Maximal neutropenia during chemotherapy and radiotherapy is significantly associated with the development of acute radiation-induced dysphagia in lung cancer patients.

BACKGROUND: Acute dysphagia is a distressing dose-limiting toxicity after concurrent chemoradiation or high-dose radiotherapy for lung cancer. We therefore identified factors associated with the occurrence of acute dysphagia in lung cancer patients receiving radiotherapy alone or combined with chemotherapy. PATIENTS AND METHODS: Radiotherapy, chemotherapy and patient characteristics were analyzed using ordinal regression analysis as possible predictors for acute dysphagia (CTCAE 3.0) in 328 lung cancer patients treated with curative intent. RESULTS: The most significant association was seen between the maximal grade of neutropenia during chemoradiation and dysphagia, with an odds ratio increasing from 1.49 [95% confidence interval (CI) 0.63-3.54, P = 0.362] for grade 1-2 neutropenia to 19.7 (95% CI 4.66-83.52, P < 0.001) for patients with grade 4 neutropenia. Twice-daily schedule, mean esophageal dose and administration of chemotherapy were significant predictive factors. By combining these factors, a high-performance predictive model was made. On an individual patient level, 64% of patients were correctly classified and only 1.2% of patients were misclassified by more than one grade. CONCLUSIONS: The maximal neutrophil toxicity during concurrent chemotherapy and radiotherapy is strongly associated with the development of acute dysphagia. A multivariate predictive model was developed.

Effects of 2-chloro-2'-deoxyadenosine on the cell cycle in the human leukemia EHEB cell line.

To explain why 2-chloro-2'-deoxyadenosine (CdA) is unable to block DNA synthesis and cell cycle progression, and paradoxically enhances progression from G1 into S phase in the CdA-resistant leukemia EHEB cell line, we studied its metabolism and effects on proteins regulating the transition from G1 to S phase. A low deoxycytidine kinase activity and CdATP accumulation, and a lack of p21 induction despite p53 phosphorylation and accumulation may account for the inability of CdA to block the cell cycle. An alternative pathway involving pRb phosphorylation seems implicated in the CdA-induced increase in G1 to S phase progression.

2-Chloro-2'-deoxyadenosine inhibits DNA repair synthesis and potentiates UVC cytotoxicity in chronic lymphocytic leukemia B lymphocytes.

2-Chloro-2'-deoxyadenosine (CdA) is a deoxyadenosine analogue which targets enzymes involved in DNA synthesis, and hence might interfere with the resynthesis step of DNA repair. We tested this hypothesis in resting B cell chronic lymphocytic leukemia (B-CLL) lymphocytes, after firstly characterizing unscheduled DNA synthesis occurring in these cells. We observed that the spontaneous incorporation of [methyl-3H]thymidine (dThd) into DNA of B-CLL cells was not completely inhibitable by hydroxyurea (HU) which blocks DNA replication. In addition, in the presence of HU, dThd incorporation could be upregulated by UVC radiation or DNA alkylation, without re-entry of the cells into S phase. CdA was found to inhibit both spontaneous and upregulated DNA synthesis in B-CLL cells. Phosphorylation of CdA was essential to exert this effect. We finally observed a strong synergistic cytotoxicity between UV light and CdA, which was correlated with activation of caspase-3 and high molecular weight DNA fragmentation, two markers of apoptosis. Taken together, these observations indicate that in B-CLL cells CdA inhibits unscheduled DNA synthesis which represents the polymerizing step of a repair process responsive to DNA aggression. Inhibition of this process by CdA, together with a combined activation of the apoptotic proteolytic cascade by CdA and UV, may explain their synergistic cytotoxicity.

Resistance to 2-chloro-2'-deoxyadenosine of the human B-cell leukemia cell line EHEB.

