Steve Jobs – the most famous Neuroendocrine Cancer Ambassador we NEVER had

steve jobs 2010
The last few years have reminded me that life is fragile

Steve Jobs died 5 Oct 2011.  RIP Steve, you certainly made a difference to the world of technology and that is still being felt today.  I have a number of google alerts setup and every day the emails arrive in my inbox. The longest email is always the Steve Jobs one, i.e. Steve Jobs is written about more than Neuroendocrine Cancer and other connected subjects. That’s interesting because Neuroendocrine Cancer is the type Steve had, not Pancreatic as is frequently reported.

There are huge differences between Pancreatic Cancer and Neuroendocrine Cancer with a pancreatic primary – click here to read more. 

pancreatic vs neuroendocrine

I’ve mentioned Steve Jobs a few times previously, mainly in my blog The Human Anatomy of Neuroendocrine Cancer. I wrote that blog when I was frustrated about the constant misreporting of Neuroendocrine Cancer as other types of cancer. Others included Nick Robinson (see blog The Devil is in the Detail) and Wilko Johnson (The Ecstasy of Wilko Johnson).  I’ve also suggested in my blog ‘Every Day is NET Cancer Day’ that we need high-profile patient Ambassadors and despite his death, Steve Jobs would have been quite a catch, had he been willing. Curiously, the same thing is happening with Dag Kittlaus (Siri creator) who was diagnosed with a pNET last year.  To add insult to injury, the 2018 death of Aretha Franklin is gong the same way.

A lot has been written about Steve’s cancer experience and much of it is full of ‘what ifs’. However, I’d like to focus on the facts that are known and we can be almost certain about. That said, the precise detail that we (as NET patients) might want, is probably only to be found in Steve Jobs’s medical documents. Many people say that Steve Jobs had a right to personal privacy and I agree, nothing I put here isn’t already in the public domain.

Diagnosis

How was it found?  In 2003, Steve was having a CT scan to examine his kidneys and ureter, as he had developed recurrent kidney stones beginning in the late 1990s. A suspicious lesion was spotted on his pancreas. To cut a long story short, he eventually had more specialist scans and then a biopsy which diagnosed a type of Neuroendocrine Tumour.  There are many mentions of Insulinoma, a pNET which is reported to have a 10% malignancy rate (ISI Book – Woltering et al). It isn’t clear whether Steve had any presentational symptoms of an Insulinoma at this point (i.e. hypoglycemia).  There is also some chatter online about his tumour being a Glucagonoma (another type of pNET).

Initial Treatment

Steve initially tried alternative medicine before having surgery 9 months after diagnosis. There are reports of his medical team urging surgery earlier and his biographer stated that Steve had later regretted this delay. One of his Doctors is reported to have said “Steve was a very thoughtful person. In deciding whether or not to have major surgery, and when, he spent a few months consulting with a number of physicians and scientists worldwide as well as his team of superb physicians. It was his decision to do this”.  He is reported to have gone on to have a ‘Whipple’ type operation in 2004.  It was only then, that his condition was made public.  During that operation, 3 lesions were reported on his liver.

Ongoing Treatment and Surveillance

Most NET patients enter this phase after their initial treatment, it’s also the period where you learn about the cancer and how best to live with it.  There’s not much written about Jobs’ illness between his surgery and his liver transplant but my research uncovered a useful timeline from Bloomberg and other sources:

June 12, 2005: Jobs talks about his fight with cancer during a commencement speech at Stanford University. He says he was diagnosed about a year earlier and that doctors told him he wouldn’t live longer than six months. The cancer turned out to be a form that was treatable with surgery, “and I’m fine now,” he says. Source Bloomberg.  {Author’s note:  an indication he had been told, or his doctors knew, it was a Neuroendocrine Tumor}

January 24, 2006:  Walt Disney chief executive Bob Iger knew early on that Steve Jobs’s cancer had returned and kept it a secret before it became public knowledge, a new biography of Apple’s late chief executive reveals. The day the deal was officially announced, Mr Iger said he was at Pixar’s headquarters for the ceremony when Jobs asked to go for a private walk. On a secluded part of the Californian campus Jobs put his arm around Mr Iger’s shoulder and revealed his cancer was back. “Frankly, they tell me I’ve got a 50-50 chance of living five years,” the Disney CEO quoted Jobs as saying.

