Short communication: the addition of carbogen and nicotinamide to a palliative fractionation schedule for locally advanced breast cancer

Clinical trials targeting hypoxia

The concept of tumour hypoxia as a cause of radiation resistance has been prevalent for over 100 years. During this time, our understanding of tumour hypoxia has matured with the recognition that oxygen tension within a tumour is influenced by both diffusion and perfusion mechanisms. In parallel, clinical strategies to modify tumour hypoxia with the expectation that this will improve response to radiation have been developed and tested in clinical trials. Despite many disappointments, meta-analysis of the data on hypoxia modification confirms a significant impact on both tumour control and survival. Early trials evaluated hyperbaric oxygen followed by a generation of studies testing oxygen mimetics such as misonidazole, pimonidazole and etanidazole. One highly significant result stands out from the use of nimorazole in advanced laryngeal cancer with a significant advantage seen for locoregional control using this radiosensitiser. More recent studies have evaluated carbogen and nicotinamide targeting both diffusion related and perfusion related hypoxia. A significant survival advantage is seen in muscle invasive bladder cancer and also for locoregional control in hypopharygeal cancer associated with a low haemoglobin. New developments include the recognition that mitochondrial complex inhibitors reducing tumour oxygen consumption are potential radiosensitising agents and atovaquone is currently in clinical trials. One shortcoming of past hypoxia modifying trials is the failure to identify oxygenation status and select those patient with significant hypoxia. A range of biomarkers are now available including histological necrosis, immunohistochemical intrinsic markers such as CAIX and Glut 1 and hypoxia gene signatures which have been shown to predict outcome and will inform the next generation of hypoxia modifying clinical trials.

Carbogen-induced increases in tumor oxygenation depend on the vascular status of the tumor: A multiparametric MRI study in two rat glioblastoma models

The alleviation of hypoxia in glioblastoma with carbogen to improve treatment has met with limited success. Our hypothesis is that the eventual benefits of carbogen depend on the capacity for vasodilation. We examined, with MRI, changes in fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent signals in response to carbogen. The analyses were performed in two xenograft models of glioma (U87 and U251) recognized to have different vascular patterns. Carbogen increased fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent signals in contralateral tissues. In the tumor core and peritumoral regions, changes were dependent on the capacity to vasodilate rather than on resting fractional cerebral blood volume. In the highly vascularised U87 tumor, carbogen induced a greater increase in fractional cerebral blood volume and blood oxygen saturation in comparison to the less vascularized U251 tumor. The blood oxygenation level dependent signal revealed a delayed response in U251 tumors relative to the contralateral tissue. Additionally, we highlight the considerable heterogeneity of fractional cerebral blood volume, blood oxygen saturation, and blood oxygenation level dependent within U251 tumor in which multiple compartments co-exist (tumor core, rim and peritumoral regions). Finally, our study underlines the complexity of the flow/metabolism interactions in different models of glioblastoma. These irregularities should be taken into account in order to palliate intratumoral hypoxia in clinical trials.

Barrier protective use of skin care to prevent chemotherapy-induced cutaneous symptoms and to maintain quality of life in patients with breast cancer

Purpose

Chemotherapy with anthracyclines, taxanes, or alkylating agents often causes cutaneous side effects. Nonspecific inhibition of the proliferative activity of keratinocytes has antidifferentiation effects that lead to defects in the barrier function and, thus, to dry, itchy, and irritable skin. These cutaneous symptoms reduce the quality of life of the patients considerably. Conditioning with topical application of niacinamide uses the cytoprotective and barrier stabilizing effect of vitamin B₃.

Patients and methods

A multicenter randomized crossover study investigated the influence of the test preparation on the quality of life compared to standard care for 73 patients with breast cancer undergoing adjuvant or neoadjuvant cytostatic therapy. Primary target parameter was the Dermatology Life Quality Index with its respective subscales after 6 weeks of a twice-daily application of the respective preparations. Additionally, specific symptoms such as pruritus, dryness, and irritability have been assessed using visual analog scales.

