Invasive lobular carcinoma of the breast: the decisions you may face

Cancer page →Second-opinion finder →

1 treatment setting, 1 with more than one named option. Each section lays out the options the standard of care names, what each is for, the trials behind them with their recorded results, the side effects and cautions on record, and questions to ask. Built from the cancer page's standard-of-care rows; nothing here is advice for your case.

Other settings

All stages

4 optionsCompare side by side →

Treated as HR-positive breast cancer: surgery planned with MRI, endocrine therapy, CDK4/6 inhibitors in advanced disease; sentinel node biopsy as in ductal disease.

The options, in plain words

Endocrine therapy (SERMs, AIs, SERDs)Standard of care

Pills that block or remove oestrogen signalling, the mainstay of treatment for hormone-driven breast cancer for 50 years.

Oral, effective, cheap (generics)

CDK4/6 inhibitorsApproved

Pills that stop the cell-division engine, added to hormone therapy for the most common type of breast cancer.

Oral, well tolerated
Adjuvant survival benefit

TamoxifenApprovedSmall-molecule SERM

The original targeted cancer drug (1977): a pill that blocks oestrogen's effect on breast cancer and halves recurrence, still essential for premenopausal women.

Letrozole (and other aromatase inhibitors)ApprovedSmall-molecule aromatase inhibitor

Daily pills that stop the body making oestrogen after menopause, the backbone of hormone therapy for most breast cancers.

Also referenced:HR-positive / HER2-negative breast cancerMastectomy

The evidence behind it

No trial record is attached to this row yet. The trials tab lists what is recruiting and the landmark trials for this cancer.

The main trade-offs on record

Endocrine therapy (SERMs, AIs, SERDs)

ESR1 mutations; menopausal symptoms, bone loss, adherence

CDK4/6 inhibitors

Neutropenia, diarrhoea (abemaciclib), QT (ribociclib)
Resistance via RB loss, CDK2, cyclin E

Tamoxifen all recorded rates →

Side effect	Any grade	Grade 3+
Hot flushes · ATAC, tamoxifen arm, US label (36% with anastrozole)	41%	-
Cataract · ATAC, tamoxifen arm, US label (6% with anastrozole)	7%	-
Venous thromboembolism · ATAC, tamoxifen arm, US label (3% with anastrozole)	5%	-
Endometrial cancer · ATAC, tamoxifen arm, women with an intact uterus, US label (0.2% with anastrozole); NSABP P-1 found 33 versus 14 invasive endometrial cancers with tamoxifen versus placebo	0.6%	-

Possible QT prolongation. Check ECG and electrolytes; review other QT-prolonging drugs.

Rates from the label or pivotal trial as recorded on the product page; each grade 3+ figure links to its source.

Letrozole (and other aromatase inhibitors)all recorded rates →

Side effect	Any grade	Grade 3+
Arthralgia/arthritis · BIG 1-98, letrozole monotherapy arm (n=2448), US label; myalgia 9.0%	25.4%	3.4%
Fatigue · BIG 1-98, letrozole monotherapy arm (lethargy, malaise, asthenia), US label	9.6%	0.2%
Hot flushes · BIG 1-98, letrozole monotherapy arm, US label	33.5%	-
Bone fracture (during 5 years of treatment) · BIG 1-98, letrozole arm at median treatment duration of 60 months (7.2% with tamoxifen), US label	10.2%	-

Rates from the label or pivotal trial as recorded on the product page; each grade 3+ figure links to its source.

Questions to ask about this decision

Between Endocrine therapy (SERMs, AIs, SERDs), CDK4/6 inhibitors, Tamoxifen and the other options, which do you recommend for me, and what about my case would make you choose differently?
Why: Guidelines list several reasonable options; the choice turns on details of your tumour, your health and your priorities.
What is each option trying to achieve: cure, long control, or relief of symptoms, and over what time?
Why: The aim shapes how much side effect and disruption is worth accepting.
Which side effects of Tamoxifen or Letrozole (and other aromatase inhibitors) are most likely for me, which are reversible, and which would make us stop?
Why: The recorded rates below come from labels and trials; your own risk depends on dose, other medicines and your health.
What happens if I delay, or decline this step for now? Is the decision reversible?
Why: Some decisions can wait for a second opinion or a trial slot; others cannot. Knowing which is part of the choice.
For my situation (all stages), which of the standard options do you recommend and why?
Why: Guideline options include: Treated as HR-positive breast cancer: surgery planned with MRI, endocrine therapy, CDK4/6 inhibitors in advanced disease; sentinel node biopsy as in ductal disease.
Am I a candidate for Tamoxifen, Letrozole (and other aromatase inhibitors), and what side effects should I expect?
Why: Knowing the expected toxicities helps you plan work, family, and supportive care.

Add these to your appointment list, or take the full question set for this cancer.