2007:  Not much out there except that he was busy launching what might be regarded as Apple’s most successful and iconic product ever – the iPhone.

June 9, 2008: Jobs, while introducing the iPhone 3G at Apple’s developers’ conference, appears thinner and frail. The company blames a “common bug.”

July 21, 2008: Responding to concerns about Jobs’s appearance, Apple says he has no plans to leave the company and that his health is a private matter. Investors aren’t reassured, and the shares fall 10 percent.

July 23, 2008: The New York Times reports that Jobs has been telling associates and Apple’s board he is cancer-free. Jobs had a surgical procedure earlier in the year to address a problem that contributed to his weight loss, the newspaper reports, citing unnamed people close to the executive. The shares climb 2.6 percent.

July 26, 2008: New York Times columnist Joe Nocera writes that he spoke two days earlier on the phone with Jobs, who said his health problems weren’t life-threatening. Jobs declines to go on the record about the nature of his ailment.

Sept. 9, 2008: Jobs, introducing new iPod media players at an event in San Francisco, still looks thin. “Reports of my death are greatly exaggerated,” Jobs jokes. Munster says that while the CEO’s appearance is unchanged since June, “Just the fact that Steve Jobs was up there was a positive.”

Oct. 3, 2008: A posting on CNN’s citizen journalist Web site, called iReport.com, says Jobs has been rushed to the hospital after a “major heart attack.” The shares fall 5.4pc. The stock rebounds after Apple says the report is false.

Dec. 16, 2008: Apple says that Jobs won’t be giving his usual speech at the Macworld conference, renewing concerns about his health. Jobs had used the forum to introduce new products for 11 straight years.

Jan. 5, 2009: Jobs says he is suffering from a hormone imbalance, causing him to lose weight. Jobs vows to remain CEO during treatment. “The remedy for this nutritional problem is relatively simple and straightforward,” Jobs says in an open letter.

Jan. 14, 2009: Jobs gives up day-to-day operations to Cook until June, saying his health problems are more complex than originally thought. Jobs says he will remain involved in major strategic decisions. “I look forward to seeing all of you this summer,” he says in a letter to employees.

By this stage, his cancer is already starting to take its toll on how he looks.

The disease takes its toll over the years

Liver Transplant 2009

It is common knowledge that Jobs had a liver transplant in 2009 in Tennessee (he was on the list in California and Tennessee).  In between his Whipple and then, he appears to have lived (and worked) with his disease and it’s consequences. His issues appear to have been exacerbated by his excessive vegan diet/fads and the effects of the Whipple surgery (many of you will be aware of these effects). For example, he would spend weeks eating the same thing and then suddenly change his mind and stop eating it. He’d also go on fasts. His condition immediately prior to the liver transplant was said to be ‘poor’ and losing more weight (he had been noticeably thinner for some time).

Did Steve Jobs get ‘experimental’ PRRT?

Jobs took a second medical absence for roughly six months in 2009. It wasn’t until June 20th, two months after the fact, that the Wall Street Journal uncovered the fact that Jobs had undergone a secret liver transplant at Methodist University Hospital in Memphis, Tennessee. However, during that absence, Fortune reported Jobs also took an unpublicized flight to Switzerland to undergo an ‘unusual radiological treatment’ (PRRT) at the University of Basel for neuroendocrine cancer, according to Jerry York, the Apple director who died in March 2010.

Post-Liver Transplant

In 2010, Jobs started to feel sick again. He would lose his appetite and begin to feel pains throughout his body. His doctors would do tests, detect nothing, and reassure him that he still seemed clear.  In early November 2010, he was in pain, stopped eating and had to be fed intravenously by a nurse who came to his house. The doctors found no sign of more tumours, and they assumed that this was just another of his periodic cycles of fighting infections and digestive maladies.

Heres’ a great bunch of TV interviews (something Jobs didn’t do very often).  “The last few years have reminded me that life is fragile”.  Click here (worth watching the whole 10 minutes). His final TV appearance was in June 2011 to the Cupertino City Council about the acquisition of land for their new campus.  Worth watching some of it: Click here.

