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ORIGINAL ARTICLE
Year : 2020  |  Volume : 9  |  Issue : 3  |  Page : 164-171

Intrinsic subtyping of breast cancer and its relevance with clinico-pathological features and outcomes in patients from North India: a single center experience


1 Department of General Surgery and Surgical oncology, Command Hospital (CC), Lucknow, Uttar Pradesh, India
2 Department of Medicine and Medical Oncology, Command Hospital (CC), Lucknow, Uttar Pradesh, India
3 Department of Radiation Oncology, Command Hospital (CC), Lucknow, Uttar Pradesh, India

Date of Submission28-May-2020
Date of Acceptance30-May-2020
Date of Web Publication30-Sep-2020

Correspondence Address:
Dr. S Anand
Department of General Surgery and Surgical Oncology, Command Hospital (CC), Lucknow - 226 002, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JDRNTRUHS.JDRNTRUHS_77_20

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  Abstract 


Background: There has been a paradigm shift in the way we understand, classify, diagnose, and treat breast cancer in the last two decades, mainly due to breakthrough in the knowledge and understanding the biology of the disease. The panel of St. Gallen meeting proposed to classify tumors based on intrinsic subtypes based on the immune-histochemical pattern for therapeutic purposes. Each subtype is unique in incidence, biological behavior, survival outcome, and response to therapy.
Aim: To analyze the relevance of intrinsic molecular subtypes of breast cancer with clinico-pathological features with regard to patient characteristics, disease biology, management, and outcome at 2 years follow-up.
Materials and Methods: St. Gallen International Expert Consensus Recommendation 2011 was used for this study. Clinico-pathological features (age, stage of disease, histological type and grade, tumor size, lymph node status, and lympho-vascular invasion) were analyzed among the subgroups.
Results: In our study, we had 64 (34.4%) luminal A, 37 (19.9%) luminal B HER2 negative, 6 (3.2%) luminal B HER2 positive, 33 (17.7%) HER2 enriched, and 46 (24.7%) triple negative breast cancer (TNBC). The disease free survival and overall survival at 2 years of follow-up was 92.2% and 100% in luminal A, 89.2% and 100% in luminal B HER2 negative, 83.3% in luminal B HER2 positive, 78.8% and 90.9% in HER2 enriched, and 71.8% and 80.4% in TNBC subgroups, respectively.
Conclusion: Intrinsic subtyping with immunohistochemistry corresponds well with clinico-pathological features and outcomes. This helps in prognosticating the outcome and administration of appropriate adjuvant therapy.

Keywords: Human epidermal growth factor receptor 2 (HER2), immunohistochemistry (IHC), luminal A, luminal B, triple negative breast cancer (TNBC)


How to cite this article:
Harish S, Anand S, Prashar M, Lohia N, Singh S, Viswanath S. Intrinsic subtyping of breast cancer and its relevance with clinico-pathological features and outcomes in patients from North India: a single center experience. J NTR Univ Health Sci 2020;9:164-71

How to cite this URL:
Harish S, Anand S, Prashar M, Lohia N, Singh S, Viswanath S. Intrinsic subtyping of breast cancer and its relevance with clinico-pathological features and outcomes in patients from North India: a single center experience. J NTR Univ Health Sci [serial online] 2020 [cited 2020 Oct 30];9:164-71. Available from: https://www.jdrntruhs.org/text.asp?2020/9/3/164/296829




  Introduction Top


Breast cancer (BC) is the leading cancer among Indian women in the urban setting across most states and is second only to cancer of the cervix in the rural population.[1] BC is a clinically heterogeneous disease with histologically similar tumors responding differently to therapy due to their molecular differences.[2] Better understanding of the molecular basis and gene expression profiling of breast cancer has led to intrinsic subtyping as proposed by Perou et al.[3] The St. Gallen Expert Consensus in 2011 adopted a new approach to the classification of BC for therapeutic purposes based on immunohistochemical (IHC) definition of estrogen and progesterone receptor (ER/PR), the detection of overexpression and/or amplification of the human epidermal growth factor receptor 2 (HER2) oncogene, and Ki-67 labeling index, a marker of cell proliferation, as the means of identifying tumor subtypes within the breast cancer spectrum.[4] Classification of BC into five molecular subtypes (luminal A, luminal B/HER2 negative, luminal B/HER2 positive, HER-2 type, triple negative) not only facilitates assorting patients into a specific treatment regimen but also helps to prognosticate them based on response patterns.