The effects of 2-chloro-2'-deoxyadenosine (CdA, cladribine), an adenosine deaminase-resistant analogue toxic for both proliferating and resting lymphoid cells, were investigated in the human leukemia cell line EHEB, which was derived from a patient with B-cell chronic lymphocytic leukemia. These cells were found to be less sensitive to CdA than B-cell chronic lymphocytic leukemia lymphocytes (approximately 25-fold) and other human lymphoblastic cell lines (10-1000-fold). Phosphorylation of CdA by deoxycytidine kinase and intracellular accumulation of 2-chloro-2'-deoxyadenosine triphosphate (CdATP) were similar in EHEB cells and in other CdA-sensitive cell lines. In contrast, the inhibitory effect of CdA on ribonucleotide reductase activity, which was investigated in situ by the conversion of cytidine into deoxyribonucleotides and its incorporation into DNA, was much less pronounced in EHEB cells than in other human lymphoblastic cells. Accordingly, concentrations of deoxynucleoside triphosphates did not decrease and even tended to rise. Unexpectedly, incorporation of thymidine and deoxycytidine into DNA was increased severalfold after a 24-h incubation with CdA. CdA also increased the activities of deoxycytidine kinase and thymidine kinase approximately 4-fold. Analysis of the cell cycle by flow cytometry showed that after 24 h, CdA provoked an increase in the proportion of cells in S phase, synthesizing DNA. We conclude that the EHEB cell line is resistant to the cytotoxic action of CdA not only because of a lack of inhibition of ribonucleotide reduction but also because CdA, in contrast with its known effects, provokes in this cell line an increase in the proportion of cells replicating their DNA. Unraveling of the mechanism of this effect may shed light on clinical resistance to CdA.

Proton RBE for early intestinal tolerance in mice after fractionated irradiation.

BACKGROUND AND PURPOSE: To determine the influence of the number of fractions (or the dose per fraction) on the proton relative biological effectiveness (RBE). MATERIALS AND METHODS: Intestinal crypt regeneration in mice was used as the biological endpoint. RBE was determined relative to cobalt-60 gamma rays for irradiations in one, three and ten fractions separated by a time interval of 3.5h. Proton irradiations were performed at the middle of a 7-cm Spread Out Bragg Peak (SOBP). RESULTS: Proton RBEs (and corresponding gamma dose per fraction) at the level of 20 regenerated crypts per circumference were found equal to 1.15+/-0.04 (10.0 Gy), 1.15+/-0.05 (4.8 Gy) and 1.14+/-0.07 (1.7 Gy) for irradiations in one, three and ten fractions, respectively. Alpha/beta ratios as derived from direct analysis of the 'quantal radiation response data' were found to be 7.6 Gy for gamma rays and 8.2 Gy for protons. Additional proton irradiations in ten fractions at the end of the SOBP were found to be more effective than at the middle of the SOBP by a factor of 1.14 (1.05-1.23). CONCLUSION: Proton RBE for crypt regeneration was found to be independent of fractionation up to ten fractions. One can expect that it remains unchanged for higher number of fractions as the lethalities for doses smaller than 3 Gy are exclusively due to direct lethal events. As a tendency for increased effectiveness at the end of the SOBP is reported in the majority of the studies, for clinical applications it would be advisable to allow for by arranging a sloping depth dose curve in the deeper part of the target volume. Finally, it must be noticed that most of in vitro and in vivo RBE values for protons are larger than the current clinical RBE (RBE=1.10).

Moderate dose-escalation of combination chemotherapy with concomitant thoracic radiotherapy in limited-disease small-cell lung cancer: prolonged intrathoracic tumor control and high central nervous system relapse rate. Groupe d'Oncologie-Pneumologie Clinique de l'Université Catholique de Louvain, Brussels and Liège, Belgium.

BACKGROUND: The role of chemotherapy dose-intensification in small-cell lung cancer (SCLC) remains unclear. This phase I-II study evaluates feasibility and outcome of combination chemotherapy at moderately elevated doses with concomitant thoracic radiotherapy in limited-disease SCLC. PATIENTS AND METHODS: Moderately elevated doses of ifosfamide-epirubicin (cycles 1 and 3) and of carboplatin-etoposide (cycles 2 and 4) were given with G-CSF and peripheral blood stem-cell (PBSC) support. Thoracic radiotherapy (40 Gy) was given once daily during the first five days of each cycle. RESULTS: Overall toxicity was acceptable; most common side-effects were myelosuppression and asthenia. All 35 eligible patients responded (23 CR, 12 PR). Median time to progression was 15 months: median overall survival was 24.6 months. Only 6 of 25 relapsing patients (24%) presented with a locoregional recurrence while 12 of 25 (48%) relapsed in the central nervous system (CNS). CONCLUSIONS: This regimen is a feasible dose-intensification with an acceptable toxicity profile. Its efficacy was demonstrated by a 100% response rate, an excellent local tumor control rate and a median survival of 24.6 months. In the absence of PCI, CNS relapse is a major problem if adequate local control is achieved.