The End

In early 2011, doctors detected the recurrence that was causing these symptoms. Ultimately, he developed liver, bone, and other metastases.  He had a further extended leave of absence from his job before stepping down as Apple CEO in Aug,  Steve Jobs eventually died 5 Oct 2011.

steve jobs 2010
The last few years have reminded me that life is fragile

References

Notwithstanding the Pancreatic Cancer vs Neuroendocrine Cancer issue, I carried out my research mainly using two articles of the many you can find out there:

  1.  “And one more thing” about Steve Jobs’ battle with cancer
    This is a long article and totally fascinating.  Some of the evidence is presented using extracts from Walter Isaacson’s book ‘Steve Jobs’
  2. A Tumor Is No Clearer in Hindsight.  This article comes to similar conclusions than the one above but it’s shorter and easier to read. It’s from the New York times and was written after the dust settled on Jobs’ death (i.e. when more facts were available). There is also input to this article from NET specialists Dr Wolin and Dr Libutti.

  3. Apple chief Steve Jobs: Health timeline since 2003.  This article is from a UK National Newspaper (The Telegraph) but via US Business Publication Bloomberg.

Personal Summary

“A tumor is no clearer in hindsight” is a good summary on the basis that I would have liked much more detail!  During my research, I found many mentions of Insulin as stated above but only one or two mentioning Glucagon, a hormone associated with another pNET type – Glucagonoma. However, looking at this tumor type in the ISI Book (Woltering et al) and the Jobs diagnostic and treatment story, I have some doubts whether this was the precise tumor type. I have some other searches in progress hoping to find something concrete.

Thinking Differently There is no doubt that Steve Jobs was an amazing and very interesting character.  You just can’t see Apple being the Apple it is today without his intervention.  He was famous for being ‘unconventional’ and ‘thinking different’ and I get that element of his character.  I just can’t help thinking that perhaps he should have been more ‘conventional’ with this thinking and approach to treating his cancer. However, we just don’t know what advice he was receiving and what advice he accepted or rejected.  As for the ‘Pancreatic Cancer’ thing – I’ve said this before, I believe patients only say or interpret what their doctors say to them in regards cancer type.

“The most famous patient ambassador we never had”.  I don’t mean any disrespect by that, I’m just emphasising that we need so much more awareness of our cancer and a high-profile patient could do so much to help in this area. If he was so inclined, Steve would have been a fantastic advocate for Neuroendocrine Cancer and there’s an area where perhaps thinking different might be the way ahead. However, I have a suspicion that very famous people don’t really want to talk about their illness and Steve Jobs might even perceive that as a weakness.

And one more thing …….  you may also find this article useful.  It’s titled “And one more thing”

 

Neuroendocrine Cancer – not as rare as you think

Background

Although initially considered rare tumours up until 10 years ago, the most recent data indicates the incidence of NETs has increased exponentially over the last 4 decades and they are as common as Myeloma, Testicular Cancer, and Hodgkin’s Lymphoma. In terms of prevalence, NETs represent the second most common gastrointestinal malignancy after colorectal cancer. Consequently, many experts are now claiming NETs are not rare (see below).  A recent study published on 5 Dec 2018 reports that even if you isolate Small Intestine NETs in the USA population, the incident rate is 9/100,000. Contrast this against the US incident rate as at 2012 of 7/100,000 for all NETs.  The rare threshold in Europe is 5/100,000 and below.

And on 7th January 2019, an internationally known NET Specialist described NETs as very common.

strosberg not rare
In fact, the graph of the SEER database figures for NETs in both 2004 and 2012 indicates the rate of incidence increase is faster than any other cancer on the planet, particularly attributed to lung, small intestine, and rectal NETs.  The World Health Organisation’s revised classification of Neuroendocrine Neoplasms in 2010, abandoned the division between benign and malignant NET as all NETs have malignant potential and should be graded accordingly.  The 2004 SEER data compiled did not take into account what might have been considered to be benign NETs.

However, the most recent USA study up to 2012 has confirmed the incidence beyond 2004 has continued to rise (and rise, and rise, and rise) and this is covered below in the section entitled “Meanwhile in USA”. One of the principal authors of both database studies has now gone public and said NETs are no longer rare. 

Incidence and Prevalence

Before I continue, it’s important to understand the difference between incidence and prevalence.  In the crudest of terms, incidence is the number of new cases of a disease being diagnosed (normally aligned to a specific quota of the population per year, generally 100,000). Prevalence normally indicates an amount of people living at any one time with a disease. It’s also important to note that different nations or groups of nations classify ‘rare’ in different ways – not really helpful when looking at worldwide statistics.

