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G DeBoer

Publications and source records attributed to G DeBoer.

At least 19 recordsLinked to original sources
PubMed2004

Comparison of histologic grade between initial and follow-up biopsy in untreated, low to intermediate grade, localized prostate cancer.

OBJECTIVE: To examine the change of histologic grade of untreated, low to intermediate grade, clinically localized prostate cancer over time on repeat prostate biopsy. METHODS AND MATERIALS: In a prospective single-arm cohort study, patients were managed with observation alone unless they met pre-defined criteria of disease progression (PSA, clinical or histologic progression). Sixty-seven (54%) of a total of 123 eligible patients underwent follow-up prostate biopsy. Median time to the follow-up biopsy was 22 months (range: 7-60). RESULTS: On the follow-up biopsy, Gleason score was unchanged in 20 patients (30%), upgraded in 19 (28%), and downgraded in 27 (40%). Twenty-one (31%) had no malignancy on the follow-up biopsy. Sixteen (37%) of 43 patients with < or = 2 positive cores on the initial biopsy had negative follow-up biopsy, while only 2 (11%) out of 18 with > or = 3 positive cores on the initial biopsy did. Five (7%) patients were upgraded to Gleason score 8. There was no correlation between the extent of grade change and baseline variables (age, clinical stage, and initial PSA) as well as PSA doubling time. CONCLUSIONS: There was no consistent histologic upgrade on the follow-up biopsy at a median of 22 months in untreated, low to intermediate grade, clinically localized prostate cancer.

Aged↗
PubMed2003

Is there a progression of histologic grade from radical prostatectomy to local recurrence in patients with clinically isolated local recurrence following surgery?

OBJECTIVE: To evaluate whether there is any histologic progression from radical prostatectomy (RP) to local recurrence in patients with clinically isolated local recurrence following RP. METHODS AND MATERIALS: A total of 43 patients with clinically isolated, biopsy proven, local recurrence following RP were retrospectively analyzed with respect to the change in Gleason score (GS) from RP to local recurrence. Central pathology review was undertaken for both RP and local recurrence biopsy specimens. The changes in primary and secondary Gleason grade (GG), and any potential correlation between the extent of GS change and other variables were also examined. RESULTS: Median age at the time of local recurrence was 67 years (range: 55-78). Median interval between RP and local recurrence was 3.6 years (range: 0.3-17.7). Eight had a short course (<3 months) of hormone therapy prior to RP. Initial GS of RP specimens was 5, 6, 7, 8, and 9 in 1, 3, 29, 1, and 9 patients, respectively. At the time of local recurrence, GS was upgraded in 13, unchanged in 23, and downgraded in 7. The extent of GS change was correlated with the interval between RP and local recurrence, but not with pathological T stage or age. CONCLUSION: There was no statistically significant change in GS from RP to local recurrence, although there was a trend toward a higher GS at the time of local recurrence. The extent of GS change was associated positively with the elapsed time to local recurrence.

Adenocarcinoma↗
PubMed2001

PSA doubling time of prostate carcinoma managed with watchful observation alone.

PURPOSE: To study prostate-specific antigen (PSA) doubling time of untreated, favorable grade, prostate carcinoma. METHODS AND MATERIALS: A prospective single-arm cohort study has been in progress to assess the feasibility of a watchful observation protocol with selective delayed intervention using clinical, histologic, or PSA progression as treatment indication in untreated, localized, favorable grade prostate adenocarcinoma (T1b-T2bN0 M0, Gleason Score < or = 7, and PSA < or = 15 ng/mL). Patients are conservatively managed with watchful observation alone, as long as they do not meet the arbitrarily defined disease progression criteria. Patients are followed regularly and undergo blood tests including PSA at each visit. PSA doubling time (Td) is estimated from a linear regression of ln(PSA) on time, assuming a simple exponential growth model. RESULTS: As of March 2000, 134 patients have been on the study for a minimum of 12 months (median, 24; range, 12-52) and have a median frequency of PSA measurement of 7 times (range, 3-15). Median age is 70 years. Median PSA at enrollment is 6.3 (range, 0.5-14.6). The distribution of Td is as follows: <2 years, 19 patients; 2-5 years, 46; 5-10 years, 25; 10-20 years, 11; 20-50 years, 6; > 50 years, 27. The median Td is 5.1 years. In 44 patients (33%), Td is greater than 10 years. There was no correlation between Td and patient age, clinical T stage, Gleason score, or initial PSA level. CONCLUSION: Td of untreated prostate cancer varies widely. In our cohort, 33% have Td > 10 years. Td may be a useful tool to guide treatment intervention for patients managed conservatively with watchful observation alone.

