LCIS found after BMX for DCIS (and immediate DIEP)

Classic LCIS (by far the most common type) is normally considered less serious than DCIS.  Other types of LCIS (such as florid, polymorphic i.e. PLCIS, etc) are probably at higher risk, more like DCIS. http://www.ucsfcme.com/2012/slides/MAP1201A/18YiC...

There is a lot we don't know about LCIS. There is a lot of controversy about LCIS.  LCIS is very difficult to study.  The incidence of known LCIS is roughly 1/7 that of DCIS (so few patients), and LCIS  does not reliably show up as an abnormality on screening, so we don't know how how many women are walking around with LCIS and don't know it.  We can't watch an LCIS lesion and see how many times it turns into invasive breast cancer. So we know little about the real risk of LCIS turning to DCIS or invasive breast cancer.

But part of the evidence that supports that LCIS is less risky than DCIS is that when they compare treated DCIS (commonly complete excision +/- radiation, antihormonals) with treated LCIS (only local excision; antihormonal use not specified but probably very low  to zilch) they get about the same incidence.

http://www.ncbi.nlm.nih.gov/pubmed/16604564

There is controversy about the LCIS name.  DCIS was discovered in roughly the 1890s, whereas LCIS was discovered in the 1940s.  They didn't know the natural history of LCIS at the time, and we don't have much information now.  Many oncologists, and the NCI do not consider LCIS as 'cancer'.

The term lobular carcinoma in situ (LCIS) is misleading. This
lesion is more appropriately termed lobular neoplasia. Strictly
speaking, it is not known to be a premalignant lesion, but rather a
marker that identifies women at an increased risk for subsequent
development of invasive breast cancer. This risk remains elevated even
beyond 2 decades, and most of the subsequent cancers are ductal rather
than lobular. LCIS is usually multicentric and is frequently bilateral.
In a large, prospective series from the National Surgical Adjuvant
Breast and Bowel Project (NSABP) with a 12-year follow-up of 182 women
with LCIS that was managed with excisional biopsy alone, 26 women
developed ipsilateral breast tumors (9 of the tumors were invasive).[1] In addition, 14 women developed contralateral breast tumors (10 of the tumors were invasive). 

http://www.cancer.gov/cancertopics/pdq/treatment/b...

That said, there is some clonal evidence that a small percentage of LCIS has the possibility (not certainty) of itself turning into DCIS or invasive breast cancer.  (This is usually called  being a nonobligate precursor in papers.)

The science of breast cancer detection for individuals is in its infancy.  With the possible exceptions of a strong family history, or items such as a personal history of chest radiation to treat cancer (such as lymphoma) (which probably takes up roughly 15% of the invasive breast cancer population) we really don't know much. The question most LCIS patients have is 'What is my risk for getting breast cancer?'  They know this information much better for groups than for individuals.  This article says that the accuracy of predicting breast cancer with the modified Gail model for individuals (the breast cancer risk model used for most women without a family history) is 'better than a coin toss, but not by much.'

http://jnci.oxfordjournals.org/content/98/23/1673.... 

The modified Gail model automatically excludes women with LCIS or DCIS, but if they know this little about the risk of the 'average' woman, you can imagine how little we know about the risk of LCIS patients.

I don't know of any papers that specifically address the future risk of breast cancer after an initial diagnosis of both DCIS and LCIS.  You can't necessarily add up the risk for 2 different breast diagnoses and say that's your risk without looking at the population of people having both diagnoses.

I have classic LCIS and a weak family history (about the same as yours) and I was told  (by an NCI certified center) my lifetime risk for breast cancer was 'something between 10% and 60%, but probably closer to 10% than 60%.'  My oncologist said 30-40%.   I think an 'average' risk estimate for classic LCIS (without a significant family history or cancer radiation) is something like 20%-40%.    This Chuba study is probably the largest long term study, and gives a 'The minimum
risk of developing IBC after LCIS is 7.1% at 10 years.'

http://jco.ascopubs.org/content/23/24/5534.long

Before roughly the 1990s, they traditionally treated LCIS with BPMs, because they knew it was multicentric (meaning there are usually many spots of it in a breast) and usually bilateral (in both breasts.)  Since you don't know reliably where the LCIS spots are without doing a biopsy, to reliably remove the LCIS, you'd have to do a mastectomy.  But they also know that after an LCIS diagnosis, subsequent invasive breast cancer is often not _at_ the site of the known LCIS.  (Maybe this is like action at a distance?) This is difficult to study, since we don't know where the LCIS spots are that turned into invasive breast cancer. We don't know about cause and effect.  So obviously we don't know how an LCIS diagnosis puts you at higher risk of breast cancer.  Its probably a complex situation.