So why the increase?  I suspect the reasons include (but are not limited to), more awareness (population and medical staff), better detection techniques and probably more accurate reporting systems, at least in USA, Norway, Canada and now in the UK i.e. a mixture of underdiagnoses and misreporting.  The Canadian study is important as it also noted the proportion of metastases at presentation decreased from 29% to 13%. This is the first study that suggests an increased incidence of NETs may be due to an increased (and earlier?) detection. This has the knock on effect of increasing prevalence as most NET Cancer patients will normally live for longer periods.  Add to this the plethora of better treatments available today, you have a highly prevalent cancer. Most of that is good news.

However, their true incidence may be higher owing to the lack of diagnosis until after death.  For example, in USA, a respected NET specialist stated that the autopsy find for (excuse the outdated terminology) ‘carcinoid‘ is 4 times the recorded diagnosis rate. In Australia, one study claimed that 0.05% of all autopsies found a Pheochromocytoma or Paraganglioma.  A very interesting slideshow from a well respected NET expert claimed there are 200,000 undiagnosed NET patients in USA. Slide below:  You may also wish to check out my article “The Invisible NET Patient Population” where this is explored further.

dana-farber-200000

US SEER 2004 – The Trigger and Turning Point

In the largest study of its kind up to that point, well-known Neuroendocrine Cancer expert James C. Yao researched the Surveillance, Epidemiology and End Results (SEER) database. His team studied 35,825 cases of Neuroendocrine Cancers in the United States covering data between 1973 and 2004. The report concluded that in 2004 there were 5.25 new cases of NETs per 100,000 people, compared with 1.09 per 100,000 in 1973 [1]. This is in contrast to the overall incidence of malignancies, which has remained relatively constant since 1992 (see the yellow line on the graph). The study also pointed out that due to increased survival durations over time, NETs are more prevalent than previously reported. If you analyse the NET data for 1994 (10 years before the end of the study period), you will see an incidence rate of approx 3.25/100,000. In 2004, the incidence rate had risen to 5.25/100,000. Although not an exact science, it does suggest the potential incidence rate at 2014 (10 years after the study period) might possibly have climbed well beyond 6/100,000 and even further if the same rate of increase displayed by the study had continued (spoiler alert – it actually came out as 7/100,000 see below under ‘Meanwhile in USA’). This study also confirmed a prevalence of 103,000 NET patients as at 2004. As this is regarded as the most accurate NET statistic ever produced, it is interesting to note that was at a time when the prognostics for NET were not as good as they are today indicating there must be a very significant increase if extrapolated to the current time. Moreover, this was prior to the WHO 2010 reclassification of NETs so more diagnoses will be counted today that were not counted in 2004. See below to see the significance of this figure (see section ‘Do the math’).

The 2004 data was an astonishing set of statistics – particularly as they were based on 12 year old data. However, there is now new data up to 2012 that overtakes the above-mentioned groundbreaking study and confirmed the incidence is now even higher.  See section entitled “Meanwhile in USA …….” 

incidence
SEER study 2004 – NETs

Meanwhile in Norway ……

Data from the Norwegian Registry of Cancer showed a similar incidence of Neuroendocrine Cancers with a 72% increase between 2000 and 2004 compared with 1993–1997 [2]. Also in Norway, an article published in 2015 entitled “Epidemiology and classification of gastroenteropancreatic neuroendocrine neoplasms using current coding criteria” indicated a high crude incidence of GEP-NEN, at 5·83 per 100 000 inhabitants over the period 2003-2013 (adjusting to 7.64 for Europe in 2013 – see diagram below extracted from cited article 2a).  It was also noted together with the statement “….a significant increasing trend over time”. [2a] Citation [2b]
extrapolation europe

Meanwhile in Canada …….

CNETs have highlighted an article published in the magazine ‘Cancer’, February 15, 2015, showing that the incidence of Neuroendocrine Tumours has markedly increased in Canada over the course of 15 years (1994-2009). The results showed that the incidence of Neuroendocrine Tumours has increased from 2.48 to 5.86 per 100,000 per year. [3] [4]

simron singh nets not rare

Meanwhile in UK …….