Results

Regarding the total score of the Dermatology Life Quality Index, no relevant differences could be observed. However, the results for the “symptoms and feelings” subscale show a significant advantage in favor of the test preparation. Significant superiority of the test preparation could also be observed in the secondary target parameters, the visual analog scales (P<0.05).

Conclusion

The results show for the first time a significant superiority of prophylactic application of niacinamide for maintaining quality of life while undergoing cytostatic treatment.

Modulation of hypoxia in murine liver metastases of colon carcinoma by nicotinamide and carbogen

There is increasing evidence that modulation of tumor hypoxia may improve therapy outcome. However, most preclinical data are derived from subcutaneous rather than orthotopic tumor models. We investigated the effect of the hypoxia-modulating agents nicotinamide and carbogen on tumor hypoxia, tumor blood perfusion, and proliferative activity in liver metastases of the murine colon carcinoma line C26a. In untreated C26a liver metastases, we observed a considerable amount of hypoxia, similar to the amount in liver metastases of patients with colorectal cancer. Compared to untreated mice, we observed a significantly smaller hypoxic fraction in the liver metastases of mice treated with nicotinamide and carbogen breathing as single treatments or in combination. In the group of mice that underwent carbogen breathing, perfusion was significantly lower than in the untreated group, but the decrease was only marginal. The proliferative activity was similar in all groups. In C26a subcutaneous tumors, a similar effect on hypoxia has been observed that was, however, combined with a decrease in proliferative activity. The different effects of nicotinamide and carbogen on parameters of the tumor microenvironment in liver metastases and subcutaneous tumors suggest that the host tissue influences the mechanism by which nicotinamide and carbogen exert their effects. Since tumor hypoxia may be a clinical problem in colorectal liver metastases, our results open possibilities for further research on the effect of hypoxia modifiers on colorectal liver metastases to improve therapy outcome.

Effects of nicotinamide and carbogen in different murine colon carcinomas: Immunohistochemical analysis of vascular architecture and microenvironmental parameters

PURPOSE

To investigate oxygenation, perfusion, and cell proliferation in two murine colon carcinoma lines with known differences in chemotherapy sensitivity and analyze the effect of nicotinamide and carbogen on these tumor characteristics.

METHODS AND MATERIALS

Mice with s.c. transplanted C38 and C26a murine colon tumors were treated with nicotinamide and carbogen and compared with control tumors. Two markers of hypoxia, CCI-103F and pimonidazole, were injected before and after treatment with nicotinamide/carbogen, respectively, allowing each tumor to serve as its own control. Hoechst33342 was used as a perfusion marker and bromodeoxyuridine (BrdUrd) as a proliferation marker. Frozen tumors were cut for multistep immunostaining and computer-controlled microscope scanning for hypoxic fractions (HF), perfused fractions (PF), vascular density, and BrdUrd-labeling index (LI).

RESULTS

Microscopic observation of C38 and C26a tumors showed extensive differences in vascular architecture, distribution patterns of hypoxia, and BrdUrd-labeling. Quantitative analysis of C38 and C26a tumors showed a decrease in HF in response to all treatment modalities. For C38 tumors, the average decrease in HF in response to carbogen containing treatments was larger than to nicotinamide alone. In C26a tumors, no difference in average decrease in HF was observed between the treatments. The PF of C38 and C26a did not change in response to treatment. The LI of C38 and C26a decreased upon all treatments, which was statistically significant in the combination treatment of C38.

CONCLUSIONS

The mechanism that can simultaneously explain all the observed changes in response to treatment may be the conversion of metabolism from less respiration toward more glycolysis due to increased glucose levels (Crabtree effect), although other mechanisms of actions cannot be excluded.