I think its important for doctors to let their patients know not only what their risks are, but how well we know that information, or at least hint at this uncertainty.  In the case of LCIS, there are a lot of unknowns.  

Its hard making choices among a lot of unknowns.  We all want to be ready for whatever is ahead.  But if you have classic LCIS, your DCIS probably put you at higher risk than the LCIS.

I am no expert on DCIS at all.  From the Gail paper cited above, I think it is highly unlikely that any doctor could give you an accurate risk factor  grade with 2 significant digits (68%) when you include LCIS.  When I put in 'DCIS + LCIS  + breast cancer risk' in Pubmed, I get 3 references. 

This whole discussion I am giving assumes you have classic LCIS.  The other, more 'exotic' forms of LCIS were discovered around 1990 or 2000, so there's no way we have enough data.

One reference looked at 26 cases of DCIS+LCIS , compared to DCIS or LCIS,all treated with excision alone, they found no significant differences between the recurrence rates.   http://www.ncbi.nlm.nih.gov/pubmed/11072784. This  study is waaay too small to make any conclusions.

The other two papers were not relevant or are 'expert opinion' (not studies that looked at larger study groups.)

So I don't know of any other papers that look at the risk of women with BOTH DCIS and LCIS diagnosed at the same time.

There is a Hall's breast cancer risk calculator (which I do NOT recommend if you have LCIS - be ready for a heart attack - it uses the modified Gail model and adds LCIS risk) that estimates subsequent breast cancer risk if you have LCIS. http://www.halls.md/breast/risk.htm When I put my numbers in around when I was diagnosed with LCIS, without tamoxifen, I could get a subsequent risk factor of almost 90%.  To its credit, this calculator says it has NOT been compared to populations, has not been peer reviewed, and is not appropriate to use for breast cancer therapy decisions.  So, that means I've been given a lifetime breast cancer risk for my classic LCIS of everything from 10% (less than the risk of an average woman in the USA) to (with the Hall's calculator) to almost 90%.  So you can see the variation in the risk factor prediction with just plain classic LCIS.

When you exclude persons with the larger risk factors like significant family history or chest radiation treatment for cancer, I have seen no other papers that claim plain LCIS gives you a risk of anywhere near 90%.  I went to genetic counseling in 2007 with a board certified genetics counselor (at an NCI certified center), and she also confirmed my lifetime cancer risk was about 30-40%. She gave me my risk of having a BRCA mutation as about the same as an _average_  woman with Ashkenazi heritage, which, if I remember right, is around 2-5%.

Your oncologist must have added up risk factors for each component (DCIS and LCIS).   While its possible this is true, I don't know where your oncologist got the data. My oncologist told me 'You've been cured!'.   Maybe she thought she was being reassuring, and its true that I never 'had breast cancer' to begin with, but I think I am certainly at higher risk than the average woman in the USA (about 13%).  She made it clear at my last appointment with her that she doesn't want to see me again, even though my higher risk continues.

IIRC, there are some breast cancer risk factors, such as alcoholism, that women with just that risk factor had a higher risk, but when you added other risk factors, the alcoholism did not increase their risk.  At least this was the opinion of some statisticians at the time.  So just because you have risk factor A and risk factor B, that does not necessarily mean your total risk is A+B. The two risk factors may interact, and since we have little to no idea how breast cancer progresses, we certainly don't understand the process.  I don't know of any data that looks at large populations of women with DCIS + LCIS diagnosed at the same time.  And these studies don't even consider we know almost nothing about individual risk in this situation ( see the 'coin toss' paper cited above.)

Just as a personal note, if this helps, if I was in your situation, from what you've said, I would likely have done exactly what you did.  I would not have wanted to go through the continued anxiety.

You're very welcome, indeed.