P5-19-05: Age-Related Changes in the Pharmacokinetics (pK), Response, and Toxicity of Weekly nab-Paclitaxel in Patients with Metastatic Breast Cancer (MBC)

Background: Although cancer is a disease of aging, few studies have evaluated the association between patient age and the pK or pharmacodynamics (pD) of cancer therapeutics. The goals of this study were 1) to evaluate the age-related changes in the pK and pD of weekly nab-paclitaxel in patients with MBC; 2) to determine response rate; and 3) to explore the relationship of age with pK and pD parameters (i.e., dose reductions, dose delays and grade ≥ 3 toxicities). Patients and Methods: Forty patients with MBC, receiving 1st or 2nd line chemotherapy, entered an IRB approved protocol to evaluate the age-related changes in the pK of weekly nab-paclitaxel administered at 100 mg/m2 IV for 3 weeks followed by a 1-week break. Patients were accrued from 4 age strata <50, 50–60, 60–70, and >70 years of age. Blood samples were collected for pK analysis with the first dose of nab-paclitaxel. Response was assessed every 2 cycles. Toxicity was graded using the NCI Common Toxicity Criteria for Adverse Events (v 3.0) and was adjudicated as attributable to nab-paclitaxel if it was possibly, probably, or definitely related. Linear regression analysis was used to examine the strength of the relationship between patient age and natural logarithm of 24 hour area under the curve (AUC). Two-sided two-sample t-tests were used to assess if there was a difference in mean age based on the presence of pD variables (i.e., dose reductions, dose delays and grade ≥ 3 toxicities). The significance level was set to 0.05.

Results: Of the 40 patients who entered the study, 39 (98%) were evaluable with a mean age of 60 (SD=13.4; min=30; max=81). Patients were accrued in the following age cohorts: <50 (n= 10; 26%), 50–60 (n= 5; 13%), 60–70 (n= 15; 38%), and >70 (n= 9; 23%) years of age. The median number of courses completed was 4 (min=1, max=21). The response rate was: 0% (n=0) CR, 31% (n=12) PR, 38% (n=15) SD. Grade 3 toxicity was experienced by 26% (n=10). We observed 8% (n=3) grade 3 hematological toxicities [neutrophils (n=1; 3%), leukocytes (n=2; 5%)] and 18% (n=7) grade 3 non-hematological toxicities [nausea and hypophosphatemia (n=1; 3%), diarrhea and infection without neutropenia (n=1; 3%), fatigue (n=2; 5%), hyponatremia (n=1; 3%), and infections without neutropenia (n=2; 5%)]. There were no cases of grade 4 or 5 toxicity. Grade 2 sensory neuropathy was experienced by 8% (n=3; no cases in the 70+ age cohort). Dose reductions or course delays were experienced by 62% (n=24) and 21% (n=8), respectively. There was a borderline significant positive association between age and natural logarithm of total nab-paclitaxel 24 hour AUC (coef=.01; se=.006; p=0.055; n=36). There were no differences in the mean ages based on the presence of grade 3 or higher toxicity (p =0.75), need for dose reductions (p=0.48), or need for dose delays (p=0.61).

Discussion: There is a borderline statistically significant relationship between age and 24 hour AUC but no differences in mean age based on pD variables (i.e., dose reductions, dose delays and grade ≥ 3 toxicities) were identified. The treatment is well-tolerated across all age groups.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-19-05.

BS3-2: Mammary Stroma as an NSAID Target; Implications for Pregnancy-Associated Breast Cancer

Utilizing a young women's breast cancer cohort from the University of Colorado Cancer Center, we show that women diagnosed as late as five-ten years postpartum have worse prognosis than nulliparous women or women diagnosed during pregnancy, and represent ∼50% of all young women's breast cancer patients. We propose that breast involution following pregnancy accounts for this poor prognosis. Characterization of involution identifies tissue remodeling programs that share similarities with microenvironments known to promote metastasis. Using SHG imaging, we find fibrillar collagen bundles with radially-aligned fibers similar to those observed in invasive tumors deposited in the involuting gland. By immunohistochemistry and FACS we find macrophages with an M2-polarization-like profile similar to tumor-associated macrophages at abundant levels during involution. In three independent mouse models for postpartum breast cancer, we isolate postpartum mammary gland involution as a driving force for cancer progression. Mammary tumors arising in the mouse involuting microenvironment express COX-2 and isolated tumor cells are motile and invasive in a collagen-1/COX-2 dependent manner. Targeting involution-macrophages as likely mediators of tumor promotion was accomplished using a previously described mouse transgenic model. Macrophage depletion during involution had catastrophic effects on normal mammary gland involution. Conversely, inhibition of COX-2 with celecoxib, aspirin or ibuprofen did not interfere with postpartum lobular regression. COX-2 inhibition did decrease tumor growth, local tumor cell dispersion and lung metastasis. NSAID treatment also suppressed collagen and tenascin-C deposition in the involuting microenvironment, suggesting that modulation of extracellular matrix proteins may be a novel mechanism by which NSAIDs exhibit chemopreventive activity. Our studies indicate two distinct roles for COX-2 in the postpartum setting. COX-2 activity within the tumor cell is required for invasiveness and COX-2 activity in the host promotes collagen fibrillogenesis. Several correlative observations implicate the collagen/COX-2 pathway in postpartum breast cancer in women: involuting breast tissue has increased collagen with radially aligned fibers, analysis of 11 publically available microarray data sets shows high COL1A and COX-2 independently correlate with decreased relapse free-survival in young breast cancer patients, and COX-2 protein is observed in DCIS lesions in postpartum cases at higher levels than nulliparous cases.

In summary, our studies suggest further research into COX-2 inhibitor use might provide a novel strategy to improve the prognosis of young women should they be diagnosed with postpartum breast cancer. The question of whether an NSAID based intervention study could be aimed at recently pregnant women at high risk for breast cancer also remains to be determined, but is an extremely desirable objective given that the ∼ 6 million pregnancies in the US per year.

Supported by grants from DoD Synergistic Idea Awards BC060531 & BC10400/001, Komen Foundation KG090629, DoD Idea Award BC074970 to PJK, ACS New England Division Postdoctoral Fellowship Spin Odyssey PF-08-257-01-CSM to TRL and DoD Predoctoral Grants BC073482 to JO and BC100910 to HM.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr BS3-2.

Scent organ development in creatonotos moths: regulation by pyrrolizidine alkaloids

7-Hydroxy-6,7-dihydro-5H-pyrolizine-1-carboxaldehyde is the major volatile component of the scent organs in males of two species of Creatonotos (Lepidoptera, Arctiidae). The biosynthesis of this presumed pheromone depends on the presence of pyrrolizidine alkaloids in plants that are ingested by the larvae. In addition, these secondary plant substances control the morphogenesis of the scent organs. This morphogenetic effect of an alkaloid has not been observed previously.

Absolute cooling rates of freely decaying fullerenes

The cooling rates of C60- have been measured in an electrostatic storage ring between several hundred mus and several tens of ms with one-photon laser excitation. The absolute energy scale is established by the photon energy, and the cooling time interval is derived from the nonexponential decay of the ensemble of hot molecules. The energy decreases due to the combined action of depletion and thermal emission of IR photons with a total energy loss rate that varies inversely proportional to time, 0.9 eV/t. The radiative component decreases from a few hundred eV/s at submillisecond time scales to several tens of eV/s at 20 ms and confirms that the crossover from depletion to predominantly radiative cooling occurs around 5 ms. The method is applicable to any large molecule or cluster which decays spontaneously, irrespective of the specific decay channel.