How to read this page. Options and results come from OnCo records with their sources; the settings are the standard-of-care rows on the cancer page, and the lines of therapy are on the sequencing grid. Where a setting names one path, the choice is usually about timing, trials and where to be treated: see expert centres. OnCo is orientation, not medical advice.

Living with cancer·Standard of care

Invasive lobular carcinoma of the breast: the decisions you may face

Cancer page →Second-opinion finder →

Other settings

All stages

4 optionsCompare side by side →

Treated as HR-positive breast cancer: surgery planned with MRI, endocrine therapy, CDK4/6 inhibitors in advanced disease; sentinel node biopsy as in ductal disease.

The options, in plain words

Endocrine therapy (SERMs, AIs, SERDs)Standard of care

Pills that block or remove oestrogen signalling, the mainstay of treatment for hormone-driven breast cancer for 50 years.

Oral, effective, cheap (generics)

CDK4/6 inhibitorsApproved

Pills that stop the cell-division engine, added to hormone therapy for the most common type of breast cancer.

Oral, well tolerated
Adjuvant survival benefit

TamoxifenApprovedSmall-molecule SERM

The original targeted cancer drug (1977): a pill that blocks oestrogen's effect on breast cancer and halves recurrence, still essential for premenopausal women.

Letrozole (and other aromatase inhibitors)ApprovedSmall-molecule aromatase inhibitor

Daily pills that stop the body making oestrogen after menopause, the backbone of hormone therapy for most breast cancers.

Also referenced:HR-positive / HER2-negative breast cancerMastectomy

The evidence behind it

No trial record is attached to this row yet. The trials tab lists what is recruiting and the landmark trials for this cancer.

The main trade-offs on record

Endocrine therapy (SERMs, AIs, SERDs)

ESR1 mutations; menopausal symptoms, bone loss, adherence

CDK4/6 inhibitors

Neutropenia, diarrhoea (abemaciclib), QT (ribociclib)
Resistance via RB loss, CDK2, cyclin E

Tamoxifen all recorded rates →

Side effect	Any grade	Grade 3+
Hot flushes · ATAC, tamoxifen arm, US label (36% with anastrozole)	41%	-
Cataract · ATAC, tamoxifen arm, US label (6% with anastrozole)	7%	-
Venous thromboembolism · ATAC, tamoxifen arm, US label (3% with anastrozole)	5%	-
Endometrial cancer · ATAC, tamoxifen arm, women with an intact uterus, US label (0.2% with anastrozole); NSABP P-1 found 33 versus 14 invasive endometrial cancers with tamoxifen versus placebo	0.6%	-

Possible QT prolongation. Check ECG and electrolytes; review other QT-prolonging drugs.

Rates from the label or pivotal trial as recorded on the product page; each grade 3+ figure links to its source.

Letrozole (and other aromatase inhibitors)all recorded rates →

Side effect	Any grade	Grade 3+
Arthralgia/arthritis · BIG 1-98, letrozole monotherapy arm (n=2448), US label; myalgia 9.0%	25.4%	3.4%
Fatigue · BIG 1-98, letrozole monotherapy arm (lethargy, malaise, asthenia), US label	9.6%	0.2%
Hot flushes · BIG 1-98, letrozole monotherapy arm, US label	33.5%	-
Bone fracture (during 5 years of treatment) · BIG 1-98, letrozole arm at median treatment duration of 60 months (7.2% with tamoxifen), US label	10.2%	-

Rates from the label or pivotal trial as recorded on the product page; each grade 3+ figure links to its source.

Questions to ask about this decision

Between Endocrine therapy (SERMs, AIs, SERDs), CDK4/6 inhibitors, Tamoxifen and the other options, which do you recommend for me, and what about my case would make you choose differently?
Why: Guidelines list several reasonable options; the choice turns on details of your tumour, your health and your priorities.
What is each option trying to achieve: cure, long control, or relief of symptoms, and over what time?
Why: The aim shapes how much side effect and disruption is worth accepting.
Which side effects of Tamoxifen or Letrozole (and other aromatase inhibitors) are most likely for me, which are reversible, and which would make us stop?
Why: The recorded rates below come from labels and trials; your own risk depends on dose, other medicines and your health.
What happens if I delay, or decline this step for now? Is the decision reversible?
Why: Some decisions can wait for a second opinion or a trial slot; others cannot. Knowing which is part of the choice.
For my situation (all stages), which of the standard options do you recommend and why?
Why: Guideline options include: Treated as HR-positive breast cancer: surgery planned with MRI, endocrine therapy, CDK4/6 inhibitors in advanced disease; sentinel node biopsy as in ductal disease.
Am I a candidate for Tamoxifen, Letrozole (and other aromatase inhibitors), and what side effects should I expect?
Why: Knowing the expected toxicities helps you plan work, family, and supportive care.

Add these to your appointment list, or take the full question set for this cancer.