Effects of radiotherapy on the bone marrow granulocytic progenitor cells (CFUc) of patients with malignant lymphomas--I. Short-term effects

Chemotherapy in Metastatic Nonanaplastic Thyroid Cancer: Experience at the Institut Gustave-Roussy

Forty-nine patients with metastatic nonanaplastic thyroid carcinoma were treated over a 10-year period. Five successive chemotherapeutic protocols were used: a combination of doxorubicin, etoposide, 5-fluorouracil and cyclophosphamide; elliptinium acetate; doxorubicin; cispiatin; and the combination of doxorubicin and cispiatin. Results obtained with the different protocols were very disappointing, with only two objective responses (3%). Phase II trials with new chemotherapeutic agents are warranted in selected cases of nonanaplastic metastatic thyroid carcinoma.

Ways of minimising hematopoietic damage induced by radiation and cytostatic drugs--the possible role of inhibitors

Acute and chronic bone marrow toxicities are the major limiting factors in the treatment of cancer. They are related to two factors. (i) The first is a decrease in the number of hematopoietic stem cells and progenitors caused by both a lethal effect of cytotoxic agents on these cells and by differentiation of stem cells provoked by a feed-back mechanism, itself induced by the depletion of more mature marrow compartments. (ii) The second factor is a reduction in self-renewal capacity of stem cells, which is also related to both direct (mutation) and indirect (ageing of stem cell population) effects. Stimulators and inhibitors of bone marrow kinetics play a prominent role in the induction of damage and recovery patterns. Acute effects can be circumvented by an increase in the number of cell divisions in the more mature compartments. This amplification is enlarged by the administration of hemopoietic growth factors which enhance regeneration and shorten the duration of blood aplasia. However, these stimulators may contribute to the exhaustion of the stem cell pool and they may increase the severity of late effects. Protection against chronic effects is difficult; however, the ability to 'switch on' and 'switch off' proliferation opens new avenues which are currently being explored. In particular, inhibitors may protect stem cells against early and late damage by maintaining them in a quiescent state during a course of radiotherapy or chemotherapy. Several inhibitors of hematopoietic stem cell proliferation have been identified during the past 5 years. AcSDKP (Seraspenide) was the first to be isolated and its protective effects against cytotoxic agents were described over a decade ago in mice. Its physiological role is now well established in mouse and man. Preliminary results of a Phase I-Phase II clinical trial strongly suggest that it may have a useful clinical role. Further research is necessary to assess the long-term protective effects of this new family of regulators.

Granulocytopoietic precursor cells and regulatory factors in irradiated human bone marrow

The effects of irradiation on committed granulopoietic progenitor cells (CFU-C) and granulopoietic humoral regulators were studied in 17 X-ray treated patients with carcinoma of the breast or of the prostate. After 45 or 70 Gy, the CFU-C decreased to 14 +/- 10% in irradiated areas. This remaining CFU-C population probably reflects a combination of radioresistance and survival in situ, and migration of CFU-C from protected marrow areas. The frequency of peripheral blood CFU-C did not change after irradiation. Endogenous colony stimulating activity (CSA), i.e., release of CSA within the marrow cell population, in post-irradiation bone marrow persisted on roughly the same level, indicating a fairly low radiosensitivity of the CSA-producing cells in the bone marrow. Colony stimulating activity in peripheral blood cells and serum remained unchanged, but there were great interindividual variations, and some of the patients with hypercellularity and CFU-C increase in nonirradiated marrow areas also had increased CSA. Serum lipoprotein inhibitors were higher in the post-treatment patients than in healthy control patients.