IHC demonstration of the receptors in BC though convenient and cost-effective has a high degree of inter laboratory variance and a false-negative rate between 30% and 60%, especially in relation to the detection of BCs with low oestrogen receptor positivity.[5] In India, the overall hormone positivity in BC is low compared to the western population owing to our patients being younger in age and having higher grade cancers.[6] The precise prevalence of the molecular subtypes in BC, their clinico-pathological profile, and surgical strategy employed are not extensively studied in our population. With these factors in consideration, we did a retrospective analysis of our data with an aim to correlate the molecular subtypes with prognostic parameters such as tumor size, tumor grade, lymph node status, and lympho-vascular invasion (LVI), treatment strategies such as neoadjuvant chemotherapy (NACT), type of surgery, and early clinical outcomes.


  Materials and Methods Top


This study is a retrospective analysis of a prospectively maintained database of BC patients treated with curative intent in a dedicated oncology clinic at a tertiary care hospital in North India between August 2014 and July 2017. The aim of the study was to analyze the relevance of intrinsic molecular subtypes of BC with regards to patient characteristics, disease features, surgical management, and early clinical outcomes after 2 years follow-up in our population.

Patients

Histologically proven 186 patients of invasive BC between the age group of 18 to 80 years, who underwent surgical treatment with a curative intent in our tertiary care center, at the Department of Oncology, were prospectively studied which included complete medical history, examination, demographic, diagnostic, treatment, and follow-up data. Patients with recurrent tumors, bilateral tumors, dual malignancies, and those who were given preoperative treatment elsewhere were excluded from the study.

Ethical approval

This study protocol was approved by the Ethical Committee of our hospital. This is an observational study of already available medical records, and only the investigators have been allowed to access data with personal information.

Methods

Clinco-pathological characteristics (age at presentation, disease stage, histological type and grade, tumor size, lymph node metastasis, lymphovascular invasion) were investigated between the intrinsic subgroups. Clinical staging was done using the AJCC 7th Edition. The expression of ER, PR, HER2, and Ki-67 were assessed with an IHC assay of formalin fixed, paraffin embedded tumor tissue according to international standards. As per literature description, interpretation for ER and PR was done for all patients, where a total score of 2 is considered positive for significant expression.[7] IHC assessment of HER2 overexpression was graded in all cases as negative (0/1+ score), equivocal (2+ score), and positive (3+ score). In equivocal cases, the expression was confirmed using FISH (Fluorescent in situ hybridization). The cell proliferation marker Ki-67 was available in majority of our cohort (183/186 patients) included in the study. The cut-off value of >14% was taken high for Ki 67 proliferation.

The classification of BC patients in five intrinsic subtypes was done according to the St. Gallen International Expert Consensus Recommendation 2011.[4]

Treatment

All patients were assessed by the multidisciplinary team, and decision NACT and choice of surgical procedure (mastectomy/breast conservation) were discussed with the patients. In patients undergoing upfront surgery, pathological T and N stages were recorded, and for NACT patients, clinical T stage was recorded. Complications like surgical site infection, seroma formation, and flap necrosis were noted. Chemotherapy/NACT used was anthracyclin and cyclophosphamide followed by Taxanes. Patients who were HER2 positive were given trastuzumab for a period of 1 year. External beam radiotherapy was given to all patients who underwent breast conservation surgery (BCS), and T3, T4 and/or node positive patients who underwent modified radical mastectomy (MRM). All patients were on follow-up for a minimum period of 24 months after completion of treatment, and last follow-up status at 24 months was recorded.



Statistical analysis

Fisher's exact probability test and analysis of variance were performed to evaluate the statistical significance. A “P” value less than 0.05 was considered statistically significant.


  Results Top


The median age at presentation for all BC patients was 49.8 years (24–80 years). The clinical and pathological parameters recorded for each intrinsic subtype determined by the expression of ER/PR, HER2 neu, and Ki-67 are shown in [Table 1]. There were 64 (34.4%) luminal A, 37 (19.9%) luminal B, 6 (3.2%) luminal B HER2 positive, 33 (17.7%) HER2 enriched, and 46 (24.7%) triple negative patients. There was no significant difference across subtypes with regards to age and histological types. The most common T stage at presentation was T2 (54.3%). Patients with HER2 enriched and triple negative subtypes presented with higher T stages (T3 or T4) compared to other subtypes (51.5% and 65.2% respectively, P < 0.0055). Higher histological grade (grades II/III) was strongly associated with Triple negative BC (TNBC) when compared to other subtypes (OR 16.76 95% CI 2.23, 127.9) [Figure 1]. LVI, a prognostic factor for distant metastases was significantly higher in luminal B (OR 4.27 95% CI 2, 9.2) and TNBC (OR 4.26 95% CI 2.11, 8.61) subtypes. While the axillary lymph-nodal metastases were 43% (80 cases) in the entire study group, HER2 enriched and TNBC subtype groups had lymph-node involvement of 60.6% and 52.2% (P < 0.001), respectively. Notably, we observed that the proportion of lymph-node metastases in HER2-enriched subtype was significantly higher than that of other subgroups (OR 2.38 95% CI 1.1, 5.15) [Figure 1].
Table 1: Clinical and Pathological Features for Intrinsic Subtypes of BC

