received total body irradiation in preparation for bone marrow transplant (typical dose: 800-1,200 cGy), and about 20% developed osteochondromas and growth retardation. Group III consists of 206 German children who in the 1940s and early 1950s received intravenous radioactive Peteosthor (Ra-224) to treat bone tuberculosis (estimated typical dose: 1,000-2,000 cGy), and 14% developed osteochondromas and growth retardation, among other benign and malignant sequelae. Combining these three exposure groups, osteochondromas and growth retardation develop in at least 6-20% of children who receive therapeutic radiation to their growing skeletons.

Chromosomal aberrations in peripheral lymphocytes of patients treated with radium-224 for ankylosing spondylitis

The aim of this study was to investigate the in vivo frequency of chromosomal aberrations (primarily dicentric chromosomes and chromatid breaks) potentially induced by (224)Ra alpha-radiation in peripheral lymphocytes. The study was designed to serve as a cytogenetic analysis along with the therapeutic procedure of ankylosing spondylitis patients who were undergoing a treatment with (224)Ra-chloride. The total administered activity was 10 MBq, and the treatment followed a schedule of 10 i.v. injections per week, each with a dose of 1 MBq of (224)Ra. The calculation of absorbed doses delivered to the blood used the models suggested by the ICRP and yielded a value of 4.7 mGy/MBq. The frequency of chromosomal aberrations observed during the course of therapy was related to the blood dose. The frequency of dicentric chromosomes induced in vivo was found to agree well with the corresponding value of dicentrics induced in vitro. However--given that peripheral lymphocytes are in the cell cycle's G(0) stage--an unexpected increase with dose in the yield of chromatid breaks was observed, with about 95% of them occurring in cells without any other chromosome-type aberrations. Reasons for the production of chromatid breaks are discussed.