this is "nightline." >> tonight, window of terror. >> he's stabbing my sister! >> the 911 call as two sisters are attacked in their own home after an ex-convict crawls in through a window. how they fought him off and fought for their lives getting help in the nick of time. amy robach with a deeply personal look at the new breast cancer controversy. and the announcement that has women up in arms. why recommendations are changing and the huge pushback from those who believe it's not worth risking lives. think you've found your ideal hotel? >> he's the guy going viral for these mill layer yus hotels. >> trying to do too many things at the same time? >> but then found the trivago guy for good reason. inside the world of spokesperson stardom. >> one tuck in, one tuck out.

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good evening. thank you for joining us. invasion. two sisters attacked by a man just days after he got out of prison. what happened next may take your brett away.

thinking -- what might you do? we begin with a chilling 911 call. >> hello? >> what do you want? what do you want? i'll give you anything you want. >> hello? >> reporter: frantic pleas for help as two sisters fight off a home intruder. >> i knew from her screams -- it was only a couple of screams that i heard but from the tone terrible. >> reporter: these just-released 911 calls depict the horror last month when two young women, bri and kalie lasly, tried to wield off a knife-wielding intruder in their new salt lake city home. >> help us, help us please! >> reporter: the sisters had just said good night around midnight when 27-year-old bri says she heard a strange sound in her dark bedroom. >> i thought i heard something outside of my window.

just a few minutes later i heard someone say "hey, girl, i'm coming in." it was then my window opened all window. >> reporter: the intruder, 48-year-old robert burger was released from prison just one week before the attack. bugger had tried to break into a different home a few doors down on the very same block. >> yeah, i just had someone break into my house. >> tell me exactly -- >> he just broke through my kitchen window. >> when did this happen, how many minutes ago? >> two minutes ago. like -- i just grabbed my phone out the window. >> reporter: later burger entered bri's window using this chair and broom. fend him off. >> he said, cooperate with me. i said, i'm not cooperating with what you want out of this situation. and he put his hand over my mouth, shoved me up against my door, and started purge ded punching me.

>> reporter: terrified little sister kalie runs to help. >> i ran into the fight. i didn't see them. i could just hear. all of a sudden i was kind of in the middle of the fight. >> reporter: the sisters say they barely had time to be afraid. all they could focus on was fighting off their attacker. >> i remember squatting down and holding on to his shorts with my left hand and punching him as hard as i could with my right hand. and kalie was behind me just beating him over the top of me. >> i think he must have kicked me down the stairs. i don't think there was any way it was a push because it was so much pressure on my chest. stairs. he's saying to us, just give me your car keys, i don't want to kill you, i don't want to rape you, just give me your car keys so i can get out of here. >> i'll give you anything you want, what do you want? >> we said, you can have your car keys, you have whatever you want, what do you want? then he just continued to beat us. so that's when we both had our

phones and i said, kalie, we need to call 911. >> hello? >> reporter: they say they and the suspect fought savagely, kicking and punching, until burger pulled out a knife. >> and i heard briane say, kalie, he has a knife. >> i just remember, this can't happen. this needs to stop. but then i knew we needed help. and that it was going to end. it was going to end quickly and badly if kalie didn't leave and get help. because unfortunately i couldn't be the one to leave. and so i yelled at kalie to go and get help. >> she started screaming, kalie, he's stabbing me. >> he's stabbing my sister! he's stabbing her! >> we were both thinking the same thing -- >> it's the last time i'm going to see my sister. >> reporter: kalie makes a heart-wrenching decision to leave the house and ask for help. her terrifying screams awakening numbers.

>> there is someone outside of my apartment screaming like bleed murder. she is screaming for help. as loud as she can. >> did you hear anything that was said or just the woman screaming? >> just -- she was screaming and she was screaming "help me." she's still screaming. >> okay. >> i can hear it, shears still screaming. >> then i saw a few people come out of their houses into the street and that's when i started saying "he's stabbing my sister, he's stabbing my sister, he's going to kill her." >> reporter: salt lake city police officer ben hohn had been on the streets responding to another report of a burglary. he rushed into the lasly home help. >> i remember looking at the officer's eyes and saying, me." he shined a light on the suspect and said, "salt lake city police department, drop the knife, drop the knife." right when he flexed -- the officer took his life and saved mine.

