Abstract P3-06-41: Upfront identification of chemoresistance in locally advanced breast cancer using 99m Tc tetrofosmin scan: A low cost technology

Abstract

Abstract With the availability of newer chemo therapeutic drugs for breast cancer with excellent efficacy; it has become essential to identify breast cancers that are chemo resistant to doxorubicin based chemotherapy early in course of treatment so that a different regimen can be used to improve response rates & survival. PET scan/ contrast MRI are used routinely used to assess response to neoadjuvant chemotherapy ( NACT) in locally advanced breast cancer (LABC). However, both these modalities are expensive & not easily available in most centres in India. 99m Tc Tetrofosmin is taken up by metabolically active breast cancer cells, is inexpensive & easily available at most centres.This study was undertaken to evaluate the ability of Tc99 tetrafosmin scan to identify upfront chemo resistance in LABC. Aims:Evaluate the role of Tc 99m-Tetrofosmin scan in distinguishing chemo sensitive from chemo resistant LABC patients. Methods:N=:65 pts. Inclusion: LABC as per TNM classification .Exclusion: Pts not fit to receive chemotherapy or refusing enrollment. Place of study: Breast Cancer Clinic, Department of Surgical Disciplines, .99m Tc Tetrofosmin Scintimammography performed in all the patients. NACT was CAF regimen Cyclophosphomide (600mg/m2), Doxorubicin (50mg/m2) and 5-Fluro-uracil (600mg/m2) 3 cycles @ 3 weekly intervals. Response evaluated after 3rd cycle. Response evaluation: Scintimammo: CR: No detectable abnormal uptake on the post-chemotherapy scan.PR: Some uptake on the post-chemotherapy scan; NR: No change in uptake when compared with pre-chemotherapy scan. evaluation. Histopathology: CR: Lesionentirely replaced by fibrosis or when only few isolated malignant cells persist. PR: Viable invasive carcinoma persisting in more than 25% of the area of the lesion. Chemosensitivity: A ROC curve was plotted for the T/B ratio & pathological response. Area under the curve was found to be 84% with a C.I. between 73%-95%. Using this curve, a cut off value of 2.55 was chosen to characterize the chemo sensitivity of the tumors. : Scintimammographic assessment of response to NACTScintimammographypathological responseCRnouptake113uptake120Sensitivity-92%, Specificity-87%, Positive predictive value-79%, Negative predictive value-95%, LR+7, LR-0.09, LR---73.3, accuracy-89% p value <0.000 shows T/B ratios When the T/B ratio was >2.55, the tumor can be considered to be chemo sensitive to Doxorubicin based NACT.On the contrary, when the T/B ratio was <2.55, it is unlikely that the tumor regresses completely following Doxorubicin based NACT. Ability of Scintimammography to assess response to NACT was done comparing post-NACT scintimammograms with the final histopathology T/B ratio & path responseScintimammographyCR (tumor no)PR(Tumor yes)p valueT/B Ratio2.55>1812<0.003T/B ratio 2.55<<<130<0.003LR+:3.3,LR-:0.07 sen:95% spe: 72% Conclusion: Tc99 tetrofosmin can accurately identify chemo sensitive breast tumors and predict response to NACT in LABC. Its low, cost, high accuracy and wider availability in developing nations makes it an attractive option in management of LABC. Citation Format: V Seenu, Rakesh Kumar, Siddharth Dattagupta. Upfront identification of chemoresistance in locally advanced breast cancer using 99m Tc tetrofosmin scan: A low cost technology [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-06-41.