Chemo-radiotherapy: radiosensitizing nucleoside analogues (review).

The available knowledge on potential radiosensitizing nucleoside analogues with special focus on fludarabine and gemcitabine is reviewed. These analogues are prodrugs whose active triphosphate forms inhibit various enzymes involved in DNA synthesis and repair. Several properties of these analogues support their use as radiosensitizers. As repair inhibitors, they have the potential to increase the amount of residual DNA and chromosome damage after irradiation, and as DNA synthesis inhibitors, they specifically target the S-phase cell component and could thus overcome the detrimental effect of tumor clonogen repopulation during fractionated irradiation. Also, through their cytotoxic effect, these analogues could increase tumor cell loss, facilitating tumor reoxygenation, and thus obviate tumor hypoxia's inhibitory effect on radioresponse. Induction of DNA damage in all phases of the cell cycle by irradiation could create DNA sites for drug incorporation, possibly inducing an apoptotic response in cells outside of S-phase. Experimental data addressing these hypotheses are reviewed and updates on ongoing clinical trials combining fludarabine or gemcitabine and irradiation are given.

The effect of 2'-2' difluorodeoxycytidine (dFdC, gemcitabine) on radiation-induced cell lethality in two human head and neck squamous carcinoma cell lines differing in intrinsic radiosensitivity.

PURPOSE: The present study investigated in vitro radio-enhancement by gemcitabine (dFdC) in two head and neck squamous cell carcinomas with different intrinsic cellular radiosensitivity. MATERIALS AND METHODS: Radiosensitive (SCC61, SF2=0.16) and radioresistant (SQD9, SF2=0.49) human head and neck squamous cell carcinomas were used. Confluent cells were incubated with dFdC and irradiated in drug-free medium with a single dose of 250 kV X-rays (0-12Gy). Cell survival curves were corrected for the toxicity of the drug alone. RESULTS: In both cell lines, radio-enhancement was observed with 5 microM dFdC incubated for 3 h prior to irradiation. Dose modification factors (DMF) at a surviving fraction level of 0.5 reached 1.3 (95% CI 1.1-1.6) and 1.5 (95% CI 1.4-1.5) for SQD9 and SCC61 cells, respectively. Radio-enhancement was associated with a modest increase in the alpha term of the linear-quadratic model. In SQD9 cells, radio-enhancement increased with dFdC incubation time. At 24h, DMF reached a value of 1.5 (95% CI 0.9-3.2). In SCC61 cells at 24h, DMF reached a value of 1.1 (95% CI 0.9-1.2). In both cell lines, radio-enhancement increased with dFdC concentration up to 5-10 microM from which values it levelled off up to 100 microM. CONCLUSIONS: The data indicated that dFdC induced a modest radio-enhancement in both cell lines. For a short incubation time, dFdC did not radio-enhance preferentially the more radio-resistant cells, whereas the opposite was observed for a longer time. In both cell lines, radio-enhancement was saturated above a dFdC concentration of 5-10 microM.

Cost-minimization analysis of treatment options for T1N0 glottic squamous cell carcinoma: comparison between external radiotherapy, laser microsurgery and partial laryngectomy.

BACKGROUND AND PURPOSE: A cost minimization analysis of radiotherapy (RT), laser microsurgery (L) or partial laryngectomy (PL), which are equally effective options for T1N0 glottic SCC was carried out from the perspective of the National Health Care System. METHODS: For each modality, the various events associated with the diagnostic procedure, the primary treatment, the complications, and the salvage treatment were individualized. The charges of each of these events weighted for the frequency of occurrence were then determined using the 'fee for service' policy established by the National Health Insurance of Belgium. RESULTS: A total cost of 5172, 5847 and 11563 EURO were calculated for RT, L and PL, respectively. For L, cost included post-operative RT applied in case of positive margins (30%). For PL, the cost of the primary treatment accounted for 68% of the total cost whereas it only accounted for 50 and 43% for L and RT, respectively. For RT, L or PL, complications accounted for less than 10% of the total cost. The cost of salvage treatment reached 19, 14 and 8% of the total cost for RT, L and PL, respectively. A sensitivity analysis indicated that reduction of the duration of hospitalization decreases the costs without affecting the ranking between the three options. Also, the cost of L could be reduced even slightly below the cost of RT by decreasing the need for post-operative RT. CONCLUSIONS: RT and L have almost the same expected average cost for the treatment of T1N0 glottic SCC, whereas PL is twice as expensive.