>> reporter: officer hohn fatally shot burger in the head. >> one female stabbed in the stomach. one male unconscious, not breathing. >> reporter: bri was stabbed three times in the thigh, the stomach, and sternum. >> i think if the officer -- he could have taken five seconds longer and she would have been killed. >> reporter: the girls say officer hohn is their hero. >> it's like -- we don't really have words for how much we love him. and his family. he really saved our lives. both of our lives. right there in that moment. >> reporter: bri and kalie's terrifying ordeal is just one of the latest in a series of recent home invasions, violent attacks, intruders crossing the threshold into the place where we're supposed to feel safe, our own homes. according to the fbi, almost 2 million players occur each year. 60% involve forcible entry. in san jose, california, this

home security cameras as an intruder broke into the home, even pulling on the door of the bedroom where she was hiding. >> i came out of my closet at that point and started banging on the door from the inside, yelling at him, "get out of here, the police are coming, they're going to shoot ju." >> reporter: in central florida, men dressed like ninjas breaking in tying up the homeowner. safety expert and former law enforcement officer steve cardian says, even though home invasions are rare, always have a game plan. >> what i suggest to people is, before something bad happens, create a plan of action. the minute they detect somebody in that house, they should code red, run to a safe room or run out of the house. but get away from him, far away. >> reporter: bri and kalie are recovering. both say they're lucky to be alive. >> i remember in the emergency room, they kept saying there's no way that didn't hit her aorta, there's no way theert no heart damage. >> reporter: they've since moved out of that house.

>> we're blessed. to say the least. to say the very least. that's right. next, why controversial announcement about breast cancer screening is ignited heated debate. meet the trivago guy. what's the like getting cat putted into fame for a funny ad campaign?ths. and that was amazing. along with support, chantix (varenicline) is proven to help people quit smoking. it absolutely reduced my urge to smoke. some people had changes in behavior, thinking or mood, hostility, agitation, depressed mood and suicidal thoughts or actions while taking or after stopping chantix. some had seizures while taking chantix. if you have any of these, stop chantix and call your doctor right away. tell your doctor about any history of mental health problems, which could get worse or of seizures. don't take chantix if you've had a serious allergic or skin reaction to it. if you have these, stop chantix and call your doctor right away as some can be life-threatening. tell your doctor if you have heart or blood vessel problems,

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we turn now to a major shift in how and when we look for breast cancer. a big announcement from the american cancer society instantly met with criticism, even outrage, from women who say they owe their lives to early detection. one of those women, our own "good morning america" coanchor, amy robach. >> i'd be dead if i hadn't done that breast exam. >> reporter: jerilynn lucas 21 years ago, diagnosed with an aggressive form of breast cancer at 27 years old with no prior family history. >> i found a lump. i didn't realize that breast cancer could happen to a woman in her 20s. i thought a woman had to be 40 to get breast cancer.

chemotherapy. she's been in remission since. lucas argues early detection was the key to saving her life. but just this week, the american cancer society making waves after they release new guidelines stating that women with an average risk of breast cancer can delay having a mammogram until the age of 45, five years later than its previous recommendation of 40, a message that outrages lucas. >> i think this is such a disservice, adding to the confusion of when to get screened, when to get checked. i feel like we've made so much progress in genetics, in research in treatment. why are we going backwards? >> reporter: the american cancer society says the new guidelines are based in evidence that mammography screening harps can include the risk of false positives in younger women. >> there's a changing risk as you get older. these guidelines have given a roadmap that a woman can follow throughout her life span.

but if you haven't started by 45, everyone should begin screening. that's really the key take-home message. there is a chance, small though it is, that a woman could die because she did not begin screening earlier. >> reporter: it's that chance that is leading the experts at memorial clone kettering cancer center to not follow the acs' new recommendations. >> the goal is not to decrease false positives, to decrease biopsies. the goal is to decrease deaths. that's why i think we are sticking with our guidelines, and that's why it concerns me that the american cancer society has changed theirs. >> having a mammogram once a year, starting at age 40, is the best way we know of to decrease deaths from breast cancer in this country. >> reporter: radiologist dr. carol lee says that the guidelines could lead to confusion among patients and that the consequences could be