The latest figures from Public Health England (PHE) indicate the incidence of NETs has risen to almost 9/100,000 (i.e. not rare) using the latest International Classification of Diseases for Oncology (ICD-O) methodology version 3 – ICD-O-3. Even that figure is understated because it does not include Lung Neuroendocrine Carcinomas (i.e. SCLC and LCNEC). As at 31 Mar 2016, the age-standardised incidence rate for NETs in England (excluding small and large cell neuroendocrine carcinomas, SCLC and LCNEC respectively) was 8.84, 8.37 in males and 9.30 in females – rising from 3.9 in 2001.  These figures are from the NET Patient Foundation and were issued as a result of a NPF and PHE (NCRAS) partnership project which has been compiling statistics on the incidence, prevalence and survival of NET Patients in England using English cancer registry data. They also have an aim to also access the rest of UK cancer registry data to get UK wide figures.

That means a new NET diagnosis every 2 hours. You can see a summary of the report   NEW:  Public Health England release new incidence data for Neuroendocrine Cancer

A slide from the recent UKINETS 2017 conference indicating an agreement from UK and Ireland NET Specialists.

IMG_20171204_214918
as presented at UKINETS 2017

Meanwhile in New Zealand …….

as presented by Unicorn Foundation NZ on 11 Mar 2017

Meanwhile in USA …….

The latest evidence of its rise is contained in the largest ever study ever conducted. It is based on data up to 2012 so it’s worth noting that this data is now 5 years old (3 years for the project prevalence figure), so even these figures may still be conservative.  The document, which was published in 2017 can be found here: Click here.  A short summary follows:

In this population-based study that included 64 971 patients with neuroendocrine tumors, age-adjusted incidence rates increased 6.4-fold between 1973 and 2012, mostly for early stage tumors.  Survival for all neuroendocrine tumors has improved, especially for distant stage gastrointestinal and pancreatic neuroendocrine tumors.

Of the 64 971 cases of NETs, 34 233 (52.7%) were women. The age-adjusted incidence rate increased 6.4-fold from 1973 (1.09 per 100 000) to 2012 (6.98 per 100 000). This increase occurred across all sites, stages, and grades. In the SEER 18 registry grouping (2000-2012), the highest incidence rates were 1.49 per 100 000 in the lung, 3.56 per 100 000 in gastroenteropancreatic sites, and 0.84 per 100 000 in NETs with an unknown primary site. The estimated 20-year limited-duration prevalence of NETs in the United States on January 1, 2014, was 171 321

Conclusion: The incidence and prevalence of NETs have continued to rise in the United States, owing to the increased diagnosis of early-stage disease and possibly stage migration. The survival of patients with NETs has improved, and this improvement has been greater for those with distant gastrointestinal NETs and, in particular, distant pancreatic NETs.

Combine that with a revised annual incidence rate of 23,000 and the very well known fact that NETs is a highly prevalent disease, it must be mathematically impossible for the figure not to be above the USA rare threshold of 200,000 in 2017.  As you can see from the graph below, the incidence rate for NETs continues to outstrip the incidence rate for all malignant neoplasms (another word for tumour).  Amazingly, the report authors even state “…….. it is likely that we have underestimated their true incidence and prevalence”.

not rare yao netrf

incidence 2012 jama
NET Cancer diagnoses continues to outstrip all other cancer diagnoses

The NET Research Foundation published an amazing infographic which summarises the output of the SEER 2012 study (although it does omit the prevalence figure ‘as at’ date).  See it below and you can read the accompanying text here.

dasari-infographic-2
Graphic from the NET Research Foundation – https://netrf.org/study-shows-rising-rates-of-net-incidence-prevalence-and-survival/

Let’s do the Math

Neuroendocrine Cancer is not only the fastest growing cancer in incidence terms but as a group of cancers, given the mounting epidemiological evidence, it can no longer be rare as a grouping of cancers.  Neuroendocrine disease IS NOT RARE.

For example, if you roughly extrapolate the US SEER data graph above to 2017 and recalculate the prevalence rate based on 23 000 per year from the 2014 figure of 171 321.  Unfortunately, some people will have passed, but it’s well documented as a highly prevalent cancer and therefore more people live. The prevalence of neuroendocrine tumors in USA was higher than the combined estimated prevalence of esophageal cancer (n = 36,857), gastric adenocarcinoma (n = 79,843) and pancreatic adenocarcinoma (n = 49,620) in 2013. In fact, one of the conclusions of the 2012 SEER report is that we are living longer with NETs. This is in line with many other cancers due to improved diagnostic and treatment regimes.  Cleary more work still needs doing.