Adenocarcinoma↗
PubMed1999

Reduced expression of the cell cycle inhibitor p27Kip1 in non-small cell lung carcinoma: a prognostic factor independent of Ras.

Levels of p27 have been found to have independent prognostic significance in a variety of tumors including breast, colon, prostate, ovary, and gastric carcinomas. We investigated p27 levels and determined ras mutational status in 136 non-small cell lung cancers. We found reduced levels of p27 in 86% of cases and showed a statistically significant inverse correlation between p27 levels and tumor grade. ras mutations were found exclusively in adenocarcinomas and showed no relationship to p27 levels. Clinical data on a subset of the patients studied indicated that all 16 patients who died of disease and 21 of 22 patients who relapsed had low p27 levels, whereas all patients with high p27 levels were alive at last follow up. These findings suggest that alteration in p27 levels plays an important role in lung tumor progression and that p27 levels may have independent prognostic significance in non-small cell lung cancer.

Carcinoma, Non-Small-Cell Lung↗
PubMed1998

Loss of cyclin-dependent kinase inhibitor p27Kip1 is a novel prognostic factor in localized human prostate adenocarcinoma.

p27Kip1 is a cyclin-dependent kinase inhibitor that negatively regulates cell proliferation by mediating cell cycle arrest in G1. This study was undertaken to assess the prognostic value of p27Kip1 in localized human prostate cancer. Archival material from 113 radical prostatectomy specimens obtained between 1985 and 1993 was stained immunohistochemically for p27Kip1 protein using a commercially available antibody. Patient charts were reviewed for preoperative serum prostate-specific antigen, clinical and pathological staging, Gleason tumor grade, time to biochemical and clinical recurrence, and survival. Strong p27Kip1 staining was uniformly seen in benign prostatic epithelial components in all tumor sections. p27Kip1 staining was reduced in most prostate cancers and was variable in prostatic intraepithelial neoplasia. Decreased p27Kip1 staining (<25% of nuclei stained positive for p27Kip1) correlated with seminal vesicle involvement (P = 0.0032) and with higher Gleason grade (P = 0.0114). On univariate analysis, low p27Kip1 predicted an increased risk of treatment failure in the node-negative cohort (P = 0.0037) and in the subset who did not receive neoadjuvant hormonal therapy (P = 0.049). Low p27Kip1 expression was an independent predictor of treatment failure on multivariate analysis of lymph node negative prostate cancers following radical retropubic prostatectomy (n = 102; P = 0.047). Seminal vesicle involvement (P = 0.034) and positive surgical margins (P = 0.047) were also independent prognostic factors for disease recurrence. In patients who received preoperative neoadjuvant hormonal therapy, low p27Kip1 in the pathological specimen was an even stronger predictor of outcome than it was in the entire group (n = 23, P = 0.015).

Adenocarcinoma↗
PubMed1997

P-glycoprotein expression: critical determinant in the response to osteosarcoma chemotherapy.

BACKGROUND: Fewer than 20% of patients with bone cancer who are treated with surgery alone are cured. Even with the best current treatment, surgery combined with chemotherapy, only 60%-80% of patients with nonmetastatic bone cancer and 10% of patients with metastatic bone cancer are cured. Thus far, the reason for treatment failure in the nonresponding subset has not been identified. It has been hypothesized that P-glycoprotein, which confers multidrug resistance, might be the cause. We sought to determine whether the expression of P-glycoprotein is associated with poor treatment outcome in osteosarcoma. METHODS: In a retrospective study, we correlated P-glycoprotein expression with the outcome of conventional chemotherapy in 62 consecutive, clinically staged patients diagnosed as having osteosarcoma between 1980 and 1989. RESULTS: P-glycoprotein was overexpressed in 27 patients but not in another 34 patients, and expression was ambiguous in the sample from one patient. At a median follow-up of 8.9 years, the 34 patients whose tumors did not express P-glycoprotein had significantly better relapse-free rates than the 27 subjects whose tumors expressed the protein (87% versus 0%; P<.00001) and had improved survival rates (94% versus 35%; P<.00001). Among the 46 patients who received chemotherapy before surgery, the 23 whose tumors were negative for P-glycoprotein showed significantly better long-term outcomes (P<.00002), although differences in tumor necrosis in response to therapy were only of borderline significance (P = .057). CONCLUSIONS: P-glycoprotein expression does correlate with treatment failure in patients with osteosarcoma. This correlation raises the possibility that inhibiting the action of P-glycoprotein as part of therapy for this disease would improve outcome.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

