Local Therapy, Systemic Benefit: Challenging the Paradigm of Biological Predeterminism

Correlation of hyperpolarized 13 C-MRI data with tissue extract measurements

Hyperpolarized (HP) 13C MRI provides the means to monitor lactate metabolism noninvasively in tumours. Since 13C -lactate signal levels obtained from HP 13C imaging depend on multiple factors, such as the rate of 13C substrate delivery via the vasculature, the expression level of monocarboxylate transporters (MCTs) and lactate dehydrogenase (LDH), and the local lactate pool size, the interpretation of HP 13C metabolic images remains challenging. In this study, ex vivo tissue extract measurements (i.e., NMR isotopomer analysis, western blot analysis) derived from an MDA-MB-231 xenograft model in nude rats were used to test for correlations between the in vivo 13C data and the ex vivo measures. The lactate-to-pyruvate ratio from HP 13C MRI was strongly correlated with [1- 13C ]lactate concentration measured from the extracts using NMR (R = 0.69, p < 0.05), as well as negatively correlated with tumour wet weight (R = -  0.60, p < 0.05). In this tumour model, both MCT1 and MCT4 expressions were positively correlated with wet weight ( ρ = 0.78 and 0.93, respectively, p < 0.01). Lactate pool size and the lactate-to-pyruvate ratio were not significantly correlated.

Probing early tumor response to radiation therapy using hyperpolarized [1-¹³C]pyruvate in MDA-MB-231 xenografts

Following radiation therapy (RT), tumor morphology may remain unchanged for days and sometimes weeks, rendering anatomical imaging methods inadequate for early detection of therapeutic response. Changes in the hyperpolarized [1-¹³C]lactate signals observed in vivo following injection of pre-polarized [1-¹³C]pyruvate has recently been shown to be a marker for tumor progression or early treatment response. In this study, the feasibility of using ¹³C metabolic imaging with [1-¹³C]pyruvate to detect early radiation treatment response in a breast cancer xenograft model was demonstrated in vivo and in vitro. Significant decreases in hyperpolarized [1-¹³C]lactate relative to [1-¹³C]pyruvate were observed in MDA-MB-231 tumors 96 hrs following a single dose of ionizing radiation. Histopathologic data from the treated tumors showed higher cellular apoptosis and senescence; and changes in the expression of membrane monocarboxylate transporters and lactate dehydrogenase B were also observed. Hyperpolarized ¹³C metabolic imaging may be a promising new tool to develop novel and adaptive therapeutic regimens for patients undergoing RT.

High mammographic breast density is independent predictor of local but not distant recurrence after lumpectomy and radiotherapy for invasive breast cancer

PURPOSE

Biologically meaningful predictors for locoregional recurrence (LRR) in patients undergoing breast-conserving surgery (BCS) and radiotherapy (RT) are lacking. Tissue components, including extracellular matrix, could confer resistance to ionizing radiation. Fibroglandular and extracellular matrix components of breast tissue relative to adipose tissue can be quantified by the mammographic breast density (MBD), the proportion of dense area relative to the total breast area on mammography. We hypothesized that the MBD might be a predictor of LRR after BCS and RT for invasive breast cancer.

METHODS AND MATERIALS

We conducted a nested case-control study of 136 women with invasive breast cancer who had undergone BCS and RT and had had the MBD ascertained before, or at, diagnosis. Women with known recurrence were matched to women without recurrence by year of diagnosis. The median follow-up was 7.7 years. The percentage of MBD was measured using a computer-based threshold method.

RESULTS

Patients with a high MBD (>/=75% density) vs. low (</=25%) were at increased risk of LRR (hazard ratio, 4.30; 95% confidence interval, 0.88-021.0; p = 0.071) but not distant recurrence. In addition, we found a complete inverse correlation between high MBD and obesity (body mass index, >/=30 kg/m(2)). In a multivariate Cox proportional hazards model, patients with MBD in the greatest quartile were at significantly greater risk of LRR (hazard ratio, 6.6; 95% confidence interval, 1.6-27.7; p = 0.01). Obesity without a high MBD also independently predicted for LRR (hazard ratio, 19.3; 95% confidence interval, 4.5-81.7; p < 0.001).

CONCLUSION

The results of our study have shown that a high MBD and obesity are significant independent predictors of LRR after BCS and RT for invasive breast cancer. Additional studies are warranted to validate these findings.

Recurrences and second primary breast cancers in older women with initial early-stage disease

BACKGROUND

The association between common breast cancer therapies and recurrences and second primary breast cancers in older women is unclear, although older women are less likely to receive common therapies.

METHODS

Women aged >or=65 years who were diagnosed with stage I or II breast cancer and who underwent mastectomy or breast-conserving surgery (BCS) from 1990 to 1994 were identified from automated data from 6 healthcare systems and then were followed for 10 years or until breast cancer recurrence, disenrollment, or death. Trained abstractors reviewed medical records to obtain recurrence, tumor, treatment and demographic data. The authors used proportional hazards models to examine predictors of recurrent and second primary breast cancers adjusted for demographic and tumor factors.

RESULTS

Of 1837 eligible women, 34% were ages 65 to 69 years, 46% were ages 70 to 79 years, and 20% were aged >or=80 years. In multivariable models that used mastectomy as the reference group, BCS without radiation therapy was associated with an increased risk of any recurrent and second primary breast cancer (hazard ratio [HR], 1.6; 95% confidence interval [CI], 1.1-2.3), particularly with the subgroup of women with local and regional recurrence (HR, 3.5; 95% CI, 2.0-6.0). Tamoxifen use for <1 year versus >or=5 years exhibited a borderline association with any recurrent or second primary breast cancer (HR, 1.9; 95% CI, 0.9-4.2).

CONCLUSIONS

Radiation therapy after BCS and 5 years of tamoxifen use were beneficial in reducing recurrences and second primary breast cancers in older women, regardless of their age or comorbidity burden.