Dr Kunz has done the math
hendifar not rare
Dr Hendifar has done the math
not rare yao netrf
Dr Yao has done the math

simron singh nets not rare
Dr Singh has done the math

strosberg not rare
Dr Strosberg has done the math

The Invisible NET Patient Population

The heading of this section is my name for those who have not yet been diagnosed with NETs but are walking around having been either misdiagnosed, diagnosed with another cancer in the same part of the anatomy, living and putting up with the symptoms whilst the tumours grow.  To add to this part of the underdiagnoses of NETs is this most amazing piece of research published in 2018 – Pan-cancer molecular classes transcending tumor lineage across 32 cancer types, multiple data platforms, and over 10,000 cases.  It was published in the American Association of Cancer Research (AACR) journal ‘Clinical Cancer Research and authored by Chad Creighton et al. D.  This was a pan cancer piece of research which indicated that Neuroendocrine disease may be more prevalent than anyone had ever thought.  There’s a summary article here which I suggest you read fully.  The rather explosive extract is as follows:

We expected that about 1 percent of

Go figure

Whilst reporting has been improved, it is most likely still not 100% accurate. Therefore, even the figures above may be understated due to an incorrect cause of death reporting and incorrect diagnosis/recording of the wrong cancers (e.g. pNETs recorded as Pancreatic Cancer, Lung NETs recorded as Lung Cancer, etc).  This is certainly still happening in UK and I suspect in most other countries. Add to that the regular reports of Neuroendocrine Tumours being found during autopsies and you have the potential for an even further unrecorded increase had these been found prior to death. In fact, according to SEER 2012, the true incidence and prevalence is most likely underestimated. In fact here is a statement straight from the horse’s mouth:

SEER 2012 Underestimated
more math

The issue is also complicated by the method used in USA for naming a disease ‘rare’. Rather than use incidence rates, the USA uses the number of people living with the disease at any one time (i.e. essentially the prevalence). This is currently 200,000 as a threshold – anything below that is considered rare.  It seems mathematically impossible for NETs to be less than 200,000 given the data provided above.

Eric Liu Not Rare

When I first started researching NETs back in 2010, the US figure (which varies from source to source) was around 125-150,000.  Why are people quoting figures less than this in 2017 when the 2014 figure has now been confirmed above? There also seems to be a selective omission of the new US incidence rate of 7/100,000.

You will also see that Dana Farber is estimating more than 200,000 people are as yet undiagnosed.  Even if that were 50% accurate, it would put the current prevalence figure in US over 300,000.

Let’s cut to the chase – NETs are not rare, they are just less common

Are we shouting loud enough about this?  I don’t think so.  ‘Rare’ is very frequently used within the NET community almost to the point of being a status symbol. Based on these figures, this looks like an outdated approach along with its associated icons.  The evidence above is so compelling that saying the group of cancers officially called Neuroendocrine Neoplasms is rare is starting to sound like fake news.

“A neoplasm on the rise.  More prevalent than you may think.  Incidence increased dramatically during past 3 decades” (Novartis)

“it’s less rare than we used to think. It’s more malignant than we previously thought” (Dr Richard Warner)

“…..it is one of the most rapidly increasing cancers in the U.S. There has been a 500-percent increase in the last 30 years” (Dr Edward Wolin)

“Estimated more than 200,000 undiagnosed cases in the US” (Dana Farber)

“I actually think NETs are not a rare cancer” (Dr James Yao)

“NETS will no longer be rare” (UKINETS 2017 one of the opening slides)

“NETs are no longer rare” (Dr Andrew Hendifar)

“…..when you think of prevalence, NETs are actually quite common” (Dr Jonathan Strosberg)

“One study showed that the number of people diagnosed has risen 50% over the last decade and unfortunately, I worry that is an underestimate” (Dr Eric Liu)

“Neuroendocrine Cancer – NETs are not rare, just less common.  We need a new paradigm” (Ronny Allan since 2015)

You may also wish to check out my article “The Invisible NET Patient Population” where this is explored further.