ARCON: a novel biology-based approach in radiotherapy

Two mechanisms of radiotherapy resistance which are of major importance in various tumour types are tumour-cell repopulation and hypoxia. ARCON (accelerated radiotherapy with carbogen and nicotinamide) is a new therapeutic strategy that combines radiation treatment modifications, with the aim of counteracting these resistance mechanisms. To limit clonogenic repopulation during therapy, the overall duration of the radiotherapy is reduced, generally by delivering several fractions per day. This accelerated radiotherapy is combined with inhalation of hyperoxic gas to decrease diffusion-limited hypoxia, and nicotinamide, a vasoactive agent, to decrease perfusion-limited hypoxia. Preclinical studies have been done to test the enhancing effects of these three components of ARCON, individually and in combination, in several experimentally induced tumours and normal tissues. In a mouse mammary carcinoma, the tumour-control rate obtained with ARCON was the same as that with conventional treatment, but with a radiation dose almost 50% lower. Phase 1 and 2 clinical trials have shown the feasibility and tolerability of ARCON, and have produced promising results in terms of tumour control. In particular in cancers of the head and neck and bladder, the local tumour-control rates are higher than in other studies, and phase 3 trials for these tumour types are underway. In conjunction with these trials, hypoxia markers detectable by immunohistochemistry are being tested for their potential use in predictive assays to select patients for ARCON and other hypoxia-modifying therapies.

The effect of nicotinamide on spontaneous and induced activity in smooth and skeletal muscle

BACKGROUND AND PURPOSE

Nicotinamide (NA) is currently undergoing clinical trials as a tumour radiosensitizer. The dose that can be administered is currently 80 mg/kg per day, but this may be restricted to 60 mg/kg per day by the high incidence of nausea and vomiting. To investigate some of NA's underlying mechanisms of action, we have used an ex vivo system to study the direct effect of this drug, over a wide range of concentrations, on isolated spontaneously active rat ileum. Effects on the gut were compared with the action of NA on skeletal and vascular smooth muscle.

MATERIALS AND METHODS

Isolated rat ileum rings were perfused with oxygenated Krebs' solution in an organ bath. NA (1 microM to 10 mM) was introduced to the perfusate and the change in amplitude of spontaneous peristaltic activity recorded. Dissected frog sartorius muscle was bathed in modified oxygenated Ringer's solution in an organ bath. The muscle was electrically stimulated to generate isometric contractions. Tension was then measured before and after the addition of a range of NA concentrations (8.2-24.6 mM) to the organ bath.

RESULTS

NA inhibited peristalsis in the ileum in a dose-dependent manner. At a drug concentration of 1 mM the amplitude of contractions was reduced to <50% of the initial control value. NA had no effect on the electrically induced contractions in the isolated frog sartorius muscle.

CONCLUSIONS

Gut smooth muscle is highly sensitive to the relaxant effect of NA producing 50% relaxation at a concentration approximately 10 fold lower than that required in rat arterial smooth muscle, while having no effect on non-mammalian skeletal smooth muscle. This may provide explanations for the occurrence of emesis in patients undergoing combined nicotinamide therapies and highlight possible alternatives available to counter this unwanted side-effect.

Enhancement of radiosensitivity of rat rhabdomyosarcoma R1H with normobaric carbogen and hyperbaric oxygen (HBO) using conventionally fractionated irradiation

