HER2 Support Group Forums - View Single Post - are her2+ (and/or EGFR+) tumors more radioresistant (ie radiation therapy doesn't

Lani · 10-31-2006, 05:18 PM

In the index cases, 56% had high HER-2 immunoreactivity, compared to 18% of the matched controls (p = 0.03). Therefore, in this small case-control series, there appeared to be a correlation between HER-2 overexpression and the risk of a local recurrence.

The current study is limited by the information available from HER-2 assessment at the time of diagnosis, which reflects a period of time prior to standardization of the scoring of HER-2 overexpression. HER-2 IHC performed at the University of Pennsylvania represented 83% of the patients tested. However, while the patients presented in this series generally had HER-2 expression assessed by IHC, the antibodies used differed during the study period and the majority of samples were scored as "positive" or "negative." Some patients interpreted as HER-2-positive might not actually overexpress the gene, especially if their IHC was in the "2+" range and amplification was not confirmed by FISH. Recent studies have shown that while 98% of HER-2 IHC 3+ cancers have gene amplification, only about 25% of HER-2 IHC 2+ cancers have amplification (31,32). Thus the evolving testing standard is to consider FISH in all HER-2 2+ cancers. This expression profile was not known during the study period, so FISH was not routinely performed.

HER-2 is an important molecular marker and prognostic indicator in breast cancer. Given the findings of two randomized trials for early stage breast cancer patients comparing adjuvant chemotherapy alone to chemotherapy plus trastuzumab (NSABP B-31 and North Central Cancer Group [NCCTG] N9831) (6,7), which showed an increase in disease-free survival in the arms including trastuzumab, routine assessment of HER-2 status has become even more important. Therefore, as data are accumulated from clinical trials and institutional experiences, it is important to examine the impact of HER-2 expression on other modalities, including radiation. In this study we found no apparent evidence for radioresistance in HER-2-positive tumors with respect to local recurrence after BCT at 5 years.

Based on the data from the present study, HER-2 overexpression does not appear to be a contraindication to BCT including definitive irradiation. Further studies in larger numbers of patients and with longer follow-up, ideally using more uniform assessment of HER-2 expression, need to be performed to confirm these findings

10-31-2006, 05:18 PM	#7
Lani Senior Member Join Date: Mar 2006 Posts: 4,778	and the end In the index cases, 56% had high HER-2 immunoreactivity, compared to 18% of the matched controls (p = 0.03). Therefore, in this small case-control series, there appeared to be a correlation between HER-2 overexpression and the risk of a local recurrence. The current study is limited by the information available from HER-2 assessment at the time of diagnosis, which reflects a period of time prior to standardization of the scoring of HER-2 overexpression. HER-2 IHC performed at the University of Pennsylvania represented 83% of the patients tested. However, while the patients presented in this series generally had HER-2 expression assessed by IHC, the antibodies used differed during the study period and the majority of samples were scored as "positive" or "negative." Some patients interpreted as HER-2-positive might not actually overexpress the gene, especially if their IHC was in the "2+" range and amplification was not confirmed by FISH. Recent studies have shown that while 98% of HER-2 IHC 3+ cancers have gene amplification, only about 25% of HER-2 IHC 2+ cancers have amplification (31,32). Thus the evolving testing standard is to consider FISH in all HER-2 2+ cancers. This expression profile was not known during the study period, so FISH was not routinely performed. HER-2 is an important molecular marker and prognostic indicator in breast cancer. Given the findings of two randomized trials for early stage breast cancer patients comparing adjuvant chemotherapy alone to chemotherapy plus trastuzumab (NSABP B-31 and North Central Cancer Group [NCCTG] N9831) (6,7), which showed an increase in disease-free survival in the arms including trastuzumab, routine assessment of HER-2 status has become even more important. Therefore, as data are accumulated from clinical trials and institutional experiences, it is important to examine the impact of HER-2 expression on other modalities, including radiation. In this study we found no apparent evidence for radioresistance in HER-2-positive tumors with respect to local recurrence after BCT at 5 years. Based on the data from the present study, HER-2 overexpression does not appear to be a contraindication to BCT including definitive irradiation. Further studies in larger numbers of patients and with longer follow-up, ideally using more uniform assessment of HER-2 expression, need to be performed to confirm these findings