The paradoxes in patterns and mechanism of bone marrow regeneration after irradiation. 2. Total body irradiation

Low dose total body irradiation (TBI) administered in small fractional doses (5-10 cGy) for the treatment of disseminated malignancies such as chronic lymphocytic leukemia (CLL) and non-Hodgkin's lymphoma can be extremely toxic with substantial bone marrow depression. We elected to study bone marrow suppression following fractionated TBI in the rabbit. New Zealand white/female rabbits were thus treated with one of the following three schedules: (1) 3 fractions of 10 cGy per week; (2) 5 fractions of 10 cGy per week; and (3) 5 fractions of 25 cGy per week. Total doses ranged from 1050 to 2625 cGy and animals were sacrificed immediately, 4 weeks, or 8 weeks following completion of therapy. With the 10 cGy/day schedules, slight depression of total WBC counts and lymphocyte numbers occurred during and to the completion of irradiation followed by a rebound to greater than normal levels. With the 25 cGy schedule, a significant WBC and lymphocyte depression occurred at an accumulated dose of 1000 cGy and continued to decrease up to 2500 cGy, followed again by a rebound to greater than normal levels. The depression with the 25 cGy fractions was significantly greater than with the 10 cGy daily fractions. Thus, the severe and persistent peripheral blood count depression observed in CLL patients treated with TBI in small fractional doses was not reproduced in the normal rabbits. Possible explanations for this paradox are offered.

The paradoxes in patterns and mechanism of bone marrow regeneration after irradiation. 1. Different volumes and doses

Bone marrow regeneration (BMR) following irradiation has been largely studied as a dose-effect phenomenon, however, a large literature has simultaneously developed utilizing a wide variety of volumes, both in clinical studies and in experimental studies. In human situations radiation treatment fields and the amount of bone marrow organ exposed have ranged from total body irradiation (small daily and total doses) to large field (half-body) single high doses encompassing 50% of the bone marrow, to segmental or localized field (50-25%). Volume factors, more than dose, determine patterns of suppression and regeneration which have been documented by a variety of assay systems. Experimental evidence is presented which indicates that high dose irradiation (500-1000 cGy) to large volumes of bone marrow (50%) does not completely suppress bone marrow regeneration but results in a rapid compensatory response. The nadir response of bone marrow CFUc-GM stem cell compartment was directly proportional to increasing doses of irradiation (200-2000 cGy) delivered to a single limb. Immediate depression of CFUc-GM was followed by an increase proliferative phase with the most notable difference observed in doses less than or greater than 1000 rad. Following doses of 500 and 1000 rad to large field (half-body), an immediate depression was again observed followed by an immediate and greater compensatory response particularly after the 1000 rad dose. Comparisons ae made between the small and larger volumes at similar doses and indicate a greater overall compensatory response after the larger field irradiation, being more rapid in onset particularly after the 1000 rad dose. Although in-field regeneration of bone marrow occurs after single dose radiation to different volumes of bone marrow, experimental and clinical evidence from protracted conventional doses of irradiation to different volumes of bone marrow (greater or less than 50%) indicate significantly different response mechanisms. From our laboratory and clinical investigations it can be determined that bone marrow is extremely sensitive to radiation insult and has different compensatory mechanisms to "fine tune" its response in proportion to the volume insulted.

Late effects on human bone marrow after extended field radiotherapy

Thirty-two patients with lymphoma were treated with extended radiotherapy (RT) at a dose of Gy and were studied by ferrokinetic studies and surface counting at various times following irradiation. Loss of hematopoietic activity in the irradiated areas is compensated by increased activity in the non-irradiated areas. Despite the return of peripheral blood counts to normal, the hyperactivity of the non-irradiated bone marrow persists over up to 13 years after RT, while the hematopoietic activity of the irradiated areas remains depressed and is only slightly higher than immediately after RT. The hypoactivity persisted even when the hemopoietic tissues had been subjected to the intense stimulation provoked by an aplasia caused by chemotherapy. However, a recovery was observed for dose of 20 Gy or lower. The hemopoietic activity of the irradiated bone marrow appears to be related to the volume of the marrow irradiated and is higher after a mantle + inverted Y field than after a mantle field. Both marrow scintigraphies with 59Fe in 7 out of 9 patients studied revealed an extension of hematopoiesis into a normally dormant area of the marrow, such as the femora. In 2 patients an erythropoietic activity was observed in spleens which had received a dose of 40 Gy, and extra medullary erythropoiesis was found in approximately two-thirds of the patients.