Comparison of external radiotherapy, laser microsurgery and partial laryngectomy for the treatment of T1N0M0 glottic carcinomas: a retrospective evaluation.

PURPOSE: The aim of this study was to retrospectively compare the efficacy and functional results of three treatment options for T1N0M0 glottic carcinomas applied in a single institution. MATERIALS AND METHODS: One hundred six charts of patients with biopsy-proven T1N0M0 glottic carcinomas treated between 1979 and 1995 were reviewed. There were 81 T1a and 25 T1b tumors. Forty-one patients were treated by radiotherapy (RT) (median dose of 64 Gy), 34 patients were treated by partial laryngectomy (PL) and 31 patients were treated by laser microsurgery (L) of which 10 received postoperative RT for positive margins. In 18 patients, a perceptual voice rating on a visual scale was performed by the patients themselves, three non-speech specialists and two speech therapists. RESULTS: With a median follow-up time of 63.5 months, the 5- and 10-year loco-regional control probabilities reached 91 and 87%, respectively, without any difference between the treatment groups. After salvage laryngectomy, the 5- and 10-year loco-regional control probabilities reached 97% without any difference between the treatment groups. For the whole population, overall survival reached 78 and 62.4% at 5 and 10 years, respectively. The actuarial incidence of second primary reached 19% at 10 years. Regarding the quality of voice, overall there was a trend towards a worse satisfaction index, more hoarseness and more breathiness after PL than after L or RT. CONCLUSIONS: Our data suggested that assuming proper selection of patients, RT and L yielded similar outcomes and functional results. Local recurrence can be adequately salvaged by surgery. On the other hand, PL appeared to yield similar loco-regional control probability but with a worse quality of voice.

Kinetics of mouse jejunum radiosensitization by 2',2'-difluorodeoxycytidine (gemcitabine) and its relationship with pharmacodynamics of DNA synthesis inhibition and cell cycle redistribution in crypt cells.

Gemcitabine (dFdC), a deoxycitidine nucleoside analogue, inhibits DNA synthesis and repair of radiation-induced chromosome breaks in vitro, radiosensitizes various human and mouse cells in vitro and shows clinical activity in several tumours. Limited data are however available on the effect of dFdC on normal tissue radiotolerance and on factors associated with dFdC's radiosensitization in vivo. The purpose of this study was to determine the effect of dFdC on mouse jejunum radiosensitization and to investigate the kinetics of DNA synthesis inhibition and cell cycle redistribution in the jejunal crypts as surrogates of radiosensitization in vivo. For assessment of jejunum tolerance, the mice were irradiated on the whole body with 60Co gamma rays (3.5-18 Gy single dose) with or without prior administration of dFdC (150 mg kg-1). Jejunum tolerance was evaluated by the number of regenerated crypts per circumference at 86 h after irradiation. For pharmacodynamic studies, dFdC (150 or 600 mg kg-1) was given i.p. and jejunum was harvested at various times (0-48 h), preceded by a pulse BrdUrd labelling. Labelled cells were detected by immunohistochemistry on paraffin-embedded sections. DNA synthesis was inhibited within 3 h after dFdC administration. After an early wave of apoptosis (3-6 h), DNA synthesis recovered by 6 h, and crypt cells became synchronized. At 48 h, the labelling index returned almost to background level. At a level of 40 regenerated crypts, radiosensitization was observed for a 3 h time interval (dose modification factor of 1.3) and was associated with DNA synthesis inhibition, whereas a slight radioprotection was observed for a 48-h time interval (dose modification factor of 0.9) when DNA synthesis has reinitiated. In conclusion, dFdC altered the radioresponse of the mouse jejunum in a schedule-dependent fashion. Our data tend to support the hypothesis that DNA synthesis inhibition and cell cycle redistribution are surrogates for radiosensitization. More data points are however required before a definite conclusion can be drawn.