Bipin M. Mehta

Preoperative chemotherapy for osteogenic sarcoma: Selection of postoperative adjuvant chemotherapy based on the response of the primary tumor to preoperative chemotherapy

Since June 1978, 57 patients with primary osteogenic sarcoma of an extremity were treated with high‐dose methotrexate (HDMTX) and citrovorum factor rescue (CFR), Adriamycin, and the combination of bleomycin, cyclophosphamide and dactinomycin (BCD) given for 4–16 weeks prior to definitive surgery. Histologic examination of the resected primary tumor determined the effect of preoperative chemotherapy with many primary tumors showing greater than 90% tumor necrosis attributable to preoperative chemotherapy. All patients having this favorable effect of chemotherapy on the primary tumor were continued on the same chemotherapy regimen postoperatively (regimen B). However, in those patients not having a good effect of preoperative chemotherapy on the primary tumor, HDMTX with CFR was subsequently deleted from their postoperative chemotherapy and they were placed on a regimen containing cisplatinum at the dose of 120mg/M2 with mannitol diuresis combined with Adriamycin in addition to BCD (regimen A). In the current study, 35 of the 57 patients did not demonstrate a good effect of chemotherapy on the primary tumor and were assigned to regimen A postoperatively. Of these 35 patients, 32 (91%) have remained continuously free of recurrent or metastatic disease from 6–34 months following the start of therapy. Among the 22 remaining patients having a good histologic response and treated with regimen B postoperatively, there has been only one relapse in a patient who had a local recurrence in the area of an inadequately resected primary tumor three months after the cessation of chemotherapy. Thus, 53 of 57 patients (93%) are continuously with no evidence of recurrent or metastatic disease from 6–35 months (median, 20 months) from the start of treatment. This study demonstrates the value of thorough histologic examination in predicting survival in responding patients and in helping identify patients whose disease‐free survival rate can be substantially increased if they are given alternative postoperative adjuvant chemotherapy after failing to have a good response to preoperative chemotherapy. This individualized chemotherapeutic strategy has yielded the highest disease‐free survival rate reported to date for osteogenic sarcoma.

Changes in FDG Tumor Uptake during and after Fractionated Radiation Therapy in a Rodent Tumor Xenograft

OBJECTIVE: The uptake of FDG was measured before, during, and after fractionated radiation in order to evaluate the potential of FDG-PET imaging as an indicator of tumor response.METHODS: The study was performed with nude rats bearing the human neuroblastoma BE(2)C tumor xenografts. Tumors were irradiated with 10 fractions of 2 Gy using a 320 kV(p) X-ray unit. Following a baseline FDG-PET scan, repeat scans were performed weekly until animal sacrifice. The rodents were given up to 10 FDG-PET scans, over a period of up to 75 days posttreatment.RESULTS AND CONCLUSIONS: Neither, the average and maximum activity/cc of FDG tumor uptake, nor the respective standardized uptake values (SUV), correlated with tumor response. Instead, the total FDG uptake (defined as the product of the average FDG activity/cc with the tumor volume) correlated better with tumor response.

INHIBITION OF MICROORGANISMS BY PYRIMIDINE NUCLEOSIDES

Successful therapy with I-P-D-arabinofuranosykytosine (ara-C) for acute leukemias and lymphomas’-4 triggered a search for more potent antitumor pyrimidine nucleosides. I-P-D-arabinofuranosyl-5-fluorocytosine (ara-FC), an analogue of ara-C, was shown to be highly active against transplanted mouse leukemias and was more active on a molar basis than ara-C a ainst a 5-fluorouracil-resistant line of mouse l e ~ k e m i a . ~ Hoshi and coworkers6.’ showed 2-2‘-anhydro-l-P-~-arabinofuranosylcytosine (anhydro ara-C) to be markedly active against mouse leukemia ~1210. Following these findings, Fox et aL8 showed oral and parenteral activity of 2-2’-a n hydroI -1-D-arabinofuranosyl-5-fluorocytosine (an hydro ara-FC) against both intraperitoneally and intracerebrally inoculated mouse leukemia. They envisioned that anhydro ara-FC might serve as a “double-barreled” precursor, first by slow release of ara-FC and further by deamination of ara-FC to ~ P D arabinofuranosyluracil (ara-FU). Determination of the concentration of drug in the tissues and body fluids of various experimental animals is essential to the successful development and use of a chemotherapeutic agent. Study of the drug-distribution kinetics in cancer chemotherapy has utilized various assay methods such as colorimetric, chromatographic, isotopic. and biological (microbiological and tissue culture). Since it is desirable to have a method that determines the drug in its active form, biological assays, and especially microbiological assays (because of their rapidity and lower cost), are preferred over the others. Pittillo and Hunt’ described ara-C sensitivity in an actinobolin-resistant strain of Streptococcus Juecalis ATCC 8043 (SF/ACB), and Hanka et a1.I’ developed an improved microbiological assay for ara-C with a limit of sensitivity up to 0.1 pg/ml. Recently, we carried out a survey of available streptococcal strains in our laboratory in an attempt to find a strain more sensitive to ara-C than SF/ACB, or a strain that is not only sensitive to ara-C but also is resistant to other antineoplastic agents. Since ara-C is extensively used in cancer chemotherapy in combination with other anticancer drugs, a strain resistant to such drugs could serve as an assay organism to determine ara-C concentrations in their presence. A strain of Streptococcus fueciurn var. durans (SF/A/MP), resistant to methotrexate (MTX) and 6-mercaptopurine (6-MP), was found to be sensitive to ara-C in the presence of MTX, 6-MP and 6-thioguanine (6-TG), the drugs commonly used in combination chemotherapy along with ara-C. The folic acid requirement for both SF/ACB and SF/A/MP in complete folic acid assay medium (Difco Laboratories) was the same (0.3 ng/ml for half-maximum growth). We found that folic acid at 0.5 ng/ml in the assay medium for both SF/ACB