An individual patient-based meta-analysis of tamoxifen versus ovarian ablation as first line endocrine therapy for premenopausal women with metastatic breast cancer.

We performed a meta-analysis of randomized trials comparing tamoxifen to ovarian ablation carried out either by surgery or irradiation as first-line hormonal therapy for pre-menopausal women with metastatic breast cancer. Patients in all trials included were required to have measurable disease and to be currently menstruating or within 1 year of cessation of menses, and to have estrogen receptor (ER) positive or unknown disease (ER negative women were admitted to one of the studies). Individual patient data were obtained from the four studies identified and the results updated to June 1992. A total of 220 eligible patients were enrolled in the four trials. There was no difference in overall response rate between tamoxifen and oophorectomy across the four trials (p = 0.94, Mantel-Haenszel test). The odds reduction for progression was 14% +/- 12% and for mortality 6% +/- 13% in favour of tamoxifen, results which were not statistically significant (p = 0.32 and 0.72, respectively). Although the design of all four studies included a cross-over to the other therapy, only 54/111 patients receiving ovarian ablation and 34/109 patients receiving tamoxifen as primary therapy actually crossed over to the other arm at the time of disease progression. Response to initial treatment with tamoxifen was predictive of subsequent response to ovarian ablation (p < 0.05), and response to initial therapy with ovarian ablation was predictive of subsequent response to tamoxifen (p < 0.05). Support curves based on log-likelihood ratios revealed that this meta-analysis provides moderate evidence rejecting a 14% advantage for ovarian ablation compared to tamoxifen in terms of odds of disease progression. A 25% advantage for ovarian ablation with respect to odds of death is also rejected with moderate evidence. We conclude that the efficacy of tamoxifen appears to be similar to that of ovarian ablation by surgery or irradiation as first-line therapy for premenopausal, ER positive metastatic breast cancer, and is unlikely to be substantially inferior.

Adult↗
PubMed1997

A randomized crossover trial of tamoxifen versus ovarian ablation for metastatic breast cancer in premenopausal women: a report of the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) trial MA.1.

We concluded a randomized crossover trial comparing tamoxifen 40 mg daily with ovarian ablation for treatment of metastatic breast cancer in premenopausal women. Objective responses (complete response (CR) plus partial response (PR)) were observed in 5/20 patients treated initially with tamoxifen and in 3/19 patients initially treated with ovarian ablation (p = 0.69). Seven additional patients were stable (SD) on tamoxifen while five additional patients were stable after ovarian ablation, for CR + PR + SD rates of 12/20 (60%) for tamoxifen and 8/19 (42%) for ovarian ablation (p = 0.34). Median time to disease progression was 184 days for tamoxifen and 126 days for ovarian ablation (p = 0.40, logrank test, odds ratio for progression 0.71). Overall survival times were also similar: a median of 2.35 years for tamoxifen and 2.46 years for ovarian ablation (p = 0.98, logrank test, odds ratio for death 1.07). Side effects from tamoxifen included hot flashes and menstrual abnormalities. With one exception, these toxicities were not sufficient to require dose reduction. In this small study, tamoxifen was associated with similar response rates, response durations, and survival times to those observed with ovarian ablation.

Adult↗
PubMed1997

MYCN protein expression as a predictor of neuroblastoma prognosis.