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Figure 1: Odds ratios (95% confidence interval) of pathological features. (a) Histological grade. (b) Lympho-vascular invasion. (c) Lymph node metastasis

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A total of 93 (50%) patients were administered NACT, whereas 63.6% of HER2 enriched (P < 0.001) and 80.4% TNBC (P < 0.001) subtypes were given NACT, significantly higher than that of other subgroups [Table 2]. BCS performed in 107 cases (57.5%) was the commonest surgical procedure among all cases of BC, while 60.6% of HER2 enriched (P < 0.001) and 65.2% of TNBC (P < 0.001) subgroups were amenable to MRM. Two patients in luminal A subgroup (3.1%) underwent MRM after BCS as they had local recurrences within the 2-year follow-up period [Table 3]. Postoperative complications like surgical site infection (SSIs) in 8.1%, seroma formation requiring aspiration in 16.7%, and secondary procedures in 2.6% of all cases were observed in study population with no significant difference among subgroups [Table 4].
Table 2: Comparison Of Neo-Adjuvant Chemotherapy (NACT) in Different Intrinsic Subtypes

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Table 3: Comparison of Type of Surgical Procedures

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Table 4: Comparison of Surgical Outcomes

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The disease free survival (DFS) at 2 years of follow-up was significantly different among subgroups of all BC patients and was 92.2% in luminal A, 89.2% in luminal B HER2 negative, 83.4% in luminal B HER2 positive, 78.8% in HER2 enriched, and 71.8% in TNBC subgroups (P = 0.027). Overall survival (OS) at 24 months was 100% in luminal A and luminal B HER2 negative, 83.4% for Luminal B HER2 positive, 90.9% for HER2 enriched, and 80.4% in TNBC subgroups. The proportion of loco-regional and distant recurrences among the subgroups were small and hence not assessed for statistical significance [Table 5].
Table 5: Comparison of Recurrence and Last Follow-Up Status

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  Discussion Top


BC is a heterogenous disease with a wide range of natural history, histological types and survival. To predict a patient's individual prognosis and tailor adjuvant therapy, gene expression profiling was suggested as an effective approach. IHC expression of hormonal receptors, HER2neu, and Ki67 values as surrogate classification of gene expression in sub-typing BC was defined by St Gallen International Expert Consensus.[4] The clinical significance of such a classification is still in a stage of evolution in Asia-Pacific region and India in particular. In the present study, we aimed at analyzing the distribution of intrinsic subtypes of BC based on IHC in relation to clinico-pathological parameters, treatment modalities, and early clinical outcomes.

The distribution of intrinsic subtypes in our study was luminal A 34.4%, luminal B-HER2 negative 19.9%, luminal B-HER2 positive 3.2%, HER2neu enriched 17.7%. and TNBC 24.7% and was not essentially different from those reported from other parts of India except that more TNBC cases were reported from North-East India.[8] Studies from other parts of Asia have reported higher percentage of luminal BC compared to nonluminal BC, but within the nonluminal BC groups, there is variation in distribution of HER2 enriched and TNBC [Table 6].[8],[9],[10],[11],[12],[13]
Table 6: Comparison Of Distribution of Intrinsic Subtypes in BC in Different Population