Calculated and TLD-based absorbed dose estimates for I-131-labeled 3F8 monoclonal antibody in a human neuroblastoma xenograft nude mouse model

Preclinical evaluation of the therapeutic potential of radiolabeled antibodies is commonly performed in a xenografted nude mouse model. To assess therapeutic efficacy it is important to estimate the absorbed dose to the tumor and normal tissues of the nude mouse. The current study was designed to accurately measure radiation does to human neuroblastoma xenografts and normal organs in nude mice treated with I-131-labeled 3F8 monoclonal antibody (MoAb) against disialoganglioside GD2 antigen. Absorbed dose estimates were obtained using two different approaches: (1) measurement with teflon-imbedded CaSO4:Dy mini-thermoluminescent dosimeters (TLDs) and (2) calculations using mouse S-factors. The calculated total dose to tumor one week after i.v. injection of the 50 microCi I-131-3F8 MoAb was 604 cGy. The corresponding decay corrected and not corrected TLD measurements were 109 +/- 9 and 48.7 +/- 3.4 cGy respectively. The calculated to TLD-derived dose ratios for tumor ranged from 6.1 at 24 h to 5.5 at 1 week. The light output fading rate was found to depend upon the tissue type within which the TLDs were implanted. The decay rate in tumor, muscle, subcutaneous tissue and in vitro, were 9.5, 5.0, 3.7 and 0.67% per day, respectively. We have demonstrated that the type of tissue in which the TLD was implanted strongly influenced the in vivo decay of light output. Even with decay correction, a significant discrepancy was observed between MIRD-based calculated and CaSO4:Dy mini-TLD measured absorbed doses. Batch dependence, pH of the tumor or other variables associated with TLDs which are not as yet well known may account for this discrepancy.

Measurement of P-glycoprotein expression in human neuroblastoma xenografts using in vitro quantitative autoradiography.

P-glycoprotein (P-gp) has a role in multidrug resistance (MDR) encountered in human cancers. In this study, we used the colchicine-resistant cell line BE(2)-C/CHCb(0.2), a strain of neuroblastoma cell line BE(2)-C, as a model to measure variations of P-gp expression in cells grown in vitro and in vivo. Cells were cultured in the medium supplemented with colchicine. At the beginning of the study the drug was withdrawn and, after 22 days, added back to the culture medium. Cells were harvested at various time points and xenografted in nude mice. P-gp content in cells was measured by self-competitive binding assay and in tumors, by quantitative autoradiography (QAR). Both assays were carried out using 125I-labeled monoclonal antibody MRK16, reactive with P-gp. Concentration of P-gp in cells varied from a maximum of 1,361 pmol/g in the presence of colchicine to a minimum of 374 pmol/g in the absence of colchicine in the culture medium. P-gp concentration in the tumors ranged from 929 to 188 pmol/g, which correlated with P-gp content in the cells at the time of their injection in the mice. QAR is an accurate and reliable method to quantify P-gp expression in tumors. Changes in colchicine concentration in the ambient medium of BE(2)-C/CHCb(0.2) cells growing in vitro resulted in a change in phenotype of P-gp expression, which was stable under conditions of in vivo growth over approximately 9 cell divisions in nude mice xenografts. Therefore, P-gp content in xenografts depends only on the level of resistance of the cells at the time of their injection in the mice.