Hypoxic clonogenic cells are an important contributory factor in tumour radioresistance. The objective of the present study was to evaluate whether hyperbaric oxygen enhances tumour radiosensitivity, using a conventionally fractionated irradiation schedule, and whether the radiosensitizing potential is different from carbogen. Experiments were performed using the rhabdomyosarcoma R1H model transplanted subcutaneously in the flank of WAG/Rij rats. A total of 30 X-ray fractions of 2 Gy were given either in air, normobaric carbogen or high pressure oxygen (HPO) (240 kPa, 2.37 atm) without anaesthesia. The time taken to achieve complete remission was 38.7 +/- 3.6 days, 36.7 +/- 2.7 days and 32.4 +/- 4.1 days for air, normobaric carbogen and HBO, respectively. The differences between air and HBO (p = 0.002) and carbogen and HBO (p = 0.015) were significant. Use of carbogen and HBO produced the same local control probability at 150 days and this was significantly higher than local control under ambient conditions (p < 0.0001). It was concluded that the time to achieve complete remission of the rat rhabdomyosarcoma R1H can be shortened by HBO. Furthermore, both HBO and carbogen give higher local control probabilities than treatment under ambient conditions when used with a conventionally fractionated radiation schedule.

Combination of fractionated irradiation with nicotinamide and carbogen in R1H-tumours of the rat and its pulmonary metastases

BACKGROUND AND PURPOSE

The combination of radiotherapy with nicotinamide and carbogen is a promising method to improve treatment outcome. The aim of the present study was to investigate its effect on rat lungs, the R1H-tumour and its pulmonary metastases.

MATERIALS AND METHODS

Subcutaneous tumours and artificially induced pulmonary metastases of the rhabdomyosarcoma R1H of the rat were treated either with fractionated irradiation alone or in combination with nicotinamide and carbogen. Local metastatic control, net growth delay and lethal lung damage were used as endpoints.

RESULTS

Radiosensitivity of the lungs of WAG/Rij rats increased by a factor of 1.13, while no positive effect of the combined treatment either on subcutaneous R1H-tumours or on pulmonary metastases could be detected. This resulted in a therapeutic loss of 18% (P = 0.003).

CONCLUSION

The results indicate that deleterious effects of the combination of radiotherapy with nicotinamide and carbogen cannot be excluded under all circumstances.

Nicotinamide as a radiosensitizer in tumours and normal tissues: the importance of drug dose and timing

BACKGROUND AND PURPOSE

Nicotinamide is a radiation sensitizer currently undergoing clinical testing. This was an experimental study to determine the importance of drug dose and time interval between drug administration and irradiation for radiosensitization.

MATERIALS AND METHODS

Nicotinamide (50-500 mg/kg) was injected intraperitoneally into CDFI or C3H mice and drug plasma pharmacokinetics were determined by HPLC. Radiosensitization was measured in tumours and normal tissues after local irradiation. The tumours were a C3H mammary carcinoma, the KHT sarcoma and the SCCVII carcinoma. Tumour response was assessed using either growth delay (C3H) or clonogenic survival (KHT/SCCVII). Normal tissue toxicities evaluated included early responding skin (development of moist desquamation of the foot) and late responding bladder (reservoir function estimated by cystometry) and lung (ventilation rate measured by plethysmography).

RESULTS

All nicotinamide peak plasma concentrations were seen within 30 min after injection. Irradiating tumours at peak times resulted in enhancement ratios (ERs) of 1.27 (C3H), 1.75 (KHT) and 1.45 (SCCVII) with high nicotinamide doses and 1.27 (C3H), 1.28 (KHT) and 1.36 (SCCVII) after giving clinically relevant doses (100-200 mg/kg). Lower ERs were observed when the time interval between drug injection and irradiation was increased beyond the peak time. Irradiating normal tissues at peak times after injecting 100-200 mg/kg nicotinamide gave ERs of 1.20 (skin), 0.90 (bladder) and 1.02 (lung).

CONCLUSIONS

Clinically achievable doses of nicotinamide will enhance tumour radiation damage while having minimal effects in normal tissues, but for the best tumour effect radiation should be given at the time of peak plasma drug concentrations.

Impact of nicotinamide on human tumour hypoxic fraction measured using the comet assay

BACKGROUND AND PURPOSE

Nicotinamide has been shown to reduce hypoxia in experimental tumours, but there are no data that measure the hypoxic fraction at the time of irradiation in humans. This study investigates whether nicotinamide with radiation can reduce human tumour hypoxia.