About half of nonlocalized neuroblastomas have MYCN gene amplification and usually progress rapidly, but the half without such amplification also do poorly, albeit progressing more slowly. We hypothesize that overexpression of MYCN protein can occur without gene amplification and that this expression reliably predicts the prognosis of neuroblastoma. To determine whether MYCN expression correlated with outcome, we assayed MYCN protein immunohistochemically in 180 archival pretreatment and posttreatment samples and stratified the 57 conventionally treated stage IVS, III, and IV patients by these conventional prognostic factors: stage, age, serum ferritin, Shimada histology, urinary catecholamine ratio, and MYCN gene status. At a median follow-up of >/=6.8 years, we found in patients with known MYCN gene status that the 23 of 37 without gene amplification fared no better than the 14 of 37 with gene amplification (P = 0.35 and 0.21, comparing relapse-free and survival rates). Conversely, in patients without MYCN gene amplification, 9 of 23 were found to overexpress MYCN protein pretreatment, and they did worse than the 14 of 23 without detectable MYCN protein (P = 0.0016 and 0.022, comparing relapse-free and survival rates). Furthermore, MYCN protein expression was prognostic without (P = 0.00001) and with (P = 0.0007) stratifying all 57 patients by MYCN gene status, each conventional prognostic factor (P ranging from 0.00001-0.013), or simultaneously by the two most important factors, stage and age (P = 0.00076). We conclude that overexpression of MYCN protein without gene amplification correlated significantly with the clinical behavior of neuroblastoma and predicted outcome independently of other prognostic factors. This strongly supports the hypothesis that expression of the MYCN oncogene is critical for progression of neuroblastoma.

Adolescent↗
PubMed1996

Chemotherapy with focal therapy can cure intraocular retinoblastoma without radiotherapy.

BACKGROUND: External beam radiotherapy is standard treatment for medium and large, or visually threatening, intraocular retinoblastoma but markedly increases the risk of cosmetic deformities and second malignant neoplasms in children with germline RB1 mutations. Large tumors and those with vitreous seeds do poorly despite radiotherapy. Chemotherapy traditionally is ineffective for intraocular retinoblastoma, perhaps because many retinoblastomas overexpress the multidrug resistance protein, P-glycoprotein. OBJECTIVE: To avoid radiotherapy in the management of intraocular retinoblastoma by using chemotherapy and focal therapy. INTERVENTIONS: We shrank retinoblastomas in 40 eyes of 31 patients that conventionally should be enucleated or receive radiotherapy by using chemotherapy (ie, vincristine-teniposide, 8 eyes; additional carboplatin, 32 eyes) combined with the administration of cyclosporine, a known multidrug-resistance-reversal agent. We then consolidated these responses to chemotherapy by subsequent 532- and 1064-nm laser therapy and cryotherapy. RESULTS: At the median follow-up of 2 2/3 [corrected] years (range, 1/10-4 3/4 years), the results of treatment were excellent. The actuarial relapse-free rate was 89% in patients not previously treated (91% for 28 eyes) and 67% in patients treated after relapse from previous therapy (70% for 12 eyes). For the eyes with the worst prognosis (ie, vitreous seeds), the relapse-free rate was 88%, better than previously reported. Cyclosporine is nontoxic and did not enhance the expected toxic effects of chemotherapy. Most eyes required laser therapy, cryotherapy, or both for consolidation of tumor control. CONCLUSIONS: This pilot study suggests that most retinoblastomas are curable by combining chemotherapy with cyclosporine therapy, laser therapy, and cryotherapy, without requiring external beam radiotherapy. We propose a randomized trial to clarify the role of cyclosporine.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Combining cyclosporin with chemotherapy controls intraocular retinoblastoma without requiring radiation.

Chemotherapy without radiation has not controlled most intraocular retinoblastoma, perhaps because of the common high expression of multidrug resistance P-glycoprotein that we found in retinoblastoma. Cyclosporin blocks P-glycoprotein-induced efflux of vincristine and teniposide in vitro, and possibly modulates responses to carboplatin. To avoid eye irradiation in bilateral retinoblastoma patients with RB1 germline mutations, which incurs a high second malignancy rate, we added cyclosporin A to a vincristine-teniposide-carboplatin protocol and consolidated chemotherapy responses with focal therapy. We scored patients requiring irradiation, enucleation, or focal ablation of central vision as failures. In 21 study patients, the overall relapse-free rate at a median follow-up of 3.3 years was 76%, with a rate of 92% for newly diagnosed and 50% for previously treated, relapsed retinoblastoma. Our results for the most unfavorable tumors with vitreous seeds (86% at 3.5 years) are better than published success rates of irradiation for similar tumors, or irradiation with the same chemotherapy without cyclosporin (45% at 2. 6 years). These results also exceeded our historic success rate with similar chemotherapy without cyclosporin, focal therapy, and/or radiation in 19 equivalently poor-risk patients (relapse-free rate 37% at a median follow-up of 5.6 years, P = 0.032), 16 of whom were previously untreated (relapse-free rate also 37%, P = 0.012). A better outcome occurred with higher cyclosporin blood levels and projected tissue exposure. Cyclosporin did not enhance the usual chemotoxicity. This clinical study suggests that cyclosporin improves the long-term response of retinoblastoma to chemotherapy, possibly by more than one mechanism.