>> what i don't want to see is a reversal, going backwards, seeing more deaths from breast cancer because fewer women get screened because they're confused about whether they need to have a mammogram. >> reporter: dr. wender says no matter a woman's age she should still be mindful about your breasts. >> your risk of breast cancer starts even earlier than 30. so we encourage all women to be aware of what their breasts feel like and not to delay if they find something that they think might be a change. even if they're not sure. bring that to the attention of a clinician. >> reporter: there are questions like, will insurance companies continue to cover mammograms for women under the age of 45? cigna health insurance in a statement to abc news saying, cigna's breast cancer screening policy is 100% coverage for women age 40 and older. we have no plans to change our policy." >> my mastectomy, the day after my 20th birthday, realizing i

be a chunk of myself -- i hadn't had any surgery, i didn't know what to do. >> reporter: today lucas is joined by a group of women -- >> my daughter wendy had breast cancer. she passed away in 2009. i say this is the face of young breast cancer. >> reporter: their stories hit close to home for me. >> now to a very, very brave moment, our dear colleague amy robach, she's one of the new staffers having a mammogram. >> reporter: in an effort to demystify the process of breast cancer screening, i was asked to have my first mammogram live on abc. >> we're hearing the word stronger and you are being so strong today, amy row back. you're going to live have a mammogram. >> reporter: my reaction was visceral. no way, no how. >> she called me and said, them me to do a mammogram live on tv. and i said, i don't think that's a good idea. it seems exploitive. you have no connection to cancer. it didn't seem authentic. >> reporter: the truth is i feared it would look like i was trying to grab the limelight.

million my dear friend robin roberts said the words i needed to hear. 85% of women who have breast cancer have no family history. that statistic sent a wave from my head to my toes. >> i went in to see robin, who is a breast cancer survivor and thriver, and she said, you know what, amy? if one life is saved because of early detection, it's all worth it. >> reporter: i was 40 years old at the time. with no prior history of breast cancer in my family. and a life busy with work and kids. i had been putting it off for a year. i finally said yes. >> amy is wrapping up her first mammogram here in the mammo van. >> reporter: little did i know that mammogram would change the course of my life. a few days later i received a call. doctors wanted to do more tests. and later, a sonogram. it was there. a dark spot on the screen. a tumor about the size of a marble growing inside me. those moments alone, scared in

i wanted to stay positive so i kept telling myself that this was why some people argued mammograms. competitive testing, false readings, unnecessary anxiety. it has to be benign. they immediately performed a biopsy. there was no escaping my new unreality. i had cancer. >> i will remember that phone call for the rest of my life. i knew it was bad news. then she said, they found a tumor, and it's malignant. >> i have decided to have a bilateral mastectomy. i'm going to be very aggressive. i'm 40 years old, i'm young, i have a lot of life ahead of me. >> reporter: the prognosis was chemotherapy, eight rounds over six months. april 24th marked my final day of chemo. today i have made it my mission to raise awareness for early detection. it's a calling that geralyn lucas shares. she's the mother of two and author of a second book called

"then came life: a warrior in the fight against breast cancer." >> i'm the lucky one. i have a 16-year-old daughter and a 9-year-old son. they were born in the same hospital where i had my mastectomy. and i have a life now. i'm the lucky one. >> reporter: for "nightline," i'm amy robach in new york. next, around the world, the trivago guy. how he literally stumbled into fame. geico motorcycle,

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think of your favorite commercials and you'll probably think of a favorite spokesperson too.

the right face can make or break a company. so trivago definitely lucked out with the guy you're about to meet whose offbeat appearance in their first commercial had hilariously unexpected results. >> did you notice there's so many prices out there for the exact same room -- >> reporter: tim williams known as the trivago guy, slightly rumpled yet approachable. he's pitching good deals but it seems lots of people want to know what his deal is. >> i come from houston, texas. i made my way up to new york a long time ago to study acting. i worked on "my so-called life." i worked on "the sopranos." >> reporter: it's williams' commercial success that has women and men obsessing over his laid-back look that also comes with criticism. >> from doug. tuck in your shirt, you badly dressed trivago guy. this is for you doug, is this enough?