MATERIALS AND METHODS

Twenty-two patients undergoing palliative radiotherapy for treatment of accessible metastatic tumours were exposed to two doses of radiation (3.5-8 Gy, median 6 Gy) separated by 1-6 days. Directly on completion of the first dose, two fine needle aspirate biopsies (FNAB) were taken and analyzed for hypoxic fraction using the alkaline comet assay. On the second day of radiation, 13 patients were given 80 mg/kg nicotinamide post-operatively on an empty stomach 2 h before treatment; the remaining nine patients acted as controls. A second comparative pair of aspirates were obtained immediately on completion of the second fraction.

RESULTS

Sixteen tumours were suitable for analysis (nine nicotinamide and seven controls). Marked inter-tumour variations in hypoxic fraction were noted (0-67%). Both nicotinamide treated tumours and controls demonstrated a significant increase in the percentage of cells containing heavily damaged DNA following the second dose of radiation (P = 0.01). A significant reduction in mean hypoxic fraction after the second radiation treatment was noted (22 to 13%, P = 0.04). This reduction was predominantly due to the nicotinamide treated group, where mean hypoxic fraction fell from 25 to 11% (P = 0.08) compared to the much smaller change in the radiation only control group, 18 to 15% (P = 0.3).

CONCLUSIONS

The decrease in hypoxic fraction suggests that nicotinamide can improve tumour hypoxia measured at the time of irradiation. Exposure to the first dose of radiation, or an effect of the first FNAB on microregional tumour blood flow may also contribute.

Radiotherapy with carbogen breathing and nicotinamide in head and neck cancer: feasibility and toxicity

The feasibility and early toxicity of radiotherapy with carbogen breathing and nicotinamide was tested in 74 head and neck cancer patients. Forty patients with laryngeal and hypopharyngeal tumors were treated with an accelerated schedule combined with carbogen alone (16) or with carbogen and nicotinamide (24). Thirty-four patients with far advanced unresectable tumors of the oral cavity and oropharynx received conventional radiotherapy with carbogen [16] or with carbogen and nicotinamide (18). Some enhancement of skin reaction was observed with nicotinamide but this remained well within limits of tolerance. With the accelerated regimen there was increased severity of mucosal damage expressed as confluent mucositis in 95% of patients which required healing times of 3-4 months in four patients. Eventually restoration of the mucosal lining was complete in all cases. Nausea and vomiting are the most frequent side effects of nicotinamide and were reported by 60% and 36% of the subjects, respectively. In 26% this was reason to discontinue drug intake. Severe renal dysfunction was associated with nicotinamide intake in two patients of this study and in one other patient who presented later. It is our conclusion that radiotherapy combined with carbogen and nicotinamide is a safe treatment with manageable side effects. We recommend not to give nicotinamide concomitantly with nephrotoxic medication or to patients who have impaired renal function. Preliminary tumor control rates are encouraging and clinical testing will be continued.

Where exactly does failure occur after radiation in head and neck cancer?

Loco-regional recurrence in squamous cell carcinoma of the head and neck can occur at the site of the original primary tumour or in the marginal zone at its periphery. While nodal recurrence may occur in previously involved nodes or in uninvolved nodes within or outside the treatment volume. The exact site of failure was determined in 89 patients treated with radical radiotherapy for carcinoma of the head and neck. Of 73 patients who failed at the primary site 71 (97%) did so within the site of the original tumour; only two patients developed a marginal recurrence. Of the 30 (93%) patients with N1-3 disease who later showed failure in the lymph nodes, 28 (93%) did so at their original site of disease. These results support the view that when radiation fails it usually does so in the centre of the tumour. In order to improve our results we need to deal with radioresistance at the site of mass disease. Ways of approaching this include the combination of surgery with radiotherapy, the addition of a sensitiser or an increase in the dose to the tumour mass by boosting a 'mini' volume using conformal techniques.