Antineoplastic Agents↗
PubMed1995

Cyclical mastopathy and premenopausal breast cancer risk. Results of a case-control study.

Cyclical mastopathy (CM) is a common clinical syndrome of premenstrual breast swelling and tenderness. Its symptoms are relieved by reduction in dietary fat intake and, because fat intake may be associated with breast cancer risk, it was hypothesized that CM may also be related to breast cancer risk. This case-control study included 192 premenopausal women with a recent history of axillary node-negative breast cancer and 192 age-matched premenopausal controls. Subjects provided information on diet and risk factors, and they recorded breast symptoms prospectively during one menstrual cycle. Symptoms in the noncancerous breast of cases and the matched (right or left) breast of controls were examined. A cyclical pattern of symptoms was identified in both groups; breast tenderness scores were similar postmenstrually (p = 0.31) but were significantly higher premenstrually in the case group (p = 0.03). Cases also had a greater premenstrual increase in breast tenderness than controls (p = 0.03). When the effects of other risk factors for breast cancer were included in multivariate analyses, the association of cyclical tenderness with breast cancer persisted (p = 0.05), the odds ratio for severe tenderness being 3.32. Thus, we have identified an association of cyclical breast tenderness with breast cancer risk in premenopausal women. The association persists after consideration of diet and the effects of other breast cancer risk factors.

Adult↗
PubMed1995

Multidrug drug resistance in pediatric sarcomas.

PURPOSE: Although P-glycoprotein overexpression is an important cause of multidrug resistance in vitro, whether this resistance mechanism is equally applicable to the clinic has still to be fully established. This review has examined the immunohistochemical and molecular biologic tools used to evaluate soft tissue sarcomas of children and adults, in order to determine whether P-glycoprotein can limit the efficacy of chemotherapy. DESIGN: Because soft tissue sarcomas are successfully treated by cytotoxic substrates of P-glycoprotein in many, but not all children, these tumors may be useful models for determining whether this drug efflux transporter is a clinically relevant cause of chemoresistance. RESULTS: Certain studies of acute myelogenous leukemia, lymphoma, and myeloma in adults and rhabdomyosarcoma, neuroblastoma, and acute lymphoblastic leukemia in children have provided the best current evidence for a strong corelation between the expression of P-glycoprotein and outcome of chemotherapy. Based on these observations, several clinical trials have been initiated to determine whether pharmacologic chemosensitization improves chemotherapy responses and cure rates in P-glycoprotein-expressing malignancies. Thus, early identification of lower levels of P-glycoprotein in tumors that still might respond to chemosensitizer-modulated chemotherapy may be highly pertinent to conducting more informative multidrug resistance reversal trials. CONCLUSION: The question of whether the multidrug resistance P-glycoprotein is a clinically relevant cause of chemoresistance may ultimately be answered by the successful prevention of chemotherapy failure by chemosensitizers that specifically reverse this drug efflux mechanism.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Multidrug resistance in pediatric malignancies.