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The mean age at diagnosis in our study was 49.8 years, reinstating the fact that age at presentation of Indian BC patients is lower compared to that of western population.[14] Among the Asia-Pacific region, the median peak age of incidence of BC in women of Taiwan and Korea is similar to our population (46–49 years) but differ from that in Japan and Australia.[15] However, there was no significant difference in mean age among subtypes of BC in our study, consistent with other studies.[16],[17] The majority of the tumors in our cohort belonged to T2 category (2–5 cm), while HER2 enriched and TNBC sub-types presented with more T3/T4 tumors. Also, our study showed that TNBC and HER2 enriched subtypes were significantly associated with higher tumor grade, higher rate of lymph node involvement, and LVI. Vikash Kumar and his colleagues have reported tumor size >5 cm in majority of their HER2 positive subtype patients and found significant correlation between HER-2neu over expression and lymph node metastasis and higher grade of tumor.[17] Suhani et al. found that TNBC patients presented with larger tumor size (mean size of 6.1 cm), higher tumor grade (grade III –29.6% of TNBC vs 11.8% of non-TNBC patients, P < 0.001), and higher proportion of nodal metastasis (59.2% TNBC vs 43.2 non-TNBC, P < 0.002) in their experience from a tertiary care center.[18] However, there is conflicting reports of relationship between node positivity and TNBC subtypes. Dent et al. while comparing 180 TNBC patients with non-TNBC subtypes observed that there was an increased incidence of nodal metastasis as the tumor size increased in non-TNBC group, while this relationship was not seen in the TNBC group, which had increased likelihood of node positivity even in smaller tumor size.[19] Lin et al. studied 2569 TNBC patients and compared their profile with HER2 enriched and luminal BC patients and found that triple-negative subtype was associated with a lower risk of node positivity (adjusted OR 0.88, 95% CI 0.80, 0.97; P < 0.001) when compared to non-TNBC patients.[20] We found that LVI positive tumors were significantly more in luminal B and TNBC subtypes when compared to other subtypes (64.9% and 65%, respectively, vs 15.5%, P < 0.001). Ryu Y J et al. in their analysis of BC patients undergoing NACT reported that LVI positivity was found more in luminal B and HER2-enriched subtypes without any significant difference between subtypes.[21] Lin N U et al. in an analysis of BC patients presenting to NCCN centers have reported LVI presence of 26% in TNBC patients and 36% in HER2-enriched subtypes.[20] P Suresh and his colleagues from India have reported that 76% of their 128 TNBC patients who presented as early BCs had LVI.[22] These results emphasize that tumor biology and behavior of TNBC vary among different populations and remain poorly understood.

A higher proportion of HER2 enriched and TNBC patients in our study received NACT compared to other subtypes (63.6% and 80.4%, respectively, vs 48.6%, P < 0.001) because of the fact that these subtypes presented with higher T and N stages. HER 2 overexpression or TNBC disease did not contraindicate breast conservation in our patients. However, due consideration was given for tumor to breast ratio, and patients' wishes were taken into account before surgical treatment. We had performed 107 (58.1%) breast conservation procedures (BCS) as opposed to 77 (41.84%) mastectomy in the entire cohort. When BCS was compared among the subtypes, proportion of luminal cases was significantly higher compared to HER2 enriched and TNBC patients (72.9% vs 39.4% and 34.8%, P < 0.001). Agarwal et al. in an analysis of TNBC vs non-TNBC patients showed that approximately 20% of patients underwent breast conservation surgery in both TNBC and non-TNBC patients.[23]

We have used Trastuzumab for our HER2 positive patients when tolerated, and hence all subtypes were compared for last follow-up status (LFU) at 24 months after completion of their treatment. There was significant difference in DFS among subgroups, where HER2 enriched and TNBC showed inferior DFS (78.8% and 71.8%, respectively). This in concordance with other published results.[17],[20] In a study by Agarwal et al. though they found that OS and DFS of TNBC patients were poorer than those of non-TNBC patients, on subgroup analysis OS differed significantly only in stage III (47.4 ± 5.3 months in TNBC vs 74.5 ± 4.4 in non-TNBC; P < 0.001).[23] We observed highest recurrence rates for TNBC subgroup with 5 (10.8%) loco-regional and 8 (17.4%) distant recurrences within 24 months, which was reflected as shorter DFS. Lin et al. in their NCCN database observed a dramatic increase in the risk of death within 2 years of diagnosis among the TNBC group, which declined substantially over time with longer follow-up. We did not compare the recurrence pattern among subgroups as the numbers were too small for significance.

The main strength of this study was that all BC samples were analyzed for hormonal receptors, HER2/neu, and Ki67 by the same team trained in oncopathology. All HER2/neu samples that scored 2 + were subjected to further analysis by FISH for confirmation, and all HER2 positive patients were given Trastuzumab as part of treatment. Our study has several limitations. Most of our patients were referred from other smaller hospitals and might suffer from a referral bias. However, the distribution of BC subtypes was similar to that from published literature.[24] Another limitation was the short follow-up time. Given the long natural history of HR+/HER2 − breast cancer, it is likely that survival estimates will evolve over time in this subset. Despite this short follow up, 28.2% of TNBC patients in our data set had a recorded recurrence event and is likely to be a reasonable reflection of outcomes.


  Conclusion Top


Intrinsic subtyping of BCs with standardized IHC facility provides a comprehensive portrait of the clinical presentation, pathological features, and clinical outcomes among the subgroups in our population and facilitate tailoring of individualized treatment. TNBCs and HER2 enriched su-types, labeled as having aggressive biology and behavior, have higher prevalence in our population and warrant planning and conduct of subtype specific clinical trials for individualized treatment in future.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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