PURPOSE: Increased expression of P-glycoprotein is an important cause of multidrug resistance in tumor cell lines in vitro. Whether this mechanism is equally relevant as a cause of clinical chemoresistance has not been established and is currently being investigated. This review has examined the immunohistochemical and molecular biologic tools suitable for assessing P-glycoprotein expression in patient samples and methodologic issues important for evaluating the results of clinical studies. Current evidence that supports a role for P-glycoprotein in limiting the efficacy of cancer chemotherapy has been reviewed. DESIGN: Malignancies that have been successfully treated by chemotherapeutic substrates of P-glycoprotein, in which a proportion of patients still fail therapy, may be the most useful models for determining whether this drug efflux transporter is a clinically relevant cause of chemoresistance. RESULTS: Studies of acute myelogenous leukemia, lymphoma, and myeloma in adults have so far provided the best evidence for a relevant role for P-glycoprotein as a cause of clinical multidrug resistance. A similar strong association has been observed between the expression of P-glycoprotein and outcome of treatment in certain malignancies in children, such as neuroblastoma, rhabdomyosarcoma, and acute lymphoblastic leukemia. Some apparent controversies related to this issue of clinical relevance may be explained by the differences in P-glycoprotein detection techniques, methodology, and experimental designs used in different studies. Because several clinical trials have already been initiated to determine whether pharmacologic chemosensitization improves the outcome of chemotherapy in certain malignancies, the successful verification of multidrug resistance limiting the cure rates of these tumors becomes a more critical issue, and identification of those patients with lower levels of P-glycoprotein expression early in the course of their disease, when they are most likely to benefit from multidrug resistance reversal, has assumed an even greater relevance. CONCLUSION: The clinical relevance of the multidrug resistance P-glycoprotein may ultimately be confirmed by the successful prevention of chemotherapy failure by chemosensitizers that specifically reverse this drug efflux mechanism.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Temporal trends in breast cancer surgery in Ontario: can one randomized trial make a difference?

OBJECTIVE: To assess the effect of a single randomized clinical trial, the National Surgical Adjuvant Breast Project (NSABP) B-06, on the surgical management of breast cancer in women. DESIGN: Retrospective cohort study. SETTING: All hospitals in Ontario. PATIENTS: A consecutive sample of 37,447 women with breast cancer newly diagnosed from Jan. 1, 1980, to Dec. 31, 1989, linked to a surgical procedure record in the Ontario Cancer Registry. MAIN OUTCOME MEASURE: The most invasive surgical procedure used within 90 days of diagnosis. RESULTS: Unilateral breast-ablative surgery (BAS) was performed in 57.3% of the women and breast-conserving surgery (BCS) in 31.6%. The annual rate of BAS declined from 77.5% in 1980 to 44.2% in 1989 and the rate of BCS rose from 12.5% in 1980 to 43.5% in 1989. The decline was linear from 1980 to 1984 and then accelerated significantly in 1985 (p < 0.0001), after the results of the NSABP B-06 trial were published. CONCLUSION: One randomized clinical trial can have an immediate and profound effect on medical practice.

Age Distribution↗
PubMed1994

Multidrug resistance. Clinical opportunities in diagnosis and circumvention.

Increased P-glycoprotein expression has been shown to be the molecular cause of multidrug resistance in tumor cell lines. Sensitive immunohistochemical and molecular biologic techniques have been developed to detect P-glycoprotein/mdr1 mRNA expression in clinical samples of tumors. We have reviewed the tools now available for assessment of P-glycoprotein expression in the clinic, the current evidence for a relevant role of the protein in mediation of resistance to chemotherapy, and one strategy used to overcome therapeutic failures due to multidrug resistance. It is now recognized that low levels of increased P-glycoprotein/mdr1 mRNA can occur at diagnosis and during the course of treatment in some cases of acute myelogenous leukemia, non-Hodgkin's lymphoma, multiple myeloma, breast carcinoma, rhabdomyosarcoma and undifferentiated sarcoma of children, neuroblastoma, and retinoblastoma, and these relatively low levels of mdr1 overexpression appear to be associated with poor prognosis. In contrast, it has not been established whether a multidrug resistance mechanism is the rate-limiting factor in response to chemotherapy in carcinomas that arise from tissues normally expressing increased P-glycoprotein. Clinical trials have been initiated to determine whether pharmacologic chemosensitization improves the outcome of chemotherapy-treated malignancies. Preliminary results suggest that chemosensitizers can modulate the effects of increased P-glycoprotein in low-expressing tumors for which effective multiagent chemotherapy is available. Further research is needed for more potent chemosensitizers or combinations of agents that can be used more effectively. The successful circumvention of chemotherapy failure by chemosensitizers will ultimately establish the clinical relevance of the P-glycoprotein efflux mechanism.

ATP Binding Cassette Transporter, Subfamily B, Mem↗